THE FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA
MINISTRY OF WATER RESOURCES
Arjo Dedessa Irrigation Project
Feasibility Study Report
VOLUME - III
Water Resources
VOLUME - HI (al
Annexure - 7 Meteorological And Hydrological Studies
Annexure - 8 Hydrogeological Studies
Way. 2017
Adils Ababa
WATER WORKS DESIGN & SUPERVISION ENTERPRISE
IN ASSOCLBTIOI WITH
JMTHeDinBffimiL e9HS(!ntifn AHO TtCHttBCBJiTS flffllfi m 1TB
POBoa:S.I \ddh Ahm.i EUiidjxj
t'd I 151H illL-ijHlI/ft-l liJWi I Hjx 1.125 IH »i1 Al? IE-null w n d * c IctQ’h «« <1ARJO-DE DESSA IRRIGATION PROJECT FEASIBILITY STUDY REPORT
CONTENTS OF THE REPORT
SERIAL NO.
1
2
3
VOLUME NO.
PARTICULARS EXECUTIVE SUMMARY MAIN REPORT
Pad I - Report
Pad II - Maps fi Drawings ANNEXURES
VOLUME -1                     SURVEY ANO INVETIGAT1ON (ANNEXURES - 1 to 31
Volume I (3]
Topographic Survey. Geomtwphoiogical Studies &
Geological & Geotechnical Investigation
Pad I - Report
5
Volume -1 (b|
Pad II - Appendices
6
VOLUME -II
NATURAL RESOURCES [ANNEXURES - 4 to S|
Forestry, Energy & Catchment Development Pier
VOLUME III
WATER RESOURCES (ANNEXURES - 7 to 11]
Volume - ill (a)
Meteorologfcai & H-ydrologis&l & Hydrogeological Studies 
Dam S Appurtenant Works
Pan I - Repurr
0
9
10
11
Volume - III (b)
Part II - Drawings 
lmgabpn & Drainage
Volume - 111 {cj
Part I - Report
Part II - Dca^ngs
Hydraulic Structures
12
13
14
15
in
Volume • III (0)
Pad I - Report
Pad II - Drawings
VOLUME IV
AGRICUTLRUE (ANNEXURES- 12 to 18|
Volume - IV (a)
Sod Survey S Land E valuation
volume - IV (b)
Ag/CiPlurai Ptannmg
Volume - IV (c)
Livestock Fisheries. Agricultural ftfecnan zalion £
Agricuhural Marketing
VOLUME ■ V
ENVIRONMENTAL AND SOCIO - ECONOMIC ASPECTS
(ANNEXURES - 19 to 25l
17
vc*mne ’ v (a)
Environment Health i Socio-economic .Aspects
18
Volume-v(b)
Organisation  &  Management  Physical  Inkaslnjciure
Reseitiefir.enr Financial i Econcen^c AnalySfSAnnexure - 7
METEOROLOGICAL AND
HYDROLOGICAL STUDIESAdo Dedeasa rnlfailcn Pn>Jwl Meteorological ana HydioJoglcal Aspects
May 2007
Table of Contents
lA BL EOF CONTENTS...
i.istor tables.™ 
LIST OF ANN ENURE..- LIST OF FIGURES.-.______
nrnitw.viiiiiHH.nM.iii
,._|V
1
•fl"— If III 11 w
I.
INTRODUCTION
The Nile Basw
ABB.AY BASIN .......... —— ■
Tur Dede.^a Catchments
II9-VIII
III—dll
>- —num i i i uh li—.i
mini
•f f-—IIWHI
I" -llinil I1BII--->III
1.       REVIEW OF PR EX lOL’S STUDIES
ivrwaiiii
II
22
2.3
24
2*
26
LaIFMaYU 1962 Sll DY —................... ................ ..................-
Land  and  Water  Resoi  *Ct$ofthf. Bi.ut Nile  Bases  Ethiopia
try wint Master Plan studies EVD5A W a PCOS1198£-90>
Sll PY BYBCEOM ■ IN aSSjQCIATXJN with i$L and BRO 1999 STUDY IIV MINIS! RV OF WaTU RESOURCES I OR LOWE* tHDLSSA (2001 I
UTILITY OF EAJtl IT* StVWES ..
-.
iimnMiMaoi
nn !• ■ i.
...
Cl IMaTCii.OGICaL. ft-A FA
Rameau.
Rjvtn Discharge
SEGMENT Data
•fl- IIUHIi
17 1? I? IB
J.
EST
IMATION OF REFERENCE
EVAPOTRANSPI
RATION .....
I*
INTRODI.CTIOS.
ME1HMMX.OGICAL Data
4.2./
422
^iVrCMijtogrraZ
XitfjGrt-j
X/f tt-w/WAlf-ivt*
III I..L-.- -l| .u.-
ll
4 2.3
42 4
4ir...
,.._..... ...
19
20
20
2/
Wi.tJ iprtd
i*
l.ll. In. ....
4.2.5
Jo/dr rg4l£ilrcm
•r-i in. ..«nii ,
....
43
pLVMAN-MOfclUrH Evcaiiun
23
23
■4f>
/>tyrrr rfm
Df5^-, 4™
24
III
5         KAI NFALL ANALYSIS
fir
n»—...i
5 I
MMMXKTM3N
.......
$2
5 ]
Raesfall internal and External Consistency
5.4
Estimation of Rainfall Rlllahility Llvei
Estimation or maximum Rainfall FxhQUtNciEs
32
<*
53
U
6. MONTHLY STREAMFlOW ANALYSIS-------------------
61
63
11YlWOUMlIC ALOBSMIVaTKJN S T ATlUNS. EXTENSION Of RECCmJli
Synthetic Flows
III
-in
■ III—fl
4«i
46
47
51
51
52
£
ESTIMATION OF Fl.OODS FOR IINCAUGED CA TCHME5TS..~. _............... Ration al Method
SCS method
Transhrriw Gauged Data
Estimation or Wetted average
synder Me moo Of Covhru rwGSx'NTMEnc Hydrograph
FLOOD FREQUENCY ANALYSIS_____ __ __ _______ ___ __
Water Works Design & Supervision Enterprise
■t.™—..                                                                           54
M
■u
t
59
!□ Associate wlih iBlereonUnenlaJ CoosuUmts and Technocrats Pvt Ud.
■■ j
K ..AimAjJfl Dedeisa Lrrl£atlDO Project
Meteorological and Hydrological Aspects
81          Introduction
8 2         E^TJMaIION OF PROBABILITY WtlGHTtD MOMENTS
8} Generalized Extreme Value Di$nuntiTxm—......................... _......
<4 Log-Logistic Dbtribvdo* ........................................ ........ ........ — .
May W7
. ..
• 
61
*1
8 5 REGIONALLY AYIKaGEDQCANTHES
..............
9.
8 6        CHOKE OF DISTRIBUTION — ............................ . ........ mu                 ...          ........................... W
PROBABLE MAXIMUM FLOOD----------
10 SEDIMENT ANALYSIS mm—timiwuwittrrtfiiii"
10 1 ESTIMA riOWOF StDMBff Viei4»
............... „.......................... 69
10 2     DtfTNBUTION Of SfXMMDCT ft THE RfSfRVtXR...........................................
II
ATER QUALI I I .fMMaMMaMMMaMMMMMaMMMMMMHWVMMWI
IT      DESIGN FLOOD.
...J$
12.1 1JL2 I3.J
SYMHRTICHvWOOXAnr
Illi I— Iff rSWI I ■—Tt ■ IVWf It—««l—MI NBtlMtm Will MM >•—>«■ i —4 BAI
Fl OOD Rot TING THROUGH THE RESERVO01• • Mt rtf —f raa—t aairr-M i a1 aiiiiai i ■ 11aaeaaaa 11 u iaaaaa ta i i tai n
Rot D4> Ofskjn Flood ai nit coi f er dam
?h
13.      RESERVOIR SIMULATION
14.
1)1.DESSA SUB-BASIN MODELING..................._............ ....
14.1      MobUJNG Inn AlUO OtDFSSA DAM FOR IRRIGATION .............. .. ............. 91
4 2 The sub basin mcxx i im,
/4.2.JT
Gfnrralir'* in             m Dam
JI J 2           Oofimai' A'utarr/ Grnrnjhcm
MJ J Heduatnn Inflii-nt (ft iMeiui Sub basur
92
‘Sfi
W2.4           CWJlUKMI.
IS. RECOMMENDATIONS ON TRAINING NEEDS
REFERENCES ■ a a aa a a*aa a • aa^iA * a a
102
Waler Works Design & Supervision Enterprise
In Associate with InterconiiBtnul Consultants and Technocrats hr LtdArjo Dcdessa Irrigation Project Meteorological and Hydrological Aspects
-W
LIST OF TABLES
Tasif U. Table 4 1
Table* 2:
table 4i.3: Table 4 4 Table 4 5 TaSl£ S I Table 5.2. Table 5.3: Table 5 4 Table 5.5 Ta«i£5£
I*tiit 5 ?:
table 5.6. Table 5.9: Table 5 IQ; Table 5 I Table B 2 Table (13. Table 5.4 Table 5.5: Table 6 G TabiE 5 7 Table 9 i Table B.2 Table 9 1 Table 9 2
TABLt 10 1:
Tabic 10 2:
Tame 10.3:
TAHLE 10 4
Table 1i.l TabiF 12 t
Table 12 2:
Table 12.3: Table 124 Table 12.5
T*£LL 13 1
TABLL132
Table 13 3:
Table u i- table 14 2
Break up of Aesay Basin Afea
TAB.E DETAtSOF HtTEOfiDLOGICAL ObSE HVATON STATIONS LOCATED 'N A^D ARC^TJC EHE^
PRCUECt AREA.
....................................... ''
Tv PE-5 CH- CUMATC 0a?a auaraBlE aT TmE VARIOUS MFTEOROLCX?!t5AL 0fl5£HV*r,i"N
Statwb -........ - ...........—............ -.....—..... —............. **
Summary of meteoroloscal Chahag^rlst cs * r Project arfa Summary of estiuaied mean £ Too* arxjOeoessa project Arfa MaGNiTL®€ Of Elo at OivEn nON-£3iE£QajnCE PROBABILITY LEVEL CROSS- CORRSIABOM MAlRiA C* Annua: RaH-jT M. i
Mean Month?,* Rainfall
Parameter EsiiAiAT^s of Wfibjiili Ostributiqh
Monthly Rainfalls Corresponding id Offered rfliao utv Lt ,.-Ei •.
Parameter Es^mates df Half-Month./ Rainfail
Half- MQNl K* Rainfall MAGMTUOES AT DlFFE RENT RELIABILITY LEViFl S
half-woji«l* Rainfall Magatudes in Percent of the Mfan Co*W’7SPqnl>ng iq Different Reliability Levels .
Maximum Aanual 24-hr Rawfall. ..................................—             .... Maximum Rainfall Magnitudes akj FrequEiCiE S
Max'-wum Rainfall M*dnitl€€3 fo» Higher OjraTiOhs Availabilif* of Streamflow Data in the RegGn — 
Mean Monthly Flow (in Mn’/reci
...
Coefficient Of vabiatidn qf Monthly ^changes .
Summary of Regional monthly flow Characteristics
Table Statistics of monthly flows at arjo De de ssa oa*i site
Reliability Level Vs Month.* Scheamflthys at Dam Site
GhaRaC "ERIETJCS of RanQOm NUMBERS USED FOR FlOV Gt NLRA TICM
Estimated Flood Quantiles B ased on GEV Ostributon
£st iuateo Flood Quantiles Base d on LLG Ds tripui ion
Table Cumulative Volume of Probable MAlwjm f loco
Design Flood Hyqrogsaph Derived trom £s timated PMF
Relationships between water discharge *>® sedwfnt lqao
MorthlyTotal Sediment Load at The Reservq* Site
Accumulated Total Se&mew Load at the Aeserycxr She
DhSTRiSuTIDN DF SECimENT in the Arjo OEDESSA Re SERVQIR
Wa FER -duality RESULT S FUR BtEES On the DEEESSA RIVER
Catchment Characteristics
Routed Design Flood at FRl Corresponding ro »352u
ROV1ED DE &GN FLOW at FRL CQRRESPUNDING TO 1555 M
ROj fed De sign Rood at FRl Cdrre spending to !355m
Routed Design Flood at Co* er dam -y amju didessa Reservoir
irrkjai icn Water Requirements for Varchjb Scenarios
Reservoir Characters tics at Dead Storage Level
Stowage Reservoir Oiajw. if ristcs *ag Rel lability levels
Total Monthly Release lirriqatkjn plus Power)opssqnsfqr YAflOusFRL values
CQMMSRED
Annual E^jERGy GENERATES at CfeDESS* DAJU FOR l HE VARIOUS DPTi&ye
js
29
1 ?i
& Vi
1 ’■
'P
44
*o
-li
is
is
4§
lm
49
iy
m
64
b?
gi
yi tj
71
7J
44
yj
£1
g2
ki
gg
gr>
yrj
qrr
■}’
Ill
Water Works Design L Supervision Enterprise
In Assoc|«e xlih IntercoBUncUla] Cons duels and TecbBocraU Pit Ltd.irj o-Dcdessa Jm ration Project
Meteorological and Hydrological Aspects
May 2M7
.annex A
Ai
A2
A3:
A4.
AS
AS
A7
A8
A9
ANNEXB
B1
B2:
B3
B4
B5
66
67:
6B AnnCjl C:
Cl
CZ
C3
C4
C5
CB
Annex C:
D1:
D2.
D3
Di
06:
06:
0?
W
09:
Aw«x£: El.
62:
E3:
E4:
E5:
LIST OF ANNEXURE
Results ca 1 atnlD from the Meteorological Analysis
£&tima!EDM€*nTemperature atarjoOedeS&aP*wxct Area(in'Ci Estimated Minimum temperature at Arjc DedESSa Project Area (in C) Estimated Maximum Temperature aF ArjO DtMSi* Project Are a (in X) Estimated Relative HumciTY at Arjg DedeSSa Project ARE* (in percen] ) E stimated Mean Daly Sunshine Duratwm at Aftjo D€DEss*. Project Area Es ti mated mean Daily £ TO cf Arjo Of dcssa Project Area
Estimated Mean Monthly ETd of Arjo DedESSa Project area
Gsl iuaTED MEAN MCWIMy RAMf *LL AT ARJO &EDE $SA PROJECT AREA Estimaied  Mean  half-Mowthlt  RainFm  at  the  Project  Area  (in  mm-hr! Results mtajneo from thi Hycrouogical analysis
estimated Monthly Flows at ar jO Dedessa Dam Site REGOMii. MONTHLY COEFFiCjEnI Of VARIATIONS (CV) .
Kl?
1 OB
103
ii5
Iu
REGKX-cAl MONTHL Y COEFfCrfcWT OF SkEwK&S ...           .                                                                        114
1B Regional mcnthi y cOEf FiCiENi of correlations fR)
Standardized probability wCighteo moments ... ........
.. IIS
Mean Monthly Total (Suspended and Bed) Sediment Load
ELEVEATiDn AREA-CAOaOTY RtLATtQNSHFSOF ARJODFDFJSa RESEHVOiR Sample Simulation Results of arjo deoessa Reservoir
STANDARDS.............. .. ........... —...... -............... ..................... . ............
CCMMONL* USED VALUES OF RUNOflf COEFFICIENTS
Ruworr coefficient for pervious Surfaces by selected myOroldg-c $chl
SCS Curve Numbers for Various CoiD^nons1
114
11 fr
i i ft
ReservO'R Flood Standards
„____ Ratios OF BASC DiM-ENSiCNi ESSHV-WO3RAPH GF THE SCS.
GvCf UNtiFOFi Interpretationso? Wafer Qualityf ch irrigation:
Meteorological Data ...           ......................... .. ..................
Details Of Mltedroldgical OBS£rvaticn Stations
Tvpf s of Climatic Data avacable at the various Meteorological mean Monthlt Rainfall at Bcdele Station
MLan MDNTHLv RAi^fALL AT JlMMA STATION Mean Monthly Ra *fall at Decessa Station MtAv Temperature at Be dele Station
Relative Humidity at BfdelE Station [*/%)
Wind Speed a r j mma stai o*j
Sunshine DuRaTsqnat ScoEle Station
Hvorologktal Data
list Of Selected Hyorocogicaj, Oeservaikjn Stations MEam Monw Sirfamf low at Cede Ssaw near Arxj Station Mean Monthly Strew flow at Dedessan NEAR Demhi Station Annual Maximum Floods
’wrHvrl iliui.ld
F - W—■ ■ I
Measured Sediment CCncemflatrc<N atC^umamaGaudSiaton
rv«H. .. i-mr-iu
-iff"? ■ Bia* .
--------------------------------------- --------------------- ---- -------------------------- -------IV Water Works Design & Supervision Enterprise
In Associate with InteocDnUaeniaJ Cumliams and Tetbaocrats pvt!»].ArjD&etkssa iniptlta Project
Meteorological and Hydro logical Aspects_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ '--^y
LIST OF FIGURES
FBfJRE 4 1        MEAN MONTHLY TEMPERATURE AT F<iuftE 4.2: MEAN MC^n-LV R=LAWE HiAhClTY AT
Acuflt 4 3              mean MCwrHLV Wimp Speed *T FGuflE 4 4 MFWj MCf/TriL?1 SiJN8>' NE MaUPS *F
IQ
Pi&JRE 4 5            MtAN MONTHLY ETD AT AJUGDtOEMA PROJECT AREA .
M
Frruftt 5 1{a):       Trend Awaltsis ex Awu*l Ra«fau at jiuma Station
41
Fislse5.1(B):      TfiEw AraltssS OF Annum Rainfall at BEDEiLE Station
42
Figure 5.l(t)        TrenoAkalvsiSof Anmj*l Raikfallat Dedes&a Station
-n
Figure 5.2(a):    Single mass Curve of Juma Ramfall
4j
FIGURE 5 3|i)c     S'NGLE Ma55 Cl*V£ OF BEDELLf RaimTALL... ................................................................................. 44
Figure 5.2(G): Single Mass curve OF &EDESSA rainfall . ....................... ....
F»CURf 3 3:          V EAn Monthly Rajnfau AT Ah jo OEDERSA PfiOJESCT Area.
Figure 12 i          Elevation-ARfA-CAPAQTV CURVES ex Arju OEdess* Reservoir
Figure 12.2:      Inflow ami Outflow flood    Hv&rographs at Ah jo Oedessa Reservoir
Figure 12.3:      Inflow and Outflow flood   i^or-l/grafhs at arjo Dedes$a Re.se rvcir FlGLtfE 12 4       A'rFfiAGi hhDROGNAfM O MaXjMuM HOWS AT AftJO  EDESSA CAM SiTE FlfiWlE 14 1.       PoftER DoRAtlCTM Cl/RwES
44
45
kj
S4
gs
06
qo
Water Works Design St Supervision Enterprise
la Associate with [iJtErmtlneaiai Cg militants and Tethaacrau Pit Ltd.Drdessa Irrigation Project Meteorological and Hydrological Aspects
1, INTRODUCTION
1.1    The Nile Basin
May 2007
Having  a  length  of  6.625  km  .  the  Nile  R*ver  takes  the  rank  di  number  one  with  respect  to
length,  m  (he  world  It  drains  a  total  drainage  area  of
2,96  M.Km ,  with
?
its  annual  total  How
of about 84 0ms As  one could appreciate, the discharge per Km2 is  small when compared to olner large nvers  of lhe world. From the Lake ViClona, io the Medilerrarvfjan Sea, lha river crosses  very  many  different areas  associated with different climate, reltei and geology. The main sources  of the river are 1he equatorial lake plateau and 1he Ethiopian Highlands The three major trioutanes  which emanale from the Ethiopian Hrghlands  are. from soulh Ed the north the Bara AkObo, the Blue Nile, familiarly  known as  Abbay  and lhe Tekeze Albara System.
1.2    Abbay Basin
The Abbay  Easin e& one of the mast imporlanl b»ims, in Ethiopia. It .-recounts  for aboul 17.5% of Ethiopian land area, 25%. of its  population and 50% of its  annual average surface
water resources. In the Lake Tana, it has  the country's  largest fresh water lake, covering an extent of 3000 km! The Abbay  has  an average annual run off of about 50 B mJ The rivers Of Abbay contribute on an average, 62% of Nile river flows in Aswan dam
The climate of lhe Abbay  Basin is  dominated by  two features, namely, it's  near equatorial location and m altitude range beiwoen 590 m.amsl lo 4000 m. amsl These influences result in rich variety  of local climates  ranging rrom hot/desen like, along the Sudan border to lhe temperate type on the high plateau with depiction al cold in the high mountains  The Basin can generally  be d escribed as  temperate a t h igher e levalion a nd tropical at lower eievalctns. However duo to tne distinctive aspects  of the highland ch mate, it is  perhaps belter to describe it using 1he local climatic  zones, that have bean established with elevat or (and resullant temperature) as controlling factors
The Qolla zone lies  below 1800 meters  and has  annual temperature range from 20’C to
2S C
a
The  Woina  Oega  zona  ties  belween  1800  meters  and  2400  maters  and  has  annual
average temperature ranging from 16“C to 20DC The Dega zone, above 2400 meters  has average annual temperature ranging from KfC to 16*C The major portion of the population inhabit in the more chrnalitaUy  pleasant and healthier upper twe Zones, which leaves lhe lower Oolla zone sparsely populated
Water Wks Design & Supervision Enterprise
In Associate ultb intercontinental CnoxulLftuts and TectjdOCraLs Fn Ltd.Arjo Dedessa [nrijsties Pralttl
Meteorological and Hydrological Aspects
There are ma^ly  3 rainy  seasons. The main one (kireml) lasts  generally  from June to September, during which. the south west winds  bnng rams  from the Atlantic  Ocean. About 70% to even up to 9Q% of the rainfall occurs  during ths  season. Ths  season obviously  S associated with minimum revels  of sunshine, low variations  m daily  temperature and high relative humidity  A dry  season (Begs) lasts  from October Ed January, during which clear skies  are associated with maximum sunshine hours, high daily  temperature variation and low relative h umiddy. F inally  1 he m ino* rainy  season |0elg) lasts  from February  to M ay, during which south east winds  bring the small rains  from the Indian Ocean The temperature range is  very  high in this  season. The precise Uming and duraLion al 1hese seasons  vary  considerably  depending upon location within Ab-bay  Basin, and to some fesser extent, year to year as well.
Generally  speaking, the low attitude depicts  the pattern of t 1.5 to even 12.5 hours  of sunshine and temperature varying only  for a email range from J’C to 7aC Ihraugh oul the year
The mean annual rainfall over the entire basin could ba reckoned at 1400 millimeters where a s  1he mean e vapotransprralion is  about 1 300 m ilKmelM. Broadly, based on 1 he rainfall pattern, 4 different areas  have been identified by  |he earlier Master Plan study lAbbay  River Basin Integrated Master Plan Project - BCEOM in assonalron with BRGM, ad ISL consulting Engineers - 19M). These are'
i)      Southern  area  covering  East  and  West  Weiiega.  Jimma  and  lllubabor  Zones  with relatively high rainfall (1400-2200 millimeters} and a lung wet season
ii)    A  central  area  covering  most  of  Western  Go^am  and  parts  ot  neighboring  zones  as well,  characterized  by  relatively  high  rainfall  (1400  -  2200  millimeters).  But  there  is a   mwe   pronounced   seasonal   pattern   associated   With   shod   wet   and   longer   dry seasons.
iii)   An  area  covering  most  ot  the  eastern  part  of  lhe  basin  mcludir-g  North  and  South Wello.  Eastern  part  of  East  Gojam  and  South  Gondar  and  much  of  North  and  North Wesl   Shewa   region,   excluding   smalt   proportion   oi   mounlam   areas   This   area   is characterized  by  relatively  low  rainfall  (less  ihan  1200  millimeter)  distributed  in  both lhe rainy seasons, depicting bimpdalily
Water Works Design & Supervision Enterprise
In Associate with l□te^tJDtl^t^tal Consultants amt Ttciuinemu Pvt. LuiIrrigtitoa Pnnjwt
Meteorological and Hydrological Aspects
May 20OT
M   The   West   and   North   west   area   cowering   fourth   Gondar   region.   The   rainfai   is about  1200  millimeters,  falling  predominantly.  in  the  mam  rainy  season  associated with high average rales gf evapotranspiration.
With reaped to Ihe hydrographic  scenano, the Basin is  dominated by  Abbay  River which rises  m the center of 1he catchment and develops  ds  course m a clock  wise spinal it coHects  Inbutaries  all along its  992 km. journey  up to Sudan border. .As  said earl er. the Abba/ Basin catchment area of 199.&12 !km7 fS encompassing the break up as below:
As  Gilgel Abbay, the mam river flows  north from its  source near Sekeba into the wide and shallow Lake Tana The lake also receives  other iribulanes  from a catchment of 15.054 kma including tributaries  Megech. Ribb and Gumara. Shortly  afier leaving the lake, the river reaches  the celebrated Tie Abbay  falls  thereafter flowing m a deep and rugged gorge on its way to Sudan Border The break-up of Abay basin caichment area is available in Table 1.1
1.3     The Dedessa Catchments
The Dedessa River is  the largest tributary  of the Abbay  m terms  of the volume of water Contribution to the total flow of Abbay  a1 the Sudan border. Draining nearly  an area of 34,000 square kilo meters, the Dedessa river o ng-nates  in me Mt.Venmo and Mt Wache ranges, flowing m an easterly  direction for about 75 kilo meters, Lhen turning rather sharply Io the north until it reaches  ihe Abbay  River. The major tributaries  of the Dedessa river are the Warns, entering from the east, the Cabana from the west, and the Angar from the east.
Oedessa Catchment is  silualed in the south-west pari al Abhay  Basin The calchmenl area at a gauging station near Ago Lown is  9.981 km7. The dimate of the Dedessa Catchment resulls  from its  location and elevalson (1220 Io 3012 meters) The catchment ts characterized by  mountainous. highly  rugged and dissected topography  with deep slopes The lowest part of ths catchment is characterized by valley floor with flat to gentle slopes
Most of Ihe ramlali m the Dedessa Calchmenl is  concentrated ?n the June 1a September period with virtual drought from November through February. Annual lotals, average from less  than 150 centimeters  to more than 200 centimeters  The Dedessa catchment, besides reflecting a marked rainfall increase with higher elevation, also receives  heavier annual quantities  than most o1 the calchmenls  in Ihe Abbay  basin. Examination of the rainfair records  from this  area shows  that this  is  due la a longer (May  through October > rainy season rather 1han heavier maximum monthly quantities
Water Works Design & Supervision Enterprise
Is Associate with Iniercoddutiital ConsuItamts and Technocrats Pvt Ltd
3ArJolkdcEsa IrdgaUOD Project
Meteorol rj^a t :i I an d fly dro 1 ogic al A spc eis 
May spot
The mean annual flow of Qedessa river at Arjo station is  about 3.800 million m3 having rt$ maximum flow m August and September (52 percent of the annual} anti minknum flow in February and March (fess chan 1.5 percent of She annual).
Further   vivid   description   of   the   climatic   factors,   rainfall   and   hydroragiaal   parameters   are made m the ensuing respective sections of this report
Table IJ:           Break up Of Atbay Basin Area
System Tributary
Joiriiiin g
From
Lake Tana North Gojam Beshilo Weleka Jemma South Gojam Muger Guder Fincha Dedessa Angar Wonbera Dabus
Bates
Dinder Rahad
Total
—
Right side
Left side
■
Right side
Left side
Catchment
2
Area (Km )
15,054
a
H
-
Right side
Left side
Right side
—
—
14.389
13.242
6.415
15,782
16.762 8.188
7.011
4,089
19,630
7.901
12,957
21.032
14.200
14.891
8.269 199,812
Waler Works Design & Supervision Enterprise
In AssucIsIe Win Tstercaiitlnetla]CddsuIMrcs and Technocrats Kt Lrd
JArjo-Dedessa lirljarlna Project
Meteorological and Hydrological Aspects _  May 200?
2. REVIEW OF PREVIOUS STUDIES
Because of the importance of the Abbay, very  many  studies  had oeen carried out in lhe past, concerning the basin Though, there was  not any  specific  siudy  for the development of
□Odessa   sub   basin   exclusively,   alt   the   studies   under   taken,   pertaining   lo   Abbay   or   the   country as   a   whole,   spoke   of   Dedessa   development.   Hence,   though   such   a   review   has   to   be   more exhaustive,   it   is   necessary   to   undertake   such   a   review,   before   attempting   Dedessa   sub   bas   n development   especially   the   aspects   connected   with   hydrology   in   this   sectoral   study,   Such   a review is presented in the following sub paragraphs.
2.1   Lah mayer 1962 Stu dy
This  was  mainly  concerned with Gilgel Abbay  Scheme Alihough, it was  not having adequate dais  base, lhe siudy  provided interesting mformation aoout Gilgel Abhay  and its  tributaries, which could be considered as a data oase for review and up dating m the light of the raw data
2.2    Land and Water Resources of the Blue Nile Basin Ethiopia
The study  was  under taken by  the United States  Department of the Interior Bureau of Reclamalron dunng 19SB - 1964 This  delailed siudy  on land and waler resources development of the Abbey  basin is  worth mentioning important study. Even at a time when there was  a little or no data, very  exhaustive ana ysis  of the available data had been earned out to establish hydrological studies, tn fact, the pioneering works  undertaken during that time has made Abbay  basin in Ethiopia, to be proud of a possessing a good net work  of nydromdric stations  for making reliable estimates. The hydrological aspects  have been covered in Appendix  III of lhe report. In 4 different sections  of this  Appendix, the venous  facets  at hydrological analysis nave been put forth as below.
*    Section I' A general description on climate, availability of water, sedimentation rates and possible i rogation requirements.
*     Section II: A presentation of the status ot historical stream flow and their elaborations,
*     Section 111. A presentation on flood flows and the analysis attempted « Section IV: A presentation on waler u$e,
s
Water Wks Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt Ltd.ArjiyDEiiesil rrnnauwi Project
Meteorological and Hydrological Aspects
.May 2007
In   the   Section   I,   on   giving   an   account   of   the   synoptic   and   climatic   situations.   the   22   stations win   tang   data   have   been   analyzed   for   precipitation   and   temperature.   The   basin   isotherm   and preop'iaiion    maps    have    been    prepared    based    on    above    analysis.    The    waler    avaliability aspecls   have   been   also   addressed   in   this   Section   I,   The   samples   analyzed   a1   5   stolons indicated   a   low   sodium   hazard:   most   of   them   showed   tow   io   medium   s   alinity   h   azard.   some samples   contained   from   none   to   a   maximum   of   0.2   ppm   of   Boron,   which   was   found   to   be tolerable   by   most   sensitive   crops.   The   samples   showing   highest   salinity   were   from   Mugger and   Dmder.   With   respect   to   sedimentation   ralmgs   were   established   at   4   stations   and   based on   extrapolation:   the   sedimenl   rate   was   computed   at   all   the   identified   palenhal   dam   siies   The pattern   of   sediment   distribution   m   reservoirs,   expected   after  50  years  of  useful  life  was  adopted uniformly  i  n  a  waler  b  alance  t  ype  cfs  initiation,  f  or  o  stabl  ishing  t  he  s  uccess  oJ   e  ach  o  f  t  he identified    projects.    In    I    he    section,    3    regions    have    been    identified    for    development    with respective     crop     projections,     cropping     calendar     and     crop     water     requirement.     The     water requirements varied from 782 millimeters «n Gilgel Abbey to 1375 millimelers in Dmder area.
The section II has addressed the stream How development for locations of the identified dam
sites by possible best set of analysis available at the time In the study period 59 gauging
stations were established, including 14 stations wtlh automatic stage records. Sy the vanous 
analysis including graphical rainfall runoff correlations, the flow series were burl I up al all dam
locations and a! salient locations. The annual mean flows at Sudan border was estimaled at
50 Bm3.
For the Dedessa at Arjo. the correlated flows were established for 8 years {1911 ip igi ? 3nd
1932).   The   mean   annual   l   ow   estimate   was   4332.82   W   (catchment   area   9486   Square   kilo meters)
For   the   Dabana   at   Abasma.   the   mean   annual   flaw   was   established   at   1757.26   Mm3    (calGhment area 3080 Square kilometers)
For   the   Angar   near   Nekemte,   the   flow   estimate   at   annual   mean   level   was   2523   33   Mm3 (Catchment area 4350 square kilometers)
b
Water Works Design & Supervision Enterprise
In Associate with IntercondncntaJ Consultants and Technocrats Pvt LtdArj ti-Deiltssa Irrigation Project Meteorological and Hydrological Aspects
May 2W
For lhe proposed Dedessa dam, with 3 catchment area of 3360 square kiio meters, the How was  estimated to be 1533.75 Mm3. Similarly, for the dam site at Dabara. with a catchment area of 2654 kilo meters, the annual flaw at mean level was  estimated a1 1515.63 Mm For lhe Angar, 2 dam sites  had been identified, one al a location with a catchmenl area of 1780 square kilo meters  (AG-2 Dam) a nd another at locahon with a catchment area of 4523 square kilo meters  (AG-6 Dam) The mean annual (taws  estimated respectively  at these two locations were. 963.125 and 2251.26 Mm1.
The section fl I, addresses  the causative factors  of floods  in Abbay  The design reinfatl for lhe basin was  estimated based on 6 representative station's  data, These are presented below,
which are forming a data base, worth for review and up dating (ar adoplton
1 day design rainfall
=
87 Mdli meters
2 day design rainfall
=■
126"
5 day design rainfall
-
165 "
10 day design rainfall
=
251 "
15 day design rainfall
=
321 *
J
The design flood was  estimated by  physical approach using unit hydrograph, storm analys-.s and design flood hydrograph convolution for 21 dam sites. F ortho others, flood frequency analysis based statistical return period floods were estimated
For Itie Dedessa OD2 reservoir, the PMF was  computed as  5300 mVsec  with a base period of 99 hours. For the Dabana storage reservoir, the PMF estimate was  al 4860 m /sec  with a base oenod of 91 hours. For the Angar-2 reservoir with a catchment area of 1 780 square Kilometers 1he PMF and the duration of the nydrograph were 3970 m3/sec  and 80 hours  respectively. Fur the Angar-6 reservoir, the above respective figures were 6180 m’/sec and 111 hours.
For the Dedessa storage dam, toe 5. 10, 25, 50.100, year floods were estimated to be 1700
1900,   2100,   2300   and   2400   mJfsec   respectively.   These   formed   a   good   data   base   for   review   In the present study.
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvi Ltd
7Arj o Dedessa Irrigation Project
Meteorological and Hydrological Aspects
The seclion IV, as indicated in the beginning deals with lhe water use studies, The 1960 waler use states was reviewed along with such water uses in villages. Then, the run off estimates have been adopted considering the envisaged irrigation and power developments m respective simulation study. Due to Dedessa dam USER study, estimated a reduction of about 139 M m in Dedessa flows to the Abbay,,
May 21X17
On  the  whole,  this  USSR  study  is  a  useful  one  for  the  basin  as  a  whole,  though  with  paucity  of data, because ot its systematic treatment of hydrological and simulation aspects.
2.3    Country wide Master Plan studies - EVDSA/WAPCOS (1988-90)
These studies  were carried out during 1988-90 for country  wide water and iand resources development, covering all nver basins. These were primarily  desk  sludies  for identifying potential irrigation and hydropower sites  based on country  wide data collection and analysis, coupled with detailed map sludies. The study  was  addressing the Abbay  basin also, along with other basins. The USSR studies  were reviewed in detail for lhe Abbay  basin, and subsequently  this  study  came out with modifications  in lhe USBR sites  in some cases  and proposed many  other sites  as  well. Though desk  study, the data base avatlable io Ihis  study, on hydrological and hydro meteorological aspects  were fairly  adequate, because of the earlier pioneering works by USBR in establishing a goad ne1 work of such data observation stations.
In Ihis  study, the rainfall as  well as  run off data for lhe vicinity  of lhe identified projects  were collected and analyzed even though elaborate consistency  checks  were not under taken, The uala gaps  lilting and extrapolation of data have been done using statistical regression analysis using mostly  bi-vahate linear as  well nan linear correlations  In certain major dams. synthetic data generation by single site multi season stochastic models as well nas peen under taken
With respect to floods, the Hood frequency  analysis  of lhe annual maximum flood series  has been carried out lor the obsenration stations, in the vicinity  of all identified potential dam sites The EVI distribution with the method of maximum likelihood fitting has  been followed in the above flood frequency  analysis. On deciding lhe appropriate design criteria for the inflow design flood for each identified dam site, lhe flood peaks  ol 1he nearest gauging station have been transferred to 1he dam site by  empirical formula. For deriving 1he shape of the complete design inflow hydrograph at tee dam site, the procedure as indicated below has been followed
--------------------------------------------------------------------------------------------------- -------------------------  8 Water Works Design & Supervision Enterprise
tn Assockats with I uwrtuiiUnental Cucsultants mid Technocrats Pvt I idArjO-Dedessa lrrijfatlon Project Meteorological and Hydrological Aspects
Hay aw
For the nearest gauging staliwi, the observed maximum flood hydrograph were isolaLed For these a relationship between time and Q/OP ratio were established (I against CyQP) where, T represents  time. Q represents  the discharge at'C and QP is  the peak; discharge. Using this pattern of rel all mi ship the dam site hydrograph has  been developed using the peak  as estimated by flood frequency analysis.
Simulation studies  have been systematically  earned out to judge the success  of a scheme at criteria based reliability  levels. Climatic  dala other than rainfall have also been documented, though wilhout del ailed processing or elaborations. The sediment rates  as  quoted by  various previous  studies  of different basins  have been adopted and used in simulation studies, considering life expectancy of projects as &0 years.
The data base on the geometry  of identified studies  could be considered to he only approximate, as  were based on purely  topographic  maps. The hydrological and hydro meteorological daia were also nol pul into rigorous  analysis, which is  called for design of identified projects  However, this  study  along wiih USSR study  back  up gave a very  good dala base.' inventory  of all possible exploitable dam sites  in Abbay  basin. This  EVDSAMAPCOS study has earned out such exercise in alt the other river basins at the country as well,
The dams  identified in the Dedessa sub basin by  this  study  is  the Ago Dedessa irrigation project This  proposal envisaged a dam, a chuie spillway, an irrigation outlet with n take structure and a canal laking oft on the right side. The project envisaged irrigation over 139,04)0 hectares  with 160% irrigation intensity. The inflow in a 75% reliable year was  estimated io be 776.80 Mm- The 10,000 year flood with a peak  of 690 cubic  meters  per second was  getting moderated to an out flow hydrograph of peak  of 642 cubic  meters  per second. The dead storage was fixed as 93 Mm , on the basis of annual rate of around 1.9 Mm .
2.4    Study by BCEOM - in association with ISL and BRG 1999
The   study   entitled   ’Abbay   River   Basin   integrated   development   Master   Plan   Project*   has   been earned oui wiin the following water resources onented objectives.
3
J
9
Water Works Design & Supervision Enterprise
tn Associate with tnierconUnenut Consu Junta and Technscuis Pvi. Ltd.Arjo D«J«53 Intaaltun Project
Mfitfiftrological and ifydrd logical Aspects_ _ _ _ _ _ _ _ _
- PreDarafton of lhe river basin development master plan that will guide lhe development
May
of the resources of 1he basin potentially with respect to occurrence, distribution. quality 
and quantity of water resources for the coming 30 to 50 years 
« To prepare water allocation and utilization plans under alternative development
scenarios and to gen&rale dala, information and knowledge that will coninbule io the
Mure waler allocation negotiations with downstream countries.
The   hydrological   and   hydro   meteorotogical   studies   are   more   relevant   for   review   in   ihis   section These aspects have been covered in Seclion II, volume III of the Master Plan Study report.
The basic  climatic  lean ires  and the climatological data of the Abhay  nver basm are discussed first. The rainiall data procured hy  the study  was  for 173 slations; the data length varied from 3 tD 40 years, with associated monthly  gaps. The data for other climatic  factors  were available for 108 stations. The field verification of these stations  and equipments  has  also been under taken The dala 15 said to have been subjected tn analysis  and some errors  connected with observations  or processing were tdentified. The study  has  perhaps  not attempted In improve lhe quality  of such data on ihe plea that it was  outside the consultant's  capacity  or responsibility. As  such, the dala base after screening and omitting such erroneous  data is staled to be good.
With   respect   Io   Hydrology   in   the   part   2ol   the   above   volume   III   the   following   aspects   nave been covered systematically.
•     Basic Hydrographic Fealures
•     The Hydrornetnc net 'work
- Review of previous studies
•     Data collection and Analysts
•     Sectoral meinodalugy
tn the bas<c hydrographic aspects, a ywd work of preparing a map of the basin has been presented dividing the basin n to reasonably homogeneous areas, named Basin Units representing each ol ihe catchment of one tributary or of several minor ones., with simitar behaviors. With respect to lhe hydrometric net work it has oeen considered 10 be adequate as
Water Wortta Design & Superrlslyn Enterprise
in Associate with htercontlnenta] consultants and Technocrats Pvt Ltd.Arjtt Dedew* Irrifallon Project
MeteorolD
gicaI
and
Hydro
logical Aspects
a<107
_ _ _ _ __ _ _ _
__
_________
___
per    WMO
nor
ms,
Igking
in
to
considerat
ion
H6
ef
fective
stations.    The
list
of
station,
their
locations,
and
drai
nage
areas
controlled
have
b
een
well
documented
in
T
ables,
appen
dices 
and maps. The master plan has  found that the spabal distribution of the stations  s  not even or eciUdlabte. The pads  of Beshilo. Wdeka and Jemma were not adequately  represented Based on visit to air accessible observation stations, the masler plan couW identify.
* in many  cases, those stations  which have been abandoned are not worth reconstruction either they  had not been inslatled at optimal locations  or ihe catchment area controlled by them was loo small
*     The numbers of automatic water level recorders stilt operational at Ihe study lime were
low.   inough   most   of   the   stations   had   been   equipped   with   such   recorders   at   the   time   of iheir installations.
*     In many gauges stations the cables of bank operated cable way were missing
*       On  1he  other  hand  most  staff  gauges  were  in  good  condition  and   water  level  data  was considered to be guile reasonable.
There    upon    recommencSaLions    have    been    spelt    out    to    be    executed    as    and    when    cudgel equipment and man power are made available.
In the first observation, n is felt that what is meant as optimum could have been indicated As 
tar as hydrological net works are concerned, optimality varies depending upon the purpose of
Ihe net work. II could be a general purpose net work or could be a specific purpose net work 
It is not clear that what is the master plan ascribed opumahty. Ferlner, since because a
gauging station controls a small catchment, it seems they have been ignored by the master
plan study.
Measurement of discharges  have a multipurpose oriented utilities  like, ascertaining the sensitive or non sensitive areas, flood rate estimation or for a specific  purpose including community  based water harvesting schemes  etc. Hence, the approach of ignoring stations with small catchments does not seem to be based on analysis of vivid concepts
Subsequently,    the    Master    Plan    has    made    a    very    brief    review    of    hydrological    a
i     of
spec s 
previous studies Again ii .$ felt mat a Master Plan of the magnitude could have reviewed in a
Water Works Design & Supervision Enterprise In Associate with [ulanooliuttai Consultants and Technocrats Pit LtdArjo-Dedessa Irrigation Project
Mntcorological and H ydrologica I As pe cte
__________May w
more elaborate manner The review could have brought out each aspect of hydrological and hydro meteorological and simulation studies  attempted by  lhe earlier studies. Only, such detailed review would hare formed the datum to appreciate the further studies taken up by the
Master Plan.
Next the data collection and analysis  part is  discussed in the report The data seis  processed were mean daily  levels, d'SGharge measurements  and suspended sediment concentration date With respect to data processing, the major study  carried out seems  to be review and reestablishing rating curves  The details  on very  many  hydrological analysis, which should have been carried out before final use of he data in basin simulation are nol rinding a place jp the hydrology volume (nol explicitly described).
With   respect   to   rating   curve   analysis   detailed   exploration   of   the   discharge   data   or   121   slahons, have been made and equation of the form
□ = a (H-Ha)6
have been fitted, which is  common practice in Hydrology. It 13 a good thing that Master Plan has  used both analytical and graphical melhods  in parallel in establishing such rating curves. For all ihe stations  analyzed, a total of 253 equations  have been arrived with good correlation coefficients of 0.90 and above in 90% of Lhe pans of data.
The   discharges   nave   been   estimated   using   ihefie   equations.   Then   Master   Plan   study   stales that on checking homogeneity the monthly values wee extracted.
II   would   hare   been   better   to   appreciate   it   the   nomenclature   o(   Homogeneity   with   ,usti(,cations had been indicated m the report.
It   is   also   slated   further   ,n   me   Mast®   Plan   that   lhe   discharges   were   compared   w.th   earner studies and lhe results, die not have major variations,
Agam   II   is   fell   that   belter   appracation   could   nave   been   made.   If   the   concept   of   mojo,   ,all
a„ „
o
had been spelt out.
12
Water Works Design & Supervision Enterprise ~ In Associate wilii IntermUntnUI Consultants uid TwhnocraU Pvt. LtdAr] [iUedessa Irritation Project Meteorological and Hydrological Aspects
Hay 200?
Subsequently, water Balance model of lhe basin has  been formulated taking only representative $ lalions  so a s  t o m ake t he m odel c  omprehen$ive without o ver loading. T he selection criteria used tor identification and inclusion of hydrometric  stations  in the model seem to be appropriate. The rnpul hydrological discharges  were established on daily  time resolution level for lhe period of 33 years  (1960-1992). The gap titling techniques  seem to have in built subjective inferences.
Wi1h respect to assessment of water availability, a mao has  been prepared on a scale of t:1000, 000 to estimate the global waler availability  to be applied to all potential water resources development sites in Abbay basin.
This  map could be of use just for a preliminary  estimate or annual flows  at pre-feasibilily  level The water availability  has  been further estimated by  detailed water balance model. In this, in lhe first run. the present scenario has  been in built and for 18 net work  sialions, and waler availability has been estimated. The salient findings of this run are as below which are in order
J
■ The annual average volume flowing across the border from Abbay River is 50.30 &m .
-   About   83%   of   the   average   annual   volume   al   border   is   flowmg   m   4   months   (July   - October),   while   the   4   months   from   February   to   May   account   for   less   than   4%   of   the mean annual flow.
•   The   average   annual   flow   at   the   out   let   from   Tana   represents   about   7%   of   the   above annual flows at border.
Floods:    The    highest    flood    hydrographs    recorded    at    each    of    the    water    balance    nel    work staboos have been put to analyses to establish the relation between lime and Ck'Qm ratios
Then flood frequency  analysis  of the annual maximum discharges  has  been earned out by Gumbei's  EV1 d.siributiori to estimate the return period flood peaks  (It is  not clear whether the annual maximum observed peaks  were converted m to instantaneous  peaks). Further another relationship connecting catchment size to hood peak  has  been derived for 2 groups  of catchment sizes, one for catchment groups  having catchment area less  than 10,t>00 km? and another one for catchment s.zes  more than 10.000 km1 It has  been concluded that the formulae derived so can be used for pro-feasibility  level studies  only. Master Plan has 
Water Works Design & Supervision Enterprise
In Associate with [ntert&ntiaenial Consultants and Technocrats p i. Ltd
1
vArJoLedBSsa lntEitlM Project Meteorological and Hydrological Aspects
May 3007
attempted io link  steps  of different catchments  with flood discharge rales, which a'so did not exhibit any  correlation II has  been opined in the Master Plan lhal rainfall runoff correlations were not applicable.
No data or study results on flood side will be of any use lo the present project specific study 
The flood studies adopted by lhe Master Plan might be useful for preliminary estimates level
Only
Sediment    transportation:    For    96    stations,    sediment    rating    curves    have    been    analyzed    w>ih available data, on lhe basis of following type dF relationships
QL = a (H-Ha)n linking water level with flow
QS = aQL* finking sediment
discharge OS with liquid discharge QL w>lh u and |i as parameters.
The total sedimentation transported is  accounted as  rhe sum of suspended sediment load and bed load. For bed load estimation, 3 different options  are indicated, with a sori of recommendation on Meyer Peter equation. However, al the end of sediment deliberations, Master Plan study  has  fell 1hat a global eshmale pt bed load transport for lhe whole Abb ay basin or for any  of the large sub basins  has  no meaning; Hence tee study  has  further staled that al Master Plan level, considering the amount of bed load transport definitely  being small compared io suspended load and considenng the size of lhe Abbay  basin, it was  not necessary lo proceed with data collection for evaluation cl bed load estimation
The    above    statement    of    Master    Plan    is    no!    able    to    be    appreciated    without    elucidation Subsequently, the Master Plan has prepared maps related to erosion
The other studies  connected with waler balance and water resources  modeling seem lo be m order. Software WATBAL has  been used m the modeling for various  scenarios  of development, after initial calibration for me present scenario.
These have been done for
14
Water Works Design & Supervision Enterprise
la Associate with Intenaqtinental Consultants and Technocrats Pvt. Ltd.Arjo-Dedessa tndfaLlnn PmjBcr
Meteorological and Hydrological A
spects
aw?
* present situation
■ Future situation encom
passing
o       Scenario
1
(identified projects 1J
o     Scenario
N’2
(identified projects 2 including Tana Belesf
o     Scenario
N’3
(identified projects in mam stream)
o Scenario N  4
c
(Full development}
The  resulLs  could  be  utilized  for  com  pan  ng  the  results  of  specific  sub  basin  oriented  modeling studies, tike the one under laken m the present study
2.5 Study by Ministry of Water resources for Lower Dedessa (2001)
This is a reconnaissance level study for the Lower Dedessa Medium hydro power project. This gives a vivid analysis ol rhe data and the Hydrological features ol the Dedessa sub basm The dam site controlling a calchment area ot 18.2UO square Kilo meters, has the following water resources potential according co this study.
Mean annual flow
=7290 Mm3
Annual Flow in 75% exceedance year-63(}D Mm4 Annual Flow in 80% exceedance ysar=6100 Mm1 Annual Flow in 90% exceedance year=5230 Mm3 Annual Flow in 95% exceedance year«460Q Mm'
The tallowing are 1he frequency floods estimates
10 Year return period flood
=  1977
cubic 
meter
per
second
20 Year relum period flood
-2210
cubic 
meter
par
second
100 Year remm period flood
=2735
cubic 
meter
per
second
i DOO Year raturn period flood
10000 Year return period Hood
=  3480  cutnc  rneler  per  second =4224 cubic meier per second
A sediment rate of 500lons  per square kilo meter per year has  been adopled. This  gives annual sediment load of 9.1 million tons  per year The 50 year sediment volume of 329 Mm ' nad been accounted lor reservoir sizing.
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt Ltd
15Arjo DuJtssi Irrigation Project
Meteorological and Hydrological Aspects
May 2007
The sludy  had analyzed lhe energy  g eneration wi1h a net head pf t33 meters  and wilh the assumption of r&gulali&n of 70% of Ihe mean annual Bow The energy  that could be generated so, was  eshmated to be 1SBO GWh per year, with an installed capacity  of 299 MW. on adopting a plant factor of 0.6. This  is  very  relevant to Dedessa sub hasin and the preseni study. The useful data were laken n io account.
2,6 Utility of Earlier Studies
AH the earlier studies  reviewed have some useful data base. All ihe useful information (data of ail ihe above studies  have been reviewed and utilized as  per need and appropriateness) However, rhe present study  is  specific  sub basin (Dedessa) development study, and as  such, systematic  hydrological and modeling studies  are warranted with modern lools  ot analysis This sectoral repon narrates these specific studies
Water Works Design & Supervision Enterprise
In Associate with lnicrefrndnBnCai CintS11lt,nls aniJ Technocrats Pvt ltd.
16ArjoHedessa Irrigation Project Meteorological and Hydrological Aspects
3. DATA BASE
May 2007
For the study  towards  the development nt the Dedessa sub basin, the data on climate, river flows  and sedimentation become relevant wrih reaped to Hydrological Modeling and Water Resources Planning.
3.1   Climatological Data
The climatological data like sunshme duration, relative humidity, wind speeds  temperature in the resofuiwn levels  of monthly  means  ot daily  means, monthly  mean of daily  maximum and monthly  mean of daily  minimum, become very  important parameters  with resped to the proposed command area development. These. in association with command area ramtatl term the basic  inputs  ter the estimation of 1he crop water requirement exercise A vivid analysis follows on ihese .mportarit parameters in the section 4 ol this report.
3.2.  Rain fall
The rainfall requires  critical analysis  ter the dam site and the upstream for appreciating and developing floods; either as  a full hydrograph or in the form of flood peak  rate, expected at different Exceedance probability  levels  (return periods). The rainfall data needs  te be analyzed wi ns  various  forms, like maximum of observed 1 day/2 day  or 3 to 15 days  values  or as  a time series  of observed annual maximum i pay  rainfall or as  monthly  ! fortnightly  totals  as  per analysis  at different sieges  The analysis  has  lo under lake the gambit of short duration rainfall intensities  as  well, in connection with design of drainages  and return period rainfall peaks  for the design of flood control works, in the downstream of the dam in and tn the vicinity  of the proposed command area.
3.3.  River Discharge
Likewise, the river flows  data time series, preferably  on monthly  or fortnightly  lime resolution levels, forms  the fore runner for establishing water resources  availability, lor performing simulation whether as  basic  historical lime series  or indirectly  through synthetically  generated lime Series  (mostly  gene/atec  by  a stocnastic  generation scheme); where as. the same flow date has  to be analyzed in a different form as  discharge (flow rales  instead of flow volumes) with tesped to flood analysis.
Water Works Design & Supervision Enterprise
In Associate with Intercontinenul Consultants and Technocrats Pyl Ltd.
I”ilrjo Dedassa Irrigation Project
Meteorological and Hydrological Aspects
May 2007
3.4.
Sedment D
ata
The
sediment   data
is   obvi
ously   req
uired
to
plan  the
siz
e   of
the
st
orages,  for
apportio
ning  lhe
active
and   inactive
storage
spaces 
and
for
determin
ing
the
revis
ed
g   eometry
ol   the
storage
after
certain   design
life,
(revised
elevat
ion
-   area
-
capa
city 
re
lationship);
as   this 
revised
relation is  used in Ute simulation modeling. The waler quality  is  another aspect, which needs  to be a ddressed i n H ydralagica I s tudy along with I ow I low a nalysis f or m and atory d ownstream releases, closely associated with the concerns of environmental and ecological aspects,
With such appreciation of the frame work  of hydrological studies  and modeling, me data base was  established, as  elaborately  discussed in the Interim report. However in |he following sections  and in 1he annexure enclosed with this  report, ihe data base on climatology, hydrology including sedimentation, floods  are indicated. All the data available in a regional sense, up io date (2004) were brought to analysis desk and appropriately included.
Water Works Design & Supervision Enterprise
fn Associate with Jnterocnthiental Consultants and Technocrats Pvt Ltd.May 2007
4.
ESTIMATION OF REFERENCE EVAPOTRANSPIRATION
meters).
been also reoorded at Oembi and Agara stations.
Climatic data for the project area such as temperalure, relative humidity, sunshine hours, wind
speed and rainfall have Peen collected and reviewed Consistency tests, data rectification and
other adjustments have been performed as necessary dale gaps have been filled using
interpolation and corrections methods as appropriate.
Ihe FAO Penman-Monteith method is  maintained as  lhe sole standard melhod for the computation of crop reference evapotranspiration <ETO) from meteorological data. This  section de&cnbes  haw the mcmth'iy  ETS is  clelermmea from temperature humidity, wind-speed and sunshine hours  data collected al Bahir Car station The ET0 calculation has  been carried oui by 
means b! a computer
The FAO Penman-Monteilh equation determines  the evapotranspiration from the hypclhelical grass  reference surtacc  and provides  a standard lo which evapotranspiration for various  crops growing in the Anq-Oedessa project command area can oe related
The methods  for catenating evapotranspiration from meteorological data require various climatological and physical parameters  Some ol the data are measured directly  in Bahir Dar
meteorological station. Other parameters  are related to commonly  measured data and can be derived with the help Of a dlrtct ar empirical relationship This  section discusses  the source and computation ol all data requ^erj for lhe flatted of me reference evapotranspiration by means erf lhe FAO Penman-Monttsuh method
Water Works Design & Supervision Enterprise
iV
!□ Asswlate with [atereonUtiental ConsiilLaocs iad Technocrats Pvt led.AtJd Dedessa Irtl^alian Project Meteorological and Hydrological Aspects
May 20(17       ■*
The meteorological factors  determining evapotranspiration are weather para meters  which provide energy  for vaporization and remove water vapour from the evaporalihg surface the principal wealher parameters  to consider are presented below The data obtained from lhe Bedoie, Dedesaa and Jimma stations  are assumed directly  applicable lo the Arjg Dedessa Irrigation Project with application of appropriate information Ransfer mechanisms
4,2    Meteorological Data
4.2.1     Meteorological Observation Stations
Five meteorological observation stations  are located in and around lhe Arja-Dedessa Irrigation Project area. These meteorological data are obtained from the National Meteorological Services  Agency  (NMSAJ, Out of these Jimma is  Class  1 slation that include observations  of rainfall, temperature, relative humidity, sunshine duration, wind speed and evaporation. Bedele and Pedessa are also Class  1 stations  but do not include sunshine duration In addition. Aggro and Oemtu are Class  3 stations  mat include observations  of rainfall and temperature. The longest record 1 hal covers  50 years  or meteorological data is  available al Jimma station tliai includes rainfall and temperature data since 1952.
Agaro and Oembi stations  are located within lhe cachment area of the proposed dam site Jimma station is  located at approximately  at 10 km from the divide of Dedessa catchment Bedelle slalion is  located close to lhe proposed irrigation command area of the project Dedessa slalion is  locaied further downstream of the command area. The details  like local ion altitude, year of establishment along with their class are available in Tapis 4 l.
Meteorological data available al the five observation stations  located in and around the project area have been collected. The lypes  of meteorological data available al these siaiions  along with the lengih ql data are given ir Table 4.2.
Jimma Airport meteorological station is  taken to be ihe most reliable Class  I station from which meteorological information relevant to the project area has  been derived. The data from Jimma stainw has  been used tor both the caichmem study  and estimation ol meteorological variables at the irrigation command area. The necessary  adjustment for lhe differences  in elevation has been made in transferring the data. Meteorological information from Agam and Dembi stations
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and TechnMtats Pvt, Lid
_________20ArfD Uede^a Irrifatlnn Project Meteorological and Hydrological Aspects
Ma >' -Ql>;;
which are located within lhe dam site calchment haw been used for catchment study, m addition Io Jimma station. Similarly. meteorological data al Bedeila and Dedessa have been used in addition to the data obtained from Jimma station for estimating rainfall and avapolranspiratian at the proposed irrigation command.
In summary. cJimarologicaSI data obtained from Bedeie. Dedessa and Jlmma stations  were found 10 be the most reliable and relevant for use in the analysis  of rainfall for lhe Arjo Dedessa irrigation project. Bedele is  geographically  the closest slalion 10 the command area Oedessa siation and lhe command area are located al the same elevation (i.e. bolh 1330 m asl}. Jimma slation (which is  Class  I) has  the Longest record of all 1he stations  withm lhe neighbourhood of the command area so as  to be index  station rn extrapolating and interpolating missing and short term of dim giro daia relevant to the Ago Dedessa catchment and command area
4.2.2     Air temperature
In Lhe project farm area, the mean monthly  lemperalure variations  throughout Lhe year are minor, being 20 O’C in December to 25 4’C in March. The mean mcwiLhly  temperatures  of lhe command area is  given in Table 4 3 and graphically  illustrated by  Figure 4 1. Temperature da1a have been used in estimating evapotranspiration rates from reference crops,
Agromeleorolcigy  is  concerned wild lhe air temperature near the revel of the crop canopy. In traditional and modern automatic  weather stations  the air ternperalure is  measured insrde shelters  (Stevenson screens  or ventilated radiation shields) placed in line wirh World Meteorological Organization (WMO) standards  al 2 m above the ground Minimum and max'mum ihermometers  record 1he minimum and maximum a<r temperature over a 24 hour penod.
Duo to the non-linearity  of humidity  data required in the FAO Pen man-Monteith equation, the vapour pressure for a certain penod should be computed as  the mean between the vapour pressure al lhe daily  maximum and minimum air temperatures  of that period. The daily maximum air temperature (T™> and daily  minimum air tempera lure (Tmin) are. respectively, lhe maximum and minimum air tempera lure observed during the 24-hour period. The mean daily air lemperature :T„,pW)is only employed in the FAO Penman-Monteilh equation to calculate ms
21
Waterworks Design & Supervision Enterprise
In Associate witii Inronjonilntiui Consultants and Technocrats Pvt. Ltd.Arji> Dedess* IrriB adon Project
Meteorological and By Jr d Logic al Aspects
,     22?’ 'qoT —
fl
s-lop-e    of    the    saturation    vapour    pressure    curves    (2),    estimating    saturation    vapour    pressure (e’(T) and <jT/ (Stefan Boltzmann law).
The solar radiation absorbed by  the atmosphere and the neat emitted by  the earth increase the air temperature The sensible heat of the surrounding air transfers  energy  to the crop and exerts  as  such a controlling influence on the rate of evapotranspiration in sunny, warm wealher the loss of water by evapotranspiration is greater than in cloudy and cool weather
4.2.3     Air humidity
Mean humidity  values  vary  between 56 63 percent in March to 88 63 percent m September The mean monthly  humidity  of ihe command area is  given in Table 4 3 and graphically illustrated by  Figure 4.2. Data of humidity  have been used in estimating evapotranspiration rates from reference crops.
The relative humidity (RH) expresses the degree erf saturation of 1he air as a ratio of the actual
(e*) to the saturation (e (T)) vapour pressure at the same temperature (T). Relative humidity is 
the ratio between ihe amount of waler the ambienl air actually holds and the amount it could
hotel at the same temperature. It is dimensionless and is commonty given as a percentage
Although the actual vapour pressure might be relatively constant throughout me day, the
relative humidity fluctuates between a maximum near sunrise and a minimum around early 
aflemoon. The variation of the relative humidity is ihe result of Ihe fact thai ihe saturation
vapour pressure is determined by the air temperature As ihe temperature changes during the
day, the relative humidity also changes substantially.
Wh<le the energy  supply  from ihe sun and surrounding air is  the main driving force for the vaporization o< waler, the difference between the water vapour pressure at Ihe evapotranspinng surface and ihe surrounding air is  the determining factor for ihe vapour removal. Well-watered fifrids  in hot dry  arid areas  consume large amounts  of waler due to the abundance of energy  and the desiccating power ol the aimosphere. In humid tropical regions, notwithstanding the high energy  input, the high humidity  of the air will reduce the evapotranspiration demand. In such an environfheni, the air is  already  close to saturation so that less  additional water can be stored anp hence the evapotransprraiion rale is  lower than m arid regions
Water Works Design it Supervision Enterprise
tn Associate with intErconiinenlal Consultants and Technocrats Pvt Ltd.
22Arjo Dedessa Irrlgattgn Project
Meteorological and Hydrological Asgects^^^^
4,2 4 Wind speed
May 2QP7
Mean wind speed values  vary  between 0.40 meter per second in November to 1 00 meler per second in April The mean monthly  wind speeds  of the command area are given in Table 4 3 and graphically  illustrated by  Figure 4 3 Average wind speed recorded al Jimma station in meters  per second (m/s) 15 taken as  wmd speed information relevant for the Arjo-D&dessa command area as  there 15 no reliable dala at other climatic  slalions  nearby  Time series  aspect of rhe wind data is  not considered as  if exhibits  unacceptable erratic  variation within the record penod. Using the mean values  against the time series  data has  been lested for ESatiir Dar station and resulted in equal result for monthly  and annual evapotranspriahon estimates However, ihe mean wind values  produced an estimated coefficient of variation (CV) of 22% instead of 2 4% eslimaled from ihe time Series-
Wind is  characterized by  its  direction and velocity. Wind direction refers  Id the direction From which the wind is  blowing. For the computation of evapotranspiration, wind speed is  ihe relevant vanable Wind speed is  measured wdh anemometers. The anemometers  commonly used in weather stations  are composed of cuds or propellers  which are turned by  the force of the wind. By  counting the number of revolutions  oven a given time period, the average wind speed ever the measuring period is computed
The process  of vapour removal depends  to a large extent on wind and air turbulence which transfers  large quantities  of air over the evaporating surface. When vaporizing water, the air above Ihe evaporating surface becomes  gradually  saturated with water vapour If ihis  air is  not continuously  replaced with drier air. Ihe driving force for water vapour removal and ihe evapotranspiration rale decreases.
4.2.5 Solar radiation
Mean sunshine duration is  0.3 hours  m December and i5 reduced to 3 7 hours  during July  The mean monlhly  sunshine durations  ol Lhe command area are given in Table 4.3 and graphically illustraled by  Figure 4 4 Data of sunshine hours  have been used in estimating evapotranspiration ra?es from reference crops
The    relative    sunshine    duration    (n/N)   ■£    another   ratio    lhal    expresses    the    ctoudmess    of    the atmosphere. Il is the ratio of Ihe actual duration of sunshine, n, to the maximum possibte
2.1
Water Works Design & Supervision Enterprise
In Associate with tnlerruntincntat Consultants and Technocrats Pvt, LtdArjo Dtflessa irrigation hojnct
Meteorologlcal and Hydrological Aspects
May 21X17
duration Qf sunshine or daylight hours  N In lhe absence of any  clouds, the actual duration of sunshine is  equal to the daylight hours  (n = N) and the ratio is  one, while on cloudy  days  n and consequently  the ratio may  be zero, in the absence of a direct measurement of R,, the relative sunshine duration, n?N, is  often used to derive solar radiation from extraterrestrial radiation As with extraterrestrial radiaiion, the day  -ength N depends  on the position of the sun and is  hence a function of latitude and date.
The evapotranspiration process  is  determined by  the amount of energy  available to vaporize water Solar radiation is  the largest energy  source and is  able to change large quantities  of liquid waler into water vapour. The potential amount of radiation that can reach lhe evaporating surface is  determined by  its  IccaliDn and time of the year Due to differences  in lhe position of lhe sun, the potential radiation differs  at various  latitudes  and in different seasons. The actual solar radiation reaching the evaporaling surface depends  on the turbidity  of lhe atmosphere and the presence of clouds  which reflect and absorb major parts  of the radiation. When assessing lhe effect of solar radiation on evapotranspiration, one should also bear in mind ihat not all available energy  is  used to vaporize water Part of the solar energy  is  used to heat up lhe atmosphere and the soil profile.
4.3    Penman-Monteith Equation
From    1he    original    Penman-Monteith    equation    and    the    equations    of    the    aerodynamic    and canopy resislance, the FAO Penman-IWontoifh equation can be expressed as follows;
ETo = Q..4O^P.£n_^Y]9OyjT 27JlLu,L -^j
+
tr
fl
1
A + y(1* 034vj
where
ET  = reference evapotranspiration (mm day' ]. Ft, = net radiaiion at the crop surface (MJ m'a day ’]. G = soil heat flux density (Mj m  day '],
T = air temoerature at 2 m height [*C],
u; = wind speed at 2 m height [ms ].
e» = saturation vapour pressure [kPa], e, = actual vapour pressure [kPa| = e, RH ^ ,
2
1
ir  n
Watet Aiirks beslgti & Supervision Enterprise
tn Aspite with IntEwntinental Consultants ad<l Technocrats Pvl Ltd.
24Arjo Dcdessa Irrigation FToJect
Meteorological and Hydrological Aspects
ej - e  = saturation vapour pressure deficit [kPa],
fl
A - stope vapour pressure curve [kPa 'C 1], y = psychrometric constant [kPa ’C ].
RH = relative humidity divided by 100 and
Rn
- Rfl* • R,:l
(22}
Rn
= 0.77 R,
(23)
R*
= (0-25 + 0.50 n/N) R,
(2.4)
R.-i
3
= ctTk* (0.34 -0 14 e? ) (0.135 Rs/Ro - 0.35)
(2.5)
R»
= [0.75 +2 (Al titudej/l 00000] R,
(2.6)
The calculation procedure consists of I he following steps'
1.      Derivation    of    some    climatic    parameters    from    the    d    a>ly    maximum    (and    minimum (Tnwd air temperature, alidade (a) and moan w.nrt speed (uj).
2.      Calculation   of   the   vapour   pressure   deficit   (et     -   e ).   The   saturation   vapour   pressure   (ej
a
is  derived from and TMl while 1he actual vapour pressure (e4) can ba derived from the dewpoml temperature (T^). from maximum (RHL«J  and minimum (RHmiq) relalive humidity, from the maximum (RH™), ar from mean relalive humidity
3.     Determi   nanon   of   the   net   radiation   («,)   as   ihe   difference   between   lhe   nei   shortwave radiation  (Rr,.j  and  1tie  net  longwave  radiation  (Rm).  |n  the  calculation  sheet,  the  effect  of soil   heat   flux   (G)   i$   ignored   tor   daily   calculations   as   lhe   magnitude   of   the   flux   in   this case   is   relatively   small   The   net   radiaLipn.   expressed   in   MJ   m’?     day'   (G     converted   to mm/day   (equivalent   evaporation)   in   the   FAO   Penman-Mmiieith   eg   nation   by   using   0   408 as the conversion factor within the equation.
4.           ET» is obtained by combining ihe results of the previous steps
The   following   values   were   selected   from   FAO   1990   {Crop   Evapotranspiration   -   Guidelines   for computing crop waler requirements - FAO IrngaLipn and drainage paper 56)
o Psychometric constant (y) for different allitutfes (z),
------------------------------------ — ------------ -------- —— ------------ ---- ---- - Water Works Design & Supervision Enterprise
_________________ 2 5
to Associate with Interedudnetital Consultants and Technocrats Pvt LtdArju D&dessa Irrigation Project
Meteorological and Hydrological Aspects
o Slope ol vapour pressure curve {a) lor different temperatures (T), o Saturation vapour pressure [(e*(T)] for different temperatures (T), & Daily extraterrestrial radiation (Rj for different latitudes,
a Mean maximum possible dayiicjlil hours (N) for different latitudes, o <rT/ (Stefan-Boltzmann law) at different temperatures (T)
May 2007
The estimated mean daily  and monthly  reference croo evapotranspiration magnitudes  (in mm) from 1 991 10 2004, based on Penman-Montenh Equalion, are presented by  Tables  4 3 and 4 4. respectively and graphically illustrated by Figure 4.5
The results of the meteorological analysis including the rainfall are provided in the annexture A. Tabla 4,1; Table Details o' Me’coioiogical Observation Stations located m ano around She preset am a
S.Nq
Latitude
Station Name            North
Deg       Miift,
1        Agara
2 Bedelle
3 Oedessa
4       Dembi
5       Jimma
07         51
08         27
09          33 08          04
LQZ          40
Longitude
East
090     Mirt.
36          36 36          20
36          06
36          37
36          50
I
Altitude            Period
1700             1980-2004
2005             1967-2004
1300             1971-2004
1950             1954.2004
1725             1952-2004
Tablv 4 2 Types Chmaiic Data avaiabla at the varous KleieorcHogicai Observation Stations
No
Station name         Vrs-       RF       Tm         RH                   so
1 lir 1 day Rda
1 Didessa
2 Bedele
3       Dembi
4       Aqaro
5 Jimma
30          X           X          X                   X
28          X           X          X                   X
20          X           X
21          X          X
50          X          X          x          X       X                        XXX
Class
1
1
3 3
1
—-J
RF        monthly rainfall
Tm       average temperature RH       relative humidity WS       wmo speed
SO        sunshine duration
1 hi-
maximum 1-hpur rainfall
1 day   maximum 1-day rainfall Rday   number of rain days
Hater Works Ueslffn & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Prt. Lid.Arjo Dodessa [rrlgadnn Project
Meteorological and Hydrological Aspects
Tabte 4.3: SummHry a/ Meteorological Ghon?cle*J*!»C$ at Pro|ec1 Area
May 2DQ7
Jan       Feb    March    ApriF     May     June      July       Aug      Sep!             Oct Nov Dec
MwjfMy Afeafl Temporatuw mcC
4waga 21.9    23.15     25 4    25-05    24 03    22.09    21.32    21.19    21 83    22.35 22.144 19.99 CV D.04S   0.044   0.036    0 065    0 071    0 029    0.028    0.031    0.027    0.038 0.0544 0,056
Skew 0.071   -0 58    0 067   -3.628    -323     0.117    0.275    0.007      0 93    0.353 -0 118 -0.02 Min 19.5    20 44   23.63    1626     15.89   20.98    19.99    19 38    21.06    20.19 19.081 16.92 Max 24 6     24 9    27.37    27.72    28.19    2341     22.72    22 34      23.2    24 25 25.051 22.68
iRe/ltiva Humidity {%)
Average 64.77   58.97    56 63    67.97    75.72   81.07    87.46    88.52    88.63    84.55 79,366 72.44 CV 0,099          0.127   0.084    0.073    0.053    0 047    0.061    0.048      0.03    0.053 0 0705 0.089
Skew -0.27    ■0.27   -0.37    0.474      -0.2     -0.87    -2.92        -2      0 249          0.19 0.287 -0.13 Min 51.5             43.2    45.09    57 42    6523      65.8    61,77    72.23    82.49    74.24 67 667 55.37
Max 77,3    71.60   64.06    82.17    86 18     90 3      98.1     97 53    95.67    94.73 93 187 85.13
Wind Spe€*d (mZs)
Average 0.62      0.8        1.0       1.06      1.04      0.86     0.62      0.51       0.5       051       0.48 Q5t
Suns/unc Hour?  (fr'S/daU
Average 8.155  7.638    7 452    7.287    7.624    6.061    3.703    4 059    6.164    7 855 8.3245 B.3DB CV 0.125          0.166   0.145    0.165    0.157    0.189    0 243      0.23      0 22    0 139 0 2139 0.104
Skew -0.47    -0.36    -0.27    •1.12    0.141    ■0.36   0.248     -0.42     -0 27    0.138 -3.525 0 971 Mm 6.05    4.905    4 592    3.304    5.428    3.364    2.277       1.6     2 622    5 778 0.1121 6 634
Max         10      9.919   9 744     9 44     10 15    8 12     5.445      6.2       9.12
tO. 08 10.201 Il’S?
A ate r Wo rks Design & Supervision Enierpri s e
[□ Associate with Mercantinenuti Consultants and Technocrats Pvt Ltd.Arjo Ikries^a Irrigation Project
Meteorologic
al and Hydrological Aspects
May 3007
Table 4.4:
Summary of Estimated Mean ETo of Afjo Decfessfl Project Area
Jan Ffrti March April May
Daily: Estimated ETo imm/dayl
June     Jury      Aug       Sapl     Oct      Nov     Dee
Average   3.7      4.11      4.52 4.51           4.33      3.58      2 96      3.11      3.81      4.03    3.79    3.44
cv    0.05 D.W 0.05 0.07 o.oa
0.08      0.08      0.08       0.09     0.06    0.12     0.05
Sstew     *0.47 -0.77           -0       -0.95 -0.65           0.19     0 33     ■0.51     -0.18    -0.27   -3.11    0 88
Mm 3.23 3.30 3.95 3.44 3.35 2.97 2.58 2.44 2.88 3.5 1.95 3.11 Max 4.03 4.49 5.24 5.13 5.06 4 15 3,46 3 59 4 49 4.47 4.24 3.96
Moofltfy. Estfmated ETo
(mm/month)
/ftwragu       115      115       143       135       134       107      91.8      96.5       114      125     114      107 CV        D.O5 0-06         0 05 0.07 0.08                0.08      0.08      0.08       0.09     0.06    0.12     0.05
Skew -0.47 -0,77 0 *0.95 -0.65 ■0.19 0 33 -0.51 -0.18 -0 27 -311 0.88 Min 100 94.0 124 103 104 89 80 75.7 86 5 109 58.6 96 4 Max 125 126 162 154 157 125 107 111 135 139 127 123
Estimated Eto fflim/dayj
inform average va/ues of data)
Average 3.69 4.08 4.58 4 48 4 28 3.57 2-95 3.10 3 75 4.00 3 79 3.44
Esbmatcd Eto (mm/month) (form average values of data)
Average
114      114       142       1 34      133       107        92         96        113       124     114      107
Note: tm. a Jrrtjtf: ETo ■ 119? iwn
---------- -
Water Works Design & Supervision Enterprise’ ’
In Associate with Intercontinental Consultants md Technocrats Pvt. LtdArJoDedessa tnl£i*tin n Project
Meteorological and Hydrological Aspects
Table 4,5:____Magnituda of ETa at given non-eMadanca probability lavsl
May 2007
WorvEid
Poc^liliiy Jan F*&
■fmm-'tfaxJ Mar    April      May    Juris July Aug
Sflpt
Oct     Now      Dec
(%}
55       3 72   4 14   4.65     4.56    4.37    3 61   2.99     3.14     3.85   4.06     3 84   3,46
60       3 75   4.1a   4 M      4.60    4.42     3 65  3.02     3.18    3 89    4.09     3.90   3.49
65        3 77   4.21   4.71     4.64    4 47     3.68  3.05    3 21     3.94   4 *2      3.96  3.51
70        3.80   4.25   4.76     4 69    4.52    3.72   3.09    3 24     3.99    4.15     4.32  3.53
75        3.83   4.29   4.79     4 74    4.57    3.77  3 12     3.28    4.04    4.19    4 09   3 56
ao        3.56   4.33   4.83     4 80    4.63    3.81   3.16     3.32    4.09    4.23    4 16   3 59
85        3.90   4.38   468      4.66    4.70    3.87   3.21     3.37    4 16    4 28     4.26   3.63
90       3.95    4.45   4.94     4.95    4.79    3.93   3.27    3 44    4.24    4.34     4.35   3.67
95       4.D2   4.54   5.03     5 07    4 93    4.04   3 35     3.53    4.36    4 43   4.51    3 74
Avg      3.70    4.11   4.62     4.51    4 33    3.58   2.96    3.11    3.81    4.03    3,79   344
Avg
1------------
Non.E.d
Prctotlllriy Jan Fob Mar April May June July Aug Sept Oct Nov Dee Annual
55        115     116    144      137       136    108    93      97.4     116    126     115      107     1405
60        116    117    145      138      137    109    94      98 4     117    127     117      106     1412
65        117    116    146      139       138    111    95      99.5     118    128     119     109     1420
70        118    119    147      141       140    112    96      101      120    129     121     110     1428
75        119     120    14B      142       142    113    97       102     121    130     123     110     1436
BO       120     121    150      144      144    114    98       103     123    131     125      111     1446
55        121     123    151      146      146    116    99       105     125    133     127     112     1457
90        122    125     153      148       149    118   101      107     127    135     131      114    1471
95         125    127     156      152       153   121    104     109     131    137     135     116     1492
115     115    143      135       134    107    92      98.5     114    125     114     107     1397
Won-Erd
Grovkfh Facfo/
Profcfti.iiiy Jan    Fct>    Mar    April       May    June July         Aug Sept    Oct        Now   Ore
55       1.01    1 01   1.01     1.01     1 01   1.01    1.01    1-01  1.01     1 01      1 01 1.01    1.005
BO       1.01   1.02   1.01     1.02      1.02   1.02    1.02    1.02   1.02     1.02       1 03 t 01
1 01
1.02    1.02   1.02     1 03      1 03   1.03    1.03    1.03   1.03     1.02       1.04 1.02
1 01B
70        1.03   1.03    1 03     1.04      1.04   1.04    1.04    1.04   1.05     1.03       1.06 1 03   1 022
75        1.04    1 04   1.04     1.05      1.06   1.05    1 05    1-06   1.06     1.04      1 08 1 04   1.028
80        1 04    1.05    1 05     1 06      1.07   1 07    1-07    1.07   1.07     1.05     1 1   1 rw    1 035
85        1 05    1.07   1.06     1.08      1.09   1.08    i oa
90        1 07    1 08    1.07      1.1       1.11    1.1     1-1
95        1.09     1.1    1.09     1.12      114    1 13    1.13     i 13   1 14      1 1        1 19 1.09   1.068
i o i. a i   11. 1019     11. 00 86       11.1152 11.0075    11 .004533
Avg          i           1 _   1          1           1        1       1         1        1          1         1
1
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt LtdArJnUedessa Irrigation Project Meteorological andl Hydrological Aspects
Figure 4 1           Mean Monthly Temperature at Ar jo Dedessa Project Area
May 2007
Figure 4.2 Mean- Monthly Relative 'Humidity al Arjo DcdKsa Projeel Area
Tnt’
Figure 4.3i Mean Monthly Wind Speed nt Arja Diuesa Project Area
Ptfluiw 4 4 M«an Monthly Sunshine Hour* al flrjn OtdtMl Pfcjact Area
Waier Works Design & Supervision Enterprise
In AsstHllfe with Interconudequl Coras nttants ™d Tsclmocrats M Ltd
MiArjo-Uetess* JrriiaMfMi Project Meteorological and Hydrological Aspects
Figure 4 5 Mean Monthly ETo at Arjo Dtidcssa Project Area
Water Works Design & Supervision Euternrlse
Mih UttramttaMui cib^ub Md TwtaoerM. Pvt.Arjs Dedessa irtigaiiiH Project Meteorological and Hydrological Aspects
5. RAINFALL ANALYSIS
5,1   Introduction
Hay 5007
The rainfall data obtained from B edele. Dedessa and Jimma stations  ware found to be the most reliable and relevant for use in the analysis  of rainfall for lhe Ago Dedessa irrigation project. Sedate is  geographically  the closest slalion io the command area. Oedessa station and the c ommand a rea a re I ocated a 11 he s ame e tevabon (i .e, b oth 1 33D m a si}. J imma s tabon (which is  Class  I) has  the longest record of all the stations  within the neighbourhood d! lhe command area so as  to be index  station in extrapolating and interpolating missing and shortage of rainfall data relevant to the Ago Dedessa catchmenl and command area
The rainfall in the Ago Didessa Catchment as  welt as  in its  surrounding is  on- modai type. Most ot lhe rainfall is  concentrated in 1he May  to September covering with virtual drought from November through March The five wettest months  cover 63 percent of the lolal annual rainfall The dry  season, being from November to February  (four months) has  a trjial rainfall of about 7% of lhe mean annual rain tall
The mean monthly rainfall for stations in the project area is given in Taoie 5,1 and their pattern
is graphically illustrated m Figure 5.3. The fenglh of reinfall da1a collected from Jimma is 
relatively more reliable compared to the data sol collected from other stations because oi ns 
long record length and shorter lime interval of observalion, Didessa and Bcdeie stations also
provide more relevant rainfall daia that can be adopted for the command area since Sedele is 
close to the project area and Didessa station is located within lhe same climatic zone as that of
the project area.
5.2   Rainfall internal and External Consistency
Though a good dal a base has  peen established for rainfall, considering the data of lhe three stations, namely. Dedessa. Jimma and Bedele it is  cuslomary  in Hydro-meteorological studies to firm up lhe consistency with statistical analysis.
The trend m the annual ramfall pattern is  a reievanl aspect with respect to the behavior of me rainfall and to compare such behavior with those of other relevant stations  involved in the study with a view to firm op external consistency. Accordingly, a 3 year moving average analysis
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pml. LtdA.rjo Dedevsa IrTtffttlM Project Meteorological and Hydrological Aspects
May :!DHr
was taken up for each of 1he 3 stations. The results are shown in the figures 5.1 (a), fb) and (c). These show similar Vends.
Similarly, an analysis with respecl to the cross correlation structure among me 3 stations was carried out. The cross correiahon malnx depicts me following status {Table 5.2) at annual time resolution level, which is not abnormal.
Then, ihe single mass curve analysis was laken up for each of these 3 stations (Figures 5 2.
(a).(b) and (c)
These also do not indicate any abnormality to reiect th>s data set.
As  such,  these  rainfall  data  were  used  in  its  different  forms  for  various  spectrums  ol  1he analysis.
5.3 Estimation of Rainfall Reliability Level
Using ihe rainfall and irngaln?n water available for the command area requires the magnitude and reliability  level of rainfall corresponding to vanous  rainfall time intervals. Annual, monthly and half monthly mLervals are chosen durations for the Ano-Oedessa irrigation project.
Rainfall reliability  level and magnitude can be analyzed by  making use of theoretical distributions. In this study Lhe Extreme Value Type ill (minimum) distribution was utilized. The distribution is also known as the Weibuli distribution eras Cumber s Limited distribution of lhe Smallest Value. Naturally  rainfalls  are bound by  zero or other higher values  on the leH. The Wetbull {or EV3) distribution can be expressed as:
(5.1)
where
Xp *E*(UE) [-ln(l-p)]1'*
Xp = magnitude of rainfall corresponding to probaoility level of p,
The mornenl estimates of lhe parameters E (the lower limit), U and a fl.e„ E, U and A) can be obtained from ihe following equation
U = Xm t Cv.Xm Y(a) E - U - Cv Xm.Z(a)
(5.2)
(5 31
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo-Dudessa Irrigation Project
Meteorological and Hydrological Aspects
where
Xm = mean value.
Cv = coefficient of variation = standard deviation divided by the mean
¥(a) = (2-C$yB
Z(a) = [S+(3-Cs)fy9
and
A = 3/(l+Cs>
Cs = skew coefficient calculated from data
The esbmated monthly and half-mon1hly parameters of Weibull Distribution are given in Table 5.3 and 5.5. respectively.
The following algonthm were used in the derivation of annual, monthly, and hali-month 55 to 95 percent reliability levels.
1.  Averages, standard deviations, standard deviation, skew coefficient of annual, morthly 
and half-monihiy averages were calculated.
2.  Weibull Distribution parameters (namely U, E and A) corresponding to annua!, monthly 
and hall-monthly rainfalls were calculated from the statistics
3.  Magnitudes of rainfalls corresponding to 55 to 95 percent reliability levels were
estimated.
The results so obtained are grven in Tables 5 4 and 5.6 for monthly and half-monthly time
intervals, respectively.
The half monthly rainfall magnitudes as a percentage of mean, corresponding io various
reliability revets are shown in Table 5.7
5.4 Estimation of Maximum Rainfall Frequencies
For internal drams  and smaller control works, the need for various  return penod rainfall and with different durations  were found to be necessary  In general, maximum rainfall magnitudes 
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo-Dedexsa InUaUon Project
Meteorological and Hydrological Aspects
May 2OD7
□1  intensity  conespoiHling
Io  various  return  periods  for  probability  avals)  tan
te  eslimated  br
' 
applying (he IdlOwng form.
It = fm (1 • CV.K(T)J
(5.4)
where
l T = rainfall intensity corresponding 1q  return period of T years f mm Im e mean of annual maximum intensity of rainfall (mntVhf),
CV - coefficient ol vanaiiqn of annual intensity al ramteiI K(T) = frequency factor
For Extreme Value Type I (<x Cumber) Distribution.
K(T) - 0770 (0.577 + In ln|T/{(T -1>]}
(55)
The maximum annual 24hr rainfall service is given in TnOfe 5 B
The results qf the maximum 24-hr and 1'hr rainfall frequencies arc presented n r able 5 9 I'u? 1-hr rainfall mlensrtiw were estimated by the formula denved for Ethiopia expressed as
In = 1^ (0 523 » 0 15 In 9j
(3.6)
where
l h - maximum rainfall intensity corresponding to duration D (mm/hrj
In = naiural logarithm
D - duration oflh (hr),
l ?J = maximum rainfall intensity corresponding Io duration 24 hours (mmfhr)
Ttte ramfall magmiLdes for higher durations, 2 days & 3 days have also been analysed using the EVI frequency distribution The results lor various return periods are showi in Table 5 10
More details uf Iho analysis .ire available m the aonexure A Results obtained from meteorological Analysis"
15
Waler Works Design 4 Supervision Enterprise
Id Associate #1te Intercontinental Consul Lams and Techiiucrats Pvt LtdArjo Deflessa. Irrigation Project
Meteorological aud Hydrological Aspects
The annual rarnfall available at different years are given betow
May 2007
Near year
75 % year
80 % year
95 % year
s              1453 mm
=              1148 mm
=              1090 mm
=■           853 mm
Tablo 5.1: Mean Monthly Rainfall
Description        Jan   Pfrb   March   April May     June   July     Aug     Sep    Oct      Nov  Dec     TflUI
Oidessa             3       6       26      49    158     274    312    277    209    104     28      8       1454
Bedele                  18    23      65     105  239   291     310    303    302    156   41     12     1864
Dembi                   25    44     101    126  223     303     307    367     290     145    52     29     2013
Agaro 24 36 88 93 149 232 234 231 174 127 54 30 1471 Jimma 33 49 88 133 172 219 208 210 1H2 103 68 36 1502
Table 5-2: Cr&Ss Correlation Matrix of Annual Rainfall
Dedessa
Dedessa                                  1
Jtmma
Bedele
—— - - - - - - - - —_ _ _ _ _
Jimma
Bedele
Oil
1
0.24
0 4fi
1
Tahle 5.3:           Parameter Esrlmate5 Ol Weibut) DistributIon
Jan   Feb   Mar    April May       June July Aug           Sept Oct      NovDec Annual
y(a> 0.5 0.6 0.6 04 0.5 0.5 0.B 0.4 0 4 z(a) 0.2 0.2 0.2 03 0.2 0.3 0.1 0.3 0.3
U 2.4    21     2.2    36     2.4     2.0     1.3    3.7     3.4
£ 18.3 21 9
61 2
0.5
0,2
2.4
1-1   0.3 -0.1 0.1 0.9 1.3
81 S 201.1 26?.3252.9257,724S.q 131.030.01J.9
-12,9-15.0-17,4-55.3 -9,8 7.3 154.1 35.9 60-9 -29 9 3 8 -4 4
U = Xm+Cv Xm'yfa) E-U C/'Xm^a)
r
0.4
0.3
32
1541
575
* - E + (U-E)’(-ln(l- 1/T) '(l7a)
i
Water Works Design & Supervision Enterprise
la Associate wiUi Ititercijnuiicnuij CoKttttuts and TftchDMrtii Nt. Ltd.ArJo-ItedESsa Irrigation Project
Meteorological and Hydrological Aspects
Table 5.4 Monthly Rainfalls Corresponding Io Drffsrcnt Reliability Levels
Reliability
Leve I Jan   Fob Mar April May           June July   Aug      Sept  Oct Nov Doc            Annua, (%)
55       10.8 12.240,9 58.1    150    213    219   221     212  91.65 18.6 7 58      1353 60     8.84 9.79 35.8 51.7     137    198    211    210    203  81 66 16.36.12       1304
65     6.92    7.4 30.8 45.3   124     184    204    200    194   71.76 14 2474        1253
70       5     5.03 25.8 38.6   111    169    197    190    134  61.82 1223.43        1202
75     3.04 2.63 20-7 31-5   97.9    154    190    178    174   51.66 10.4 2.16     1148 60    0.990.16 15.5 23.8     84.2    138    183    166    164  41.13 8 83 0.92      1090
05       0        0 9.97 15.2    69.4    120    177    152    152  29.86 7.36 0           1025
90        0        0 3,07 4 84    52.9   997     170    135    138   17.29 6.02 0           951
95       0            ooo           327    737     163    113    119   1.974 4.82 Q           853
Avg 15.318.453.6 69,5 180,8243 0245.9238.3228.6115.531412 J 1453
Table 5.5:           P-^rameter Estimates af Hal^ Monthly Rainfall Mantfi Parameters of We/buff d/str/btrf/on
May ?co?
1/a         y&
ifaj          O              £
1.1
0.8
0.1
1.5
8.6
4.3
1.2
09
00
1.1
8.1
-2 8
2,1
1.2
'0.1
0.9
7.7
-4 0
2.2
0.8
0.1
15
11.0
-6.1
3.1
0.6
0.2
10
24 3
-14.6
32
0.6
02
20
377
-11 7
4.1
06
02
1.9
26.5
-135
4.2
05
0.2
2.4
54.5
-25.0
5.1
0.6
0.2
1.9
87 6
-11 2
5.2
0.6
0.2
2.0
112.7
75
6.1
0.5
0.3
2.8
134 3
-19.8
6.2
0.5
0.2
25
135
10.4
7.1
07
02
17
130
40.7
7.2
0.9
01
1.2
126
80.9
8.1
0.5
0.3
2.9
128
8.2
52
05
0.3
2.7
131
37.4
9.1
0.6
0.2
2.2
128
49,2
9.2
04
0.3
36
1196
-6 2
10.1
0.5
0.2
24
03.5
-177
10.2
0.7
0.1
16
47.1
’117
11.1
0.0
0.1
1.3
21 5
32
11..2
12
0.1
0.9
10.3
-3.0
12.1
1.1
0.0
1.0
5.8
12.2
3.3
1.3
-0.1
0.9
5.1
-3 7
Annual
0.4
0.3
3.2
1541.2
575.1
Water Works Design & Supervision Enterprise
Ln AssuciitE with InicrcentinenLU ConsuJunU :liM Ttcluiocrais Pvi Ltd,
17At}d DRtJessA Irrigation Project
Meteorological and Hydrological Aspects
Table 5.6: Ha If-Monthly Rainfall Magnitudes at Different Reliability Levels
May 2007
Month Aug
7.5
1.1
7.8
Reliability level
55V. 50% 65% 70% 75%TM% 85% 90% 95%
4.41      3 43      2.49      1 58    0.69       0            0          0           0
4         3.09      2.24      1.45     0.7        0          0          0           0
1.2
8.8
246
1 38
041
0
0
0
0
0
0
2.1
9.6
5.52
4.22
2.98
1.77
0.6
0
0
0
0
22
20.6
13 2
10.5
7.87
5.25
2.64
0
0
0
0
3.1
33.0
24.4
21.1
17 9
14.6
11.4
8.08
4 61
0.82
0
3.2
22 7
152
12 4
9.67
6 99
4.32
1.61
0
0
0
4.1
46.7
34 9
30
25.1
20.1
15.1
9.86
4.25
0
0
4.2
78 2
59.6
52.8
46.1
39.5
33
26 3
194
5.1
11.9
3.32
102.6
84.27
77 2
70.28
6342
56 51
49.43
42.02
33 96
5.2
24 5
119.8
101
92 5
83.9
75.1
65.9
56.3
45.7
6.1
33.6
123.2
18.3
106
98.2
90 7
83 2
75 5
6.2
57,4
122
103.9
58.7
48.9
36.8
97.46
91.26
85.17
79.13
7.1
73.04
66.70
7.2
1239
116 5
60.14
110
102
TOB
95.7
52.6
102
88.9
99.2
82
96
74.9
a.1
121 8
120
108.5
73.7
4i.a
93
67 3
110
108
97 9
58 7
29.2
13.1
4.15
90.1
59
104
103
92.1
52 5
24 9
11.1
2.92
87.2
49 3
84 2
37
8,2
AA
9.2
9.1
10.1
10.2
11.1
19.7
11.8
11.2
6.1
99
97.6
86.1
46 2
20.8
9.3
1 83
93.6
92.7
80
40
16.8
7.54
0.85
2.02
87.9
87.6
73.4
33 6
12.8
5.83
0
82
82.4
66.3
27
8.77
4 16
75.6
76.9
58.4
19.9
4 68
25
68.2
70.8
48 9
12
0 38
0 82
59,1
S3 5
36 1
2 37
0
D
0
1.21
0
□ 46
0
u
12.1
12.2
6.6
0
0.83
0
o
0
0
0
un
0
0
0
0
0
U
0
1453
Annual
7353      1304    1253    T202   114a   7090      1025   950.5      853
Water works Design 4 Supervision Enterprise
?8
>aA
SSM atewlu lllttreMUoMtalCoilsu|uolsi|iai[[
,,
^e^
[r   is   iuArjc Orissa itrlgaUon Project
Meteorological and Hydrological Aspects
Maj 2007
Tabfe 5.T:         Half-ManthJy Rainfair Magnitude* in Percent of the Mean Carreapondlrtg to Different Reliability Levels
Month
1.1
1.2
2.1
22
3.1
32
4.1
4 2
54
52
6.1
Avg
100
100
1OQ
100
100
Retiabitity level   ___________________ 55%       60%      65%       70%     75%       80%       85%      90%     95%
59         46         33        21         9          D           0            0          0
51         40         29        19        9         0            0          0          0
26         16          5            0            0         0          0          0            0
53         44         31        18        6          0          0          0            0
64         51         38        25        13        0            0            0          0
100        74         84         54        44        35       24        14         2          0
100        67         55         43        31        19        7          0          0          0
100        75         64         54        43       32        21           9          0          0
100          76         68         59        51        42        34         25        15           4
100        82         75         60        62       55       48        41        33        24
100
6-2             100
04 77 70 63 55 47 38 28 15
06 80 74 68 61 55 48 40 30
7,1             100        35         80         75        70       65        60        55        49        43
7.2
81
TOO       89         86         82        80        77        75          73        70        68
100
82             100
9.1             100
9.2             100
10.1            100        80         71         63        54        46       37        27        16           3
8S         82         76        70       64        58       51         42          32
90         85        81         77       72        67          62        56        49
90         86         81        77       73        69        64        59        53
90 85 79 74 68 61 54 45 33
10.2
11.1
11.2
12.1
12.2
Annual
100
100
100
100
100
100
70         60         50        40       31        21          IT         1           0
66         56         47        38        30       21        13         4            0
35         25         16         7         0          0          0            0             0
33         20          8          0         0          0            0          0             0
13          0           0          0         0          0          0          0             0
93           90         86        83       79        75         71       65        59
Water Works Design & Supervision Enterprise
In Associate with Intercontinental. Consultants and Technocrats Pyl LtdArjo Bedfissa Irrigation Project Meteorological and Hydrological Aspects Table 5.8 Maximum Annual 24-hr Rainfall
May 2007
Kear (mm/tfj
Year     prjm/d)
Year    (mm/cy
1967      47.1               1980      45.6                 1993       50.1
I960      47.0               1981
1994       57 8
1969      64.0               1983      50.0                 1995       61.0
1970      57 0               1984      51.7                 1996       60.1
1971      70.0               1985      62.2                 1997       104.5
1972      45.2               1986      64.6                 1998       63.5
1973 35 9 1987 56.4 1999 63.0
1974 51 8 1966 53 2 2000 47.9
1975 36.4 1989 46.8 2001 69.0
1970 47 1 1990 49.5 2002 57.0
1970
1991      87.8                 2003
1979      45.0               1992      51 6                 2004       39.1
Average 54.14
CV 0.206
Skew 2E-04
Table 5.9 Maximum Rainfall Magnitudes and Frequencies
Return             Frequency                  Rainfall Magnitude (mm)
Peiod (T)
Factor (K)
24-hr
1-hr
2
-0.16
51
27
5
0.72
66
10
35
1.30
76
15
40
1.64
82
20
43
1.86
85
25
44
2.04
88
30
46
2.20
91
46
40
2.40
94
49
50                  2.61
98
51
lAatci Works Design & Supervision Enterprise
Io AssflCllk with Intercontinental CvasulUnti and Technocrats Pvl Ltd
40Ar] o-ftctfesSA Irrigation Pro] act
Meteorological and Hydrological Aspects
TaD/e 5.1 a Maximum Rainfall Magnitudes fo< Higher Curations
May aiiJ7
Roturn
Period, T
(Years)
EVI Factor
KCD
Max 2day
Rainfall (mm)
Iday Avg. of Max.
Max. 3day                  3 day Rainfall
Rainfall (mm)
iniml
2
5
10
15
20
25
50
100
■0164 76 9
0.719 94 6
1.304 106.3
1 634 112.9
1.865 117 5
2.043                  121.0
2 591                  132 0
3.135                  142.9
92.7
112.7
125.9
133 4
138.6
142 6
155.0
167.3
29.8
37.8
43.2
46.2
43.3
49.9
54.9
59.9
Waterworks Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt. Ltd
4]Ar>DEdP44a IrMiSAUOO PrUtcl Meteorological and Hydrological Aspects
May
figure 5.1(a )> Trend Analysis ol Annual Rainfall at Jifnmj Station
Figure 5.1(b)-     7 rend Ana lysis dI Annual fUdnfall at Bedell» Si»t|qn
Water Works Design & Supervision Enterprise
tn Associate with IntereonUncntnl Consultants and Technocrats Pvt. LtdArjo Dedtssa irrigation Projeci Meteorological and Hydrological Aspects
May £007
v*ar
Figure 5.1(c): Trend Analysis  f Annuel Rainfall at Dedcssa Station
n
Y*«rs
Fig ure 5.2{a|: Single Mast curv» of Ji mma fl
fn
ai n a
Water Works Design & Supervision Enteri^- - - - - - - - - - - - - - - - - - - -
i« JssMai. with interMmuwnui Co„slllBJlts
ic         OeMls p«. lid
am t  h nummii IMIk* Annwtt R«lnrall Imnnfr
Cummul»1l« Annual RalnFal I f<run|
Arjo -Dedtssi Irrigation Project Meteorological and Hydrological Aspects
May
Years
Figure 5.2(b): Single Mass Curve cl Bedi-lle Rainfall
Figure 5.2(c)" Single Mass Curve of Drdossa Rainfall
Water Works Design & Supervision Enterprise
In Associate with Intern ntinenul Consultants and Technocrats Pvt LtdI
I
I
I
I
I
I
I
I
I
I
I
■
■
fl N
fl
fl
Arji? Dedessa trnjatiuo Project
Meteorql&gkat and Hydrological Aspects
May 2007
45Arjo Dedessa Irrigation Project
Meteorological and Hydrological Aspects __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____^__S!2L^22L
g,          monthly streamflow analysis
GJ    Hydrological Observation Stations
Hydrometric stations on lhe Dcdessa river and the neighbouring rivers within the Abbay basm the Omo-Ghibe basin have also been identified The hydrological daia are obtained from the Hydrology Department of the Ministry of Waler Resources {McWR}.
Ihare are Iwd hyrfrolagicai observation stations  located du the Dedessa River These are Dedessa near Arjo town (Station No. 114001) and Odessa near Dembi town (Station No. 114014). SlaLiDn 114001 wiih catchment area of 9981 km2 is located about 44 km downstream of the proposed dam site and has  become operational since I960 where as  Station 114014 with a catchment area of 1806 km2 is located about 137 km upstream of the proposed dam site and has become operational since 1985.
Besides  the iwo hydrological observation stations  located on the main Cedessa nver several hydrological observation stations  are located on iis  tributaries. In addition, hydrological observation stetionson I he neighboring Dabana n ear Abasma (Station No 1 14005). (Gilgel Ghibe near Assendaba {Station No. D91008). and Gojeb near Shebe (Station No 091012] have been found to be relevant to the study.
The  list  of  hydrological  observation  stations  for  which  data  have  been  collected  along  with other details like their lotauon and catchmeni area is available in Table 6.1
6.2 Extension of records
Streamflow gauging slams have been installed on the Oedessa River near Arjo town (Station 14001} since 1960 and near Dembi town (Station 14014} since 1965. Before the streamflow analysis, date obtained from Station 114001 (Didessa near Arjo) and Station 114014 (Dicfessa near Dem tn) were checked far temporal and spatial homogeneity. The investigation of
homogeneity was concentrated mainly on lhe outliers of ihe monthly data series of the record Extremely high or low values of each senes, that has occurred at time T(i) in each month M(i)
was checked against lhe records of the month M(i-1) ano M(i+1) that has occurred ai the same year T(i) so as 10 judge, whether the relation ■$ still more or less lhe same as that of the other years. Whenever lhe oulliers were rejected by this test, again another test was performed with
46
Water Works Design & Supervision Enterprise
In Associate with, Intereontlneocal Consultants and Technocrats Pvt. Ltd.Arjo-BedessaIrrigation Project Meteorological and Hydrological Aspects
May 2007
other data senes of Station 114005 (Dabana near Abasina), Staton 91008 (Gilgel Ghibe near Assendabo) and Station 91012 (Gojeb near Shebe) for toe same penod T(i).
The data were checked for its consistency before use for different analysis. The investigation will concentrated mainly on the outliers of ths monthly and daily data series. Extremely high or low values that occurred a1 a given lime were checKed against records of other near by rivers (such as  Oabana) If the outliers  are found to be inconsistent with others, then they  were replaced by  new values  ihat were generated regionally  from data sei obtained from other stations.
6.3 Synthetic flows
In this section, analysis of monthly flows is made with the intension of improving information required fro reservoir storage design. Reservoir storage design on the basis  of generated (synlhetic) flows is preassumed
It was  realized that the specific  sequence o1 histone events  was  a random occurrence that would certainly  never occur again in the same way. To get some idea about other possible sequence within the population, tn order to improve reservoir design, generating a tong streamflow series is a highly accepted procedure by hydrolagisis. However, it has been pointed out synthetic (generated) flows do not improve poor records but merely improve the quality of designs made with whalever records are available.
Mean monthJy  discharges, coefficient al variation ot monthly  flows, summary  of 'egional monthly flow characteristics, statistics of monthly flows at Arjo Dedessa Dam Site are shown by Tables 6.2. 6.3. 6.4. 6 5 respectively The monthly stream flows at different reliability level are available in Table 6 6.
tn order to maintain the historical skewness in the generated flows, lhe Weibull distribution has been Ailed Io lhe standardized residuals  of the monthly  series  Accordingly, the estimated parameters  of the random generator that were used In the Thomas-Fierrmg model are presenled m Table 6.7
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvi Ltd.
47Arjo H*u ess-a irrigation Project Meteorological and Hydrological Aspects
May 2007
Mone   details   on   various   results   are   shown   in   the   annexure   B   ‘Resulls   obtained   from hydrological analysis."
The flaws at ihe dam site at annual level are as below.
Mear year -
75% year =
2328 Mm’
1729 Mm’
80 % year
=
1625 ‘
90% year
=
1384 “
95% year
=
1224 -
Table & 1 Availability of Slreamflow Data in the Region
SI Nd
St.
No
Slalicm ns me and Location Lat
North
Long
East
Arsa
(KMZ)
Flew         Runoff
(Mm3/yr> (mm)
1     114001      □edessa near Arju
8.41       36.25      9961       3826         383
2      114014     Upper Oedessa near Dembi       8.02       36.28       1806       1221         676
3      114005     □abana near Abasina Gibbe near
4      091008     Asendabo
5     091012      Gojeb near Shebe                     7 25       36.23       3494       1803         516
Table 6.2:          Mean Monthly Flow (in Mm'/set)
9.02 36.03 2251 187Q 820
7.45      37.11      2966       1211         408
St. No       Jan Feb Watch April May June July                  Aug Sap Oct
Now Dire
114001
114014
114005
091008
901012
41,9 26 7 26 33.5 63.6 216 646 1050 902 526 148 3Q ?
12.2 9.5 11.5169 364 1124 228.9 306.9 262.8 154.3 484 20 5
35.4 19.8     16.3 17 0 35.1 107.0 258.8 433 0 473.4 313 9 1Q33
56 ,r
147 13.5 12.2 15.9 33 9 100.3 216 5 319.2 277 6 137 602 245
31.3 22.1 22.1 31 3 86 4 159 2 323 7 415.6 400.9 202.3 32.B 46 5
Annual
— 3761
1221 1870 1211 1B03
Table 6.3:          Coefficient of Variation of Mianlhly Discharges
St. No
114001 114014 114005 091008 901012
Jan     Feb     March    April    May    June    July    Aug     Sep     Oct     Nov    Dec —fc—-  II         —  —
0.66     O.fifl    0.62   0.45   0 35     0.3      0.33     0.67     0.62     0 59 0.48     0.56    0 69     0.53   0 29    0.27     0.30     0.56     0.81     0 53
0.33     0.43    0 60   0.47   0 20    0.16     0.25     0.44     0.30       0 34
0.78    045     0 43   0 36   0.22    0.28     0.27     0.51     079      0 58
0.34    0.43    0 63   0 44   0.31    0 26     0.34     0.49     0.54     070
Water Works Design & Supervision Enterprise "
In Associate with lulercontlnental Consultants and Technocrats Pvt Ltd
4,<ArJa Dedessi Irrigation Project
Meteorological and Hydrological Aspects
Table 6,4 Summary of Regional monthly flow characteristics
Hay 2OT7
Param    year    Jan Feb Mar April Ma f June July Aug Sep Oct Nev Dec
cv
Shew
R
a
194    0.51     D.68 0.595 0.58 0.61 0.47 0 33 0.29               0 32 0 58 0 66 0.57 151    1.80     166 1.503 0.86 1.65 1.05 0.12 0.7                  0-59 0 94 2 19 2 02 194   0.38     0.57 0.527 0.45 0.49 0.66 0 53 056 0.51                    0 5 0.56 0.51
194
0 34    0.76 0 46 0.44 0.52 0.51 0.37               0.5     0.56 0.91 0.64 0.44
I
Table 6.5
Param
Table Statistics of monthly flows at A/jo Dedessa dam site
(in Million m1
Jan Feb Mar
Apr May Jun Jul
Aug Sep Oct Nov
r—--------- 1--------- -—
Dec Annual
Average 25 00 16 97 17 86 24.2145.26 157 2 412.6 633 540.6 299.8 105.9 46 11 2328
Sltfev     12.81 9.72    11 82 16.41 29.69 70.67 143.?    189 6 179.2 180 5 89.35 27.17 619.3
Skew       0.626 0.743  1 067 0.937 1 629 0.891 D. 126   0 037 0.264 0.565 1.866   0.96 0.4EJ8
Max        59 09 40.3    46.01 68.61 144 9 366.1 751.5        1043 905.1 661 400.8 120.1 40B9
MjO   6.806 3.462 1.775 4.586 9.685 3B.71 143.8 298 2195.6 49 3212.69 4.808            1124
R      0.446 0.828 0.889 0 59 0,298 0.785 0.45        0.529 0 436 0.431 0 796 O 704 B     0.21 0.628 1.081 0-819 0.54 1.868 0 912        0.701 Q.412 0.434 0.394 O.?14
Table 6.6:           Reliability Level Vs Monthly Streamflows at Dam Site
nft Mni 3,i
Reliability
Lev»l
(%)
55
60
65
70
75
80
85
90
95
Avg
Apr May     Jun     Jul       Aug     Sep Oct          Nov
“T~1
■ ‘-----  -—I
20.2 12.7  14.1 19.3 37 5  131.4 371.1     568.8 480.4 239.0 75.8 35 5 2114 10 0 11 6  13.0 17 4 34 7 122.3 348.4    542.5 454.6 216 6 59 9 33 2 2019 17 910 6   12.0 15 6 32.0 113.5 325.3    516.7 429.0 194 7 64 5 31 1  1924 '6.9 9.5     11.013 8 29 5  104.0 301.3    490.8 403.3 173.1 59 6 29 2 1828 160     8 7 10.1 11.9   27.1  96.4 276.0 464.5  376.9  1516 55 0 27 4 1729
5 0    ; 3    9 2 10 1 24 9  87 8 248.5 437.3    349.4  129.7 50.9 25 7   1625 14.2   6.9      8 3 8.1 22.6  78.9 217.8 408.3  319.8 107 0 47 0 24 1   1512
13 3    6.1     7 4 6.0 20.4  69.5 181.2 376 4  286.7 82.5 43 5 22 6        1384
12 5 5.2 6 5 3.5 18.2 59.0 132.1 337 9 246.0 544402212 1224
Water Works Design & Supervision Enterprise In Associate with Intercontinental Consultants anti Technocrats Pvt LtdArjo Dtttessa [rrlgatlon Project
Meteorological and Hydrological Aspects
Table 6.7 Characteristics of Random Numbers Used for Flow Generation
May 2007
Param
Jan Feb Mar       Apr 1     4sy     Jun      Jul         Aug     Sep       Oct
I
NOV □.e
Average 0 00 0.00 0.00            0.00     0.00     0.00     0.00     0 00     0.00     0.00     0.00     0.00 cv         0.51 D 66 D.60         058     0.61     0.47     0 33     0.29     0.32     0.58     0.66     0.57
Skew         1.80 1.66 1.50       0.66     1 65     1.05     0.12     0.70     0.59     0.94     2.19    2.02
oaa
Va 0 933              7 0.834 D 620 0 883 0.683 0 373 0.567 0-530 0.647 1.063 1.00/ 006
y(a) 0.033             7 0 083 0.100 0.058 0 158 0 313 0.217 0.235 0.177*0.032-0.003
1.15
1(a)       1031       6 1.262 1.973 1.162 1.713 3.543 2.241 2 444 1.860 0.048 0-993
WejtiuJ Dfstnrbufror?
U~Xm *Cv'Xm’y(a) ______ e = U - Cv-Xm^a)
Water Wyrks Design & Supervision Enterprise "                — In Associate with intercoaiinentaL CnnsiiLbrnts and Ttchnocnits Pvt. Ltd
50Aijo Dedessa rnigallon Project
Me ten rological and Hydrological Aspects
7 ESTIMATION OF FLOODS FOR UNGAUGED CATCHMENTS
May 2007
In the hydrologic  analyses  for dams, weirs, bridges  and drainage structures. it must be recognized that there are many  variabte factors  that affect floods. Some of lhe factors  that need be recognized and considered on an individual site by sile basis are:
o rainfall amount and slarm distribution.
q catchment area size, shape and orientation;
o ground cover;
o type of soil;
o slopes of terrain and stream (S);
o antecedent moisture condition.
a storage potential (qverbank, ponds, wetlands, reservoirs, channel, etc.); and
o catchment area.
Jn g enerai, three 1 ypes of e stimation floods magnitudes {namely: t he R alional M elhod, S CS method and Transferring Gauged Data method) can be applied for the proged area.
7.1 Rational Method
The Rational Method can be applied 10 small catchments if they do no1 exceed 12.fi km? (or 5 square mite) at the most (Gray, 1971). The consequences of applying the Rational Method to larger catchmenls is to produce an over estimate of discharge and a conservative design. The method is  nevertheless  frequently  used in standard or modified form for much larger calchrrents. This  is  because of its  relatively  simplicity. The vast majority  of catchments producing floods  imposed on the command drainage system lie within the validity  of the Rational Method and it has been used as the pnncipal method of estimating design discharges of dykes, culverts, drainage channels, etc
The Rational Method is based on the following focmula-
Qm- 0.2778 C.I.A.Fr
(7.1}
where
Qm = peak flow corresponding to return period of t years in m’/sec
C = a 'runoff coefficient expressing the ratio of rate of runoff to rate of r^nfall
(see Annex Cl and C2};
Water Works Design & Supervision Enterprise
tn Associate with intercontJnenui Consultants and Technocrats Pvt. Ltd.7
Arjo Dedessa Irrigation Project
M ethnological and Hydrologic/it .-Upi'cis___________________________________ ::;,J''
I = average maximum intensity of rainfall in mm/hr, for a duration equal to the time of concentration;
A = drainage area in km ;
Fr = 15 me areal reduction factor (this faclcrfs improves lhe calchment limitations 
imposed on the use of rational method).
Coefficient of runoff C for the formula are given by many soil and water conservation lexts (see Anne* C 1). Information on rainfall intensity I in a time of concentration (time period required for flow ro reach lhe ouitei from lhe mosi remole point in the catchment) is required and can be estimated by  lhe following formula. The selection of the correct value of C '  presents  some difficulty. It represents  a parameter that can influence runoff including: sols  type, antecedent soil conditions, land use. vegetation and seasonal growth, Therefore, lhe value of C ' can vary from one moment to another according to changes, especially soil moisture conditions
Tc - (1 /30(JO)xL'154 H *
4  14* (Kirpich equation)
(7.2)
where
Tc = time of concentration (m hours)
L = maximum fength of mam stream (m meters).
H = eievaLion difference of upper and outlet of catchment, (in meters).
The area reduction (actor (Fr) is introduced to account for the spanal vanabinty of
po nt
i  ramfall
over the catchment. This is not s^n.fleant for small catchments Out becomes so as catchment size increases. The relationship adopted for 'Fr' is based on that developed for the East African condition (Fiddes, 1997}. The relationship can be expressed as:
where
Fr= 1 0.02 O u ” A °M
D = duration m hours; A ■ drainage area in km :
(7.3)
1
™! eauanon
lo , slwrrB ol uo „ a ,ours duratw Fw |<w9er dwaiions
catchments lhe value ot D can be taken as & for use in the above formula
Water Works Design & Supervision Eaterprise
In Assochie Wtdi liitertontinenul CtmsiiKants and Technoernts Pvt Ltd
52Arjn Bcdessi JETlgatJon FTufccI
Meteorological and Hydrological Aspects_________________________________ Mar _
7.2    SCS Method
A  relationship  belween  accumulated  rgmfaU  and  accumulated  runoff  was  derived  by  SCS  (Soil Conservation   Service}.   The   SCS   runoff   equation   is   therefore   a   rnelhod   of   estimating   direct runoff fwn 24-hour or T-day storm rainfall, The aquation is:
Q = (P- ta) /(P -la) + S
z
P A)
wnara
O = accumufated direct mnoff, mm
P = accumulated rainfall (potential maximum runoff}, mm
la = initial abstraction including surface storage, inception, and infiltration prior to
runoff, mm
S = potential maximum retention, mm
The TaFafionahio between la and S was  developed from experimental catchment area data. Il removes  the necessity  for estimating la for common usage. The empirical relationship used in the SCS runoff equation is;
la • 0 2xS
(7 5j
Substituting 02xS for tain equation 7.4. the SCS rainfall-runoff equation becomes
Q = (P-0.2S)*f(P+0.8S)
(7-6}
S  is  related  to  son  and  cover  conditions  of  the  catchmeni  area  through  ON.  CN  has  a  range  of D Io 100 (can he obtained from Annex C3 and ERA 2002). and S is related to CN by
S - 254x[(10QOt) -1|
(7.7)
Conversion f rom a vcrage a ntecedenl m oisture c onditions t o w ef c ondihons c a n t> e d one by multiplying the average CN values by Cf (where Cf - (CNffOQ}jtl*|
Waterworks Design & Supervision Enterprise
In Associate with Tnttrcontijiei)tai Coesulunts and Technocrats Pvt Ltd.Ujo              rrTl<iri.afl Frg|rrc
Meteorological and Hydro logical Aspects
7 3 Transferring Gauged Data
May OTi'
■ l.iuged dal a may be transferred 1n an ungaugod sirn of interest provided such da’o ate *v«jpi «
0   within   the   -..imo   hydrotogiC   region,   .ind   -here   .ire   no   major   tributaries   or   gr.-ers   nr   s between   me   gnge   and   the   s<te   of   interest)   Hies*   procedures   make   use   of   the   constants 
obtained n developir^g |!i« regression egit.iliijns These procedures are adopted
■t Admasu i l9B9i jsWm
tno a :<■
where
Ou - Og (A.j.Agf<q
<7 81 : j - m+Mn unnuai Ll.aily nuiKimum Mow .il ungauged site i^'-sl
Qg = mean annual j-Lniy maximum flow jt nearby gauged site lm ''si
Au = ungaugod arte calchmonl area (krriJ|,
Ag = gauged site catch muni area (km ).
The  estimate  Cdrty  (or  me  24-hr)  annual  ma  win  uni  flood  couid  he  converted  into  a  mcme^taf. peak as
J
Op = Cf Qu
(7 9)
Here. Ct js factor estimated as Cf - i * o 5/Tc (where To is time of concentration]
7.4     Estimation of Weighted Average
in general, the Rational method. SCS method and Transferring Gauged Da!a are recommended lor r&teflvefy  small medium and large catchments  respectsely  Howler r $ very  important to establish a smooth pattern or transition from small to medium and from medium to farge caichments
AcecwL’.ngiy. the recommended weighed a.eraqe estimate d [wak rioca can oe aven .is
Q* - W| Q, * W; Q; * 'A . 0,
’ TO)
Water Works Design & Supervision Enterprise
In u.-iuciair with iDltrcooUnHiUtJ Gmsulunts md Tfctuwtati fM LtdArjo Dedessa I rrlRarin-n Project Meteorological and Hydrological Aspects
where:
May W
0,.  Q?.  and  Qj  are  mean  annual  momenlary  peaks  estimated  by  Rational,  SCS  and Transferring Gauged Data methods, respectively
Wi,W  and W3 are weighing factors of mean momentary peak estimates by Rational.
z
SCS and Transferring Gauged Daia methods, respectively 
and
W, = 12.57(12.5*Au)
(7.11)
1
W3 =(Au/Ag) "
(7.12)
W;=1^(W + W )
11
(7.13)
Where Ag and Ati are gauged and ungauged site catchment areas, re spec live-y
7.5     Synder Method of Constructing Synthetic Hydrograph
The   Syndcr   method   has   been   used   extensively   to   provide   a   means   of   generating   a   synthetic unit hydrograph. The folJowing steps are used
Step  1-  Determine  the  lag  time,
L      of  the  unit  hydrograph,  The  lag  time  is  the  time  from  the T.
centroid   of   the   excess   rainfall   to   the   io   lhe   hydrograph   peak   Synder   derived   the   following empirical equation for lag time:
Tl = Cl (L.Lta)03
(7.14)
where,
Tl = lag time (In hrs),
L = length along lhe mam channel from outlet to divide (in km),
Lea  =  length  along  ihe  mam  channel  from  the  outlet  1q   the  point  opposite  the  cafchment area centroid in km, and
Ct   =   an   empirical   coeflicent   ranging   from   1.36   to   1.66.   For   Ethiopian   condition,   Cl   can be estimated as: Ct = 1 + 0.33x S'0’
S = slope of the mam stream,
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt LtdArJ-nOeilessa. [rrinatiM Project
Meteorological and Hydrological Aspects
Step 3' Determination of hydrograph duralron. Ths relationship developed by Synder for the duration oi lhe excess ram fail, Tr in hours, is a funclipn of Urn lag time computed above.
nay zoo?
T R - T /5.5
L
(5-15)
This  results  in an initial value tor of TJS-S. However, a relationship has  been deve'oped to adjust the computed lag time for older durations. This  is  necessary  because the equation above results  m in-con ven-a n1 values  of unit hydrograph duration. The adfustmeni relationship is;
T (adj) = T  + 0.25(T
L
l                           Rm
-T)
r
(7,16}
where Ti(adj} is the adjusted lag lime for lhe new duration, TR(,
The unit peak, discharge can be determined from the following equation Up = (V2940)x(0.94 - la/P)x(6.t>0 - In Tc)14
where
Up = unit peak discharge (in inVsWfmm).
Tc - time of concentration (in hrs).
The peak discharge Qp is computed from:
Op - Up A. (P - 0 2S/ 7(?4Q.BS)
and the time from rise of the hydrograph to the peak, Tp, is computed from
(7 17)
(7 10)
Tp - 0 5TfttJ
+ T (ad|)
L
(5.19)
Finally, the hydrograph can tie constructed using T/Tp and Q/Q  values presented in fabfe C5
p
56
Water Works Design & Supervision Enterprise
In Associate with lawonttoental Consultants a nd Technocrats Pvt LtdDedesss Irrigation Project
Meteorological and Hydrological Aspects 
May 2M?
Tables  5  1  to  5  3  show  csli  mated  mean  floods  at  seven  relatively  large  ciithmenis  crossing  the command area from 1hc left and nijht hank directions.
Table 5,1 Location of Proposed Cross Drainages and Catchment Characteristics
Cnc/rffj- dTAf
Area          Stream i.L'll£[tl
Max- Elev \fjn_ Kiev.
Slrrarn
Slope
C H.lor
Rahonul
Mech&di
CN
5CS Method
|km‘)     Lm) (m«|)
Im ash
(%)
1       CDR-16     27.IJ          15.50      2460          1336       0.0725          0.24               71
2       CDR-19       40,25     13.50      2360          1339        0.0756          0.24               71
3      CDR-28        33.00     17.40      2480          1338       0.0656          0.23               71
4        CDL-3         29.60       9.00      17«0          1340       O.W89          0.22               71
5       CDL-25       300.00      44 00      2480          1335       0.0260          0.21                70
6       CDL-28        61.00     27.00      1900          1335        0.0209          0.21               70
7       CDL-33        70.00     17 50      1990          1330       0.0377          0.22               71
Table 5.2 Characteristics of Flood Hydrographs
Cadrm-
iwr
Base
Flow
Ct
i‘c   (lime of cone.
/>
T«
ii(ad[)
—
Tjif atib
Ous)
in
lkm.i
Im 7s)
(hrs)
Ihrs)          (hrsj
Ihrs)
(hrs)
______
I      CDR-16      0.935        1 43         1.50        0.27        6.32          6 15             6.76            90 95
2     CDR-19      1337        1.43         1.33        0.24        5 80          5.65             6.19            89.39
3     CDR-2S      1.137        I 43         1-71        0.31        6.81           6.62             7.32            92.43
4       CDL-3       1 020       1.45         I-15        0.21        4 63           4.49             4.97            85.88
5     CDI.-25       10 34        I 48         4.98         0.90       12.62         12.06           14.09          109.87
6     CDL-28       2.102        1 49        3.72        0.68        9.48           9.06            10.58          100.44
7     CDL-33       2.412        1.46        2 12        0.39        7 03          6.79             7.66            lJ3O9
57
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt. LtdV
I I
■
I
Arjo Dedtsss Irrigation Project
Meteoroiogical anti Hydrological Aspects 
Table 5.3 Estimated Average Moods
May 2007
Cachtn«nt
Q(O
kjEiOnaF
Method
Q(21
SOS
Method
Q|3l
Admuju'%
Method
Qavjg
(Wrtyhted
Average 1
Unit
Runoff
(M
(hr)
(tarnrlir))
(li/vlcm')
■
■
CDR-16
CDR-19
CDR-2B
CDL-3
34.94
1898
30.37
10.35
55 45
12 32
37.95
43.2S
127.43
35.63
62.30
2t 15
CD1 -25
a
CDL-28
CDL-33
23.20
90.45
22.24
37.56
10.72
9.93
50.25
16,48
18.14
?O3 7.T9
6S7
78i
264
559
Hi
i
i
i
i
i
i
i
i
i
i
i
i
i
Waler Worts Design it Supervision Enterprise
Iq Associate wth JmercQDtluentaj and Tethnocmts m Lu_Arjo Dedessa Irrtgitlati Project Meteorological and Hydrological Aspects
8 FLOOD FREQUENCY ANALYSIS 8.1     introduction
May 200?
In flood frequency  analysis, the abjective is  to estimate a flood magnitude corresponding to any required return period of occurrence The resulting relationship between magnitude and return period is  referred as  the Q-T relationship Return period, T. may  be defined as  the time-interval (on the average) for which a particular flood having magnitude Qr {also known as  qunatife) is expected la be exceeded.
A  reliable  estimate  of  the  entire  Q-T  relationship  cannot  be  obtained  from  small  samples  of  at- sito   dala.   The   benefits   of   regionalizalipn   m   flood   frequency   analysis   have   been   recognized   3t toast   since   the   work   of   Delrymple   {I960).   Nowadays,   lhe   regional   izatton   approach   to   flood frequency analysis (particularly the mdex-flood method) is becoming more popular
An essenliaf prerequisite for the index-flood method 13 the standardization of the flood dala from sites  with different flood magnitudes. The most common praclice used also in this  stLHjy, is to standardize data by division by an esiimate of the at-sile mean, thus:
Xi - Qi.'Qm
(8-U
Where   Xi   is   the   ilh   standardized  flaw,  Qi  is  the  i"'  annual  maximum  flaw.  Qm  is  me   average value of al-site annual maximum flow series.
Then 1he quanhle QT is estimated as
Ot =
Om.XT
(3 j)
Thus,  the  mean  annual  Hood  is  the  index-flood,  The  parameters  of  the  distnbution  of  X  are oblamed from the combined sei of regional data
In   this   study,   iwo   d.siribulions   have   been   used   for   flood   frequency   analysis,   These   distributions are:
(a)        Generalized Exireme Value (GEV) distnbuiion (Jenkinson 1969}
(b)        Log-Logistic (LLG) dislnbution (Ahmed et al., 1980)
$9
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Ptl Ltd.Arjci Derf Essa tmgatlOQ Project
Meteorological and Hydrological Aspects 
8.2 Estimation of Probability Weighted Moments
■?—-'^L  —
a
P obabiliiy   w&ghled
r
momenls   (PWM)   are   useful   for   estimating   the   parameters   d1   distributions 
whose inverse forms  can explicitly  be defined such as  GEV and LLG {Greenwood. el. Al., 1979. and Hosking, 19&6). Accordingly, probability  weighted moments  (PWMs) for unbiased sample Estimates can be calculated as:
N
01** = . IWX^I -F^
i=1
(8 3)
where
Xi < flood having ranked order of i
Fi = (i - 0.35)fN = plotting position of the flh ranked flood
N = record tengih
The regionally averaged probability weighted moments were computed as follows:
1.  The standardised PWMs were computed for each sile as
Xi - OVQni
where Xi is the i,n standardized flow. Qi is lhe i" ranked flow and Qm is the average of the data se1
2.      For each annual maximum flood record the first two probability weighted moments, PWMs, i.e. ruia, k - 1 and 2) were computed using Equation (1)
3 For each k, weighted average values of PWMs over M sites included m the region were calculated asfo'lows;
M
E Xi.Nj.fmuM
M s _J2l-----------------------------------=
lh
(8.4)
M
i X,.N|
1-1
These M10k values were then ireated exactly as sample estimates cl PWMs for the regional standardized annual maximum flood population LLG and GEV were filled to the standardized regional PWMs.
Water Works Design & Supervision Enterprise
In Associate with Iutercontlnentai Consultants and Technocrats p^t. LtdAf jo Dedessa Irrigation Project
Meteorological and Hydrological Aspects 
PWMs             Ml GO- 1 MOO
Midi- 0.411964
M1O2 = 0.250375
8.3 Generalized Extreme Value Distribution
sow
Jenkison (1M9) ml reduced the Generalized Extreme Value (GEV) distribution for modeling
f’-oeds  11  has  become  mare  important  in  hydrology  since  it  was  rccommend&d  by  NERO  (1975) for modeling annual maximum streamflows of Bnlish rivers.
The GEV distribution is defined as
X= u * (a/k) (1-(4n F)T}
(86)
The shape parameter k, can be esiimated as.
k= 7.659 C + 2.9554 C?
(8.7)
where
-___0^12} - M-.gij____ - In 2
{2 Mio»-€.Miqii+3.MI,oi) in 3
the  scale  parameter
a — k-lMta — 2-Mim)
0’2*)T(1+k)
and th& tacaiion parameter u = MlW- (afkj.fi -| (1+k)}
GEV Parameters               C =      -0.00061 Gama =        1.0023
u = 0.879426 a - 0.253011
Jt =       -0,004 fl J 8.4 Lag-Lcgistic Distribution
16.8}
Water Works Design t Supervision Enterprise
I» tasotMl MU, interamlnentai Cottsullants and Technocrats Pvt. Ltd.
.ml       J j drArjn-Dedessa IrtltiUou Project
Meteorological and Hydrological Aspects
Log-Logisitc {LLG) distribution was introduced for flood frequency analysis by Ahmed et al. The LLG distribution is defined as;
Mi_Y 2007
—■— ■■■
X= a * b.{Fr(l-F))c
The parameters c, b, and a can be estimated as follows. The shape parameter.
(a.11)
c -
4
i  fi. kJ i«j2
(8.12)
(he scale parameter
b=
and the location parameter
Mifii
C.G
(8.13)
a  -  M'm   ~  b.
G
{&.14)
where
G= . s cj/sifirt c)
(a 15)
LLG Paameters
6=
1051033
a = -0.01767
b = O.36S257
C= 0.773074
0.5 Regionally averaged quantiles
Generally, the differences between estimates of standardized distributions increases with increase in return periods in ail observed for the large return peripds where LLG distribution r
quantiles by GEV and LLG cases dear differences are
gwes larger quantiles compared io
6EV    dislnbuaon.    Estimated    Hood    quantile.    based    on    GEV    and    LLG    d’sl^L's    erB      ^sentM in Tables 8 1 and 8,2, respectively.
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consultants and Technocrats Pvt, Ltd
62ArJoUedessa Irrigation Project Meteorological and Hydrological Aspects
May 2007
Log’Logistic  (LLG)  disirrbubon  was  introduced  for  flood  frequency  analysis  by  Ahmed  et  al (1908),
The LLG distribution is defined as;
X = a * b.(F/(1-F)}c
The parameters c. b, and a can be estimated as follows. The shape parameter
C“ Mit>9*6Mipj tfi.M, iq Mioo-2.MiQ.t
the scale parameter
b=            Myqr2.Mwn 
c.G
and the location parameter
a  -  Miop  -  b.  G
where
G= . n cysimr.c)
LLG Paameiera G= 1.051033
a= -0.01707
b~ 0.958257
c- 0.173014
8.5    Regionally averaged quantiles
(8.11)
(8.12)
(8.13)
(8.14)
(8.15)
Generally, the differences  between estimates  of standardized quantiles  by  GEV and LLG distributions  increases  with increase in return penods. In at cases  dear drtlerences  are observed for the large return periods  where LLG dsWtobon gms  larger quant.les  compared to GEV distribution. Estimated flood quantiles  based on GEV and LLG distnbut.ons  are presented in Tables 8.1 and 8.2. respectively.
62
Water Works Design & Supervision Enterprise
tn Associate with IntereontfnenUJ Consultants and Technocrats Pvt Ltd.Bf—<
ArJO Mess* Irrtfition Project
Meteorological and Hydrological Aspects 
M*y 2007
'
— 
___ _. ww ■ -■■» —
8,6    Choice of Distribution
Robustness  as  a criteria has  receded widespread attention few choice of disiribuhon for an annual maximum flood (AMF). Robustness  is  assumed to test whether a distribution and method of parameter estimation, considered jointly, are insensitive io departures  rrom assumptions  made m their use. In this  regard. LLG.'PWM has  bean found to be more robust than GEV.'PWM (Admasu. 1989).
Often, a compromise has  id be reached between flexibility  and sensitivity  to ouihers. One may need to compromise on some kind of rmd-way  solution. The compromise could be to use a Ihree-pgrameter distribution such as  GEV and LLG. However, for this  purpose. LLG has  been found la be more attractive than GEV.
In a ddition. L LG i s t ess s ensitive (compared r o G EV} t o c hanges e n ! ha s malt v al ues o f t he annual maximum floods  Therefore, LLG/PWM is  better than GEV.'PWM for modeling AM samples that display a dog-leg shape when plotted on probability paper.
In general. LLG/PWM has  been found io be more appropriate for modeling annual maximum Hoods  (AMF) compared 10 ocher distributions. Therefore. LLGfPWM has  been applied for estimating design floods required fry the protect.
Thus, based on probability  weighted moments  method and using LLW distribution on a regional flood frequency  approach the return penod floods  have been arrived at for the proposed dam site. The monetary  peaks  discharges  at various  levels  ol probability  of exceedance (return periods) are summarized below.
10 yr return period flood = 575 m’/sec
20 yr reiurn period flood = 654 m'Jsec 
5(1 yr relum period flood = T/lm^sec
100 yr return period flood = 8?lm rsec
500 yr return period flood - 1155 m^sec 1000 yr reiurn period flood = 1303 m\'sec tOOOO yr return period flood = I948m fsec
J
a
61
Water Works Design & Supervision Enterprise
to Associate with Intercontinental Consultants and Technocrats Pvt. Ltd4rjo Dcdessa JrrlpAtlOC Project
Meteorological and Hydrological Aspects 
Table 6-i Estimated Flood Quantiles 8ased on GEV Distributton
May 2007
I.               ■        -
—
T
Return
period
xt
Grosvth
factor
Afaart Maz. Daily Discharge                       Momentary PeaJf
Gauging
Sue (11-
Gtiugng
Site I2i
Wama at
Junction
flam
■site
Gaug-ng
SiteH i
Gauging
. Srte (2j
years      (ratio!      . r .s         m/s.         (nv/sj    (mVs)     (mVs) |
'/Jama at
Junction t site
■:rnJ/5i      irn3/s)
2           0 95        670          214          238        354         788           272           264           392
5           1.2-3       669          278          309        460        1D22         353           342           509
10           1 42      1001         320          356        530        1178        406           395           586
20          1 60       1129         361          402         597        1329         45B           445          661
50           1.63       1296         414          459        686        152E         526           505           759
100          201        1422         455          505        752        1674         577           559           833
200 2 19 1549 495 550 619
500 2 43 1716 549 610 90S
1000 2.61 1644 589 655 975
2000 2 79 1972 631 700 1043 2321 801 776 1155
5000 3 03 2143 685 761 1134 2522 870 842 1255
1B22         629           609          507
2020          697          S76          1005
2170          749           726          1080
££S*SS.___ 7       x.. ™ W 257
TOOOD   — 3 —   22— J 4
2273         727         808        1203      2675          923           895         1331
374       832           287           278           414
Wote The analysis is based an regional ftocd frequency analysis based on General Extreme Vatoe
r1icrr T"^
distebufion ^parameters estimated t>y pratmbMy ^ghted mamnnts method
, 1 rfi■ ii ! LJi.r.l^
rr
-id. - —r i. . — . l ■ ■ .
■_
Table 8.2 Estimated Flood Quantiles 6ased on LLG Distribution
T
Retu’-n
E-e^cd
Xt
Growth
factor
Mean  J Gauging Site
(h1)X     ■
'az. Daily Dis charge GaugiGngauWgamrgnyWaat rn;) at Dam
(years) (ratio}
2             0 95
5             1.21
10            1 39
20            1 58
-   -- (rrrfc)
672
854
982
1118
50            1.86           1317
100            21             1488
200           2.38            1630
500           2 79            1972
site 356
452 519 591 697 787 8flS
Afomarttery Peak
Gauging Gauging Wam& a1 ' Dam
. Site ii S46.2- Junction SJf4I
791
1005
1156
1315
1550
1751
1977
1003
3 15
2225
2000
3.55
2511
5000
4 17
2947
10000
4.71
3326
Sep i2i I Junction l.m /S)   ’   .'.--II’ .
215 273 314 357 421 476 537 630 711 503 942 1063
1043       2320
1177       2619
1329       2956
1559       3468
1760     3915
226           251          374
Aftjfc; TJJB analysis is (Msed onreg^^i'floM irequenCT^anaivsS^iH mlft parameters estimated by pr&batewy weighted mcmente- metecd
Avfi/age
1
707
832
273
347
399
454
535
604
582
800
903
1020
1196
l 35D
287
264
336
386
439
517
564
662
776
676
987
1159
1309
278
394
500
575
654
771
871
984
1155
1383
1471
1726
194a
4’ 14
°9^9TsfJc (IL GJ disfr>terf»n
Water Works Design & Supervision Enterprise
In Associate wltb Intercontinental Consult^ and Technocrats Pvt. tldArjcBedessa Irrigation Project
Meteorological and Hydrological Aspects 9. PROBABLE MAXIMUM FLOOD
May 2007
The   probaWe   maximum   flood   is   defmed   as   lhe   most   severe   flood   considered   reasonably possible lo occur It is cuslpmanly oota.necf oy using unrt hydrographs and rainfall information.
Annex  C4 gives  the recommended reservoir flood standards  for three main categories  ol reservoirs. Category  A has  the most stringent standards, since lor such a reservoir a breach in the dam would endanger the lives  of people congregated in a lawn or village downstream. The worsl camjilions  are envisaged, lire spitiway  already  taking lhe average daily  inflow when the probable maximum fluod iP'MFj arrives  and Lhe wave surcharge allowance must be for heights greater than 0.6 m. Categories B and C have decreasing standard requirements.
In Elhmpia. the sludy  ol design Hoods  on the basis  of PMF requires  further investigation The challenging problem is  particularly  thai of storm rainfall and lhe varying temporal pattern of intensities  throughout a storm’s  duration, the occurrence of the Desk  intensity  is  a variable lo be considered for further study  at nanonal revel. The initial state of lhe calchmenl is  also of great significance in rhe generation of an extreme flood. A thorough knowledge of a catchment and of Its  varying responses  during adverse conditions  is  essential for an engineering hydrologist to evaluate design floods  and such situation need to be investigated ar an institute level.
However. In such a situation where there <$ maximum rainfall data, Hersfield (1961) suggests 
rhe   use   of   following   equation   io
eS irnate
|         24-hr   PMP   in   region   $o   as   te   superimpose   ,t   on
design unit hydrograph to give the PMF PMP  = Pm +K.Sn = Pm (1+K CV)
m
{9 1}
Where
PMPji - 24-hr probable maximum precipnaucn
Pm = mean ol the 24-hr annual maximum over the pencxj of record
$n = slandanj deviation of lhe 24-hr annual maximum
CV = Pm/Sn = coefficient of vanaton
K = a constant equal to 15
Water Works Design & Supervision Enterprise
in Associate with Intercontinental CnnHanis and Technocrats PvtArjo Dedessa Irrigation Project Meteorological and Hydrological Aspects 
May zw
The mean annual maximum 24-hr rainfall for Bedele and Jimma are 55.5 mm and 51,3 mm,
respectively, and also the coefficient of variation for Bedele and Jimma are 0. 198 and 0.201.
respectively. For the Arjo Dedessa dam catchment
Pm = (55.5+51.3^2 = 53,4 mm
CV = (0.193+0.201}/2 = 0.20
Sn = 0.20x 53 4 = 10.68
K = 15
Then
PMPja = Pm *K.Sn
■ Pm(1+K,CV)
4 QI ‘Pm
= 4 01x53.4 = 214 mntfday
Total volume ol daily rainfall
Vp= A. PMPj« = 5310*214 = 1129 5 MmJ
Assuming   runoff   coefficient   C   that   corresponds   to   the   occurrence   of   continuous   rainfall   1c   be 0 68, the estimated rainfall depth that produces probable maximum flood becomes
Vpe=C.Vp= 0.6H’1129.5 = T68.5 Mm3
Using 1he catchment characteristics given in Table 12.1 and applying me dimensionless hydrograph given by Table C4 the Hood peak component due to the probable maximum rainfall becomes 3502 m fe. Assuming ihe a base flow of 188 m /s the total peak flood
s
3
becomes:
Qp - base flow + peak due to storm = 18B + 3502 - 3690 rir/s
Cumulative   volumes   of   Probable   Maximum   FFoods   (PMF}   derived   from   probable   maximum   24
hr  rainfall  ,s  g>ven  by  Table  9.1  while  design  Hood  hydrograph  derived  from  estimated  PMF  is given by 9.2.
Water Works Design & Supervision Enterprise
In Associate with intercontinental Consultants and Technocrats Pvt Ltd.
6ftAijo DedEssa Irrigation Project
Meteorological and Hydrological Aspects
Table 9.1: Table Curnulalive Volume of Probable Maximum Flood
Ma/ 2007
T
Time
(hrs)
Cum. Volume        Time
Cum. Volume       Time
—
0.00       O.ODO        0.00
fl.50        0.440         0.05
9.00        2 936          038
13.50 9.339 r 22 1300 21.87 2.85
22.50 42.15 5.48
(Mm3!
r  (%)
(hrs)
(Mm3)  Lw
. (bra)
Cum. Volume
(Mm3) (%)
103.50        667 6        89.5       207 00         765.3           99.6
108.00       698 7         90.9       211.50         765.8           99.6
112 50       708.3         92.2       216. DO      766.1            99.7
117 00       716.4        93 2       220.50         766 5           99.7
121 50        723 2        94.1       225.00         766.8           99.8
126 00       729.1         94.9       229 50        767.1            99.8
27.00       71.51         9-37       130.50        734.4         95.6        234 00        767.3           99.8
31.50       11D.5         14.4       13500         739.0        96 2        238 50        767.5            999
36.00       157 6         20.5        139.60        743.0        96.7       243.00        767.7           99.9
40.50       210.4         27.4        144 00        746.5        97 7        24 7.50       767.9           99.9
45.00 266.4 34.7
49.50       322.6         42 0
54.00       376.4          49 0
58.50       426.4          55.5
63.00 471.6 67 4
67 50 511.8 66.6
72.00 546.4 77.7
76.50 576.0 75.0
81 DO 601.7 78.3
85.50 623 9 81.2
146.50 749.3 97.5 252.00 768.1 99.9
153.00       751.7        97.8        256.50        768.2           100.0
157.50       753.6        98.1       261.00        768 3           100.0
162.00       755.5        98.3       265.50         768.4           100.0
166.50       757.2        98.5       270.00         763.5           100.0
171.00       758.6         98 7        274 50        768.5          ! 00.0
175.50       759.9        98.9
180.00      761.0        99.0
184.50       762 0        99.2
189.00      762 9        99.3
90.00       643 4          83.7       193.50       763 6        99 4
94.50      660.4         85.9       198.00       764 3         994
99 00 675.1 87 9 202 50 764 8 99.5
Water Works Design & Supervision Enterprise
in Associate with toKrttmtineDUil Consultants and Technocrats PVL Ltd.
67■irjs iJedeEss Irrl^allnn Project
Meteorological and Hydrological Aspects
Table 9.2 Design Flood Hydrograph Derived from Estimated PMF
1-----------
May
Ti
fhfi
Qi Ti Qi
/hfj
Ti
Qi             n I   Qr
Ti
a>
M
flirt .
OK          TB0       45.00      3690    90.00       1309
135.00     451       180 00        251
2.25         216       47.25      3555     92.25      1239      137.25     433        182.25        248
4.50 241 49 50 3620 94.50 T169 139.50 419
6.75 339 51 75 3515 96 75 1099 14175 402
9.00 451 54.00 3410 99.00 1028 144.00 384
11 25 573 56 25 3270 101 25 958 145.25 367
13.50 748
15.75 958
58 50      3130     103.50      923       148.50     349
184 50 244
186.75 241
189.00 237
191 25 234
193.50 230
60.75      2990    105.75      853       150.75     332       195 75         230
1800        1169        6300      2815    108 00      810       153.00     314       198.00         227
20.25       1449      65 25      2574     110.25      783       155 25     297      200.25         223
| 22.50        1694      67.50      2499     112.50      748       157.50     314       202.50         220
24.75       2009       69.75      2324     114 75      678       159.75     307       204 75         220
27.00       2289       72.00      2149     117.90      643       162 00     300       207 DO       216
29.25       2604       74.25      2009     119.25      608       164.25     290       209 25         216
31.50       2865       76 50      1904    121.50      573       186 50     283       211,50         213
33 75 3095 78 75 1754 123 75 552
36.00 3305 81.00 1659 126.00 531
168.75 279 213 75 213
171.00 272 216. DD 209
38.25       3445       83.25      1554     128.25      514        17325     269        218 25        209
40 50       3585
85.50      1484     130.50      496       175 50     262        220.50        209
42.75       3655 1——
£7 75 1379 132.75 472 177.75 258
1
222 75         206
Water Works Design & Supervision Enterprise
In Associate with intercanlinfint.il Consultants and Technocrats Pvt Ltd,Ar]c Dedessa Irrigation Project Meteorological and Hydrological Aspects 10 SEDIMENT ANALYSIS
10.1   Estimation of Sediment yield
May 2007
Suspended    sediment    data    from    Stations    14001,    14Q14    and    14005    were    obtained.    These discharges are given in Annex E5. Suspended concentration rates varying between 45 mg At to
1670 mg/il were observed from Didessg river..
Relationships  between water discharge and sedimenl toads  at various  sites  in the region are presented in Table 10.1. Absite and regional approach has  been used to to estimate sediment rates  from the estimated streamflows  at the dam site Accordingly, the farlowing relationship has been derived;
Gs = 0.07&Q1s
(10.1}
Where
Gs = sediment toad (in gm)
Q = monthly mean discharge (in It/s/km*).
Careful assessment regarding reservoir sedimentation will be required in the site as the life oi
1he storage created by a dam is dependant of the sedimentation silualion Accordingly 
reservoir planning will include assessment of the probable rale of sedimentation in order Io
predict the useful life of ihe proposed reservoir
In estimating reservoir sedimentation, materials  originating as  bed toad will be assumed to have a density  of 1.4 gmfcc  ano material earned in suspension will oe assumed lo have a density  of 1.2 grrVcc, The ben load at the dam sites  shall be assumed to be 15 percenl of lhe suspended load
Monthly   total   sediment   toad   (suspended   and   bed   toad)   and   accumulated   total   sediment   load   at the reservoir site are given by Table 10.2 arid 10.3, respectively,
Water Works Design & Supervision Enterprise
In Associate with Intercendnenial Consultants and Technocnits Pvt Ltd.Ar jo Dodessa Irrigation FtflJ-erl
Meteorological and Hydrological Aspects 1 * ■■ r ~~
_
10.2 Distribution of sediment in the reservoir
May 200?
■*———
So far the Sediment load likely  to deposit in rhe reservoir has  been estimated But estimating Ifie sedimeni inflow to the reservoir is  not enough as  how high rhe sediment wdl accumulate in lhe reservoir is  also important, Accordingly. Area-Increment method has  been used for th’S purpose. The method is expressed as:
(10,2)
Where
V$ = Ao(H-Ho) + Vo
Vs = sediment volume to be distributed
Vo = sediment below the new 2ero elevation
H - original reservoir depih from the stream bed level
Ho heigld 1o which the reservoir is completely filled with sediment, i.e. = height of lhe new zero elevation
Ap surface areas pf rhe reservoir at lhe new zero eievaiion and is the = area correction factor.
The results sp obtemed from the analysis of distribution of sediment in me Arjo-Dedessa Reservoir are given in Table 10.4.
Table 10.1 Relationships between waler discharge and sediman! load
Station
Area
(kmz)
Module Loss Vales of C in:
10’Vyr Ukm^y Qs =C.(Qwj15
JOOS Guder at Guder
4007 Little Anger near Gulin
4Q05 Dabana near Abasina
4002 Anagar near Meqemte
6002 Abbay at Sudan Border
Ar jo Dedessa Darn site
524            77           90           0.025 1975          176             89           0.096 2581          453           157           0.059 4674          702           150          0.051
172254 335170           1946           0.165 5278        776         f47         0.078
Waterworks Design & Supervision Enterprise
hi Associate with Intermtinwrtal Consultants and Technocrats Py , Ltd.
tArjaffedessa tnrigatton Project Meteorological and Hydrological Aspects
May 2007
Table 10-2: Monthly Total Sediment Load at the Reservoir Site
3
(tn 1000 m )_________________ __________________ Jan Fob March April May June July Aug Sep Oct
Avg     2.48 1.33      1.14 Stddev    1.71 1.01     1.11
cv      3.63 4.01     5.15 Skew    7.36 6 29     8. S3
1.71 4,51 27.2 131.1 248.5 211 5
172 4.2 17.6 62.72 96. 19 92.6
5  31  4.91  3  42  2  528  2.086  2.311
7.54 11.4 7.48 3.696 0.678 3.509
120.1
99.01
4.349
7.051
19 29 6.87 14.7 4.95
4 024 3.8 1092 8.77
Nov Doc Annual
775.6
304.5
2.07
4.57
r-----
Dec
Annual
Table to 3 Accumulated Total Sediment Load at lhe Reservoir Site
25
50
0 0 6 0.03 0.03 0 04 0,11 O.08
f'rrj Mm')                                3 28           6,2 5 29         3,00  0 40
75
Y»»rs
100
125
0.12 0.07 0.06 0.09 0.23 1.36
|jin jwai^AprillMay jjune jjuty |auq 0.19 0 t 0 0.09 0 1 3 0 34 2.D4
0.25 0 13 0.11 0.17 0 45 2.72
0.31 0.17 0 14 0 21 0.56 3.40
150
0.37 0,20 0.17 0.26 0.68 4 08
175 0.43 0 23 0.20 0.30 079 476
200 0.50 0.27 0 23 0.34 0.90 5.44
6 6          12,4 10 6     [Oct Nov
6.0  0 96 9.8          16.6 15,9           9.0  1 45
13.1     24.B     21.1         12.0  1.93 16.4         31.1 26 4         15.0 2.41 19 7         37,3 317          18.0  2 89 22.9          43.5 37.0         21.0  3.38
26.2     497      42 3         24.0  3.ao
017
19.39 0.34
38.7B
0 52
58.17
0 69      77 56
0 86      96.95
103
116.3
1 20
135.7 1.37
155 1 ——_____
71
Water Works Design & Supervision Enterprise
mm
lnl
«
M11Itall[al CoiMIa „KAlJo tledfSSA [jTlgadon Project
Meteorological and Hydrological Aspects_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  May w Table TO.4: DistObuliOrt of Sediment in the Arjo Dedessa Reservoir
50 ycurt sediment foad
Ho = 2.03m
_ Afl_« f.52Mn?J
14W yeJr'S iedirrurnf I'tucf
Hoi 3.42 m
_J____________ Ao = 3.15 Mm'
fifc#
OwpiVuJ
■WVi
■MmJl
G7Tgln#r
cjpnc/l
■Al
DtfptlS
l**V
JetfitM
nt
wpIt/CHf
r?rvr.«»d
■rpf
,W!
R-f-FTJ-td
trip* rif
EJfv
. Al
I'm <i<i
Onpwnji' CvAgin-ji
*<** rtpKifr
.MUti’i , .V1m'.-
CM-pth
__tDtL
■Sedirnrrtf
rd.Mjrnv
ffevue
J >r?j
‘Afrn’l
cjyucify
iMrn';
LI
2        3        4    rd            6         7       1         2         3         4            5          6           7
1346 56 76 629.6 27 38 7 55.24 591.1 1346 56 76 629 8 27 77.4 53.61 552 4
1343 46.13 466 4 24 34.2 46.61 432 2 1343 48.13 466,4 24 68 44.98 398.4
1340 39 92 331 8   21     29.6   38 41  302.2  1340 39.92 331 8     21       56 6    36.78    273.3
133? 32.17   224     1B    25.1   30.66  198.9 1337 32 17 224         18       49 1    29 03    174 8
1334  24.93  140 7   15    20.5 23.4 T   120 2 t334 24 93 140 7       iS         39 7 21.78       101
1331  16 24 79.64   12      16    16 72  63 87 1331 18.24 79.64     12        302     16 09     49.4
1326 12.19 38 24    9      11 4   10.68  26.82  1326 12.19 38.24      9          20.8 9.046      17.44
1325 6 911  13.6     6      6.88    5395  6.724 1325 6.911 13.6        6          11 4 3.765      2.239
1322 2 619 2.322     3     2.33
150 years sediment load Ho = 4.69 m
Ao = 4.90 Atm2
1322 2.619 2 322      3        1.92
200 years sediment load Ho - 5.89 m
Ao = 6.73 Mm1
-
Origin^
CVii/yi*! rjpjof
Ml
SecMnv
Etev
f-m ■Si'
flrviseJ
cjpiei'r
JU*J           7   j
an* tap*vitVDtpth
1
y
,MmJ.
-J ■Wr.r'i
J-
,-Wffl1
. 2       L.3          4 I 5        . 6
7
Lj 2
, ,m.
J r**      ■■4p»city
ijW.nr
2
3
5   EjsZ
jMrt,’. 1---
7
56.76 629.8    27     116   51.86  513.3
40.13 466.4    24     102   43.24  364.6
39.92 331.8   21     37.1   35 03  244,7
32.17 224 18 72.4 27.28 151.5 24 93 140.7 15 57,7 20.03 82.96 18.24 79.64 12 43 13 34 36 6 12.19 38.24 9 28.4 7.297 9 887 6.911 13.6 6 13 7
1346 56,76
1343 4&.13
1340 39 92
1337 32.17
1334 24,93
1331 18.24
529.8 27 155 50 02 474 7
466.4 24 135 41.4 331.5
331.3 21 115 33.19 217.1
224 18 94 5 25.44 129.4
140.7
79.64
15       74.3   18.19      66 37
1326 12.19 33.24 1325 6 911 13 6
12
9
6      13.7
54 1 11 5 25.52
33.9 5.457 4 326
-J
Water Works Design & Supervision Enterprise ‘ la Associate with fniercontlnenul Consultants and Ttchnacrats Pvt. ltd*rjo iwtssa lrriffatlon Project
Meteorological and Hydrological Aspects
11. WATER QUALITY
May 2007
The water quality status of the Dedessa nver is evaluated using the data collected front MoWR database, Abbay  River &asm Master Plan Study  Report { 1990}. The samples  were taken as 
□an  d!  the  supporting  measurement  for  the  aquatic  study  and  appear  to  represent  the  only available   data   an   water   quality   within   the   catchment.   Table   11.1   shows   water   quality measurements  laken  tor  Dedessa  at  two  sites.  The  samples  were  taken  as  part  of  1he supporting measurement For the aquatic sludy and appear to represent the only available data on  water  quality  wiihin  the  catchment  The  samples  shown  in  Table  ill  were  taken  after  the start  of  lhe  rainy  season  and  presumably  all  tributanes  of  the  river  exhibited  adequate  water quality at lhe time of sampling
Total Dissolved Sofrds fTDS) and Electrical Conductivity (EC)
Total dissolved solids characterized mainly by  major anions and cations are directly related to the electrical conductivity  of the water The low Electrical Conductivity  (EC) and TDS value in general shows  that the waler is  soil in nature and has  tow Salinity, Moreover, the low conductivity is sign of low fertility of the water wnh regard to aquatic life Electrical conductivity (EC) measurements  were very  low al all the sampled sites. EC is  lhe ability  of the water Io conduct etoclric current and directly related to lhe amount of cations and anions in the water
pH
The pH value i$ lhe measure of Lhe concentration of hydrogen (H+) and hydroxyl (OH-) ions in the waler It is io determine the acidity or alkalinity of ine substance.
Sodium and Pofasslum
The Na and K'  reading expressed m terms  ol Sodi-jm Adsorption Ratio (SAR) is  the useful parameter for the evaluation of the waler body  for irrigation purpose For irngaticn waler n 1S important to measure lhe sodium adsorption ratio as follows
SAR = -------------------------- — 
(9.1)
Water Works Design & Supervision Enterprise “
in Associate with Intercontinental ttnsoUanLj andTochnucrats Pvt l edArj u UtdEssa [rrigatton Project Meteorological and Hydrological Aspects
May 2007
The higher lhe SA.R value of the waler the less  suitable wifi be for Irrigation purposes. The maximum computed value among the readings  is  0.29 which is  less  than 10. This  illustrates that lhe water1 is very much suitable lor nrigairon purpose
Chloride
The chloride conceflirahoft of (ho rivers  stipulated in Tallies  11.1 is  very  low (1 0 1q 2.0 al times  al sampling. Hi?nee the parameter was  m conformity  with the standard sei by  EPA (ZSOmgfl for aquatic species).
Table 11,1           Water quality results for sites on the Dedossa river
Sampling
Sample date
et BhcJhPh bridge      al Glmbi ibdrige      Comment
■— 13/06/96             14708/96
Elevation (m asl)                         1300                    1200 IDS (gm/3)                                    20                        20
EC (Osfcm)
so
P H                                                   674
Na"
K' Ca" (mgfl)
3.3
1.9
6.4
Mig** (mg/l)                                  243
CT {mg/l) SAR
1__________ ;uiY I'e'ir Mftinr
1.0
0.29
50
6.97
3.0
2.5
9.6
1.4
20
0.25
N
N
N
H
N
H
N
N
N
study f998/
Water Works Design & Supervisen EnterpdTe- — “ In Assoclatfl with Imflrcon tibial Consults and toftnocrats PvL Ltd
■4Arjfl Dedem Irrigation Project Meieoroioglcai and Hydrological Aspects
12. DESIGN FLOOD
12.1 Synthetic Hydrograph
May W7
Among Sfevaral known methods  of un«t hydrographs. Ihfi one developed by  Syrder 1i-KIBi s most commonly  used The method is  derived from drainage basins  n I he Appalachian Mountain regions  in lhe Untied Slates  ranging in areas  from 25 km to 25.000 km He relations  of unit hydrograph characterishcs  and catchment characteristics  are expressed as lollows
Tp = CKtL.Lc)01
(12.1)
Where
Tp = lag lime from lhe mid point ol lhe ramfail-excess duration Tr Io me
peak of a unit hydrograph (hr).
Cr = coefficient deponding on basin characteristics
Lc - river distance from lhe slanon to rhe pomi of interest nearest the
cantroid of lhe drainage area (krn)
L - river distance from lhe -station Io lhe upstream limits ol the drainage
area |krn]
The  catchment character)sties (such as L. Lc, Area. Slope) o( Cesessa at  Uh?  Ago Oedassa 0am Site .s given by Table 12 1
The U S Sol Conservation Service (SCS) developed a dimension less hydrograph ihai i.as As ordinale values expressed as the dimension less ratio. TiHp Qi is the discharge al any time Ti
The shape of the unit hydrograph dimensionless hydrograph and Tp s the period corresponding Io peak as shown in Annex Table C5 For a given catchment once lhe jalue al Tp is defined using Equations 12 I. the unit hydrograph can be constructed
12.2 Flood Routing Through the Reservoir
The dam is located where Failure may probaWy oe confined to ihe wngatbon command and the dam itself No excesstve toss of human tile would be expected For such condition a deSign Hood corresponding to alO 000 year return penod has been proposed The volume of (tow ,n HXlO-yfear return period Hood hydrograph is about -tOOMm'
Water Works Design & Supervision Enterprise
tn Associate with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjii ftedessa irrteacfoo Project
Meteorological and Hydrological Aspects_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ WA>
The daia used to complete surcharge storage due to the desrgn ftcod and routing calculations were inflow hydrograph for all selected design storms, elevation-storage relations lor proposed storage facility, and stage-discharge relations for ail outlet control structures.
The step-by-step melhod of reservoir routing method has been used The data required for the method IO construct the outflow hydrograph i$- (al the inflow hydrograph, rfyj the elevation- capacity  relation curve oi lhe reservoir, and (c) the outflow elevation curve or the outflow equation
Using these data a design procedure is  used io route the inflow hydrograph through the storage facility  with different surcharge storage and spillway  crest toutlet| geometry  until 1he desired outflow hydrograph has Peen achieved
A spillway wdh ogco shaped crested weir has ooar* assumed Fhe equation generally used for such broad-crested weir is
where
Q = CLH'4
Q    = disctwije, in
C    = broad-erftsted  wear coefficient L     = Ixoad cfBsJed wm lengih. nn H       head ower woir crest, m
(122)
II Ihe UCSi™m adg, „! a ws„ . M romaea M „
,
pw
and ir lte ynco n)
crast  is  as  (real  as  m0   toss  ol  head  d™  to  Incimn.  How  wl  pass  through  m,cal  oaiMh  a, weir crest thus gives an average C value ol 2 2
The following procedures were used io perform routing trough the rSaerVm Qieveloprig ah mll« hydros. stage-tHschatga a™ 1« ths prapospd
facility 
y
$fag_2 Selecting a routing time period. Di. fo provide lhe in I low hydrograph
at least fwe pools on ide n5ing i.mb of
Waterworks Design & Supervision Enterprise
In AuttUie with incontinent Consulunis ami Teehnwrau
M L(dArJfl-DcdEssa irrigation Project Meteorological and Hydrological Aspects
May 2W
Step 3: Us<ng the storage^discharge tfa“a from Step 1 to develop storage characteristics curves that provide varue S (+A) (Q/2). Dt versus stage
Step 4~ Foe a given time interval, 11 and 12 are known Give toe depth of storage or stage. Hi. at toe beginning of that time interval. S1 - (Ol/2}.Dt can be determined from the appropriate storage characteristics curve
Step 6: Determining the value of S2 * (02/2). Di from the following equaVon:
S2 + (Q2/2}.OI = [S1 - (Q1/2}.0l) ♦ [11 + 12X2.01]
where
S2 = storage volume at time 2, m^/sec
Q2 = outflow rate at time 2. mJ/sec
Dt " routing time period, sec
S1 = storage volume at Itme 2, m3
Q1 = outflow rate at tune 1, n?/sec
11  = inflow rate at time 1, mVsec
12  = inflow rale at time 2, m’/sec
SifiP  Enter  the  storage  characteristics  curve  at  the  calculated  value  of  S2  +  (Q2/2)  Dt determined in Step 5 and read off a new depth of water. H2.
Determine m   value of Q2. wmeft corresponds 10 a stage oi H2 determined
e
in Step 6.
using the slage-discharge curve,
Repeal Step 1 through 7 by setting values of 11, Qi SI, and Hl equal to tee previous 12, Q2. S2 and H2. and using a new 12 value. This process is continued unlit the entire inflow hydrograph has been routed through ihe storage basin.
Since Equation (12.3) contains two unknowns, slepwse trial and error procedure is used Results of touieo design Hoods based on LLG distribution. haW-PMF and tulkPMF afe
presented by Table 12.2,. 12.3 and 12 4, respectively. The etevalion - area capacjLy
Qf
the  reservoir  are  shown  in  Figure  12.1,  The  lOOOQyr  return  period  des.gn  inlkw  and   Outriow hydrographs are shown m Figure 12 2. Such inflow and outflow hydrographs for smaller return
Water Works Design & Supervision Enterprise
In Associate with Intercontinental Consulunis and Technocrats Pvt. Ltd.
7?Arjo Dedessa trri^tloD Project Meteorological and Hydrological Aspects
May 2W
periods  like  10.  20,  50  and  100  year  return  periods  are  shown  in  Figure  12.3.  The  average hydrograph of maximum flow at the dam site is available in Figure 12.4
12.3 Routed Design Flood at the Coffer Dam
Velocity Formula
The velocity equation through me pipe outlet »s given by
V = (2gH )
L
9i
(10.4)
where
A = cross-sectional area of barrel (or pipe). V = velocity through the barrel,
Hi - 1ata3 head toss through the barrel. Fk =(1.5 + fUD)VI/2g
L = length of Ihe barrel/pipe
D/4 = R = hydraulic mean radius of the barrel D = diameter of barrei/pipe
V = velocity through the barrel/pipe 7 = coefficient of friction
(12.5)
Manning's Formula
It is one ol the most common formula. winch .s wmmonly used for the analysis of problems ol to* through channel,, but often used for the analys.s of pipe Sow problems too. According to Illis formula the discharge Q through pipes is given Dy:
V = (Fm).D '
1 3 S1<s
(12.0)
Where
V = velocity ihrough Ihe pipe,
r> - Manning’s roughness coeftasnl (a value of 0 .065 has been selected (or old concrete pipe),
O = diameier of (he pipe.
Water Warks Design & Supervision Enterprise ~ to Associate with hjisrcuDtincnial ConsuJianls and Technocrats Pvt. LtdArJtF Dridsts,! Irrlfatlntj Prnjncl Meteorological anti Hydrological ^specLs
Miy W
-*
t ■ "T
—T -
■w
S slope of the hydraulic gradient rsr energy slope hi L
F is constant rnrual fo 0 39685
L - length of I he pipe fm i
h. = heikJ toss 1hroy0h lhe pipe • m i
Equation 1? S can be .jrranged in express the relations for he.Kl loss through i
h. = I |(n.'F) VtD’ Y
Combined Formula
(12 7}
Ccmtuniria Equalion 12 5 and 12 f the aboye fwo expressions for velocity reduced ’«
H <15/2fl*L [(/nF > O ■'  >| } V’
1J
end
■jlvr
V lH.'(l 5/2g + L i(wF>D"Y}.l''■
Q A lH/{l ^g * L ((r F>D"YU
N
r
(rfr 4J .H | r ^Zg r L |(rvF> D "Y)f* 'AJNifo A ii rifiHii i-jclicvi.il unjj of pipe in rn’
02 8>
(12 H (12 101
SubititLttirHf II ■ 11) I ri’j J IJ Bl in tquabun 'Z H -..ill hH tupm-feted lCl '■      (OO7M53+L |OQ415/Z Dz'Yl
i hi io d/ipvj.sm [0.041V/ Y;j"
■J 10 /BV IT’, in (00/0453+I |0<M 157/  ‘ Y'li
RW4JI1S Cd -buiur! dtisign Hf«d n CoMcr Darn or Ago Olde«  n
u    cwr>)1(f j<e prpswiw , 1 ,lCMr.
12 5 Thew revjiH u/e .walabl« lor 10 20 50 dnu 100 r t
t lim prr od Ito-xjs a< .
,q■
x
’Ll rhfl criltr-d lhe .ipi.trjpr-.4n tbmjIV, ■ ixflj h« .nJnpirMi ror deigns.
Water Works Uesiun & Supervision Entrrprlsp
In Assucixtr with Itii+rronimrtiljd CoiuulUnu ,nfl Terlstiwrata M. LidAtjoDedtssa Irrigation Project Meteorological and Hydrological Aspects
_
? U07
Table 12.1 Catchment Characteristics
Arjo Dedessa Catchment
Characteristics
Area (km2)
Length (km}
Centroid distance (km) Max elevation (m asl) Minimum elevation (m asl.) Devalrcn difference (m)
S (m/'m) Ct Tc (hrs)
Tl (hrs)
Tn (hrs}
Dimension
5278
199
141
3012
1315
1697
0.0085
1.53
24.00
33.00
4.40
(hrs)
3800
Tp (hrs)
45.00
Table 12.2 Routed Design Flood at FRL Corresponding to 1352 m (at) flased on LLG distribution
_ L(m)        j Qout (m^s) I             HIEL
Max Surface
Area (Km )
2
50                    871
75                    1031
1 co                  1154
125                   1253
150                   1333
175                   1399
3.97
339
87.06
85.20
3.02                     84.01
2.75
2.54
83.14
82.47
__
(b) Based an Haif-PMF
2.36                     81.91
. Pea* J/rfloLv = .1950 m3/s
Surcharge
Storage iMm3)
1340,1
1288.0
1255.0
1231 4
T2?3 1
1198,3
L L                    Qout (m /s)
3
H(m)
Max Surface Surcharge
1
J
Area (Km ) Storage lMm )
50 798 3 75
75 941 3.19
100 1051 2.84
125 1140 2.58
150 1212 2.38
175 1273 2.22
86.34 84 56
8343
02.61 81.97
81.45
PJir                                — ■i"Tfli
1319.8
12703
1239.1
1216.9
1199 7
1186.0
Water Works Design & Supervision Enterprise
60
In Associate with Intercontinental Consultants and Technocrats pvt. Ltd.Arja-Dcdessa rrrkgaclon Project
Meteonifogjcal and Hydrological Aspects Miy a«P
Based1 on PAfF
L(m)
50
*
Qout I'm /s) H (mJ
Max Surface
Area (Km )
2
Surcharge
Storage (Mm ;
J
I860
6.13
93.95
75 2 DOS 5.29
100 2265 4.73
125 2466 4 32
150                   2826
3 99
175                   2756                     3.71
Peafc /rtfltow = 3650 m3/$
91.28
89.50
88.16
87.10
8624
1539.8
1461.3
1409.5
1371.3
1341.2
13168
Table   12.3   Routed   Design   Flood   at   FRL   Corresponding   to   1555 {a) Based on LLG distribution
(b) Based on HalbPMF
L(m)
Qout (ni^s) _H{m)
J
Max Surface Surcharge
Area (Km;) Storage (Mm i
50
75
100
125
150
175
746
881
988
1075
1148
1208
3.58
3.06
272
2.48
2.30
2.14
55.61
93 98
92.95
92 20
91.63
91.16
1560.6
1527.9
1495.0
1471.6
1453.7
Peak inflow - 1730 m3/s 
_
14392
SI
Water Works Design & Supervision Enterprise "
in locate leuKontlnenml Con.,^
L[(JArjo Dedessa Irrigation Project Meteorological and Hydrological Aspects
(C) Based on PMF
May 2007
L(mj_          Qout (m /s)
3
Max Surface
Area (Km )
z
Surcharge
Storage (Mm )
3
50 1540 5.81
75 1857 5.04
too 2118 4 53
125 2320 4.14
102.52
1811 9
100.13                     1730.7
150 2483
175 2618
3.84
3.59
98.54
97.36
96.41
95.64
1677.1
1637.8
1606 3
1581 3
Peak inflow = 3690 mj/s
Table 12.4 Routed Design Flood at FRL Corresponding to 135Grn
(a) Based on LLG distribution
L (m)            Qout                          H (m)
Max Surface
Area (Km )
2
Surcharge
Storage I’Mmi
50 300 3.75
75 951 3.2i
100 1069 2.87
125 1165 2.62
150 1248 2.42
175 1314 2 27
99.11
97 49
96.45
95.71
95.12
94.65
Peak iflfajw = 7950 m3/s
1693.0
1637 i
1602.0
1577.0
1557.7
1 54? 0
(b) Based on Half-PMF
LW
Qout (m /s i
3
Max Surface
2                       Surcharge
735
869
975
1061
1134
1195
3.55
3.03
2.70
2.46
2.28
2 13
Area :Km )
98.49
96 93
95 94
95 23 94.68
___ 94.23
Storage (Mm3)
1671.5
1618.2
1584.9
1561.2
1543 1
1528.5
r                 ^.Jrvrrr - ri-OUfHJ/5
Water Works Design & Supervision Enterprise
to Associate with Intercontinental Consultants and Technocrats Pvt. Itn
i              ML
LArjo Dedcssa Jnigadfln Prujcct Meteorological and Hydrological Aspects
(c) Based on PMF
way 2007
. Hrn)
Ctou!
Max Surface
2
Area (Km )
50 1515 575
75 1836 4 99
100 2088 4.48
12S 2289 4.11
150 2453 3.81
175 2588 3,56
105.09
102.81
101.30
100.17
99.28
98.53
Surcharge
5
Storage iMm' )
1905.2
1823.3
1769.3
1729.8
1698.5
16729
Peak inflow = 3690 mj/s
Table 12.5: Routed Design Flood at Coffer Oam of Arjo Didessa Reservoir
T ~ 10 yrs. Peak  = 654 m /s
3
7 = 20 yrs, Peak           “ 654 mVs
D              0                   Efev (mis?             fm asfJ
5.0            210              1337.98 5.5            223              1333.01
6.0            239              1330.00
6.5            258              1328.08
2x4.0          220              1334.18
2x4.5          243              1329 86
D
___M____
Bev
(m3/s)
5.0            211                1338.22
5.5             225               1333 29
6.0             243                1330.32
6.5            263               1328.40
2x4 O          222               1334 45
2x4 5          247
1330.19
T = 50 yrs, Peaft = 771 m ZS
J
T = 700 yrs, Pea A = 871
D
Jm.l
□
(mis;
Bev
(m ast?
D
imj
Q                   Eiev
imisi
;'m as/)
5.0             213              1338.59
5.5            229              1333 70
6.0            248              1330 79
6.5            271              1328 90
2x4.0 225 1334.86 2x4,5 253 1330.89
IM&te Length of pipe, L = 400 m
5.0             215               1338.89
5.5            232               1334 05
6.0             253               1331 19
6 5             277               1329 32
2x4.0 228 1335 20 2x4.5 . 257 1331.10
Water Works Uesi&n & Supervision Enterprise ’ Lit Associate wiui inLereonUMutnil Consultants and Technocrats Pvt. LtdArj® Dtdesja Frriftbvn Project Meteorological and Hydrological Aspects
May 2007
Cmiw <flr Arjp Didvvvs Riwnwlr
i$q Kml
fJgur* 13.1            ElevilWn-Arti-Capaciliji Curv»i q| Arjo Dtdttftj flmrrair
Inlkiw JAU fruiow
a i DuliflJfe rep B*rveU
Figure 12.2:       Inltow uod OutiFow Flood Hydrojrjpn* J( Arjo D»d»va Raatrvolr
Water Works Design & Supervision Enterprise
la Associate with rcierconUneBtal Coasuttanu and Technocrats Pvt Ltd
Si
ItlVVlbefl |in|Due ha r#Q?*
Dwohirfigrt
Arjo Detfessa irrigation Project Meteorological and Hydrological Aspects
MayE0Q7
i.Htw                                  Tyin>jra^n« v &««u Caflw
I
Wlw »"d Oakl a. MTprtii^pin ac Ai|+ pid'hiA
»-
Fi"a | fa!>||
F.gur* 12.3: Inflow anti Outflow Flood Hydrogr.phi at Arjo D» „
d M fte5efVo|r
Waler Works Design & Supervision Enterprise "
In Awclata with intercontinental Conaulunu and Technocrats Pvl Ltd
S3Arjn Dtdessi Jrrtgatl-OD Project Meteorological and Bydroiogical Aspects
May 200?
Atfertga Hydroptaph ql Mjrimwm Flows ac Arja Didav^a Dam silt
Fiflurs 12.4. Average Hydrograph of Maximum flows at Arjo Cedessa Dam Site
Waterworks Design & Supervision EnternrisT’- - - - - - - - - - - - - io Associate urJth IntereoDUdODul Coasujujju T^hnoeraU Pvt. Ltd.
86Atjd utdMss imcaiion Fnojeci
Meteorological and Hydrologlcat Aspects 13 RESERVOIR SIMULATION
May 21)07
Determining design capacity of Arjp DedeSsa reservoir required reservoir simulation study. The factors  ihat has  been considered m the analysis  include ihe following This  pedicular section deals wjlh the dam/ reservoir simulation for esfabltshing lhe viability of contemplated mgatton
u Useable Row tHUwean reservoir and diversion,
□ Spin past diversion weir.
o Flow into lihe reservoir
o Evapprali&n from the reservoir,
<? Ramfall on the reservoir,
o Total irrigation demand, and
g Irrigfliiori waler release from the reservoir
The  simulation  sample  is  pnwkfed  m  annexure  B  -  fl.  the  description  of  various  column, referred tP ttiers in are as below:
Water Wnrl< o
i„,
— — 
s  e! Ents pen ]sionl
87
b e»«t>tiga with Ummnm (O1BU11MK Md Ttc Lr raB PnLlaArjc-Dedtssa [irigaUnn Prajwt Meteorological and Hydrological Aspects
May EflUJ
Co/umn
Abbrev
Description
Cd W
Year
Year
Coi{2J
Nonin
Monih
CoS [3}
Inflow
Mm’
ftalural inflow Io the reservoir as simulated by Ttomas-
Feinng model (monthly flows for 1000 years >
Cat {4}
DF
Mm1
Natural How (corresponding to 75% reliability level)
between the dam site and diversion site
Ed-RI
Mm
Evaporation minus ramfall over the reservoir. Eo is 
evaporation at 75% exceedance level as estimated from
ETo and Rf is monthly rainfall al 75% reliability level
Cd/6/
1WD
Mm1
negation water requirement (given by Table 13.1)
Cat [7}
(Eo-Rf}
Mm3
Col [5] converted 1o volume covering the entire
command area
Cal{8j
SL
Mm1
Seepage loss (assumed to be 1% percent ol Ihe
existing storage in the reservoir)
Cd (9}
IWR
MmJ
Irrigation water release from the reservoir (Col|&j-Cd|4J)
Caipoi
cs
Mm3
Change  m  storage  between  the  ends  ihe  previous 
and current months
Col{11J
Storage
Mn?
Reservoir storage at Ihe end of month
Cd {12}
Area
Km*
Reservoir average surface area between beginning and
end of monih
Cat {13}
Level
m. asl
Reservoir storage at rhe end of month
Col [14]
Spill
Mm*
Spilt from the reservoir between beginning and end of
month
Cot [15}
$TRQ
Mm’
Total annual storage requirement
Cd {16}
T Spill
Mm3
Annua, spilt from ihe reservoir (sum of Col[ 14] from
month 1 to 12}
The details of simulation inputs are provided in the Tables hk ,,
detailed irrigation targeted simuialion runs  are Provided ,n Tahl' /-2‘ r/1e abstract of the
contempiated irrigation (Tawe 13.1} are success^ a( various XSes^h
Water Works Design & Supervision Enterprise
^^^ters (he
In Association with tutercontinenUl Consultants ana Technocrats Pvt. Ltd.Arju [kdcssa trrifiuon Project
Meteorological and Hydrological Aspects
Tabla 13.1: Irrlgabon Water fie quire man t s for Various Scenarios (for 13700 ha in Mm )
May 2007
1
Phase 1
Ph»en
Monlh
Rail
Ftoli
Roil
Rol2
Sep
a.38
8.43
12.43
12.45
Oct
10.41
10.69
13.19
1372
Nov
2.B9
2.90
3 *6
3.29
One
11.04
12 49
14,02
16 07
Jan
19.00
22 18
24 64
28.61
Feb
23 25
27.87
29.98
.34 92
Mar
10 49
22 15
22.99
26.4 f
Apr
4.98
521
5 09
5.3D
May
201
2.01
2.01
2.01
Jun
21 64
21 64
32 42
3242
Jul
5.97
5 97
8.95
8.95
Aug
6.89
6 89
10.33
10 33
Tola!
134.93
na.w
179.22
m.49
Tab!e13 2 Reservoir Characteristics al Dead Description
Uni}if-,
Quna/jfy
Minimum drawdown level Minimum nve< bad level Area at dead storage level Dead storage
F1- "' 
m.a.g.l
h---- - _i
1350.0
m.a.s i             1320.0
km1
67.88
874.7
Waler Works Design & Supervision Enterprise
la Sedation with lnicr«
nUnf[1(jl
t Consultants and Tochnwrats hi LidArjoDedem irrtE&uon Project
Meteorological and Hydrological Aspects
Table 13.3 Storage Reservoir Characteristics and Reliability Levels
2007
Description
Phase I, Rot 1
Dam hcjghtfal spillway
75%
Reliability level
80
% $5% 90% 95%
cl)
m
30.89     30 99      31.08      31.24      31,4?
m a.s.l 7350.99 1350.98 1351.08 1351.24 1351.42 km2 70797 71.094 71.424 71.952 72 546 Mm3 67 3 74 4 82.3 95.1 109.4 Mm3 942.0 949,1 957.0 9697 984.1 Mm3 1800.0 1799.0 1754 0 1703.0 1640.0
2674      24.17      21.30      17.92      14.98 1
rn
m a.s.l
km2
31.05      31.14      31.24      31.41      31.59
1351.05 1351.14  1351.24  1351 41   1351 59
71 325   71 622    71.952    72 513    73.107
Mm3 80.0 87.1 95.1 >08.6 123.1 Mm’ 954.6 961.8 969 7 983 3 997.8
t7B6.O   1785.0    t 740.0    1689 0    1626 0 22.34      20.49      18.31      15.55      13.21
---- I
_
cl)
Spillway crest level
Area al normal water level Live storage
Total storage
Spill over the spillway Spill to live storage ratio Phase I, Rot 2
Dam heightfat spillway c.l) Spillway crest level
Area al normal waLer level live storage
Total storage
Spill over the spillway Spill to live storage ratio Phase II, Rot 1
Dam herghtfat spillway
Spillway crest level
Area at normal water level Lwe storage
Total slorage
Spill over trie spillway Spi-i to five storage ratio Phase II, Rot 2
Dam herghtfat spillway
m
m a.s.l
1351.14 1351 22 1351.33 1351.50 1351 68
71.822 71 886 72.249 72.810 73 404
31.14      31.22     31.33       31 5
31.68
km'
Mm3               87 1        93.5       102.2      115.9      130 4
Mm
Mm         197651580    19765841.0    1977069.9.0    1959508.5.0
20.15
1877      16.72      14.31      12 24
1005 0
1595 0
C.I)
Spillway crest level
Area al normal water level Live storage
Total storage
Spill over the spillway Spill to five storage ratio
m
<n.a.s.l
1351.32  1351.39 1351.52  1351.69
31 32      31 39      31.52      31 69      31.87
km
Mm1
Mm3
Mm3
72.216 72.447 72.876 73.437 74 031
101.4 107.0 117.5 131 2 14$ 7
1351 87
476.1      981.7
992 1
1739.0   1738.0    1693.0
17 14      16.24      14.41      12.52      10 84
1005 8
1020.4 16420     1579 0
Water Works Design & Supervision Enterprise
in Association with Intercontinental Consultants anil Technocrats Pvt Lt«f
■inAr]o Uedtssa Irrigation Project
Meteorological and Hydrological Aspects
14 DEDESSA SUB-BASIN MODELING
Ma^ 2007
14,1. Modeling for Arjo Dcdessa dam for irrigation
The simmlaiians  dtscussad in previous  sections  is  for a comprehensive analysis  of Dedessa dam, which is lhe main focus of lhe TOR. A detailed Ms-Excel based model, using 1000 years of monthly  data of inflows, generated synthetically, were incorporated in the various  runs. Io obtain the results as indicated in the Taare 13.3. As can be seen from lhe waler requirement available al Table 13.1, for the uliimale development phase II, of the Oedessa dam lhe opiimal water abstraction is for RdT 2, scenario cropping pattern. Based on various combinations of the stmulalion runs, which are very  exhaustive, it could be stated that there could be two net phases of development The designs  however need io be made far the phase II development. The firmed up geometry of the reservoir at Dedessa dam for lhese two phases could as below This  fs for lhe success of imgalion at 80% reliability. The following abstracts are based on the results of simulation considering only contemplated irrigation
□ For phase I development of Dedessa dam
•    Imgaiion command
■ Full reservoir level
•    Storage at lull reservoir
•    Deed storage level
•    Volume al Dead stage level
•    Live sigrage
•    River bed level
•    Area at Dead storage level
•    Area at full reservoirs level
•    Irrigation Demand
□ For phase II dfivalopm&nl of Dedessa dam
13,700 ha 13S1 14 m 561 8 Mm3 1350.00 m 874 67 Mm3 87 10 Mm3 1320 00m 67.88 km? 71 t4kn?
l48.43MmJ
' I
rrigation command
13,700 he
*
Full reservoir level
1351.39 m
*
Storage al full reservoir revel
981.7 Mm1
■
Dead storage level
1350.00m
*
Volumes at dead storage level
874.67 Mm]
Water Works Design & Supervision Enterprise
m AssuciaiiDo with Intercontinental Consultants and Technocrats Pvt. LtdAt jo4Mtssa Irrigation Project
Meteorological and Hydrological Aspects
May 2007
• Live storage
107.00 Mm’
■   River bed level
1320.00 m
■   Area at dead storage level
67.38 Km’
■   Area at full reservoir level
72 07 km?
■   Irrigation Demand
1B4d9Mm3
Thus bDih the above phases satisfy contemplated irrigabort with 80% reliability In the phase t and phase II. the cropping patterns  envisaged are different. However, for the final design of Deddesa dam. it has ip be based on phase II development with lhe above dam features if lhe development is For irrigation only.
14.2 The sub basin modeling
When the aspect of me development of Dedessa sub basin as a whole, mciLKiing lhe present proposal of Dedessa dam, is taken for considerations, the need for (he simulation of me sub basin becomes  relevant. The details  and components  of such sub basin simulation modeling could be for lhe following objectives.
»  To  explore  the  possibility  of  power  generation  al  Dedessa  dam  Since  only  a  small fraction  of  the  total  inflow  is  to  be  used  fg<  irrigation,  looking  at  power  development oplrons at lhe site by raising the dam height is an important consideration
- In such a scenario as above, that is, lull scale upper optimal development of Dedessa
dam. it becomes  a necessity  to check  that this  optimal water abstraction does  not ieopard«ze Mura developments  in the whole of 1he Dedossa sub-basin. This  requires basin modelling at a larger scale considering contemplated developments upstream and downstream.
In this  report, simulation exercise has  been earned out to address  lhe first objective. A tailor made sub basin modeling was  carried out by  developing a Fortran source code named
■Arjoslm' to quickly undertake simuLaiion exercise of various components with alternatives
Water Works Design &■ Supervision Enterprise
In Asscciatltra with IntErcoiiUnenul Consultants and Technocrats Pvt. Ltd
92Arjo Dertessa, Irrigation Project
Meteorological and Hydrological Aspects
14.2.1 Power Generation in Dedessa Dam
May 2007
The Dedessa dam with its. phase 11 configuration, could irrigate 13,700ha at BD% reliability Since, lefl and right bank  main canals  lake off from the dam. no ncidental power can be generated as such Hence, power development options are sought by raising the dam height Io have additional storage for separate power releases. The FRL for optimal phase II irrigation development is 1351.39 m. Two scenarios for Higher FRL, values are considered with FRL of 1353 m, and 1356 m. For each FRL considered, four different power release oplions are taken up for the simulation as depicted in Table 14,1. It should be noted that the given releases are total monthly releases for irrigation and hydropower. That is. (he given total releases less the monthly  irrigalion r epuiremenl shalt beused (or power generation There will be a separate culler for power at the same level as that of irrigation outlet, lhal rs. al 1350.00m
The reservoir characteristics at the two FRLs considered for 1he Simula non are. Full Reservoir Level = 1353 m
*    Storage at lull reservoir level ’ Live Storage
•    Dead storage level
■   Volume at dead storage level
■   Area al full reservoir level Full Reservoir Level = 1356 m
1092.51 Mm3 217.33 Mm3
nso.Wm
674.67 MmJ 77.86 km2
• 
Storage al full reservoir level
1341.1f> Mm3
• 
Live storage
466.49 Mm*
■
Dead storage level
135a.00rn
■
Volume al dead storage level
874.67 Mm1
• 
Area at full reservoir level
87.35 km2
Water Works Resign £ Supervision Enterprise
tn towtliu with Intercontinental Consultants m Technocrats Pvl Ltd.
93Arjo DedessA [rrtgatiau Project Meteorological and Hydrological Aspects
Maj 2007
The effective turbine center was  fixed at 1322.00 m elevation, This  of course, needs  to be finalized as  per ground condition and darn head/or otherwise, other location based powerhouse. Also, the plan! factor adopted in the basin simulation runs  is  unity, and with unrestricted Installed capacity. 6 ased on actual budget and power requirement analysis  by Hydropower and Dam des^n engineer, these installed capacities  could be changed or power generation cou'd be restricted. The results  presenled in lhe Hydrological simulation are with these assumptions on turbine center level and plant factor. However at detailed design stags, with those firmed up figures, the sub basin models could be re-run in short time.
The power duration turves  for rhe various  runs  are shown in Figures  14,1 tai) io 14 1 (b4). These figures  are useful to reckon I he monihly  power generation at various  exceedance probability  levels  al proposed FRLs  of 1353 and 1356 With respect to annual energy production lhe results are presen led in the Table 14.2 for Dedessa dam. This piture of energy generation is  alter satisfying irngafion needs  fully  al 30% reliability  However the quantum of energy and power are ol npl very allrautive type
14.2.2 Optimal Power Generation
With  FRL  upto  1966  as  seen  above,  1  hough  irrigation  is  successful,  the  power  generation scenario  is  not  attractive.  Hence  the  simulation  model  'Anjasim'  was,  slightly  recoded  'or making  simulations  for  increased  FRL  considerations  and  exploring  the  possibility  of  power generation at a higher level, though the exercises are beyond 1he scope of the present TOR A large  number  of  runs  of  Arjosim'  were  undertaken  oncer  3  different  domains  of  preposition These are
Domain 1: k eepmg lhe power outlet al a lower I evel of 1 346 m and increasing I he F R(_ i n siages. with various monthly power release patterns.
Domain 2: keep:ng lhe power outlet at t V-6 m and increasing the FRL m stages as abovt ■ hu- wilh model in built decision suppon based power releases.
Water Works Design & Supervision Enterprise “
94
in AiswlatlM with Interconuneuml Cousultanis and TeehnotnUs
p . Im
rtArjo Odessa IrrtEillcti Project Meteorological and Hydrological Aspects
May 2007
Domain 3: keeping the power outlet al the same level as that of irrigation oulfet (of course, a separate power outlet] and increasing the FRL »n stages, with decision support based power releases by ihe model
Domain 1 Simulations
A set of 12 different runs were attempted within me FRL ranges from U7O to 1376 m, and wil-h different monthly power release pattern. Some of the optreal ones are:
I. Wild FRL 1370, the 07% power is 11.22 MW
Ii. With FRL 1372, me 97% power is 13 30IWV
III With FRL 1374, the 97% power is 13.62MW
Beyond FRL 1374. there were no encouraging improvements n power generation.
Domain 2 Simulations
These runs lotalmg la id were made wilh decision support based power releases, m built in the model This  obviously  increases  the power generation for the set of FRLs  The optimal runs indicated the following situation.
i With FRL at 1372, Ihe 97% power is 16.49MW
n Wilh FRL at 1374, Ihe Finn power is 17.20MW
in Wnh FRL at 1376, the firm power is t7.&DMW
iv With FRL at 1373. ihe firm power is 19.50 MW
Domain 3 Simulations
Hara, in adtMton to dtciawn support poorer retaases. the outlet was  best at 1150W ,nslead o1 1346M adopted in me preareus  domains. This  mproved (he sduatren Some of the Mirent model runs yielded She loHowing scenarios.
1. Ac FRL 1370. che firn power at 97% 15 17MW ik AC FRL 1372m the 97% power is 10.1 MW m AC FRL 1374m. the 97% pow&r is 1B.95MW
AC FRL 1376m, che 97% power Is 20MW
Water Works Design & Supervision EnterprhT —- - - - - - - - - - - - - - - - - - - - - tn AsswlJUten with taHTMdtlneiital Ccnsuluuis and TeehDOcrata Fix Ltd
95Arjo Dedessa Irrigation Project
Meteorological and Hydrological Aspects _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ May 2007
14.2.3 Reduction In flows at Dedessa Sub-basin
In either of the cases, covering 8 runs  of simulation, there is  no detrimental effect on the downstream f lows  of Dedessa sub basin The maximum consumptive utilization Is  only  far
irrigation, which is only 194.49Mm  annually, as the additional
J
releases made few power are not
for consumptive uses  The power releases  flows  downstream. Thus, a net reduction m the
sub basin flows will be up to a datum o1 195mm! even without accounting for any regenergiion
from irrigation. The sub basin of Dedessa contributes at its end annually to Aooay a auualum
of 14,033mmJ  (BCEOM Master Plan study}. This will get reduced to 13,83&mm  because of
J
the
proposed ago Dedessa project which is  only  a negligible reduction of 1 39%. As  such, the Arjo Dedessa Dam proposal is  not going to jeopardise the overall developments  of the sub basin considering various identified projects of the sub basin
14.2.4 Conclusions
The simu'alion runs could be made for lurther different scenano At this stage, 11 could be said that 1he optimal power generation would be with FRL at 1376 m and wilh power ouile! at 1350 m. The tail race is assumed 10 be at 1322 m in all the runs. With a plant factor of 0.6, the installed capacity  could be around 33MW. Hydrologtcally, the simulations  can be performed fudher without any  constraints, provided that Were are no geological, geolh&chmcal design, environmental social and other constraints, The power generation al different reliability percentages are shown in the Figure 14.2 for lhe last run.
However. »lorn, up power jeneraHon. even a, higher FRLs. a prefeaSib,l,iv sludy  is  reared for exploring the p«M« of increasing lhe heigh, p| dam arKl esfoMlsHng ,h* ,eehn.cai feasibility ano economic viability for generation of hydro-power
Waterworks Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjelfalessa IJT|fsil&n Frsjwt Meteonlogical and Hydrological Aspects
May 2M7
Table 14.1:           Total Monthly Release (Irrigation plus Power} options for various FFtL values
coniiderad
Options
FRL= 1353 m
FRL = 1356 m
Option 1          75 Mn? for all months            Twice of monthly irrigation releases
Option II
75 Mm  - May to                    TTireS Mmes monthly 
3
September 4 So Mm  -
3
irngairon releases
Oct. to April
Option III
75 Mm  - May 1o
3
September & 40 Mm  -
3
100 Mm3 for all
months
Oct. 10 April
Option IV
150 Mm  - May to August
7
3
a 40 Mm1 - Oct. id
March, 75 Mm in Sept &
April
75 Mm3 - September
io April 5 10QMCM -
May. io Augusi
Table 14.2: Annual E borgy ge nergons al Dedessa dam for the Various options
FRL Scenario
Release
Annual Energy Pradudion (GWh) at Exceedance
Probability Levels of
Options Meen 50% 75% 90% 95% 97%
Level
1353 m                J
II
32.0           323          29.8          27 3          25.2
III
IV                43.6          44 7          43.3          40.1           36.3           26.3 ■ Jbli rr-                      1                 H.9          12.0          11.9          11.8           11,7           f i 7—
38 0 28.9 26.5 24.3 22.7 20 S
25.3 25.9 25 5 22.9 21.3 19 5
II
III
24.5
54.0
24.5
56.2
IV                47,6          48.5          47.5          48 8          40.9           36 1
24.3
50.6
24 a
45 9
23.8
42.9
23.6
39 2
Water Works Design & Supervision Enteipils^- - - - - - - - - - - - - - - - - - - - - - - ’
in ftssedaden witii Hfeiuitort tamjuoii and Teehnecrafe
L[<)Ar| o Dfilum JrrlfAtl-jn rraprt
Wei^arnto^LcnL ind Hydra I a? Ical Aspects
H±jr 3007
F>fluf» I* 1 POwWOuFlfltHI Cur*<<
3
I
Ftfctiii Ptiwwr i»Equ*H*d ar ExiZaadvd. %
(a. J) Power duration curvQ for FRL - TJSJm - Option I
(a.2) Power duration curve for FRL = f 353m - Option II
20             -«o eo bo
P«rc*ft| Powwr i« L<iujllrtd of E*c««d«d S
< J 3) Po*e dur a UOn curve for FRL = 13S3m - Ophq/i
f
Water Works Design & Supervision Enterprise
____ __ '»>
In AtsodaUon *iih lnterronunenul r«niuJt>nu and Tfchnotratj Ph hdV|fll>drt«j IrrifitliMi PTnl«-t
MciflorologlcaI and Hyrtrological Aspects
May W
P«rc«nl Pow»r •» Equalled o< Eiti:»»dod ,
fj.4) Power durjfton curve far FRL = 7 J5Jm • Option IV
Cl
Jf)                          40
Porcvni Powfr i«Equ4llAU ur
K
qu 
' LMJ
%
ft), 1J Power duration curve tor Ff?L = 1356m - Option /
9
Petctnl PoMf ■» Equalled or Eictecivd *,
(b.2) Power duration curve for FRL = 1356m - Option M
Waterworks Design & Supervision Enterprise
In Association With IniertxMKlnrntal Consultants and T« hitocnts Pn LtdVJfl O*d«M irrQProjerl
Meteora logical and Hydrological Aspect
Wiy 2007
ib. J) Power duration Ci/fVfl for ERL = 1 JSfim - DphiSri III
tb.4h Power duration curve for ERL * TJ56jn - C^fah fV
Water Works Design & Supervision Enterprise
In JlMorl^Uaq until In trrton Linen iat Cornu II anta and Ttehawctxls ptt Lid.Ar] 0 Dedessa lrrigaUon Project
Meteorological and Hydrological Aspects
■■- - - - - - - - - “
15. RECOMMENDATIONS ON TRAINING NEEDS
May 2007
It is  very  hearten-ng development that the water resources  exploitation for optimal utilization towards  economic  stability  is  gelling the major thrust in Ethiopia WUh phage of activities, soon, ihe rich river basins will be impounded in different storages associated with a number of runoff the river schemes eilher for irrigation or power or in a multi objective sense. As such, m the present scenario, the hydrological planning and design are m the usage. However, 'when the basins, in the near fulure, become stuffed with many projects, then, the real time operation of those projects  will be the dire necessity. Judicial operation al a multi reservoir ■'project system has a lot of benefits in combating floods, tiding over drought., reduction in water losses and others, However, such real time operation would require a complete knowledge (in the hydrological sense? of the basin system, and hydrology  and simulation techniques  (simulation coupled with ophmi?a1it>n models}. Such a scenario of real lime operation will have to be backed up by  Itood forecasting networks, advance prediction of seasonal rainfall adequate telemetry  (for iransfer of data), dedicated computers, telecommunication soft ware in addition to subject matter (hydrotcgy/simulation) soilware. The personnel heading such operalions  in a basin, and 1hose working in such a learn need to be trained in the above mentioned aspect so as  to undertake operation which has  immerse advantages. H ence. it is  recommended that experts  on Hydrology  and Hydrological modeling should be identified for undergoing such trainings  in institulions/umversities  in appropriate countries. Though there coukl be many  such institutes, the consultant teels for such mulli system operation, adequate expertise is available in countries like U.S.A and India, where many institutions, Universilws. River basin authorities, and research stations  could be identified for offenng Such trainings  Such teamed personnel, wih expertise in hydrology  will be able to head future river basin authorities  for optimal real time operation of the systems.
Water Works Design & Supervision Enterprise - - - - - - - - - - - - - - - - - - - - - - - ID AssdUtoB with Intercontinental Consultants and Technocrats Pvl Ltd.Arjo Dedessa Irrigation Project Meteorological and Hydrological Aspects
REFERENCES
M*y -w'-- - - - - - - - - - -
Admasu Gebeyehu. 19&8: Regional Analysis on Some Aspects of Streamflow Characteristics in Ethiopia. (Unpublished Draft Report). August 19&6
Admasu Gebeyehu, 1989: Regional flood Frequency Analyses PhD thesis. Royal Insbtute of Technology, Bulletin No TRITA-V8I-148, Stockholm, Sweden
BCEOM. 1999. Abbay River Bam Integrated Development Master Plan Project. Phase 2: Data Colleclron, Sue lnvest>gat»on Survey and Analysis Section II. Sectoral Studies Volume III: Water Resources: Part I - Climatology and Part 11 - Hydrology BCEOM - French Engineering Consultants - in association with ISL and BRGM.
ERA (Ethiopian Roads Aulhonty), 2002: Drainage Design Manual, Hydrology
Fitfdes D, 1977: Flood estimation for small East African rural catchmenls. Proceeding Institution of Cm! Engineers. Part 2. 63, 21-34 (1977)
Gray, DM Eddor In Chief. 1971 ■ Handbook on the Pnncrptes of Hydrology.
Haan. C.T, 1977. Statistical Methods in Hydrology. The Iowa Stale University Press. Ames Hersfiefd DM., T 961 Estimating the provable maximum precipitation; ASCE, J. Hyd. Div.. 87
No Hy 5, 99-116
Maialas. N C.. 1963: Probability Distribution of Low Flaws Statistical Studies in Hydrology.
Geol. Survey Prof. Paper 434-A
Shaw, EHzabelh M.. 1986 Hydrology in Practice International Van Nostrand Reinhold. USBR (United Stales Department of the interior Bureau ol Reclamation), 1964 Land and
Water Studies of the Blue Nile Basin. Ethiopia. Appendix III - Hydrology WAPCOS (Water and Power Consultancy Services (India) Ltd.), 1990. Preliminary Water
Resources Development Master Plan lor Ethiopia Final Report Volume III Annex A: Hydrology & Hydrogeology. Addis Ababa
Water Works Design & Supervision Enterprise
in Association with Intercontinental Consultants and Technocrats Pvt LtdArjo DedBSH Irrigation Project
Meteorological and Hydrological Aspects
annexes
Annex A- Results obtained from the Meteorological Analysis
Al: Estimated Mean Temperature at Arjo Dedessa Project Area (innC)
May 2007
Year
1961
1962
1963
Jan Fob March
sai 21.0 24.7
April May June July
24 o 232 21 5 20.7
Aug Sept Oct Nov Dec
20 2 21 5 22 0 21 9 197
200       21 8      24.9
22.5     23 2     21 0    20.0    20 0     21 3     22 1      202     19 0
21 7      23.2      24 3      16 3     15.9    21.6    21 1    20 8    21 4     21 7    24.5     21 3
1964
21 7      22 9      254      24 5     23 7     21 5    20.4     20 4    21 4     22 0     21 5    200
1965
196fi
21 5      21.8      24 0
24 6     23 5     21 6     21 3    20 8    21.5     22 4      232    20 5
22 7       23 8     25 3      24.6     24.1     21 7     21 4
208      21.5     22 3     22 0     18 8
1967
1966
19.5      22 5     25.1      24 B     23.7    21.2     20 7    20 5     21 3     21 1     23.0     18 7
19.9      22.4     23 6      24 5     24 1     21 0     21.6    21.1     21.2     21 4     21 2     19 S
1969 22 4 23 2 25 1 24 6 24 22 0 20 7 20 7 21.5 21 7 21 2 18 9
1970 21 5 22 9 250 24 9 24 3 22 a 21 4 20.6 21.6 22.3 198 18 2
1971 21 6 20 4 23.9 24 7 237 21 1 21 0 199 21 1 224 21 7 182
1972 21 S 23.1 24.2 24.9 23.2 21 0 21 8 21.3 21 6 223 22 8 20 2
1973 22.7 22.6 25.a 26 0 24,1 21 B 21 3 20 8 21.5 21 7 217 17 4
1974 21.2 23 3 25.3 23.9 23.9 21.0 2a 6 21.3 21 3 21.2 19.1 19.0
1975 21.0 23 6 25 9 24 0 23.7 217 20.5 20.2 21 3 21 9 20.4 189
1976 20.8 239 24.3 24.3 23.1 21 0 21.0 20 6 21 6 22 4 22 5 19.7
1977
1970
1979 22 2 235 24 7 24 2 24.2 21 9 21.3
1980 22.3 24 1 26,1 25 8 24 4 223 21.1
21.1      22.0     25 1      26 6      238     21 9    20 9    21 2    21 1     223      20.9     20.4
23 0      23 5      24.9     25.3      244     21 4     21 0    21 5     21.9     23.5     23.0     20.9
1951 22 4 22.6 26 2
1962 22 7 22 3 23 8
1983 20.3 23 6 26 1 25.6 25 0 22 0 22.3
1984 206 20 6 25 4 26.2 24 5 21 9 20.9
25 i 24 7 223 20.6
24 9 23 5 21 9 21 2
1965     21.5      22 9      25 7
19B6
1967
1991     23 0      236      25.1
1992    22 1       24 1     25.2
1993    22.6      23 5      243
1966     22 4      24.5     25.1      25 8     25,3     225     21 3
1989     21 3      22 3      24.6      24 5     23.3    21.9    21 3
1990    21 0      21.9      24 0      26 1      106     224     21 4
21 5 24 7 239 24 3 24.6 22.0 21 3
21 8 23.0 25 4 25.1 24.2 22 6 22 2
25 1     24.0    21 7    2D 6
2000 21 6 22.9 26.fi
2001 23.0 24 3 260
2D02 23 2 23 6 26 0
1994 21 6 24 2 268 24.9 24 3 22 3 21.1
1995 223 24 5 26 4 26.5 25.3 23.1 219
1996 22.6 24.1 26 3 25 9 24 7 21 9 21.7
1997     23 4      224       26 9     25 5     24 4    23 1     22 3
1990     24i6      24 9     27 4      27 7     26 2    23 4     22 4
1999     21 9      22 8      26 2      26 3     24 9     228     21 6
25 I 24 6 226 21.3
25 2 24.6 223 21.1
25 B 24.4 22 7 21 4
26 6     25 5    22 6    21 9
26 4 25 5 23.0 22 0 22 2
21.6     22 0     22 3     21.6     20.9
208     22.0     22.0     22 0     19 5
21 t      21 5     220      21 6     19.2
20 7     21 6     21 0     23 0     20
2i 8      21 7     22.4     22 3     136
20.7     21 1     20.2     23 4     20 6 2C4     21.5     21 5     22 1     19? 21 1     21 2     21 7     22.0    20 4
21.6     21.9     23 1     22 7     20.2 21.6     21 9     22 5     20.6     18.8 21 6     21.7     22 0     21 9     21 6 i 21 4     21 9     22 1     22 4     20.9 20 B    22 0     21 4     21 4     182 21.3     21 0     22 7     21 a     21.3 21.4     21.8     22 9     21 7     19.6
21.5    213      22 0     233      20.0
22.1     22 3     23 9     233      22.2
21 8     22.4     22 4     27.0     20.2
22.3    23.2     24 0     25 1     229
22 3    23.1     24 2     22 0     19 1 21 3    22 9     23 5     2r o      198 2i 0      23.0     24 0     23.5     20 a
2003    21 9      24 b     26.4      25.7     25,0    23 2    22.0
25.9     25.0     228     22.7
22 2
2  2 2 300    24 2    23 6    2l 6
23 3    23 1    22 7
2004    24.2       24 2      26?      265      25.6    22.8    21.5    22 1    2?
22.2     22 7     23 0     23 5     20 6 22 6     23 2    21 a
Waterworks Design S> Supervision fnterurii?- - - - - - - - - - - - - - - - - - - - -
In tts.rl.um w,u>l.urrmUnr.u! Cmmlwu ,M Technocrats m
u LiftIrjtJtatessi [rr Ifatloo Project
Meteorological and Hydrological Aspects _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
An ■
Ax. Year
CMinIOICU miiiiiiiuni iniupvi
Jan Fob March April May
w
*+ Ann nt'des&J Project Ar&J |tn "Cj
June  *July Aug_ISept            Oct..        Nov [
-
D&r
1961 97 10.5 13 0 S4.7 14.9 14.6 14 7 14.3 14 5 13.0 1&.3 0.0
1962    a &       iOS      13 9      is.a      15.0     143    14 2    14 2     14 4     13 0       9.5        7 7
1963 9.5 11 2 13 6 9.9 10 3 14.7 150 14.7 14 4 12 6 11 6 B 6
1964 9 5 11 1 14.2 15.0 15,3 146 14.5 144 14.4 13.0 10.1 5 5
1965 94 106 13.9 151 15.1 14.7 15.1 147 13 2 104 8.3
1966 99 11.4 14 2 15.1 15.5 14 0 15.2 14.7 14.5 132 10 3 7.6
1967
I960
1969
1970
1971 9.5 99 13 4 16.1 15 3 14 3 14.3 14.1 14 2 13.2 10.2 7.4
1972 9 4 112 13 5 15 2 14 9 14.3 154 15.1 14 0 13.2 108 8.2
1973     99       10.9     14 4     16 3     155     14 9    15.1    14.7     14.5     12U      10.2       7 1
1974     93       11 3     14 2     14.6     15.4    14 0    14 8    15.1     14.3     12.6       9.0        7.7
1975    9.2      11 4     14.5     15 1     153     14 8    14 5    14.3     14.4     12 9       9.6        7 7
1976     9.0       11.6     13 9      148      14 9    14.3    14.9     147     14.5     13.2      10.6        80
a s t0.9 14 1 151 15.3 14 4 14.7 14 5 14.3 12.5 IQB 7.6
0 7 10.8 13 2 15.0 155 14 7 15.3 14.9 14.3 12 6 10 0 3.0
9 6 11.2 H0 150 15.5 14.9 14 7 14.6 14.5 125 1OO 69
94 11 1 140 15 2 15.7 14 9 152 14.7 14 5 13.5 9 3 7.4
1977
1978
1979
1900
1981
1962
1903
10.1 114 14.0 15.4 150 T4.S i 4.9 15 1 14 8 13.9 10.8 a.s
92 11 0 14.0 15.6 *5.3 14.9 14,0 15.0 14 2 13.2 9.8 8.3
9 7      11 4      138      14 8     15.5     I4 9    15.1     15 3     14 0     13.2      10.2        35
96 11 7 146 15.7 15.0 15.1 15.0 14 7 14 S 130 10.3 /.9
98        tttfl       14.7      153      16 0   15.1     14.fi     149     14.5     130       102        7.3
5.9      106      133      15.2     15 1    14 9    15 1     14.7    14.5     12.9       108       3.4
6.9      11 4     14.6     15.6     16.1    15.5    15.6     155     14 6     13.J      10 5       7.6
1904 90 10.0 142 16.0 15 8 14.9 14 8 14 6 142 11.9 110 8.4
1985     94      11.1      144      153      15.5    14 8    14.&    14.4    145      127       10.4       8.0
1986    9 4       120      13 4      ISO     158      150    15.1     u 9     14 3     12.3      103        8 3
1987     0 5      11.1     14J2     153      15.6   15 4     158     1SJ     145      13.6      1Q 7        82
1980 96 119 too 157 16 3 15.3 151 15 3 14 5 13 3 9 7 76
1989 9 3 iQ.e 13.6 14 9 150 14 9 15.1 153 14 6 13 0 10 3 8.8
1990 97 10.6 139 153 12 0 152 15 2 152 130 10 6 8.5
1991 10.1 51 4 14.0 15.3 15.9 154 15.1 14.7 148 126 10 1 7.4
1992     9.7      11.6     14.1     15 4     15.0   >5 1     15.0    15.1     14 7     13 4       103         86
1993
1994
1995
1996
1997
1998
1999
2600
99      11.4     13.6      156      15.7   1S.4    15.2    15.2     14 7     13 5      10 2        79
95 11 7 15.0 152 15.7 152 15.0 15.2 14 7 13 0 11 0 8 1
90         119      148      162      16.3     157    15.5    15.6     150      136        n.o         90
9.9 116 14 f 15 a 160 14.9 15.4 15.4 IS 1 13 3 1IU 82
102     10 5     15.1      156     15.8    15 7    15.8     153     15.6     14 2      11 0       5 3
10 8     12,1     15.3     16.9     16.9     159     159    15.3     15.6     14 3      10 3        78
96      11.0      14 7      160     16.1    15 5     15.4       IS 1     15.4     13 9      9.9         80
9.5      11.1       149      162      104     IS 4    15 0     154     15.5     14 2     11 1
84
2001
2002
2003 9-6 11.0 14 8 16 7 15.0 156 IS 7 15.3 136 11.0
2004 106 11.7 14 7 162 16 5 15.5 15 3 157 15 2 13.4 10.9
10 i 11.6 146 16 1 165 156 156 157 155 14 3 11 1 8 8
10 2 11.4 150 is 8 155 16 1 15 7 15.4 13 0 ID 9 9 2
84
88
Water Works Design & Supervision Enterprise
Jufaitirtfr with incftrcontlieiita] Coosulladta and Technocrats Pvt LtdAjJq fcdessa Irrigation Project
Meteorological and Hydrological Aspects
AJ: Eslimaledl Maximum Temperature at Arjo Odessa Project Area (In _C)
May LW
Year Jan Feb March Aorrt May June July Aug Sept Ocl NOV
1961 34.7 33.0 35 6 33 6 31.7 28 6 26.7 26 1 244 30.9 33.5
Dec
31 4
1962 31.2 330 35 6 31 6 31 8 27.9 25 6 25 0 24 2 31-1 30 9 30.4
1963 33.9 35 2 3J.9 22 8 21.7 28 8 27.2 26.9 24 2 30.6 37 6 34.0
1964   33.9     34 7     366      3J4      324    28 6    26.3    26 4    24.2     31.0      32 9      333
1965 33.6 33 1 35.7 34 7 32 1 23.6 27.5 26.9 24.3 31.5 3S.S 32.8
1966   35 4     35 8     36.5     34 7     32 9    28.9    27 6    26.9    24 4     31.4       336
1967
1966
30 4 34 1 36.2 34 7 32 4 28.2 267 265 24,1 296 35 1
31 1 33.9 34 0 34 3 32 9 20 8 27 8 273 24 0 30 1 32.4
30 1
29 9
31 3
1969 35.0 352 35 1 344 32 8 29 2 26 7 26 7 24 3 30 6 32 4 27 0
1970 33 6 346 36.0 34.8 33.3 29.2 276 26.9 24 4 32 1 30 2 29.1
1971 33.7 31.0 34.5 346 32 4 28.0 27.0 25.7 23 9 31.5 33 1
1972 33 6 35 0 346 346 31.7 27 9 28.1 27 5 24.5 31 4 34 9
1973    354      34 2     □7 1      375     32 9     290    27 5    26 9    24 4     30 5      33 1
1974   33.1     35.3     365      33 5     32 7    28.9    28 B    27 6    24 1     29 9      29 2
1975   32 8     35 7     37.3     34 a     32J    28.9    26 5    26 1    24.2     3D 0      31 2
1976    322     36.2     35.7     34 1     31 5    27 9    27 0    26.9    24.4     31 5      34 5
1977 35 9 35.6 353 35.4 33 4 2B.5 27 1 27 6 24 8 33.0 35.2
1976 32 9 34.S 37.5 35.9 32 5 29.2 27.0 27.4 23 9 31.4 31 9
1979 34.7 35.5 35 6 339 33 1 29 1 275 279 24 g 31 4 33.1
1980
1961
1982 35.4 33 7 34.3 34 8 32.1 29.2 27.4 26 8 24,4 30 7 35.2
1983 31 7 35.7 37.6 356 34 2 30 4 28.8 28.2 246 31 S 34 1
34 8 36 5 37.5 36 1 33 4 296 27 3 26 9 24 9 30 9 33 6
35 0 34.2 37. B 35 I 33.8 29.6 26 6 27.2 24 4 30 9 33.1
1984
1965
1986
1967
32.2 31.2 36.5 36.7 33.5 29 1 27 0 26.7 23 9 28 4 35 8
33.8 34.6 37Q 35 2 328 26 9 26 5 264 24 3 303 33 8
1988    35.0     37 2     36.1      361      346     29 9    27 5    27.9    24 8     31 7      31 5
33.6 37.5 U S 34.4 336 29 3 27 5 27 3 24 0 30 5
34.0 34.a 36 5 35.1 33.1 30.1 28 6 27 9 24 8 32 5
33 6
29 1
323
27 8
30 3
30 2
31 5
33 4
32. B 33 4
31 2
305
32.9 29B
33 0
31 4
32 6
34 7      32 3
1989 33 2 33 6 35.4 34 2 31 9 29.1 27 5 27.9 24 6 30 9
1990 32 8 33 2 35.7 36.2 254 29 8 27 5 27.7 24 3 31 1
33.5
30 I
34 5
1991   35 9     35.a     36.1     35 2     33 7    30 1    27 5     269    24 9     30.1       32 7
34 3      33.4
1992 345 36.5 36 3 35 3 33.6 29 6 27 2 27 5 24 7 37 0
1993 35 3 35 5 350 35 9 33 4 30 1 27.6 27 7 24 7 32 2
1994 33 7 36 7 366 34 8 33 3 29 7 27 3 27 B 24 7 31 0
1995 34 8 37 2 3BQ 37 2 34 6 30 8 28 2 28.5 25.3 32 3
33 3
29 1
34 0
1996    35.3     36.5     37.9     36.3     33 5     29 2    20 0    28 2    25 4
33 2 31 3
35 7 31 9
35 6 35.5
1997
31 5      33 7      323
1990
365      33.y      388      33 7     33.4    30 8    26 7    28.9    26 3
33 8      38 3      36.6
1999
34.2     34 5     37 fi     36 8     34 1    30.4    27 9    27 6    25 9
384     37 7     39.4     38 8     35.8   31 1    28 9    28 9    76 l
34 1      33 6      30.5
2000
33 7     34 7     35.2     37 3     34 8   30 1    28.3    28 2    26 0
33 0      3? 1      31 6
2001 35 9 368 37.4 3f 0 34.9 30 5 28.4 28.7 26.0
2002 38 2 35 7 30 7 36.2 35 2 30.3 29.3 28 7 25 a
2003 34 2 37 1 36 0 36.0 35.3 30 0 28 4 2$ 7 25 7
2004 37.8 366 37 B 37 2 35 0 304 278 20 6 25 5
33 7      3fi 0
34 1      3R 7
32 8
32 3 35 Q
31.8      35 5
332
346
36 2
33 0
34 H
Water Works Design & Supervision Enterprise
In Assodauon wiUi Inttirconitaenta] Consultants and T^hnacrats Pvt. Ltd1/1*              TH< j 114<
uni ll/itr^hsuk.il; ViDrrtii.
W IF
>4           ■ timwNrf ?ar*ftlv« MutHHflify i-l 4kj>1u Dede *44 Frp^l *r*4 parties'!)
'4*              Jjs         f #b     MrlP ' n
lltfj       Jwn
July        M
,n J1
S
CM                    T»r
IfHt
4?
V
ifl
11
7!
"B
it?
4?
42
42
rid
72
"M;
F8
Ito
44
’1
to
41
M
M
fcfi
96
to
44
41         "2          4J           13          14          u
■ *4        • i
IW*. 4" w
17 4 Ji "5 13
to          to           '4
19 91 VJ 43 47 to
14 14 12 M n to
11 ii 14 42 ■to to
41        ■M          Jirt          * k          ?t        MS       4fl        KIJ          41            I4i          110         49
IM'
>1
17
M
"4
11
11
19
W
111
to
to
ISM
to
44
j
'to
71
41
14
■■
Bl
40
41
to
to
M
44
■>9
71
13
14
49
4B
lH)
f?
ii
<9?
M
42
44
40
N
’9
r fah
■12
40
HWl
73
is
Ifll/T
®
■1
50
44
74
rtl
47
Mk
47
47
42
to
1972
44
<1
rf!
70
7l
79
IM
il
OH
bMk
43
to
WJ
44
MS
V
tM
71
■if
12
4H
»
44
7/
ISk4
si
-k
19
VI
to
74
4i
KJ
Ml
91
43
72
13
IB?5
w
T«
11
70
•*1
dI
dM
13
90
44
p:i
Aft
19**
$4
ki
44
V
41
70
•1
92
il
197 7
91
11
■it
32
40
■nd
.■
41
fll
49
irt
i|?
■k.
■9*a       M           1B                 to           44          71        7 7
42
to
i9r®       6rt
•si          •M          70         77
IMO        W           4d          s.v          u           74         dl iyai         M         4-k          to          43          72
■M2       47           *2           V>          41          71         10
I9U        •W           41
7fJ         79         to
iMJ SGl 1 - I" Ml 74 » IMS MS MJ H 4/ ft to "9W Mj 3/ 40 71
IfflT        SO        44           «           40           ri         01
19B4      Q         ■u          19          13          ?5        *2
IW9       4J         41           K)           M        ?3        ■’9
IMO <P ■M 13 to 77 1i IM' 4d -/J MJ K 74 03
itfyj
n."          >k         *M          ■r,i        44
ij$3 49 QJ to ?5 90 45
1»4 V SJ 5ft 47 fa Be
4? sn 44 44 71 15 44 43 4ft rtt 49 17 di- 47 M 79 71 ni Art iM 41 42 7?
1J1 90 IM 47 to to 11 49 to- in 42 to 14 471 ■Nl 74 ■12 to Mi il 17 di 7? 70
47         47                       B2          73         • -s 41          i'j          W          41          7-j         71
*JT         03        47          7J          w 11          M         ■Ji           64          42          ta U                af            ji             to          to          ’ i
! jNj 91 i'Ji 92 73 to 'Ki 14 44 49 M to
M          49
to          42          IM
■ MS     40         54          1?          F2
r                MJ
■v
ijy*
to          U         U           71         SO        45 M         13         72        7ft        41
'4         44          42          44          ?9
'Jd
1$W 91 i4 M 4* 74 90
2£iX- la W 41 47 Fl Si
as
4n 19 aa?? 91 *9 to
to          tt          sc
"4 "4 9J. i2 to i 7
JM 49 73 to
K! 'JJ 34 ai
*
to
3DOI       i7
jffl
ao
if
to           w           fl'          K
TJ
*T
<
n
Hj 93
to
M
M
"4
2002       71           TO         42          >a           It         as 2Ws       71         MJ          W          4*          W
20W Ml to OJ *4 si
9i          #2
Al
*_
Ml
19
3”
*3 •M
to          12          to
to
■*
to
r           to         M        t3           to          'd
fc 1
*’"' Wark. B..IHU 4 Sup.nm^
.....
~ ' — • -             M. u*Arjo Drdessa Irrigation Project
Meteorological and Hydrological Aspects
tin hrs/dayl
Year     Jan       Feb March
‘April  May   June   July
A5:
1961  Es0t.i3mated7M.3ean D7a.1ily Su6n.s6hine5D.4uratio6n.5at A4r j3o Dedessa Project Area
Aug Sept Oct Nov Dec
62 9.1 9.2 0 9 7.4
1962
67        6 9       8.2        7.0       9.0      6.3      2.9      2.0      6.3      6.5       7 0      7 5
1963
1964
7.2        62        84
6.8       7.3      4.4      2,6      3.8      S3       0 0      9 1      53
9.6        6.3       7.7       B.0      a.r       5.8      3.0      3.0      6.8      9 1       90      10.0
1965
1966
9.1 8.3 6.6 6.5 83 3.4 4.3 5.5 7.9 7 4 8.4 8.1
73 8 2 7.1 85 7.8 5.3 4.2 3.8 8.0 9 2 9 8 83
1957
I960
7.9        96        64
72       9.1      8.1       49       52        83       8 5       78       9.0
1969
8.1        8.0       7 7       6 1       6,0      aa       23       32       5.7       6.5     10. i     8.3
8 2        7 5       7 5       73        7.6      6.1      3.7
1970
1971
10.0 9.5 9 7
8.2 7.6 7.5
?.a       94       8.0      48
4 1 6.2 7 9 8 3 83
4 7 7.5 7.9 H 3 83
1972 92 88 7 4 94 0.3 04 5.4 4 8 8.0 a.6 9 9 7 7
1973 as 09 8-5 84 10 1 73 3.2 4.1 72 9.5 9 5 90
1974 7.9 0.1 7.3 67 9 1 59 n.a 4 8 5.8 5.6 0 1 0 3
1975 94 8.3 7.5 64 7 1 5.0 3 1 1 6 4.1 7.5 8.4 9 2
1976 90 8.7 7,8 8.7 6.0 7 1 37 4 1 52 66 67 0 1
73        7.6      6.1      3.7      4.1      6.2      7.G      B 3      8 3
1977
1978
1979
1900
1981
6.2        6.3       6.5       7.2      7.4      SB       37       4.1      5 3       69        82       53
9.4 58 75
5.3 6B 60
6 t 5.3 5 8
1962
1903
1904
8 5        86        4 6       5.9       79       5.8      37
7.6       7.8      6.1      2 3      3.8      5.5      6.8       8.9      7.1
70       6.7      51       2.4
6 5       7.4      s.a      3.6      3198       45..29       57..89       77,.88      8765
7.4 a.o 83
60 7.6 7.1
8 i 99 8.1
6 5       7.1      6.8      3.9
60        66       78       5.4      336.7      8578       7555      06.46      8723
4 5      2.6      5 5       96       7.9
1985      86         76        75        68        64       5.9      2.0
89        6.6       60       4 7      4 3       70      W 1      05       0 1
1986 6 9 62 5,5
19^7 B 1 7 B 6.2
1286      04         7.0       9 S       0.4       0.3       70      2.7
5.3 7.2 3.7 33
8.3 5.0 5.0 4.9
1909     8.6        84        7 3
1990
1991
1992
1993
1994
92         49        63
7.2 96 73 3.7
3 3 54 4.6 3 7
8 3        7.3       7.1        6.0       54       65       4 3
67         69        8.2       7,0       90        63      2S      26..20      96.31       9625       0765       7745
3 l 58 7,5 0 7 7 B 40 4 1 74 94 0 2
4 2      7 4       7,6      8.3      11 o 49       5.5       05      10.2     U 1 5-1      6.3       53       8.2      66
3.9      5.9       95       8.9      9.2
9.6        0 3       7.7       80        0.7      5.8      3.0
7 2        6.2       6.4        6.0       7.3      4.4      2.0      3.0      5.8       80       9 1      83
1995     91         63        86
65        63      3.4      4.3
1996      70         82        7.1        8 5       78      5.3      4.2
1997      7.9        9.6       8 4
1998
1999
2000
02 76 75
10 0 95 9 7
6.1        8.0       7 7       8 1       6 8       68       23
7 2      9.1       8 t       49       52       0 3       05       7.a      90
30       6 0      9.1       90      10 0
5.5      7 9      7.4      H 4      8 1
3.8      6 0       92       98       83
7 3 76 6 1 3 7
7 6       94       80       4 0
7.3       76      6 1      3.7
94        8.3      64       54
4  32 1       56.27      67.95     180.31     B 3
4 7       75       79       83
83
2001 52 76 75
2OD2 92 88 74
8.3
2003
2004
8.5        69        0 5       84       10.1     7.3      3.2
41
4a
52
80
7.9
8a
83 8 3
99 7 7
7.9        6.1        73
6 7       9 1      5.9      4 a
4.1 7.2 9.5 5 5 9Q
4.a      sa     8.6      0 1
83
Waler Works Design t snpmislw Enterorts<r~—
In hafliwn WIU> WraBtaMM e.
Kutonu M(
r
Etllwrat!
wAr|nWessa Irrigation Project
Meteorohgical and Hydrological Aspects
A6: Estimaled Mean Daily ETo of Arjo Dedessa Project Area
Year
(in mm/day)
Jan Feb
; March Apni . May | Jur»i July ' Aug I Sept j Oct | Nov , Dec
1961 3 73 393 4 49 4 26 3.73 3.64 3.0* 3.54 4 43 4 27 3 86 324
1962    3 23       375      4 66      4 32     4 43     3 49   2 63       2.5           3 72 3.63     3 48     3 19
1963     3 46       372      4.66      3 44     3.36     311    2.71         3            3 63 3 98     4 22     3 56
1964 1 3 95        4 18        4 85      4.66     4.52     3.45       2 72      2 79      3 97      4 25      3 8B      3 82
1965 3 84 4 13 4 83 4 25 4 43 2.97 3.1 3.43 4 13 3.08 3 92 3 45
1966 3 68 422 4.47 4 73 4 35 3.4 3 07 3 3.7 4 31 4.09 3 35
1967
196B
345       4 44
4 77      4.45      4.6      3.95    3,15     3.32     4 22     4 03     3 72     3 46
3.53      4 06       4.5       4.64       4 1     3.71     2.63      2 9      3 59     3 59     4.06      34
1969    371       4 06       4 5        4 43        4.28     356     2.91    3.06    3.72      3 94       37      3 19
1970
4 01
4 45
5 06
4 50     4 76
4.01
3 21
3 22
4.06
4 04
3 58     3.2B
1971
3 66
39
449
4.49     4 24
3 49
2.93
3 Q1
3 69
4
3 75     3 29
1972
3 B6
4.34
4.5
503      4.34
3 55
3.39
3 .26
4 17
4 23
4 2      3 34
1973
3 81
43
4 87
4.S2     431
3 B*
2 81
3.09
3 97
4 32
1974
401     3 34
3 58
4 18
453
4 24     4,61
3 51
3.3
3 29
3 62
1975
4.07
3.82
4 27
4 66
4 34     4.09
1 95    3.35
33
2.73
2 44
3.2
1976      373       4 38      4.65      4 75     4.02
3 07
3 64      3.49
1977 34 3 05
1978 3 05 3 62
4 J4      4.49     4.24
3 63       293  3 06     3.5        3 69     3 46     3.38
3 46        2.9  3.1       3 70
3 87      3 06     352
1979 3 38 3 89 418 4 37 4 06 3 36 2.04 3.07 3 3
1980 3 29 3G3 4 21 4 39 4 32 3 50 2.93 3 05 3.7
4 64       47       4 39     3.S7     2 Sfi  3 04    3.53       3 74     3 79     3 23
1931      378       425      3.90      4.13     4 42     3 63    2 91      3.2     2.86       3 64     4 01      3.3
IS       3.84     3 3*1 3 00     3 66     3 44
1962 3,6 3.74 4 63 4.32 4.13 3.77 2 96 2 96 3 87
1903 354 4 14 4 55 4 76 4.15 406 3 43 303 361
-3 66 3.49 3 3
3 7 3 82 3.32
1985
1985
1967
1984     3.58      4 31      4 73      5.02     4.08     3 55    3.14     3 11     157       4 3      3 98     3.46
3 73       4 04      4 59      4.36     3.93     3 53    2 71     2.61   3.63       386      3 88     3.32
3 43       3.94     4.31      4 03     4 22
3 67      4 14     4.31      4 74     3 03
1905
1939     372       4 13      4 42      4 39     4 64
3 76       4.2       504      4 82     4 50     3 78    2.71     3 34     3,59
3 W 2 85 3 08 3 22
3 5 3.27 316 4 06
3 82     4 01     3 46 4           3 83     3 96
4 17 4 02 3 48
1990    3.82       3.38     4 31      3.57     3 35     3 25    2 92     3.07    359
3 83    2 97     3.35   3.77       4 06     3.74     3. 24 1
1992
1993
1994
1991     3 79-      4 05      4 43      4 31      W        3-72    3 06     3.59    4.49     4 37     3 92     367
3 42       3 94      471       4.62     4.65     3   63   2   73   2.59   3   75     4 22     3 &4     3.11
1995
3 94 4.3 4 79 4.65 4 55
3 92 4 34 405 4.34 4.53
3.54      3 75      4 68      4 29     4 25     3.21    2.72     3Q4     357       3 7      3 51     3 30
1996     368       4 29     4.57      4 88     4.37
1997     3.77      4 43      4.05      4 46     4 65     407            3.23     3 46     4 41
3 5      2 75    2 63     3.91 3 98 3n 3.52 j2l
3.35    3 09    3.Q3    377
1993 3.91 4.33 4 8 4 93 4 24
1999 3.60 4.07 4.57 4.57 4 36
3.65 2,66         2.05     3 74 3.63    2.98     3.11     3 83
2001 3.76 4 21 4 56 4.64 4 42
2002 4 4 39 4 75 5.13 4.59
2003 3 75 4 49 4 92 4,82 5.06
2004 364 4 28 4.50 4 51 4.83
2000     4 03       4.45      524      4 79      4 06     4   15 3.31 3.35 4
1£)
3 05   2 98    3 3B
3 71   3.46     3 *        4 29 3 80   2 65    3. jfi      4  yg
3 6    3 22    3.35     3 72
4 09 3 91 3 4
4 26 4 06 3 75
3 94 3 92 3 59
4 31 4.09 3 46
4 32 39 385
3 83 4.12 3.36
4 11 3 7 342
4 16 3 92 3 5
4 19 3 92 3 57
4 34     4 24     3 54
4 47     4 19     3 63
4 21     2 06     361
m2 
, ,aAr]o Dedessa Irrigation Project
Meteorological and Hydrological Aspe cts
A7: Estimated Mean Monthly ETo of Arjo Dedoss a Project Area
May 2007
Year ■ Jan j Feb |March April . May , Jungj JiHy i Aug [ Sept I Oct | Nov | Doc |j Annual
1961
1962
116      110     139     12B     116    109    94 2      110    133    132    116     100         1403
1963
1964
100     105    144      130     137     105   81 6   77 4    112    112    104      99
108 104 145 103 104 93 2 aa 92.9 109 124 127 no
1965
1966
122 117 144 140 140 104 84.3 86 6 116 132 116
119 116 150 128 137 69 96.2 106 124 120 118
114      118    138     142     13S    102   95 1   93.1    111    134    123
1967
107     124     148     133     143    118    97 7    103    127    125   111
119
107
104
107
1968
1D9     114     140     139
127    111    01 4   89 9    108   111    122     105
1969      115     114     140     133     153    107   90 1   94 0    112    122   111      99
1970    124     124    157      137     148    120   90.4   99 7    122    125    107     102
1971    113     109    130     135     132    105    908    932     111   124    113     102
1972    120     122    140     151     135    106    105    102     125   131     126     104
1973    110     120    151      149     152     115   67 2   95 9    119    134    120     104
1974     lit       117     140     12?     143    105    102    1D2    109               586    104
1975
1976
1977
118     120    144      130     127     99    84.7   75.7     96     120    109     108
116     123    144      143     125    111    908    94.8    105    115    104     105
1976    119     101     144     141     136    107     B0    94 2    106    116    114
105     100    135      135     132     104     90      96      113    120    116     109
1979
1980
104      109    130     131     126    101     ai g   95.3              109    109
1961
1982
1983
102     102    130      132     134    107   90.9   94.5    111    123    110
117     119    124      124     137    106   90 1   99 2   86 5   113    120     102
112      105    144      129     128    113   92 3   92 5    116    120    105     102
110     116    141      143     129    122    106     94      100    115    115     103
100
104
107
1984
1985
111 121 145 151
H6 113 142 131
127    107   97.4 ■ JB 5    116    133    120     107
1986 106 110 134 921
1987 114 116 134 142
1986    117     110    156      145     142     113    04?   103     ioa    129
122 106 84.1 B7 1 109 120 116
131 91 3 88.2 95.6 965 H8 120
119 ws 101 98 122 124 115
1969    115     117    137      132
121
1990 118 94 B 133 107 104 974 90.6 95 til 136 117
1991 117 113 137 129 119 112 94 8 111 135 131 115
144     H5      92     105     113    126    112
1992    106     110    146     139     144    109    a* 5    803    113    115
103
107
123
108
100
114
90 4
1993 110 105 145 129 132 96 4 4 94 3 110 127 117
1994    122     120    149     139
1995 122 121 154 13Q 114401 6190.45 9865 42 81709B 112176 112322 1' 2IB2
108     105
1996 114 120 142 147
1997 117 124 153 134
1996 121 121 149 149
1999 114 114 145 137
20 CO 125 124 162 144
135    101   95 B    94      113   134    123
144 122 1O0 107 132 134 117 119
132 115 82 6 91 9 112 1 19 124 104
135 109 92 4 963 115 127 111 106
105
116
1 1 0 171
2001
117       B8    144     139
151    12S    103     IC4      126
2OO
2   124     123     14?     154
2003 116 126 153 145
2004 119 120 L42 135
137 110 92 4 96 115
142 111 107 106 129
129 118 109
130 118 111
15?    117    68 2    98      122   139    126
135    127
150      IM    100    104     112    130
110
112
1308
1308
1420
1410
1400
1444
1358
1369
1466
1366
1466
1464
1346
1332
1375
1362 1359 1299 1343 1338 1358 1401 1432 1 349 1320 1412 1443 140B
131a
1411
1360
1355
1437 1439 1425 1505 1419 1402 1518 1429 1515 149B
61.7     112
Waler Works Desigo Supervision Eni^prke- - - - - - - - - - - - - - - - - - - - - - - - - - - In Asttdrtu wltn infercwilBMUtf Consul^ and TectajM^ Kl Lllt
109Arjo &td*EE3 itriEaiJon Project
Meteorological and Hydrological Aspects
AH: Estimated Mean Monthly Rarnfair al Arjo Ded^ssa Project Area
111
----------- 1
.
Ywr
Jan F»b  March   April   May   June   July     Aug    Sept     Ocl      N&V     Oec      Annual
1987    15 6   0      M.3     21 7     172       172 i*o       220     220    1115     151    0 12       1320
I960     O   57 6    0.75     36.4    93.8     189     186    207      192   9097    21 7   MS       1070
1969   37 7 35 9    53 7     140     121    144      iSfi    212     165   56 39    7.39      *          1132
1970   29 2   30     513     21 2     149    154     249      162     256    107 2   4.44   4 34       1217
1971    11 3 0.32    207     30 8     14?     193     1AO    135     262    188 2   323    14 1       1210
1972    156  11 1     15      89 1      53      166     188     157     170   49 48     69    9 24       990,6
1973      0     997    5.66     29 4    236     155     186     233     143   58 82    122    5 77       1075
1974   38 7 7 96   31 8     514     287     205     242      168     219    7? 78   4 6?    16 7       1292
1975   23 5 55.1    21.1     60 4     116     124     189     159     14t    131.3    115    12 5       1045
1976   237   16?    903      55B     154    154     192     215     273    88 58     38     5.37       1303 1978     3     35     565      103     122    154     206     206     181   122 6   0 58   12.5       1181
1979    156  8.89      V       256    97 5    202     235      159     15J   64 94    31 2   T2.5       1024
1989    15 5 17.0    57 3     118     164      IM      136     176     246   4987     287      0          1110
1983    15.6 8 23    27 6     356     149    213     296     270     177    1139    57 2      0          1361
1984    156    0      31 5    69 0     234     249     443      198     230   8 716    ?B8   5.77        1514
1985   270     0      12,3     105     257    341     242     212     315     482     32.5   37 7       1607
1936      0   39i.2    *6.9     58.4    37 5    315     274     244     191    103 8   35 9   0.46        1345
1987   289  17.2   BE.6    79.0     123    282     488     326      183   116.4   42.3   34 3       1785
1989    14 1 43 7    74.3     16.3    335     325     177     297     343    259 9    154   3.8?        1903
1933     25 6 26 7    763      106     245     2a*     318     332     297    189 3   61.3   47 1       ZOOS 1990    B 77 37 3    50 4     833     90.6    436     228     319     241    7389    33 4   3 12        1607
1«1      26.4 7.91    68 2     74 4     139    106     3*4     309     222   98 59     35      13         1464
1992    2*4J 32.8     ioe      105     222     225     287     291     250    ID4 7   53.6   15 5       1697 ma     1 CM 31     09 5     100     213     313     217    347      168   149 4   3 03      0          1609
11.2 1.15   20.1      539     127    227     255     228     2?9    a 467    13.7     0          1223
1995      0    22 9    75.5     109     222     195     2?9     310     279    36 40   11.2   23 3        1563
1996   46.5 19 1     162     71 7    338     225     ?45     197     2i5     74 57   44 6   7 B6       F645
199?     39 6  097
1993     13    04     81 1      152     152    200     264     272    239    2359    67 2    1 04       16JB
1999     31 7 2.91      15      92 3     393     427     257     239     309    197 3   B 69 42 1        2014
139     293     314     205     291     ZM      213     40.4   2 51       1530
2000 O 0 3,89 105 195 MS 222 260 274 255 34,4 7 39
2001 0 32 55 5 60 3 327 346 293 292 312 206 3 199 24 1
2002    17 7 2 1&   39 ?     42 2     106    252     274      153
1702
1983
2003   5 Bl  63.5    117      121    58 9    358     232     300     1S5   51 59    11 5   1 86       I486
59 11    l 84   53.1       1226
2004   4 96  2 1     61 2     51.5     ISO    353     326     243     249    193 9   40 7   13 1
IgAS
Avir«fl«  15.3 Tfl.4    53 6     59.6   J60 5 2435   245 9  238.2  228 6   115.5    3i 4    12 7     1459 5
GV O.S3 0 96 0 68 0.55 0.49 0 J7 0.31 &2S ftJJ 0 591 09 f 13
Skwi 0320. ? B 0 74 0 f 0.62 0 38 I 44 t? .07 0 J7 0 635 2.33 T 4£f
“ ’•OX
0 209
0.16
JS5  57 6   raT 7   139 9  392 7  437.6  4^7.6  3*6 6  M21    263 3   T5CJ 753 1      2014 5
Min     1 0£?  00      0.8       5 f      37 5   I00.J  136.2  J 35.3 ?4J 3    a s      u        ft .□       yso. 6 waterworks Design & Supervision Enterprise ^—
-
luAssacwElaowiUi [oiercQndnnitai Consultants and Technocrats hi lid
r.iAr jo Dedessa IrrlEaltoD Project
Meteorological and Hydrological Aspects
May 2007
8.2     9.1     92      10
10
11.1   11
1Z1     12
7<?M/
Year
1967
7ft    7 79     0        0     22 4  73 9    0     21.7  75.2  96 97    112  60 8   6B 4   71 7  110
110   132   B7 7  110  1.92  75.7   75   0 12    0
1968     0       0     57 3  029      0     0.75  1 27 35 1    31     62S    81.4  B7 4   825     101  121  06 1   76 5  115  76 ft  14 2    0     21.7 10 3  4 25 1969  26.1   116   14,7  21 2   376   16 1  6.75   133    18    103 1  72.3  71.9   552    103   106  106   83 6  81 7   36   20 4  3 46  392     0       0
1320
1070
1132
1970 2 1 27 1 7 27 22.7 23 6 27 7 1 73 195 34 3 114.3 49.4 104 127 4 122 81.7 79 8 94 4 162 50 57.3 4.44 0 0 4.04 1217
1971 11 0.27 0.32 0 462 16 30 4 0 40 42 1 99.B6 62.2 131 63.4 116 61.4 73.9 125 137 104 B4 3 26 6 5.46 3 17 11 1210
1972
1973
7.6 7 79 4.31 6.84 0 15 36 5 52 6 25 5 27.53 78.1 87 9 07 2 99 89 7 67.2 94.2 756 25.7 23.8 61 3 769 0 9 24 990.6
0 0 997 0 0 566 254 404 140 96.39 96.2 58 9 91 6 94 2 108 125 78.8 64 1 57 1 1.73 122 0 0 5.77 1075
1974 306 8 12 2 26 5 72 19 9 11 9 0 29 4 85 188 98.87 102 103 1195 123 101 67 5 102 110 44.4 2B.3 0 462 4.6? 12.1 1292
1975 0 23.5 47 7 74 0 69 20 4 5 14 55 2 67 5 48 89 00.ft 43 3 75,2 113 62.1 96 9 92 5 48 8 86.9 44.4 11 5 0 6 06 6.46 1045
1976 23 7 0 103 5 89 57 9 324 322 23.5 7B.8 74 B1 72 81 8 102 9 69 1 51.9 163 19B 74 2 40.1 4B.5 32 3.98 2 09 2 48 1303
1976 I 3 □ 35 0 58 4 10.1 12 4 90.9 49.1 73.14 87 e 66 79 7 127
1979 70 7 79 8 89 0 046 105 11.6 14 57 2 40.35 99.6 102 145 90.3
71.2  134   34 a  96 5   72    50.5  0 56    0    6 06  6 46  1181
85 5
i960    76    7.79  8 89  8.89  27.7  29.6  2ft 6  ftg.a  642    100 3  41.6   587    656     70.6   99
1963 7 8 7 79 798 0.25 18.7 ft 89 20 7 14 9 54 3 94 53 89 7 123 168 1 128 134
198** 7.8 7.79 0 0 4 73 26 9 17 3 525 53.9 180 3 138 111 2326 211 51.6
■90S 03 2 49 0 0 1.5 10.8 57.5 47 B 121 136 6 168 173 94.1 148 826
736   97 2   57   40 4  24.5  15.6  15.6 6 06  6.46  1024 76.5  138   109  26.3  23.5  11.9  169     0       0        mo 136   69 9  86.7  78 7  352   44.2   13      0       0
1362
147   66 7   163  7 16  1 56  15.2  11 6  4.96  0.61
1514
130   160   155  37 2   11   24.9  7.50  36 9  0.01
1607
1966 0 0 275 36 4 152 31 7 28 1 28 3 1 24 36.22 195 119 147 6 127 110 134 114 77 1 65 189 26.2 7 66 0.23 023 1345
1967 0 2 89 0 T7.2 48 1 40.5 693 72 9 192 104 3 158 124 224.5 263 215 112 116 66 6 01 4 36 31 2 11 34 3 0 178$
1988 94 4.73 2 66 40 57 173 0.98 14.3 145 190.2 172 154 75.1 102 175 122 179 164 155 104 154 0 0 3 87 1903
1989 186 7.03 26 07 43 9 32 5 65 3 42.7 148 96 74 182 102 2OB.4 1D7 186
?99O 0 8 77 13.1 24 7 21 6 28.6 0 83 3 60 3 30 3 253 185 123 T 105 108
1991 14 2 122 0 7 91 37.6 30.6 1 27 732 09 9 4904 133 93 1 195 1 169 179
145   194   104  91.5  97 8  295   31.0   196  27 3 211   90 1   143  53.4  20.4   324   1.03  312     0
2008
1607
131    144   779   97 3  1.27  10$  245 12.7    0 29
1464
1697
I
11992     0     24 ft   17 7   15 2  252   00 6  3 34   102   152   70 12  82 1   143   161.3   106   159  131   102   140  61 4  233     29    245 1 15    14.7
111*£
in — ■&. K.
u> ©
* SP.
rd
3:
3
1-
£
o
CJ
O.
Cfl
C
E
TH
>1
m
□ ■o <J
&
o>
£3
a
L«
o
£
Qi
43 sAj-Jg tcdessa JmgairoB Project MeteorofogicaJ and Hydrological Aspects
Annex B Rfrs-ufts obtained from th.* Hydr-afo<|ical Analysis
Bt ■ EslimalEtf Monthly Flows at Arjo Dodesss Oam Site
May 200?
jnri
r? iiimj ri
rar ,■
1 Yair Jan
Mjr
J if ft
Jul
Airg
fort
Nov
jchM
f™-
Feb
Ap<
May
‘ IM 30 74 26 02 25.73 6H.61 49 ?8 207 7 751.5 972 5 900 661 291 8 101 4
5962 34.66 18 98 1947 $973 21 39 157.2 397 6 5608 700 8 5122 84 92 31 95
I9&J 22 72 123 12.25 30 86 111.6 235 3 429.5 526.3 622 8 223 9 111.8 97.23
lAj.r't.fwlvfi"erl* —
4<M9
2525
2735
5964    '7642   24 32                 24 21    41.69      167       670      784 4    7D5 4    521.4      307      42 0 3       3413
1965   33.05    r& 1     1 ?.2B   34 56    21.07    122.1     532 7    633 6    410 3   573.5     194 6    90.12
2673
1 19&6 42 41 403 39 61 5361 4741 134 3 547.5 654 6 726.3 49 32 25.38 11.62 2372
1967   6.806    5.364    TS 57   14 73    19 24   B2.H       452 6   764 7      719 5   634 8     400 8      120 1       3236
1969 M4 29 71 46 01 26 59 55.55 253.9 807 857 565 3 174 2 53.61 26 41
197U 20.36 5 351 9245 24 21 34.36 209 3 593.4 635.7 673.2 121.1 1102 35 46
1971 22.1 1044 7 454 9.919 406 175 5 S25 6 705 6 568.4 450 3 T84 3 60 15
1972 I 31 3 ifl 9? 13 43 25 78 42 79 5561 512.9 74$ 2 IJD.7 125 4 71.09 29.98
2728
2472
2763
2134
1973   15 44   7 121    3 221    4.586    82.96     181 5   158.2     633      839 1    354 5     90.45        37          2405
5974   21 79   10.31     9.837                 71 15      190      409.S    770.6     195 6   63 73     7? 32       27 9         1859
1979    10J7    7 905     5B15   16 56    35 l&     94 19       340$    497 5     371      1$7 1i    57 07     25.13 I960   10.73    9.737   6 839   *9 66     144.9    366 1    564 3     777        745     2315     62 71       52.8
1961    47 75   27.57    29 73   25 53    40 74    38 71   412.8     833     544>.$   3152      19.55     7 138 1982   35 71      19 2     19 63   13 95    34.65     150 3     451.6    571.2    414 &   455 6      107 4     53 96
259      20 13    23 4     16 88     39.8     111 $     361 4     66?       668 2   517 ft     2B2.5    $9.26
1619
3045
2139
2355
2924
1964   23 01     10 69   a K6      5 654    21 59     134 7     449 2    40F 2    3t 1 8    ?3 3fl     12 69     4S08         1463
IMS   7 F52   3 4&Z   1775      5 54     47.33     123 a     280       559      $04 1    155 7     4531      25 72 1&86   10+9     6 052    11 Q2   9993     9 $85    86 35     2B8.9     2962     438 4    132.9     50 52     28 15
1«7j 7 768     3 775   5.501      12.5     2F.&2    157.2      4128     633       402.9   231.4     97 47       38.7
1156fi   24 16     77 49    14.79    5 553    25.08    203 6     364 E    689 1     905 1   315 2      114 9     46 11
1969      25      14 84    13 97   24 24    2056     87.63      174.3    301 1      e$i 3   315.2     65.15     70 31
ISM   31.93    19.11    23 19    44 0a    31 91     114.4     219.3    1043      $69.7   280 5     46 23     23 01
19$1     16 3     12.32   10.51    18 94   44.17     113.8   517.4     964.2     486 9   310.9     29.61       21 7
1992   14.62      1523   9 *35     14 96    42 85     1166       2351     497 2    338.1   482.9     99 78       4 s 9
»i
1993|   254     17 72    16 74    39.56    79 85    226 9     383 1     59ft 7     377 5   243 a    107 6     36 17 1994   23 32     1?4$    10.62    11 34   46.32     1601      341.3     736 3     514     S3 66    41 3B
21 0A 1995   12 1fl    7.787    i0 15      14 06   29 04     60 34     143.8    343 1      291      93 56    36 4<       82 R 1996   29 25    18 44   26 36    21 96     107 7    271.3      462 2     5152     35-a     225.1     71 57     49 76
2001     503     37 86   45 32    41.35    97 36     291 4     4711      630.3     602 2   4038       13D $     6Q 7ft 2002    59.09    36 38   37.91    45.85     35 1       127      292.1     366 4     346      1262      70 05     4 7 88 2003    33 66    23 05    38 53   53.75     364T     87 39    347 2      393 2     S40S   315.2     &Q27     46 11 2004     31 2     25 55    20 76    20 73    49 4?     146 8    336 3     365 2     384.9   3223      6$ 26     46 IT
1764
1369
2634
2719
1764
2546
2547
1909
2263
2011
1124
2157
2865
1590
2005
1845
Water Works Design & Supsprislon Ent^ris^--------------- j 0 fendiUM mlmemotHe.uiCeuniint, and TrcllDH1Crata
■mrwmhIrjoDrfttjj [nlfitlaQ Project
Meteorological and Hydrological Aspects 62. Reglonar monthly coefficient of variation* <CV]
Mar 2W
Sfsforj    rear   Jan     Fob            Mar jflinrtf Afav'Jt/ne Jufy 4yg _  Sap Oct Nov          Dsc |------
114001 I 35 <i Si 0 57 0.66 068 0 62 0.45 0 35 03 0.33 067 0 52 0.59
II 14014
20
0 4*
044
0.48    0 56    0 69    0 53     0 27
0.33
0 28
0 56    O6T
0 53
114005
23
0 26
041
033     043    06      0 4?      02
0 16
0.25
044     0.3
G34
114004
22
0.33
0 42
0.45     0 56   O.M     043      05?
0 38
043
0.64    0.36
033
114003
21
0 51
0.83
057     0.71    ow      058      0.35
0 25
0 36
0.56    0 46
0 55
91006
38
o«
13
0.7       06      061     6 46     020
0.32
0.20
O&4     1
096
91012
35
0.61
0.49
0 76     0.49    OS?    0 42      0.3
0 29
0 32
0 52    0 9
0 59
B3: Regional monthly coefficient of skewness
Sfaton rear Jan Feb Mar r~
114001
35      0.63       0.74       1 07    094      1.63    089      0 13   004     0.25     0.99    1.37      0 96
114014 20
114006 23
91008 3fi
3 35 031 0 47 o.ai 065 1.03 ■0.5 0.93 0 69 0.67 2.6 1 96
0.33 U48 0.59 -0.1 2 10 154 0 07 0.45 0.61 0 4? 0.52 1.09
2.73 0 29 3.26 0 77 1 14 051 0.17 1.14 1 13 0 77 3 14 2 65
91012     35      3 37       4 94       1.22      1 5     2.34    1 15     0 43       0 94         0 05       1.0     285      2.79 L ii  ■  ' -i
04:       1& Regional monlhly c&efficiWHl o( correlations (R)
Sfaton Vear Jan Feb Mar dprfl May June July 4<j9
Sep Ocf Mow    Dec
114001 35          -0 1        0.83        089     O.B D.3 O?e 045
114014 20 0.36 0.6 ?7 0.56 062 0 61 046 0 54 0 28 -0.04 0.65 0 7fi
114005 23 iW 0.5 0 36 0.3 0 64 0 38 0 40 O&ft 06 0 83 0.25 0 16
1114004 22 0.8 0 52 021 0 52 Ofl 0.S8 0 58 0 89 0 01 0 77 037 l'l 14
0 53        044        0 48   0 74       0 78
■114003 21        0 94         0.3         0 18    052 0.45 073 0 68
9100B 3fl
0 27 0.33 0 37 02? 0.53 0.59 0 54 0 55 0 46 0 45 0 77 0 62
0.12 D.B3 0.72 0 4fl o.4t 0 ?2 0.5J Q4t 0.40 0.31 0 44 OK
066           0 58       0.82   0.56        0 i
91012 35
1 I--------i
Water Works Design & Supervision Enterprise------------- “
10 AssociailoQ with [□terwotbmtat Couakuts Snj TcehmriUs l[d
114AijDUtdrssa tmjaiiDn Pr-oJttL Meteorological aaafl Hydro logical Aspects
May ;Wr/
aunoaraifea |iroc3 pm ry weigr Station               Nnmn qf Station
ll«Q riDiriKno
Area     Record
PWMs
Deg N, Deg E.  4lun2)   («r>g<h,N                 m,n -           _"hn_ ,
1 114001 OetJesiS near Arja
Upper DedesH reht
2 114014 Demb.
8 41 36.25   9981         23           0 40739    0.243171 5 02 36.28         1806         15          0.420504   0.262951
3 1140Q5 Cabana near Abasrna                      9.02 36.03   2681         ia          0.414042   0.253945
4    910WJ Giigel Qhibe
5 91012 Gojab near Sheba
Angar Gulin near
6 114007 Neqemie
7 114004 Wama near Weq&mfe
7.45 37.11        2966         37           0.400025   0 240847
7.25 36 23   3494         34           0 408619   0 248091
1975       20         0 421145   0.254033
0.53 36.47 844 21 0 419805 0.254029
8 114003 Sitfa war Neqemte                        0.52 35.45         951         20         0.416527   0.251324
9 115000 AleUu a1 Neja
10 1DT001 Sor at Metu
11 91013 Ghibe-Limu near Limu
12 91001 Great Ghi be near AbeHr
9.30 35.3 155 7 0.400261 0 247562 6.19 35 85 1622 17 0.401323 0244656 S35 37.13 663 10 0.425296 0.261749 8 14 37 15 15460 19 0 424754 0 26C656
I
We/gMed* Average
255
0.411964  0.250375
Water Works Design t Supervision Enterpn^T~~
115
taaMMtattoairiftfct
B COI
r    ii ^c m d «    ^^^
1     I    S   1   [tMd
WL L(r)ArioDtdeBis trrlf (cIm Frti]eci
logical and HydrologicaJ Aspects
B&:      M&jn Monthly TfllaJ (Suspended and Bed} Sedimanl Load at Ar jo tJedeasa Dam Sit* (in IQQtl m )
May 2007
1
tear   Jin       Feb    Mirth         April      May    June    July     Aug    Sep      Oct     Wov             Annual
——J 1961  T7F        1 75        1.27         5.73       3.U        33*       315      523       470     372       523       15.3        1711 1962    2 56    0 94        0.61          1 07      3.18      22.4         It4        2i6       319      109      0 92      2.41         670 9 1963      13     0.47         0J9           1.6       11.3      40 9       129       403      204       504     IS. 5      14 3        932 5
196a     1 76    1.32       0 71         1.07      2.34      236        262       370      322      367       19.7      3 74          1197
196$    ?3?     0 72        0 34         1.91      0 79      14.3       102       263      135      227        io i        12.7         880 6
i960
154
3 13
2.54
3 66
266
22 4
190
277
338
102
40.6
9.14
995.4
1967
6 64
0 57
(is?
0.49
3 <9
22-4
140
356
333
352
71 4
20 1
1300
1989
5 73
222
052
0 22
226
2.27
123
255
299
19?
10 4
2 97
915.6
i 1969
207
1.92
3 22
1 *2
371
<A 1
2?4
4?7
205
102
5.13
1 78
1024
19*0
1«
0.75
0.4
0.23
1.72
336
216
246
205
102
16.1
2.65
826.7
1971
1.25
0.36
0.18
□ 2?
2 25
25.0
176
316
226
IS4
36.0
5.64
949.3
19??
2 17
0.68
0 45
1_2
2 44
6.09
171
342
140
190
9
2.19
701.9
1973
07
0.2
0.05
0 06
7.04
26A
123
245
425
105
11,9
3.05
948 8
1974
i.a
0.35
0 29
0.13
551
29
lift
300
205
102
6 23
1 94
833.7
^979    191      1.29        065          0 59      1.79      9 43       9BA       179      115       28 0    5 63       1 6J         434.5
1980    0 39      03           015          341        V.2      82 B       211       355     352       54 6     6 55      5 39           1096
19B2    2 59     056          063         0 45     1.74      26 7       140      223      136         W     15.5      5 00          711.7
1913    T 61     1.03        1 09         0.61      2 19      123       97.7      300     296        339      2«A      8 32          1069
1 1904     1.33    0.35         0.2          0.14      0 62      16.7       136       127     973        9 39     15.5     5 74         402.1 1965      02     Q.CH5    0 02          0.2       2 67      14.5       05        216      186     29 JE     4 31      1 71
19B6    0 36     0 15         913         0.26      0 23       3.2l      66.3       ?8       151     21.9        155        5*              Mt
1987    0 23     0 07        0 22         036       1.23      22.4      9! 7      301      132        53 l      13.3     3.28          616 6
iue
1989
2 36
0.76        0 52          0.1        1 24       324      940       246     205        102      17.0      1 31          ?03 4
0.63
0 46
1.06
076
04
30 4
60.1
294
102
6.95
H 52
1990
2 2«
0 95
100
262
1.53
12.9
44
525 4
246
205
102
15 5
5 24
639.8
1992
0 62
026
05
2.45
13.3
49 1
179
99 4
17?
13 fl
3 72
1993
156
084
D.EJ
2 37
603
36.5
107
SL4A7
J-* *, f
309
119
57 7
IS 5
2 94
I9M
1 36
6 46
0.31
0.32
2 60
22
66() fi
89 2
335
194
12.5
J 37
19M
0 46
0 23
029
0.45
1 24
1.35
4.63
22 4
667 4
98.7
70 2
12 5
0 71
2 75
5 24
1996
1.71
W
0.93
10.7
51 2
145
* 1/
169
109
102
155
49
eji 5
2001
4 72
2.63
3.15
2.55
9.1
57 5
150
201
?5O
129
2l I
7 7Q
2002
6 01
2.65
2 37
301
1.76
152
105
899 3
103
20 1
7 32
aa1
2003
2 44
i 25
2.43
■3 86
1 ^9
6 37
123
123
205
341.1
102
15 5
5 24
20C4
2 16
1.43
Oft
ft 34
3 08
594 5
19 2
67 a
119
122
S0.2
10 7
5.24
_           L—
461A
Water Works Design 4 Supervision Enteric' ~ "
Lift
LO CHUM Witt lDl«
CM1  aEata
il      i Cea^lWs 
Twtahjm< pyfArjo Dedessa Irrigation Project
Meteorological and Hydrological Aspects
B7:_ Eleveation-Area-Capaclty
Elevation Area Volume
jmisl)
_ (Mm1)
Relationship* of Arjo
Elevetion Area
(mas!)
May 2007
Dedessa Reservoir
Volume
3
(Mm )
1930            0.54              0.0             1356            87 85           1341 2
1321             099              0.8
1322            2.39             2.5
1323            3.78              55
1324            fii.11             10.0
1325             664              159
1326             803             23.2
1327            9.46            31 9
1328           10.07           42.1
1329           12 67            53 9
1330           14 40            674
1331            15 89           82.5
1332           17 74           99.4
1333           19.46          118.0
1334           23.59           139.5
1335           26 66          164 6
1336           29 05           192.5
1337           31 73           2229 131a           34.24           255.8 1339           35.62           2913 1340           39.45           329.3
1341           41 97           370 0
1342           44 25          413.1
1343           47.05           458 6
1344
49.95
507 3
1345
53 11
558 8
1345
56 31
613.5
1347
59 15
67t.2
1348
61.56
738.8
1349
63 97
808.7
1350
67 88
874 7
1351
70 62
943.9
1332
74 35
1015.4
1353
77.68
1Q3C.fi
1354
01 26
1172 1
1355
84.51
12550
1357 90.75 1430.5
1356            94 IB            1522 9
1359 97 23 1618.6
1360           100 54          1717.5
1361           103 64          1819 6
1362           106.39          1924 6
1363 109 00 2032 3
1364 111.91 2142 8
1365           115 05          2256 3
1366           117.68          2372 6
1367           120.20          2491 6
1368           122 76          2613.0
1369           125 28          2737.1
1370           127 69          2863 5
1371           130 25          2992.5
1372 133 03 3124 2
1373 135 45 3258.4
1374 138 08 3395 2
1375 142 38 3535 4
1376 145 27 3679.2
1377 148.00 3825 8
1378 150.75 3975 2
1379 153.73 4127 5
1380 156 02 4282 3
1381 159 09 4439 9
1332 162 13 4600.5
1383           166 96          4765 0
1384           173 01           4935.0
1385           178.58          5110.8
138&           183 38          5291 8
1387 188 10 5477 5
1388 19328 5668 2
1389 197.36 5863 6
1390 201 96 6063.2
Water Works Design & Supervision Enterprise ~
In Association with lotertoatlaentaJ Ccnsulunti and Technocrats
Pvt. Ltd.Arjo Uedessi IrriKfctloa Protect
Meteorological and Hydrological Aspects__________________________________«>y goo?
——         1—
rn
Simulation Results of Ario Dedessa Reservoir
I
Year Month’
13
Inflow
3
DF
(nrf'sj
4.
Ec-Rf
fmnV
$
IWD
(MmJJ
6
(Eo.RI) SI           1WR
cs 
(Mm3J (Mmj;
fMntJ/
.7              8          9
w
I                   "T       RflServo/r Status
Stotag?
11
Area
12            13
Spill
14
5TRQ
15
r.spw
18
404
Sep
$77.4
00
0
00
0.0
10
0.0
576 4
1006 3
74 1
135V9
57G 4
404
Od
JK.3
0.0
111
0.0
82
1.0
0.0
324 1
1006 3
74 1
1351 9
324 1
404
New
102.7
00
143
46 2
106
10
46 2
44 9
1006 3
74 1
1351 9
44 9
404
Doc
47.7
00
135
60 0
10.0
10
60 0
-23 4
982 9
73.1
1351 5
0.0
404
Jan
22,5
00
146
74 0
10 7
10
74,0
-63.2
919 7
70.4
1350.7
0.0
404       F«?        T2.J 404        Mar          T6.J 404       AP'         16 8
404       Ma>  j 40.1
404        Juri         180 9
404        Jul        400 3
404       Aug       647.4
406       Sep       717 9
0.0 147 05 0 104 0 9
00 164 504 109 0.6
86.0
50 4
0.0         146        7.4
94       0.8
0.0          ao          0.0                     5.1       oe
0.0           o          0.0
0.0           0           0.0
0.0           0            00
0.0           0           0.0
0.0 0.6
00       1 0
0.0       1.0
00       1 0
82       1.0
7.4
0.0
00
00
0.0
oo
0.0
■84 0        635 6        66.7 459         7B9 9        64.6 ‘0.9          769.0        64.6
34 1         623.1        68.1
>60.1        983.2        73.1
390 3       1006.3       74 1
6464        1006.3       74.1
716.9       1006.3       74 1
768 6        10053       74 1
13494       0.0
1348.7      0.0
1346 f       0.0
1349.2       00
1351 5      0.0
1351 9    376.3
1351 9    846.4
1351 9     7169
1351 9    700 6
7«9
405        Oct - ------ J
777.8
—
0.0
______
111          00
Water Works Design &. Supervision EnternrR*Arjo Onteua Irrigation Project
Meteorological and Hydrological Aspects
Bfir j.......continued?
May ZXJ07
<23
405 NOV 4M.T
4
6
T
a
.
9                      >< J
1J
14
t
0.0 143 45.2 106 1.0 46.2
75
405 Dec 193.8 0.0 135 ao.o 100 1.0
405 Jan 70.5 0.0 146 740 10. B 1.0
405 Feo
405 Mar
405 Af*'
405 May
405 Jun
4B.7        00         147       85.0
10. B     1.0
60.0
74.0
66 0
46.9         0.0         154        50.4                   11.7      0.9
31.3
43,5
149,4
0.0 146 7.4 10.3 0.9
00 80 00 5.7 09
0.0 0 00 0.0 1.0
405       Jul        466.8         00           0          0.0
00       1.0
50 4
74
0.0
0.0
0.0
347.3       1006.3       74.1
1228        1006.3       74.1
-15 3         990.9        73.5
-48. t 942 8 71 4 -16 2 926 6 70.7
12.6         939 2        71.3 36.9         976.1        72 0 14B4        10063       74.1
1351.9    347,3 1351 9    122 8
1351.7       00
1351.0       00
1350 8       00
1350.9      0.0
405       Aug       640.7       0.0           0           0.0                     00        10
406       Sep       5)6.8        0.0           0           0.0
oo        10
0.0
o.o
406       Oct       402.5       0.0         111        0.0                     8.2       1.0
0.0
406       Nov       168.2       0.0         143        46 2                   10.6      1.0
452
406       Dec        71.S       0.0         135      GOQ                   10.0      1.0
60 0
465.8        1006.3       74.1
639 7        1006 3       74.1
SIS 8       1006.3       74.1
393.3        1006.3       74.1
106 4        1006 3       74.1
05          1006 3       74 1
1351.4      0.0
1351.9     118,3
1351 9    465.8
1351 &    639.7
1351.9     515 8
1351.9      3933
1351.9     108 4 1351 9       0.5
026 6
406       Jan
50 1
00          146        74 0                    108       1.0
74 0
-54.1         952.1         71.8      1351.1       00
406       Feft        28.8         0.0         147        65.0                   10.6       1.0
85.0
406       My |       17.0        0.0         154        50.4                    11.3      0.9
50.4
406       Apr         13.5         00          145         74
9.7       08
7,4
-71.7         060 5        68.7      1350.1       0.0
-45.6         634.9        66.7      1349 4       0.0
-4.5          830 4         66 5      1349.4       00
Waler Works Design & Sunemsinn Fnnmrf»I
I
I
I I I I I I
f-      CD
to
rt
d
O
8 ri
pO
e
oQ
in
Oo
o         G>      <D
s to
tfl <7?
sto
s
B-    T-        «/!■     J5       CM                  co        CD
5>
to
T«
n“l
to
*=■
Lfl
TO
w=
8
s
TO
8
to
«—■
CD
rJ
to
■r“
CD
TO
a
TO
T-
»=■
uD
to
»=
£
T"
in
rt
h-       in       cn      CM     to
V
to
CM     n-
o
■•r s
s
in
CD
h-
TO
TO
CD
O
o
p
o
p
p
p
O
CD
TO
TO    CD
d
C
■»“
•*
**
■?_
■”
¥“
*“■
O
O
TO        d
Ci
to
O
a
G>
o
r-H
O
TO
TO
TO
uS
■M      e>
O
o
o
a
cd
o
d
■='
O
o
•"
£
Oi
■n         o
i
3
C
C
c
u
TO
TO
tfj
Mb
id
TO
t*
m
TO
o 13
e* cm
M>
r-_
s
*-
3
T-
2
■*
ri
n
ooo
ddd
CO IO
ci
sa
■f-i      TO   8
*M        5   □                  < -jj
C       ■*            ? &   O        s   a   c
oi5
nj
“k
WatBT Wnrlft? Fia^e,■Aijo DAtasa Irrigation Project MBteorological and Hydrological Aspects 
__
May ao?
Annex C: Standards
U i;        G e mm only u Sed Vai u e? ot runon tuei i il,ph i i ls Class         Description of catchment
A        Flal ru bvalefi and ijlck collpn MiJS
0             Flat partly cullivaled stiff soils
Runoff
percentage
10
15
c
Average catchment
20
D
H:lls and plains with tittle cultivation
E
Very hilly and Steep, with little ar no cultival i-r
35 J
45
C2: Rif naff tcbefTici^rkt for porwiou S surfaces by selected hydrologic soil
groupings and slope ranges
Terrain Type
Soil Type
.A.
c
D
Flat, <2%                              0.04-0.09                   0.07 -0.12
Rolling, 2 - 6%                      0.09-0 14
012-0.17
Mountain. 6-15% 0.13-0.16 0.16-0.24
Escarpment. >15% 0.16-022 0.24 - 0.30
0.11 -0.16                0.15-0 20
0,16-0.21                0.20 - 0 25
0.23 - 0.31               0.28 - 0 38
0 30-040                0 38 - 0.48
Nate Where A. 0. C. jnd D aelmed *s Shown =n Cj
Water Works Design & Supervision Eiiterpr^T” In undrttewMi IdUnanttoaiitai Consultants ■nHedinMrMs
111
Pvt Ltd.Arjo DttfKsa JtrigaUan Project
Meteorological and Hydrological Aspects 
C3:            SCS Curve Numbers for Various Conditions1 Coizer Description
Mm jow
Cover type
I Fallow Bare soil
Crop .residue cover (CRi
I Pasiure, grassland, or range- ' continuous lorage for grazing31
Mearfow-raniinuous grass, protected from grazing
Bfush-weed-grass mixture with brush the maror element’ Wuods-grass combination5
1
. Woods6
Hyd’roj'ogi'
c
conrftfo/i
* Poor Good Poor Farr Good
— Poor
Fair Good Poor Fair Good Poor Fair Good
Curve numbers for
hydrologic soil group
ABCD
Farms-burfdings, lanes, driveways                — and surrounding lols
77           86            91             94 76            05            90             93 74             as             88             90 68             79            86             89 49             69             79             84
39            61             74             00
35             59             72             79
48             67             77             83
35             56             70             77 30’            48             65             73 57             73             82             S6 43             65             76             82 32             58             72              79 45             86             77             03 36             60             73             79 30*            55             70
59 74 82 8767
4rid and semi-arid rangelandse                      Hyd
can<jT
Mixture or grass, weeds, and tow
Poor
—
growing brush, with brush the minor
80
Fair
.—
87
element___________________
71
Good
81
—
Mountain brush mixture of small
62
Poor
74
trues and brush
—
Fair
Good
66
74
48
57
—
Small trees with grass understory
30
Poor
Fair
Good
41
75
85
—
SB
73
Brush with grass undef story
41
Poor
Fair
Good
61
67
BO
51
—
63
Desert shrub brush
Poor
35
47
63
Fair
Good
77
55
85
72
49
81
68
79
Water Works Design & Supervision Enterprise
tn AsSirtlaUMi wlUi Intercontinental Consultants and Technocrats Pvt. Ltd.
122ArjoDedessa Irrigation Project Meteorological and Hydrological Aspects
CJr (... corff/PWMfJ_______________________________ „_____________________________________ _
Average runoff condition, and I* = 0.2S
' Poor < 50% ground cover or heavily QW&d with no mutch
Fjt 50 io 75% ground cower wf nol heavily grazed
Good > 75% ground cover and iighlly or only occasionally grazed
3 Poor c £0% ground cover
Fa< 50 1o T5% groixxf cover
Good > 75% ground cover
4 Actual curve number is tees- than 34); use CN = 30 for runoff computahons.
5 CNs shown were computed tor areas wrih 50% grass (pasture) cover Othec combmalions of condrliors may be compulcd from QN$ ?or woods and pasture.
* Poor Forest Irtler. small trees, and brvsh are destroyed by heavy grazing ex regular
burning
Fair Woods grazed but not burned, and soma foresl litter covers lhe sexi
Good Woods proicctcd from gra/hg. litter brush adequately cover sod
Poor < 3D % ground cover (litter, grass, and brush oversEory)
Fa* : 30 Io 70 % ground cover            Good' > 70 % ground cover
Sort Groups
Grow A Sand, loamy  sand or sandy  loam. Soife having a low runoff potential due to high infiltration rates. These soils  primarily  consist of deep, weiJ-dramed sands  and gravels
GtolielB. Sin loam. or team Sols having a mwlerately low runoff potential due lo
moderate infihraiten rales These soils primarily consist of moderately deep io trenn
moderately well to waU drained soils with moderately fine to moderately coarse texlures
GfOb!E_C:  Sandy  clay  loam.  Soils  having  a  moderately  high  runoff  Dotf-nlml  m  a infilirahon rates These so-te pnmanly consist of sods in which a layer exisls n^r
Gr[)tj0 p- Clay  loam, silty  day  team, sandy  clay. s»lty  clay  or clay. Soils  having a high runoff potential due lo very  slow infiltration rates  These sods  primarily  consist o( days with high sweiimg potential, sols  with permanently-high water lables, S&.I& with a clay pan or day  layer at or near ttie surface, and shallow soils  over nearly  impervious  parent material
Water Works Design & Supervision Enterprise----------- '— ------------- ’ ]n AssoclaUon with Intercontinental Consultants and Technocrats fM LtdIrjrUrtessi trrtpooa Ptojwi
Mek pro logical and JJy^uJjLi cal A.5pect3
Dam oTffj/gn Wood tnffow
Mm. sfandenft
Category of reservoir      frwWaT
General
flare
cofldirJon1
_______ w_ai aiu? _
Wind speed,
Min. wave
surcharge
A: Breach endangers in
SpUiing long lerm av Daily
fives in commentary          Inflow          PMF
Larger of 0.5 PMF or 10,000 year flood
B: Breach may
endanger lives not in
a community.
extensive drainage            Full
C: Breach wth negligible nsk to hfe and causing limited
Larger of
0 5 PMF or Larger of 0.3
Average annual max hourly wind Wave surcharge
10,000 year      PMF Or 1.000              allowance > D.6
?lood Larger of
year flood                  m
Av. Annual max. hourly wind Wave
0.3 PMF or        Langer of 0.2
surcharge
1.000 year         PMF Of ISO               allowance >04
damage
Full
flood
year flood                  m
<W erf PMF rhe Qfdmares trf the GOfflpulW PMF JtytfrOtfnjpfi
.jrrr mufflipfed by fihe .tVOp^.rj.r-H
Water Works Design & Supervision Enterprise'-------------_ [ QissHistkn with intewntlitMital Consultant and l^chDflcrats Pil LtdAjJd Orttssa Irrigation Proprt
.Meteprdogkal and Hydro logical Aspects
C& Ratiocof the basjc dSmanslontes* hydrograph of rhe SCS
May ^flor/
T/Tp          CwQp          TifTp           Qi/Qp
00
0.05            0.000
0.1              0.015
0J5             0.043
0.2              0.075
025             0.11
0-3               0.16
0.35              0,22
0.4               0.26
0.45              0.36
0.5               0.43
0 55              0.52
06                0.6
1.05 0 99
11 0.98
1.15 0.95
THTp QifQp
2.6                0.13
2.7                0.11
2.8               0.09S
1.2 0.92 2.9 0.08&
1.25 0.80 3 0.075
1 3 0.84 3.2 0 05«
1.35 0.80
1 4 0,75
1.45 0.71
1.50 0.65
1.55 0.61
1.6 0.56
1.7 0.49
3.5                0.036 3.7                0.027
4                 0.018 42                0.014 4,5                0.009 4.7              D.OO?
5                 0,004
0.65
0 69
1.8
0 42
07
0.77
1.9
0.37
0.75
0.63
2.0
032
08
0.09
2,1
0 20
085
0.93
2.2
0,24
0,9
0.97
2,3
021
0.95
0 99
24
o.ia
1
1
25
0.16
Water Works Design & Supervision Enterprise
rn UfldatiM With tnitrcontinenial Consultants anfl Technocrats Pvt. Ltdtajo-Dedtssi irrieadoD Project
Meieorolo^ical and Hydrological Aspects
C6; Guidelines for Interpretations of Water Quality for Irrigation
May EMfl
Water parameter SALINITY
Salt Content
Symbol          Unit1
Usual range in irrigation water
Electrical Conductivity
ECW
dS/m
0-3
dS/m
(or)
TolaJ Dissolved Solids
TDS
mg/l
0-2000
mgfl
Gallons and Anions
Calcium
Ca”
me/i
0-20
me/l
Magnesium
Mg”
me?l
0-5
me/l
Sodium
Na*
meJl
0-40
me/l
Chiorde
or
med
0-30
mart
NUTRIENTS'
Potassium
K‘
mg/l
0-2
mg/l
MISCELLANEOUS
Acia/Basicily
pH
SAR
1-14
Sodium Adsorptwn Ratio"
(mall) ,
11
$.0-0.5
0-15
Source FAO. 19W. Iftfer Ouaftty forAfl^uft/re.
Drg.nage Paper No Ret, f ffopmfetl. 1994
Waler Works ^Ign 4 Supervision Enteinriw " "------------------------ ---------- 12,1
S
t.M .d.tonwiu.i«t «»
[      Mt.ic«1UunBa„dTK no I
“B!n^do-Derlessa. [niRaUOn Prtjdfil MHeprokigical and Hydra logical Aspects
Annex E):                   MeUuru lorica I Dara D1- Details at Meteorological Observation Stations
May 2007
Station Name
Latitude
North
Longitude
East
S.Wo
Altitude
|m)
1
Class
Dea.       Mln,         □•g.     Min.
Period
Agano                         07         51           36          36              2030             1980 2004                1
2
Arjo
08
45
36
30
2565
1972-2004
3
3
BedeJIe
08
27
36
20
2030
1967-2004
1
4
Dedessa
09
23
36
06
1200
1971-2004
l
5
Oemoi
08
04
36
27
1950
1954-2004
3
6
Gimbr
09
10
35
47
1970
1978-2004
1
7
Jimma
07
40
36
50
1726
1952-2004
1
a
Kone
oa
41
36
47
2000
I979-2GD4
4
a
Meko
oa
41
36
02
2000
1980-1969
4
10
Nekemle
09
D5
36
28
2080
1971-2004
11
Wama
1
0B
59
36
40
1450
1060-1987
3
D2:        T roes cf C lima tic Data j vail a bis at the va ri qms M eteoroCogic a I Observation Stations
Altitude
S.No.    Station Warns
(rn)            Yrs       RF
1 Agara 2030 25 )
2 ArjO 2565 33 1
3         Bedelle
2D3D            38
I
4         □edessa                         1200            34            J 5         C&mtii                             1950            51
6         Gtmbr
197D            27            J
7         Jimma                          1725            63            J
8         Kone                               2000            26            J
9         Meko                              2000            10
10       Nekamte                       2080        34
11        Warns                             1450             8             J Yrs           refer io fainlail series
TM
x
X
X
X
X
X
X
RH WS
XX
X
XX
XX
xX
SO
s
X X X X
n
X
X
x
x
RF           rnonlhiy rainfall
Tm          .tvCMcje lemperatae
RH           relative hurmdity
WS        w-ivj speed
" Dels .'ifnyrft refers fo Wai'n/aff and r properj-Jq^
SD
1 hr
1 day Rday
sunshine durabon majumum 1 -haur rainfall n  mu amxi bme ur mof 1ra-dmay daraysmLill
Wiur Works Design & Supervision EnJ^.—
I 27
In                Oim uunentlnmu)
[anB T r
. LJZ,u pn
: Ltd.Arjo-Dcdessa Irrigation Project Meteorological and Hydrological Aspects
May 2007
D3:
Mean Month
ly Rainfall at Bedele Station
pn mm}
Year
Jan fret*
Marenlhprll flH.V
Uuhr U"0 Is—V* lost Ittv. IpesAnnual
1967
1969
1MS
1970
1971
1972
1973
1974
1975
1976
1970
1979
1930
1933
1984
1993
1994
1995
1996
1997
1993
1999
0        0       153     33      181     221     212    .381     380      167      253
0
2000
2001
2002
2003
2004
0      100      1        55      153       0       323     360     324      137       35        22
67      59      01      19B    210     250     275     368     286       98         7          0
54      50      B9     256     2sa      266     432     280     444      186       0          7
20       1       41       53     34E     334     311     234     455      526       56        25
0       20       42      17B    116     263     33?     287     287      110      122       26
0       19       10      51      337      269      322     403     248      102      21         ID
66      13      55       9       49/      355     351     292     36B      126       8         29
44     101      37      105    202     215     327     376     245      228       20         0
41      29      156     97        0       267     333     373     472      154       62         9
5        7       115     179    204     267      310    303     281      204       4T         12
0        0        29      44      169     350     408     276     267      113        0          0
0        0         0       208     205     174     236    3D4     363       86        50         0
0        8        43       62      237     369     493     468     306      197       99         0
0        0        45      B6     241      275     489     211     242        9         25         5
2       34       60     141     243     222      2ta     357     2M       183       1          0
17       2        33      106     225     281     250     250     276      21        17         0
0       17      102     130    26?     292     257     618     353       77        10        24
40      34      208      83      317     232     290     203     120      70        45        13 S3       2        50      142     340     307     221     3D4    232      309       38         4 13      15      B7      57      203     332     314     327     291      245       59         1 28       3        13     147    431     441      319     242     324      328        B         39
0        0         4       123     256     420      186     27J     286      242       29         0
0       33      87       72      322     390     297     329     370     211       29        14
16       4        63       38      169     2^8      296     202     253       63         3         46
7       66       64      131      37      320      276    258     197      52        13         3 6        3        46      61      246     447      299     256     273      168      62         15
1980
1539
1897
2322
2101
1700
1790
2171
1796
1993
1926
1655
1706
2293
1637
1660
1464
1637
1670
2001
1942
2321
1B27
2155
1450 1440 1917
i,2a   T 2S   0.77    0 50   0.434  0312   024?    0.21   0.266
10       23       65      >05    239     231     310     203     302      156      41
cv
Star*.
Ml*
Mln
0.563
r .15     L6     1 09    0.68  0.058   -0.9 f   0.837   □ 56   0.345  0.375
68     >01     700     250      497      44 7      499                472     328      253       46
1 256
2.913
0         0         0         9         0         0         rst     202     128       9         0
T2
1 114
1.172
0
law
0.14
0.16
2322
1446
Water Works Design & Supervision Enteric---------------------------- AaocUU™ .Uh l»ttrainOnralal CoMolttlll, ,nd Tectaoeriu, Pi1 M
12SArJo-lMessa IrrlgiUon Project MeUoroloKiealandBydrotogical Aspects
_l _         _ _ -ay
f-------
Ywr Jan fet) March April May Juntf July Aug Sept
C4: Mean Monthly Rainfall a
rtn ml
Jirnm* Station
Oct       Nov          Bee        Annual
1953
1954
1955
1956
1957
1958
1959
1960
1961
1963
1964
1965
1966
1967
1968
1969
197D
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
19BB
1989
1990
1991
1992
33 49 58 133 ?72 203 399 211 256
a         49        88       TJ3      93      210      194      214       152
33        49        88       135       94        2?B     235      244       169
91           25       100      109        «      183     288      254       215
29         4         83       2fiQ     142     226     160      195       249
0 52 117 215 225 278 185 169 5?
« 06 53 130 141 202 203 215 280
81       149        w        130     103     170     27?      138       151
11        39       104      145     284      2f®     135      210       212
0         86        90       225      197     237     272      262       243
40 57 131 116 106 206 221 206 225
43         4         39       203      102     249     205      191
56
21 73 1DQ 153 122 161 ■307 172 139
4 15 196 82 157 273 207 283 250
3 74 63 106 154 233 173 248 210
5S       61       199       91       109     165
189      135       104
70 135 91 160 103 288 197 263 148
10 3 58 81 267 153 205 204 201
12        74       127      115     101      161     159      193       167
20           11          7        149     148     160     297      160       181
5         5B        76       103      320     165     221      265       240
4         65       100      171      120      I9B     252      194       151
36        85       107      112      1&9     324     211      233       190
73        56        54        16      130     197     203      768       191
5         71        42       136     204     22?     184      215       203
32       118      111       23       116     232     153      164       1 15
23        42       500      301      108     189      96       164      141
1          7         136       62       252     114     193      250       154
105       43        61        136     211      253     141      192       157
20        40        97       161       27B       166     1 74      229       299
24 11 32 83 191 183 211 166 18?
25 20 77 147 203 135 260 163 128
0 40 62 115 151 250 233 134 163
26 09 156 BO 180 204 186 160 136
01 59 31 67 182 165 185 2&4 220
20 47 136 179 102 170 232 213 204
25 46 133 56 to* 320 280 200 246
79 01 62 169 1 so 223 200 246 140
20        50         56       152     144
?87
_ 21?      344      J 75
115         1            3 27          68          76
TffS 36 23 50 16 96
118         3
0fi          75         11
07          16         42
130         58         32
35          66         28
97        221         73
154        24         109
10?        116        25
56          17          13 132       215          2 31          59          55
85         3S          5
149        68          36
124        107        44
56         163         0
57         SO         10
25          1            1 90           7           55 93         118         25 229        61          15 64          57          30
75           &          22
109        27         26 3i          127         1
94         21?         37
1411        54           ? 12         138        50
63          50          12
09          14           47
116        46          52
172         2            0 107        28         170 23         93          19 01          6           79
__ iso   __ 70      _ 36
1743
1270
1507
1523
1500
1446
1604
1509
1494
2012
1&06
1341
1333
1019
140B
1283
1743
1405
1 350
1537
1479
1414
1723
1491
1442
1165
1320
1337
161 1
1614
1208
1297
1331
1440
1477
1627
1712
1445
Waterworks Design it Supervision EmernrtHu —
129
“                    WKK ixumUMou,! Craun™, ai„|
Tec noc aB
’'
Lt(LArjo DEdessa [rrtfitJirfi pfojcct
Meteorological and Hydrological Aspects
Water Works Design & Supervision Enterprise ’ —
130
rn Association with IntartMlliientid Consultants and Tectmacrats 
L(±Arjo Dedessa IrTigadDn Project Meteorological and Hydrological Aspects
D5: Mean Monthly Rainfall al Dedessa Station
______ {Irnnmj
May ?Oir/_ _
March April |way bun*
!*“&       _Sppl__ Oct
Nov
Year Jan Feb
1971
1972
1973
1976
1977
1978
1979
1980
1981
1983
1984 1985
1986
1987
1986
1989
1990
1991
1997
1993
1994
1995
1996 1997
1998
1999 2000 2001 2002 2003
2004
152 40 11 6 5 90 167 283 497 219 161 123 6S 0 0 3 41 266 273 203 209 146
00
0          0           0         83        80 00000
217       196        ’04        121         60 49          20
191 245 197 239 193 14
0          0          2         13       320     285     272       240       130        96           7
0         40        39        68       150
0 0 35 It 244 207
ZDS                     39          68
00
334     625      401        196       107         32
A¥VM0* CV Skfw Mu Mm
1 91     1 07     1 28      008     051 2.10     2 7tt     2 75     0.94    ■0 25
21        48        160      154     275
00000
0          0          9         20       221      306     297       309       123         0            8 1          0         47        09       219     316     373      296       158       146         27 0          5         12        73       90       104      339      259        22i          04           S 4          3         25        29       141      399     428       296       215        97          54 1          9         32         8        275      341     370      442       300        24!           3 0          0        160       36       243     289      337      289       305        120         22 4         10        39         2         11      280     402       245       152        53          19 7         17        33        74       101     21S     355      304       132         5             1 4          0           0          0         64       197     153      207       171        183         65 0          8         26        95       141     224      307      264       170       132         15 0          0           1         79
0          0         24        19       01       112     265      241        177        09          10
21         4           79        60       239     311      300      380       370         c            12
13         0         13       154      184      203     277      247        147         0           60
0          D         13        14      251      399      196      371       254       191         29
10         0          0         47       176      306     151      274       351        141         17
0          0          0        154     241      448      136      347       300        192         22
0         11        27         3i        143     214      196      224       254        125         40
6          IS        30        31        77      203     252       126       102        17           0
0         35        50         0         73      366     417       302       193        67          36
0          5          6         35       106     252      427      210        140       147         36
3          6         26        49       150     274     312      277       209        104         28
0 29 0 37 0 25 0 30 0 54 0.75
025 0 64 0 35 0.67 -0.04 0.59
«0 625 442 lao 241 60
112     136       126       102         0            0
Dec
0
14
5 0 0 4 0 0 14 23
1
1
0 76 0 10 6
0
0 0 0 II
0 29
8 5 0 8
2 OS 3 66
78
1679
1222
704
1128
1278
1695
1306
1695
1284
1691
2101
1880
1216
1251
1069
1382
1032
1656
1299
1717
1494
1042
1296
665
1544
1470
1426
6 23
0.05
2101
Waterworks Design & Supervision EnteruS--------------------- - — In AUKtatlon with IntErcoutlnenuj Consultants abd Techno Ll(J
HlAjjo DfitesEa irrifaclM Project
Meteorological and Hydrological Aspects DO. Mean Temperature at BeMt Slation
May 2007
YMi
(in oC i Jan
-------- r
Jun
Jul I Aug I Sep [ Oct J No* 1 P**
1971     179     19.9    2i 2      20 6
20.4      18.2      16.7
16 6
15.5
1972
19.5
20.9     184
19 fl
10.3
15.4
15 B
17 2
is.a
1973     179     10 7    21 5    ?1 5
17.9      14 3      16 4
1974 17 7 198 19.3
1975 173 19.3 197
20.2
19B
18.2     16.9
157
*6.0 17 3
17 2 17.1
17 ?
16 7
16 2      17 7
IB 1
174 2J 9 179 170 17.2
1976     17 9
19.1    18 fl
170      17.6      17 2     17 1
17.7      17.0      16.7
1977
1fi 2
IS 1
l&O
16 fl
:60
I 1978  1 17.3      ia*      19.3     IB 9     ts 5     17 5                                 160
13.1
165
1979                21.D    20.5     197     19.5      7.9      15.6       173      17-3      175
19®?
I9B1     17.3     17.5    17 1 1 1M2
192     191      176       172       16 9     17 4 17 Q
170
19 7
*7.6
174
S9B3
7.5     19.1     20 1    17.6     17.4     17.B      18 3     18 7      >9 0      194      20.3
1984                 21 4     21 2     220    19 7     18.0      169       173      17.4      136       189       196
1985     26 5     20 5    21 4     205    18.6     1B.D      172      17.1      17 3      17 7      18 fl
189
1906     19 9     206     20.8    20 9    21 4     18 1      174       17 0     17.7      162
13 7      184
1987     194     20.0    20.4
18.1
18 2      10.3      190
I9B8
1989
T990
19.7    20.3    20.8      ?I6      196    1B.1      170      17.3      17.5      10 3      1B2      17.9
17.8 18 7 19 1 19 3 19.0 178 15.0 173 17.7 17.5
Ifl 1 187 19 5 20.2 19.3 ifl 5 17 4 17 4 i7.a 102
10.0 17 0
18.9 19.1
1991 193 208 207 21.0 204 103 17 4 18 2 134
1992 1? 1 20 1 21 3 208 20 7 19.5 104 180 156 19 I
1993
18 7
16.fl
20 Q
20 6
1994     20.9     209      22 0    21 3     19.5                  17 0       177       1B2      190       196       166
1995     205      20.8    21 3     21 4     19 9     194       176       18 t      10 $      18 0
1996 19.2 2l,0 PQ 5 20 7 191 18.4 17.8 180 10.3
1957 192 199 21 5 109 19.3 18.6 178 18 0 188
I8.9
195
18 3      13.5      13 7
1996      139     21 2     21.2     23.2    21.0     W.3      IB 1       18 3     IB .9      19 2                    192
1999 1  196     21 7     21.7     21 0     191     19 7       173      17 7      186      17 9
2009 J
17.7       17,9      18.5
19.1    20.9     20 7     21 2     19.9     18 0      17.5      17.7      18 6      19 4                     192
16 9
19 2
16 9
1 2002      19.2     21.1     21.6     2i 0     21.2     10.5     18 3       17$      16 1
2603      2GG    ?| s      211      21 2    21 9     18,7       176      18.1      10.6
1 20W !     20 8    21 0     22 1     21 5     200     18.3      173      18.1      10 6
IB I
19.0
18.7
169
19.6
cv        0.08    are       0 05     0 05     0.06     0 #2      0.05      0.04      0 05 -1 2#    -3 96   -J T9    -0 08    0 00    ■4 24     -2G5     ■0 36    -0 58
MIO       13.5    75       17. T    Jfl.J     J7.0      7.5       14.3       IS 7       t6Q *« 1   20.9     27.7     22 J     232     21.9     20.4     18.4       ■ fi J   J9 6
18.7     19.7     20 5     20 6     r$.e      rs.o       J73        r?j       #7.9      ?S0
0.05
-0.54
15.5
19 4
Water Works Design & Supervision Enterprise ~ In Association with Intercontinental Consultants and Technocrats Pvt. ltd.ArJ» Didessj Irrigation Project
Meteorotogical and Hydrological Aspects
07:        Relative Humidity a! Beetle Station iin%)
Yea* Jan Frb Mar 1 Ap» May Jun Jul Aug Sop
Nay 200?
19B7
BO
Oct Nov 1. G?c
30 69 53
1988      63        80        sa        52        70        78         89          04           83         78         63         50
1939      51        S3        67        62        68       BO        83        ■85        34         72         64         75
1990      59       B2        56        60        70        79         82         80         80         70         69         60
1591      55        48        56        67        78        80         82          84           77 1992                  65        56        62        66        75         77         01         74 1993
1594      53        48        48        57        78        63         85         72        01
71 65 85
72 69 04
61 66 51
1995      46       SO       Si        59       72        75         85         83         76         69         69         67
199S      59        5*        63        62        75        82         83         84         80 1997       Bl
72         63         64
199B      E5        55
6J
19M       59        50        49        55        76        76         84         34         80         73         54         63
2000       58
82         84         02
2001 62 62 65 w 73 83 84 84 83
2002 I 69 60 66 65 67 81 85 86 03
80 74 70
00 74 67
2M3
62
55
63
60
57
81
86
86
84
73
69
61
2004
61
54
56
62
66
si
85
E4
a?
74
70
69
4 wag*
60
57
58
6?
70
78
84
63
87
69
63
60
Water Works Design i Supervision Enterprise " In Association with Intercontinental Consultants and Technocrats
PVT. Ltd,Arja HedEEEa Irrt^uiaQ Project
Meteorological and Hydrological Aspects
D0- Wind Speed at Jimma Station (rn rn/sj
May 2007
Year
1973
1974
1975
1973
1977
1978 1979 1930 1981 19S2 S901 19B4 1905 1906 1987 198B 1939 1990 1991 199? 1993 1994 1995 1996 1997 1998 1999 200U
2001 2002 2093
March April May Jun* July _Aug
08        0 8        09         0 9         08 09        i.i         1 ?       0.9       1 i       09      0.9       0.8        0 9        1 1         09
09       1.2       08        1 3       1.4         09      0.8        08         0.9        0.0         0 8
08        07        1 0       1 0       09       09      0.6        09        0.9        09         0.0
0.7       06        09        09        to       0.8      08        09        0.9         08         0.7
07        06        1 2       1.1       09       0.9      0.7        03         08         08          10
09        08        00        09       06       0 9      0 7       o.a        08         0 7         06
07        08        09        09       08       07       07        07         07         0.6         06
0.7       0 8       09       0.7       0.8       06      0.6       0 7        0 6        0 5         95
0 7       0.0       06       0.8       0.8       07      Ob        06         0 7         06         0.6 0.6       0 6        08        07       07       07       06        06         0.6        0 6         06 06         ■         ■■                   0.6       06      0 5        06        0.6         06          05 05        06        07        06       06       05      0 5       OS        0.5        0.4         0 3 0.5      OS       06        06       05       0.5      a s        04        0.4        0.3         02
O.i       0 1       0.2        02       02      0.1      0 1       0.1        0.1        0-1         0 1
01       0 1       0 1        0 t       OS        0.1      0.1       0.1        0.1        0 1         0 1
05        06       0.6       0.6       06      0.6       05        0.6        05         0.6         0 6
0 1       0 1       0.1       0.1       0.1      0.2      0.1       0.1        0.1        0 1         0.1 06        06        07        07       0 7      D.6      0.5       0.5        05         0 5         05
05        05        06       0.6       0.5      OS       05        05         05         0.5        U.S 0.1       0.1        04        0.2       03      0.1      0.1       O.i        0.2         o.i         0.1
04        06       0 6       0.5      0 5      0.4      0.4       0.4        0.4        0.4         0 4
0.4       0.5       0.6      O.S      0.4       04       0.4       0.4        0.4        0 4         □ 4
0.4       0.5       0 5       0.5       0.5      0.4       04        0.4         04         0.4         0 3 Q.4      0 4        05       O.S       04         05      0.3        03        0.4         04          03 0.3       0.3       0.3       0.3       0.3       03      0.3       0.2        0.2         0?         0 2 02        03        0.3       03       0.3      03      0.2        03        0 3        0.2        D ?
0.2       03
03
03       0.3      0.3      0.2       0.2
o.i
2004
4rcr>pr CV
S***
02        0.2       02       0.3       02      0.1        02         02         0 1
0.3
0.2
0 1       0 t        0.2       0.2      0.1       03     0. IQ     0.11      0.09      0 19
U1
02
ni
062
0 52 
■Q£W
0 75
0 42
0 76
0.35
0.32
0 33
032
0 19
0 S3
0 39/
063
.
Q 02
0.3
4       0 3?       0.29 006
Water Works Design & Supervision Ente^rt.p ‘
in Mndadu ™Iwtrel„ „
u
(BBI C„KU|1„,S andArjo-Ccdessa Irrigation Project
MeteoroJogical and Hydrological Aspects
09:        Sunshine Duration at Bedefe Station
inhrs/davl
<ea- Jan Fob Mar Aj>r May Jun Jul , Au?
May 3W7
■“j
Sep
Oct       Nov      Dec
1MS 8 5 82 79 7 9 7.4 6 3.8 5J 6 5 7.9 8.0 6.4 1998 89 56 7.7 64 82 64 3.0 4.8 6 9 6 6 7 9 1991 79 8 1 68 53 7 1 4.5 2.7 34 5-9 3 0.4 7
1992                   57       7.7      7 1       03       6 1        34         22        6.7        6.2         62         8 3
3993      7.6       6.6       7.5       55
1994                  7.7       75        77       76         ■         24         34        5.8        9 S        04         93
1995      SB       66       7 7      6.5        ■                       ■           »           +           ■           ■           tr 1996        *          -        7.9                   ■«        a-         37         43        6 7         9          7.9        7 0
1987
1988
7 9 72 6 9 0.5 5.6 6 5.3 6.7 84 8 0.3 8,3
9.3 71 6.5 82 79 64 26 4 2 5.1 97 y b
1997
1998
1999
72       92       7.5       60        7        6 1        4 1         4.6       8.4        7.8        6.7        8 3
75 77 64 8.7 6.4 6.7 2.9 3.3 4.7 54 9 4 9 2
6 1 9 1 8.8 76 7.6 66 3.5 4.6 66 58 9.0 0.8
2KD        9         88         9        6.1       7 8        8 2001
Hr ■ 5-5 6.4
■
+
2002
2003
2004
Avwjg*
■■       8.2       7 5      9 1       3.4       6 1        5.6        3.1        6.9        6 0        8.3        7.6
79        86       7.3       8.8      9.6       57        2.9         36        6,1        9 5         87         8 6
7 5       79        6         57       7 4       4 3        4.2        4.5        3.6        0.2       a. 3      7,7
a 2 7.6 7.5 7.3 76 6 r 17 4,1 52 7.9 S3 0.3
Water Works Design & SupervjsioIe^nSSArjtiiDedKs a WcatlMi Project
Meteorological and ElydralogicaI-Aspects
Annex E:           HydrologicaJ Data
Ej__ Lia-I of Selected Hydral'ogiCal Obsp-rv-iMtpn SldEi-ons
May !!OU;
s.
No
Station
Nd.
Station Name
Latitude. N I Longitude. E
I-
Deg      Min.      Dog.
Min,
Catch. Area
2
(km )
-1
1 1  ! 114001     Oedesw near Arm
2    114002     Angar near Nekeml L-_ . .* — ■—           —
114005     Dabana near Abasing
08
4T    L36
29
9981
!
!4
5
09
09
30 36 35 3742
02 36 03 2BBi
114007     Angar near Gubn 114008     Yabu a" Yabu
07
48
36
36
29
42      -47
s    114009     Urgessa near Gtfthbe
07
50
19
7
114013   D-abana near Bwnno BedeHe
06
24
36
39
1?
47
8
114014     Dedessa near Demb* (Tobap
QB
1806
9
114016     Lokd near N-ekamt
09
—— ------------------------ _—
03
22
36 27
3B        36
375
10
114019
Temssa near Agarn                   07
51           36        35
47.5
11    113004     Weiks near Gudei
0B
12
113038     lutfris near Guder
oa
d
56
io
37 44
37 45
13   101006     uka ai uka
06
35
14 -I
091008     Giigelgb be iwar Asendabo
0?        45
3?
22
li
3B
nr 52.5
2966
15   091012     Gdjeb near SllEbe
WJ
25
36
23
3577
Par lod
i960-2004
1994-2004
1963-1984
1990-2003
1979-2004
1979-2004
1964.2003
1965-2DB3
1997-2004
1989-2004
1998-2004
1386-2004
1980-2004
1967-2004
1970-2004
'.Vater Works Deslo & Supervision
to Assads tra Interconttnemjil Consultants ano T«
’       - - - - - - - - - - - 1«Arju-Detfessa Irrigation Project
Meteorological and Hydrological Aspects
Annex E2' Mean Monthly Streamflow at lledessan near Arjo Station
May 2007
Tea/
1 Jan
11
Feb War Apf
May 1   Jun
Jul
Aug
Sep
Oct
Nov^[   Dec
i960
1061 1962 1953 1&64 1965 IMS 1967 196ft 1969 1970 1971 1972 1673 1974 1975 1976 1977 197B 1979 i960
19&1 1962 19BJ 19G4
1985 1936 1907 183b 1989 1990 1991 1992 1993 1994
-
■        w                             1054       1124              *           II
51 5   44 0    J7 5   94 9    656      ?B6      11?6      1613      1503      1304      280        177.5 S8 1   29.8     284-          -                             622        930      1170       655      107          55 9 36 1    19.3   179    42 7 14F 1     324        672      1370         IMO       374      104       170-3
382-         -             549      230      1049     1301       1176     1337      205          73 6 554     25 3   16 4   47 8   27 0     160        034     1051         665       957      320        157 0 710    63.4    57.7   74 1     62.5-                  057      1086       1212 -
22 7   20.4 -                            7PB      1268      1201      1260      459        210.4
&60     539    21 4-
-
138          53 7
5Q 9  46 7   87 1   3B.7    732      349        950      1421         944       291         09          46 2
M 1-           -                       <5 3         m        929
-
101           62 i
37.0 16.4 10.fi 12 5 53.5 241 823 1175 949 752 304 105.3
524 29.8 19.6 35 7 564 118 aoi 1237 7lfi 209 117 52 5
25.9    11.2     4 7      6 3 109.3      2M                                   1401
t49          64 B
365     162    14.4     9 1    93.7     261        641      1278                                    119          46 9
24 5    21.9    11.5-
48.3   37 8    24 7-
25.9   18.1    12.7
-
..
II
151 59 5
-■ »
55.5     201-             12.4    80.1-
■ 324 120 7
r
■ 22 a 464 130 533 a?5 610 262 94 44 o ia.o 15 3 10.0 60 6 190 9 504 914 1280 1244 393 103 92 5 BOO 43 4 43 3 35.4 53.7 S3
698     302    28 6    19 3   457      248        707        947
43 4    31 7   34 1     233    52.4     153
692       761       177
385    16 7    11 9     9.5    286      105        ?03       &65        521        131
566      1139       1116     1231       255
j,!+ j
121.3
12 0      54      2.6    118    62.4      169        430        927
176 9 5 181 13.8 12 8 119
13.0     5 9    124    17.3     367-
452 491
-
042 260
732 222
79          45 0
40.5 27.5 21 6 7.7 37 0 200 555
23 3    204    33.5    271      121         273
67J 366 160 67 B
139 *
S3.5   30.0     338   60 9   42.0
1S7        343
543      1143
409       Ki0? -
---
107 123 1
■ :»
24.5    23.9     138   20 7    565     161        360        824        564        606      154
42.5    27 9   24 4     547  105 2     312      GOO      1159        631
39 1    196    15 5    15.7    597      220        534     1221
407      177
858
156
60
30 1
73 4
63.3
36 9
Water Works Design 1 Supervision Enternn^ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
in taMUUO «M li>.« «l„.„al C.orutanrv «, TeX,’™ 
t
Ll( ,ArjfrMsu Irrigation Pr&Jrct
Meteorological and Hydrological Aspects
£2. (. , , Continued)
May 2007
year   ban
Feb
Mar
Apr
May
Jun       ■Lil      'Aug Sep
Oct
Nov
Dflc
IMS
190$ 1937 1&93
i&gs
3MD 1 2001
2002
MM
2D04
20 4   12.2    14B      ifl4     363       83        225        569        4&fi        !5E        6fl
■        -        -              304 141 a     373        723        954          5M -            -
67.2
41.4   19 Q -         ■
■*-
-
a
■-
-
-
-
-■
242        135.7
85 1   &9.S   66.1    57 2 128 3    4D1        740      1045      10D5       674      215        1117
M.O   57.2    56.3   63 4   4B 2      175        457
f
591         576
tn       115          33.9
56.4   36-2     562   74 3    40.0      120-                     652-
52 3 40 2 30.3 287 65.2 202 526 639 643 536 140
CV SJcriv Max
Mlfl
46.2     287    26.0    332   66.5     223        654      1007         859       581       177           969 0.47    0.52    0.66    071    0 59    0.46      0 34      0.30        0 32      0 68    0.51         0.50
0.66    0.65    1,14   0.54   1.54     0.74        022      4 16        0.43       0.73     1 26          1.00
990    63 4   67.1             190.9    SUM    11761   1612 8 1502.5      1337 4   459.2        210.4
12.0      54      2.6     6.3    12.9     53.2     225 0    491 1      485.9    130.8     59 9          36 9
M^n annual Elaw = 3fijT Mm3}
Water Works Design aSnpen tal(111
,
I. teucUUHi .llh lourvenumala,Coos ltMB
,
Tk J,m'B M , M
---------
I?'ArJoDedtssa Irric ariott Project
Meteorological and Hydrological Aspects
E3: 41 Mean Monthly Stream flow at Dedessan near Dembi station
;Million ni3i
May 2(107
Year      Jan     Feb |  Mar    Apr
May    Jun
Jul
Aug
Sep
Oct
Nov
Dec
1985
15B6
*■987
i9BB
1989
1990
1991
1992
1993
1S94
1995
1996
1997
1998
1999
2000 2001 2002 2003
2«U
64      3.7      4 2      78    26.8        92          85        185        302        272     70.2        21.9 8.5       55      9.7     8.4     9.4        50        262        206        299         67       229        11 5 5.9      J 5      97     9 2    18 5      105        243        342         216       104     44.1         27 i 179    157    12 5      64    23 9     153        217        392         489       142      52.0        18 8
ItO     7.6      4 5    11.5     0.2       31        167        253        272        142     24 8        13 5 18 3      58*     5.0   22 7     9.9        52        252        564         362        126     20.9           94
72       63      66    125    29 5        76        305        522         263        140     13 4           39 78    15 3    12.9     8 8    36 6        78        138        269        1B3       219      45 2       17 1
112    172     i6.a    376   bo a     252        334        378       2CM        110     43.7        14 7
12 3    13.5   16 B   22.5   37.6      112        274        381         282          59       266        16.4
129    12 1    16 5    238    46.7        07        190        272        331        101      32 5        33 7
12 9      9 4     165    238    48.6        07        190        272        331        101      32 5       .33 7
21 2    130    23.2   38 1     552      142        219        343         204        262      13R        56.1
28.1     135    20.3   12.7   31 1       HO        272        415         299        329     88 0        21 1
13.0      6 5      83      95     549      148        242        245         214        302     46 4        13.3
102       56      4 5     9.7   41J2      119       29C        309         242        209      32 0       21 .9
12.7      9.6    11.2    145    55 5     226        330        322         296        JI 2      58.6        22.5 65      69       66     9.0     6.5       63        192        255         195         66      27 7        14 9
7 4      4.0       92   24.0     6.7        59       241         223        324          82      20 3        10 o 13 0   13.0   13.7    33.0    98.5     19B        208        208         145          39     19 0        18 6
A wipe
CV
SfcfW jWjx
Mrn
12 2     947    11.5    ?69    36.4   112.4     232.4     316.9         273    154.3     48 4        20 5
0 47 0 45 0 48 0 56 £159 0 526 0.27 0326 0.28 *551 □ er O.5S
f 35    03?     0.47   o.ai    0 85    t.n?5     ■0.47     0.927        0 89
28 t     172    23 2   37 6    98.5      252        334        564         489        329    187 9        Sfi i 59     3.7       42     6.4     5.5       31          03         ids         MS          39     73.4          8.9
2,6      J 9-H
Mean annual How = 1255 MmJi
Water Works Design & Supervision Enterprise
In tasMkaiiMi with Intercontinental Consultants and Technocrats M LtdArjo Dtdtssa Irrigation Project
Meteorological and Hydrological Aspects
E4:       Annual Maximum Floods
i in mJtefr
May 2007
Year
Oe-uessj
wing'
Upper ntjr Dema-
Djibjflj
raiar
AtW-jifUi
OJJprt GJW±i< ne*r
■4«71CTjb<>
nrjir Sbrbc
jflngj-/ jm at
n eq cm Co
/IngAT rcc-jp
Guhfi
1
2
4
5
6
7
8
9
W
11
12
13
14
15
16
17
ia
ifi
20
21
22
23
24
25
26
27
28
29
30
633
1173
SQ3
789
850
951
814
H65
701
634
696
721
490
645
554
1083
369
480
502
574
771
750
646
804
353
525
525
744
312
601
213
206
212
243
354
228
200
151
189
262
164
175
226
175
211
244
271
300
370
287
487
264
434
449
247
196
257
ISO
314
341
238
202
248
151           132 198           272 130           176 330           127 151           231 167           110 705           116
168
129
148
151
223
135
149
119
92
96
127
143
85
121
247
86
106
192
237
159
255
100
174
339          180 185          258 186          241 284          217
214
140
249
177
268
138
297
314
104
150
203
226
132
245
366
164
164
261
164
150
202
132
193
199
439
236
336
361
209
247
256
157
271
252
128
141
73
55
124
107
134
105
125
142
136
142
149
176
172
109
106
79
181
128
Waterworks Design * Supervision EnlernrR, Action wW.
140
. " ASMMeteorological aad By ilrologic al Aspects 
May 2&07
E5; Measured Sc dime nt Ounce titration at Gumara Gauging Station Field
I
rI
sample Lab
No .
Mo River / SUeam
I
Slation
Date    &    Time    Time    G^haight    Flow
Depth
-       — 1
-of Sampling (Sec) (m)
■ nrVsl x     _l£QL_
Sediment
Width ■ Concert . Remarks
(m)
1
□ede&sa
Toba
15 Mar >90
4.16
0.26
0.70
0.35
0.54
0.80
0.39
6.9
13.8
51.56
485
2
Dedessa
Toba
15-Mar-90
4 16
406
3
Dede»&a
Toba
15-Mar-M
4 16
20 7
40.00
42.81
6G4
1
Dede&sa
Toba
21-Mar-M
5.41
5.41
5.41
9.14
7.0
59 69
665
2
Dedessa
Toba
21-Mar-90
656
3
Oede^sa
Toba
21-Mar-90
1057
1
Dedessa
Toba
8 40
1058
1059
1190
1191
1192
1223
1224
1225
2690
2699
2700
2704
2705
2705
2
9 14
8 00
J
Odessa
Dedessa
7 00
1
2
3
Dedessa
Odessa
Dedessa
Odessa
Dtfd&ssd
Odessa
Dedessa
Dedessa
Toba
Toba
Toba
Tuba
Toba
Toba
Toba
Toba
Toba
Toba
2-Jul-QO
2-JuUBO
2-Jul-90
173.13
90.63
215,31
135.62
22'Dec-90
22- De€-&0
22-Dec-90
18-Sep-90
50
50
50
9.14
4.37
4.37
0 43
14.0
6.1
6.6
13.3
19.9
70
190.00
90.94
14 0
99 37
1
2
3
4.37
0.74
0.46
21.0
63.13
96 50
1&Sep-90
16-Sep-90
IGMay-93
16-May-93
90.50
1
2
3
1
2
3
96 50
45
141.56
187.62
124.69
2.89
0 66
45
87 90
Odessa
Dtdessa
Oedessa
Ouessa
Toba
Tot>a
Tooa
Toba
2 69
0.61
iBMay-93
12'Ap<-93
12-Apr-93
40
108.63
2.89
8.01
0.71
81 40
8 01
73 05       64.61
8.01
61 59
59 20
III       Water Works Design & Sn»»r.,uu—ES;____ conttnuecO
Field                             River ■*
o.        sample     Lab.No.         Stream
No
r—
Station Date & Time
l-------------- 1
Time Gfhcighl Flow
of Sampling       (8®c)
T-
Depth
[m)
I Sediment
Width Cancan Remarks
<n?L     im0/l|                 AV
M1          1        179/04       Dedcssa           Arjo         10-Aug-04       30        2 45
M2 2
543 3
Dedessa Arjo 10-Aug-04 26 2 45
Oedessa Afjo 10-Atig.D4 26 2.45
544         1        100/04       Deaessa           Arjo         11-Aug-04       32        2 55
545         2
Dedessu           Arjo         11-Aug-04       20        2.56
546 3 Dedessa Arjo 11-Aug-04 27 2.56
559 1 1 05/04 Dedessa Arp 1-Sep-04 29 351
560         2
□Odessa           Arjrj          1-Sep-04        20           3.61
561         3                           Dedtssa            Arjo           t-Sep-04        29        361
143.12      9.05lt        17.5 ' 143.12     9 111       35 0 14312       e.stt        52.5
196.11        im          18.0
196.11       9.6ft        36.0
196.11       9 6ft        54 0
611.23      137ft       10.0
611.23      14 3fl        370
611 23      1.46ft       55.0
1417 50
1739 74
1740 74
1652.86
1716.12
1639 31
1360.22
1326.61
1438.44
142
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Annexure - 8
HYDROGEOLOGICAL
STUDIESAljG DrtessifrrlgatlM PrajKt
Hyprogeologlcal In^esUgadoos
May 2007
TABLE OF CONTENTS
TABLE OF CONTENTS _... LIST ar TABLES.
LIST OF F Id RES.
IIIII1IM..
I. INTRODUCTION
Ill
iii riHiirt—f i if-! II
tun
1.1 General
Illtlllll lllll■llli
1.2 Location
.I
1.3 Physjqgiwk* .
2
■ P’l5"fll-TIIIIB III II.II
4
1 .>4 TWgGKJLDffY AND APPROACHES
■f--^iiirwiii i 11111 iiiiiaii
4
2. PHYSICAL HYDROGEOLOGY
2.1 HfMOGCClQGlCAL SETUP
2 2 Hf CROGEOlOGiC units
22.1 Fradu wl antf/of weafNerttf rtta/ic W*S 2.2.2 dffuvnW                .................. 22 3             sftrffrnOflTS
2.3 ikVENlO*Y AND WEU. DATA
2.4 HYOftOOYAAMlC PARAMETERS OF A«Wf fES
XCROLiNDWAIT R POTENTIAL____________
Pfff—■ Illi II I L il. ..U.il—....
IIL.il..
..—6 6
.7 A
A
5
ll"HIIIUMJ —441—.
A
.9
r
3.1 Gjwjwwater re charge esttmaton 3. f. 1 cto sa 00 vr Art jJyxis 
31.2 HWW AatertCe iTitrtftatf 4. WATER QUALITY — 
4 T WAffA $ A MF-LES
“"tut num
—— •inrun i.4.
II
4J
4J
$AWP<ING TECMNtCXJES ANO ANALYSIS
PKTOWJL REPRESJENTAriON5 OF WATER QUAuTv ANALYSIS
16
4.J.T Pp»f tfWflfBITJ
4 3 2 Sdioeitor (flagra/nt
4.3 3 Snff engram
44       AtfRlCULTURAVlHfllCAnOM WATER QUALITY
$. PIEZOMEIERS OBSERVATION WELLS AND WELL FILED..
51 DtJTRieuIl&l OP PlEZOUETEft$/0BSEftYRT»DN WtLLS
5.2 PUTUflt WELL FIELD
t U ATEft LOGGING AND DRAINAGE______ ,_____
6 1 TOPMftA^mC FtANJRES AND $Q<L CHARACTERISTICS
6.2 Eating GROvmOwater table ..
’1*141*—..
-■1—....
—-ir—l.I.
lll.^i
IIIU1.
Ui
III.
III.
•■mu
6.3
ti ... 12
i.ifr
16 16
jy
IP 2 27 2T
. 2A
30
7.
FinUHt GROL'MDWATfR TABLE AND RECHARGE FROM iRRjGATIOM SALINITY AND SODICITY
■ — '• — Mr.ll—,,!,!                                           30
••‘--—Il
31
E. mrilNC AND Fl TIRE PROSPECT OF GROUNDWATER
8.1 EXtSTlNGGROlfflDWATEROEYfcLQPWfNT 8 2 Future oroumswater prospect
II.
.-49
'■»•■■—III
41
Water Works Design & Supervision Enterprise
In Association with latcreoatliiestal CoasulULnu aad Technocrats Pvt Ltd.Arjo Dedessa. Irrigation Project
Hydrogeological Investigations
May 2007
LIST OF TABLES
TaNa 2.] Detail's of borehofes in the study ares....................... .. ......   ................................... - «...- • *
Table 3.1       Monthly Iota? (tow. and Minimum flow of Dedessa river near Arjo ............................ 12
Table 4.1       SAR and EC values in terms imgalron water suitability 23
Table 4.2 SAR and EC values (or surface and groundwater in Arjc-Oedessa area..
Table 5.1 Locations o( the Proposed Piezometers......................................... .....................................27
Table 6.1 Annual gross crap water requirement al primary canal head
Table 6.2 Estimation of welled area for Arjo- Dedessa irrigalton canal ■ •-! i.ii uBuiahk...- 35
Tabla 6 3 Seepage loss from undined Arjo- Dedessa irrigation canal ............................... .33
LIST OF FIGURES
. .. 31
Figure 1.1 Figure 1.2
Figure 2 1
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4-Ba
Figure 5.1
Figure 6.1
Figure 6.2
Figure B. 1
Location map of Arjo- Dedessa irrigation project
A map showing 3- D new of Dedessa nvar Catchment. ..
A map showing hydrogeoiogic units of Dedessa nver cathmem Location o< waLer sample points.
III I I.
5
.. 10 17
Piper TriJinear Diagram tor Water Samples Schoeiler diagram for water samples 
Slrtf diagram for water samples
...... -........... ...... -.......... . ........... .□....... . 20
21
•22
Electrical conductivity (EC) in psfcm and Total Dissolved Solids (TDS) in
mg/Lfor
rm
-"■•••■I.-.,.........................................
Map Showog Contour for TDS
Proposed Piezometers/Observation wells 
Profiles along different lines in the command area
A map showing lines Df profiles in the command area A map showing groundwater potential areas
24
26
29
I■
■■•
. 37
JR
■  -!l I--. ,
r
.... .. 42
Water Works Design i Supervision Enterprise
Ln jusoclaUon *1tb lntuconttncntal Consultants and Technocrats Pvt ltd.
IIAfjo-Miua Irri^uUDu Project
Hydrogeological investigations
1 INTRODUCTION
1.1 General
May EOCT7
Hydrogeology  refers- io the occurrence, movement, chemistry  (quality), etc  ot groundwater in general. It has  a diversified application in developing, utilizing and managing groundwater. Furthermore, different aspects  of groundwater such as  recharge-discharge condition, aquifer type and set up. its  interaction wi1h surface water, etc  are treated under this  discipline The nature of groundwater and how it behaves, when subjected .u nalure or man-made activities  Is  sludied fur different purposes  such as  for water supply  (domestic agriculture and industry) and construction of surface and sub surface engineering structures {eg., dam. tunned, drainages, etc), in order to devprop and manage groundwater, one has Io know its potential, quality and movement
Ethiopia has  diversified hydrogeological features  I hat are attributed to its  geology, structure hydrometeorology, topography, etc. The hydrogeology  of th* caunlry  has  not been studied thoroughly  so far. With the exception of few areas such as  Rift valley that has been mapped at scale Of 1:250,000. the counlry  has  only  small scale (1:2,000,000) hydrogeological map. Hydrogeology  is  usually  applied for locating borehole sites  in light of waler supply. Groundwater has  been used without detail understanding al th* resource In spite of ample groundwater resources  of the country, very  hHta been studied and used so far. Currently, however, not only  groundwater development and/or utilization pul also its  management is geltmg an attention.
Since any  development relies  generally  on proper utilization of natural resources  the government has  also given focus  On water resource development both for domestic  waler Supply  and imgatipn As  part of this  water resource development. Integrated Master Plan Study  Of vanoos  River basins  has  been undertaken in the country  s,nce some years  The Abay  River basin is  one of them Ago-Dedessa irrigation project has  been identified as  one Of the projects during the Abay River Basin Master Plan study.
Hydrogeological investigation andstudythal mainly focuses on g roundwaler occurrenc movement, chemistry, etc has been included as one of the components of the leZZ' study and design of the project Accordingly, this sludy a( Feas|b|jty
undertaken
Water Works Design &
"-
I D Assrrclatloe with Iwertoactaeottl C
Ior       .
W(M(S aQd Tec D C ftlB Fn LtJ
idL’rfll
.f'*ArJn ^BdeRsai Trrif BUfin Ffd-JbcU |yrfFOgeDiogi£al Lni'estigatians 
______________________ May 20P7            __
1.2 Location
Ths  project area is  located within Dsdesw River sub-basin which is  rn Sum tocated in Abay River basin. 11 is  wilhin lhe Western Orc-ma National Regional State; particularly  nt ki
junction of Easi Wollega, llubabor and Jima zones  The sub basin of the irrigation project is bordered bydmo-Gibe River basin on eastern side and Baro Akobo iRiver basin on SW s*d&. The lotal area of lhe catchment at I he proposed dam is  about 5,632-64 k  rn9 The project location is shown in Fig. 1 1
The project area can be reached from Addis  Ababa through two alternative high ways  ihat lake eilher in Bedete or Nakemt. The all- -weather gravel road that takes  from Neikemi to Beetle passes  ihrough the project area. Hence, in general 1he project area is  about 480kin from Addis Ababa Ihrough Jima and Bedele
Water Works Oestg-n 4 Suteresu,^ — — ..± l.»  o
rE   DU..I>w Cm,um,b
2Ftff 1-1 Location map of Ar/o-Dedassa frrtgafion project
\Arja Dtfessa IrrlgsiSon Proftd Hydrogeologfatf In instigations
May 2007
■
1.1 Physiography
Ti:e basin drams a part of Jima high lands including Goma jAgaro), Setema, Sigimo. Umu Saka, ard pari of Jlubabcx including BorecM, Dedessa. GkN and Bedclle* Woredas above lhe proposed dam Arjo, Nunu Kumba  Sitxi Sire and Warns Bonaya woredas are also
r
within Else catchment. The command area is drained by river Dedessa and other tributaries such as Wama River. The general stope of the ba&n/or catchment is toward NE, E and NW dueclions. The area has  generally  a rugged topography  with the hrghest and rawest elevatoms about 2 890 a nd T 030 m amsl respedivfrly located at S iguno-G<era area and Dedessa river valley. The river basin has mainly a dendritic drainage pattern 3- D view of Dedessa river catchment a shown m Fig 1.2.
1.4 Mcthodofogy and approaches
In order to undertake the hydrogetfgoical investigation of AfjO-Dedessa irrigation project area, the following methodology and approaches have been used:
■   Reviewing of lhe previous works and data available with different institutions such as MoWR.  Institute  of  Geological  Survey.  Regional  Water  Resources  Bureau  and Offices, Regional Water Works Construction Enterprises.
■   Field survey to colled pnmary information on geotagy. hydrogeology, geomorphology, and other physical features of the area.
4Fig. 1-2 A map showing 3-D view of Dedessa river catchmentArjoUcdtEM   Irrigation   Project
Hy ijr DgeDloglcil investigations
2. PHYSICAL HYDROGEOLOGY
2.1 Hydrogeological setup
Muy W
The basin comprises volcanic lava flows mainly basalts and ignimbrite as well as pyroclastic falls on Jima side: where as on llubabar and WcJrega sides, the oulcrop is mainly basaltic lava flows  except within the Dedessa River Vaftey. wnere the outcrop is  crystalline basement of various granites, gneisses and pegmatite The volcanic rocks on J«ma side are referred to as Lower part of Jima volcanics comprising flood basalt with minor saiics on the western, southwestern, eastern and southeastern part of the river catchment; especially on lhe high land However, at the lowland part of the catchment along the Dedessa River, the outcrop is  referred to as  Alghe group comprising biolite and horn blende gneisses, granulite and migmatite with minor Meta-Sedimentary gneisses
The  volcanics  are  of  Late  Eocene-  Laie  Ollgocene  age;  where  as  the  gneisses  are  of Archean  age  The  volcanic  rocks  (basaltic  :ava  flow)  in  Budele  area  is  referred  to  as Makonn<m basalt composing flood basalts. Il directly overites lhe crystalline has&ment that shows  lhe  unconformaWe  relalion  for  the  two  outcrops  II  is  OlK)0cene-Mx>cene  age Similarly. Ago area is comprised by such Hood hasaHs of the so-called Makonneri basalt
Based on the investigations made in lhe area, various aquifer sat up
aquifers are weathered and for fractured basaltic lava flows and other acidic volcanic cocks such as rhyokte and rgn-nbrite The aquifers of volcanic origin have both confmed and unconFned character; for example the volcanic rocks in Agaro area show both characters The Manning layer in this particular area is h^hly weaihered volcanic ash of cla
revealed from existing wtfl dnlling data There are aquifers that a B dttfibuted ,0
,
espadally aiiuv.al sediments along river valley and streams, and colluvial s^ment mcvnrams and escarpment. In addition to ihese there are also minor aquifer atlribui^T
weathered basement rocks (granites and granitic pegmatites). This laEl aq(J(fef t
°
""" sigeMao » <he area due » .he,r
arM1 WM an(J
J’""*’
The  cesence  el  .hemal  aonegs.  cole  g<euna„al&   ana   saline   sptings    ,n
drversiiication of the hydrogeological set
up
of the river catchmem
-——- ---—. xt:::::;
water Works Design & Supervision Enterprise
n Asseciauua with Imercomlnenui CoasultaaU and Technocrats Pvt. LtdArj©            Irrigation Projfcl
Hydrogeological investigations_ _ _ _ _ _ _ _ _ _ „ ~ "
?
l3
■■
diws.slficam   geotogicat   structures   mainly   faults   play   Significant   role   Pn   groundwater dynamics and quaMy of lhe area
Wilkin Dedessa River valley. deep penetration of groundwater may be hindered by 
underlying massive basement crystalline rocks except whw Ihey are controlled by 
geological structures as revealed by the presence of thermal springs m the nv«r valley.
The volcanic ash a nd clay I arm I he confining layer far water-bearing formation I aquifer). Aqvtijr m Agaro area can be mentioned as  an example The volcanic  lava Hows  are highly wealhered (Iracfared) enhancing the infiltration of precipitation fmainly  rainfall) for groundwater recharge Groundwater recharge in the area is  very  maximal due fa different reasons, among them are the high precipitation, dense vegetation cover, and highly weathered and/or fractured volcanic lava flows
The main groundwater recharge of 1he area is the SE, SW dfid ihe N E part Qf “ ha rivet catchment The pyroclaslsc (alls of mainly volcanic ash composition is found al mo-si pans of 1he aver calchmam such as in Seiema and Atnago area The irvte^caialbons of the volcanic ash with fractured and/tx  weathered volcanic  lava flows  cause the emergency  of many springs in the nvfif catchmecii ol 1he area.
However, the presences  of thermal springs. wi1h in the Dede&sa river valley  are attributed mainly  to geological structures. faults  The physicochemical characteristics  of 1he thermal springs  highly  vary  from upstream to down stream along Dedessa River wlh.n the project area Although it needs  farther inveitigalkM to verify  the physfao-chemfagi variation. the longer residence time of mo-waler interaction while ground water flows  from upstream to down stream could be on& possible reason
The  typography  Of  the  area  along  with  the  prevail^  hydro.meteoroJogfaai  comings  favofs lhe exigence of well damarcgled ground waler racharge dncJ discharge area
2.2 Hydregeofagic units
6™——' «««.»», ™emanl nnd ,uaMy are maWy g<wr(iad the
Hjdroqeolosre «™». The phrase h^ro eotog,c unit refers
,
trtCWSOlidalfcd) forming the frame work lor groundwater occurred
,n 9
ji i +K (
e ockg (consolidated ar
'■urrence. movement and
Water Wks Design & Supervision EnterurtsT "- - - - - - - - - - - - - - - - - - '
qushly
7Arjo Beir-raa Lrrijadoa Project
Hydrogeological investigations
Way 2007
The *iydrogeoiogic  units  in Dedessa river catchment have been categorized into the fcilo^ng units  They  have been shown on map avaitabte at Fig 2.1 eM have been discussed here unde? m brief
2.2  ,1 Fractured and/or weathered volcanic rocks
This  comprises  basaltrc  lava flows, acidic  lava flows  and falls  such as  ignmbnl«s  and pyfOdaslic  falls  In this  category  of hydragenlogic  unit, secondary  porosities  such as fractures  produced due Io wealhering and geological structures  play  immeasurable role as compared io I he primary  porosily/permeabilify  The a#eaf coverage ol this  hydrogeology 
J
unit m DMesta nver caichment fs 6.189 35 Km (?9.56%)
2.2  2 Alluvial sediments
As  the name implies  these are conceniraled along rivers  and streams, and it comprises various sediments ranging in size from ciay through sand and gravel io boulders The areal coverage of thus hydrogeotogic urvt m Dedessa river catchment is 1651 05 Km; (16 04%).
2.2  3 Delluvfil sediments
These sediments exist al t he t f&nsdiqn zone from lhe mountaineer plateaus Io I he river
.airey  They  are  derived  from  dowi  slope  moving  earth  material*  from  mountain*  mainly 
due lo gwiritttaiat
From hydrogeological point of w. there ,,re no afi Such
demarcated piopertMis  betweon alluvial sediments  and delluvials. However for I he convenience of descnpOon. Ihis  hydrogeotog.c  unit nas been described separately  Dalldvial sediments with v> the project area have covaraye of 452.91 Km’ (4 40 % |
2.3  Inventory and well data
|
in order to undertake derailed investigation of the  no
fl      Unt Watpf o.
schemes have been mvernoned and their geogfaphIC£t| Radons nave been d .
OPS
MSp.«
«««
analy5JS o( hyd wl
,^"
KM
^ “®
u
Lhough complete wen data are not available in ih* afea Scrrir. |r
*
5
narrt been undertaken fa waler supply 
dur,fly
e &^a5ur*men1s
parameters of water quaMy by using field test Kits such as rne pu
phyfiica|
^«TDS, ph and temperalure meter
Water Works Denigsi
10 Aa'drtO W!W
------------------ -—
CottSU|(lnu ;ind ?Arjo Dedcssa [rrtgadon Project
Hydrogeological investigations
May 2007
In adcfiti&n La these primary  data, secondary  tfala have also been collected Ort both water quality  and other Well date. S atdiile rmages  and aerial Ipholos  have b sen i nterpreted I o identify  geologies  I sEnuchjres  and other lithological bou ndary  demarcation trial have been verified by field work
2.4   Hydrodynamic parameters of aquifers
As  it has  been mentioned previously. She mam aquifers  in Arjo-Dedessa project area are fractured and/or weathered volcano lava flows  (basaltic  and acidic  lava flows  j and sedimentg. (afiluvigE and colluvial}.The boreholes  m the fractured volcanic  rocks  and sediments  are either with partial well data or totally  without well date Table 2 1 shows  I tie boreholes drilled previously m the study area and their depths.
Table 2, i              Delates of barehples in the study area
No
Well No
PA/vlllage
Depth (mJ
SWL
1
Wen 1
Metta
55.75
16
2
Well 2
Meita
43$
12
3
■—
wen 3
k
Metta
43.5
17
4
HT-2
Qolto Sih
27
5
HT.&
I-
Cbilalo Blldima
72
15
HT-7
Chafe Anani
57
7
Wei 1
Chuli
52
1.3
0
Well 2
Chuli
’ _r.T- -----— - —
41
1.7
3
Weil 3
n'i
Chuli
25
2.1
10
„
Well 4
Chuli
30
21
11
Well 5
'---7--- T-------- -
Well 6
Chui
—------------------
25.5
15
12
42.5
2.2
13
L——
Ntada TaWa
Chui
■ ■         ——
____
Bakalcha Biftu
52
—
14
Iftu Biftu
____________
Bakalcha Bittu
3555
Water Works
“ *............ .. .......
SupervlsloiTSi^r;- - - - - - - - - - - - - - - - - - - - - - - - -
rJF'ff. ?-f £ rnjp stowfog
unjrs of dr/o-£3«fes sa rirar cjftfimwi
W. ' ,:lil           i 1. ■ dmArjo Dettau Irrigation Fn)ect Hydrogeological Investigations
3. GROUNDWATER POTENTIAL
3.1 Groundwater recharge estimation
May 2007
in  order  ip  develop  groundwaler  of  an  area,  its  pdentiaI  including  its  annual  replenishment
W h«h is  usualy  referred to as  groundwater recharge, has  to be known. Groundwaler recharge of an area can be estimated based on different approaches  One of the best approaches  is  through water balance method. In order to employ  this  method of groundwater potential estimation, Ihe necessary  data have been acquired for analysis. In supplementary  to this  method, base now analysis  for River/stream flow (Dedessa River) have been undertaken to derive some coefficients  for water balance Hence, in the groundwater potential estimation ot Dedessa River catchment both methods  have been employed in order to come up with concrete result as much as possible
3.1.1 Base flow analysis
In order lo employ base flow analysis approach for groundwater recharge estimation, the
monlNy discharge of Oedessa River from 1961 - 2002 for a total of 15 years have been
used The river flow data is not consecutive due lo soma missing data tor some years 
Accordingly, the mean monthly minimum flow of Aqo-Dedessa on 3nnual base ts shown in
TaWe 3.1
The difference between 1he total flow and ihe Minimum monthly flow is Supposed 1o be Ihe surface runoff Accordingly, the surface runoff for Oedessa river calchmem at the gauged station i$ 2,105,796.874 m1 Where as  the 1o1al minimum monthly  flow of 1he uver is 1,962,092,938 m3 as  shown in the Table 3.1 The basic  assumption in deriving groundwaler recharge from base flow analysis  is  that ihe monthly  minimum stream discharge is  equal to the base taw. This  approach has  been ment.oned by  Wundl (1978) tha1 the monthly minium siream discharge best approximates 1he base how. especially. fw humicJ chfT atft '
,
Therefore, the b ase flow that i s supposed to correspond to t he groundwater recharge ■ s found to be 196.6mm. This vatoe >s obtained by dividing 1,962.092.938m’ by the area of the
2
gauged catchments, which IS 9.981 km  This amount of ground waler recharge
Water Works Design & Supervision Enterprise
Id Association with teteJtontlDctttal CodsuUmu and Technocrats Pvt Ltd
11ArjoHed«5A Irrigation Project Hydrogeological investlgatiOQS
May W
minimal as rt amounts to onty about 13 53% of rhe total annual preopdahori of the area which is 1452.9mm.
Furthsrrwe. based on the same method. the surface runoff of lhe River catchment has Man estimated as the difference between ’he total river Haw of Dedesse flnd ihe minimum flow cn annual base and worts out to 2,105.796,874 n? that ts attributed 10 Surface runqll This value is used to derive the run off coefficient of the river catchment to asses 1he surface run off I or Cha e nbra Dadessa caichmant that wil be used in the water b alarice approach of the groundwater recharge estimation in the next sectaXV
Table 3.1 Monthly- total flow and M<n m-..m flow of Oadessa river near Arjo
Parameters
Qia
Difference
Months
M’jse
€
M’.'mortth
OjMA
It/mc M’Vmonth M’.'se
c
M^month
J
17 6*
4723W4i
4 4J3
119M483
F
12 <
lAswaw
2 35
1443300
M                  1O.«               ??97»~2<
0.960
2587134
A                 15 64                 aosarMa
4 557
llfll I74-;
M              79 14               ?eCS2J2li
10364
37758938
.. J
9847             255236832
_ 43 433
117762335
J             263 37              7JJMM956
13 16 £5257565
0 15 24551009
9.48 ^5496589
"1 OB ?8? '51AM
*8 79 50293386
53 IX ll374.?44Qn
137.J65
*            42139          11341)09026
ZMkftSJ
367910415
53099431/
s
0
N
Olnl
im3l
Q,- UM
343 2 ■ h •: ?
58 32
Ji ti5
- __.....
801 *91981 50569 ?5l3 17W4554
Z1T.F77 i
5644?7toi
»1^7 1563561)57
25 250 5aO6Q73fi
.IM;
ag74
7h i 5
tap,a
4? 56
1J.JSE                3694 Q493            2’ $6
33749054? 54 30147i39 3$713907
_____ W934Q556 lUyU; igld
59544046
4.06T.MM11
i s*2 Q93
(m\Ku Q ; M........ nun- ^o'rlhli d^ia,^
B
atf ' ; X X*tatWMn
ihe local monihi^ discharge
3 1.2 Water balance melhad
e, tatanu II « mean! scaling « tal nana me amixlnl Q,
.
rta„!9 tor a g.«en sjaam. such as hydrageelog le system, over a g,^r duratj()|1 ,w ,
8tea Hence..... dynamtoeystera.t Delay. 1997l The dramgge basiWM catchmeni. ^roundwaier bash, soi|
plural or artificial).
' v surface /refer reservoir
Dir
WIJ ater  Mlance  is  a  valuable  Idol  in  the  anal^  of  waler  ava-abrWv 
■-       — 
can M employed for different purposes campulalion of
X 1,1 J region The method
jn    .  _  r
_____________ 9^undvrater recharge, euapo.
Water Worts Design & Supervision EnTeTori^
to AiuclaUoa with Jaipur, Enui toiuDIfl
riaiinn milh lm>trnnH .^i p.
n
.
" UMIA|Jnbe
Tetlmocrau ([(J
32Arjo Oedewa Irrlgillsn Project HydrogeQjQgical Investigations
Hay 2007
twsjxabon. continuous  record of soil moisture, anti stream flow from a mtfleorfrkjgcal r-ecord and a f-aw observations- on the serf and vegetation. seasonal and geographic patterns oHmgation demand. 1 fie Mux of waler to lakes, prediction of human effect on h ydrologic cycle. ■ileopcld awt Chrw.
In this study bhfr waler balance melhcd is aimed al estimation of groundwaler recharge The banc assumption that is considered m this case is that rhe surface water divide coincides with the subsurface drainage basin Accordingly, othtf than the water that is percolated!
wlhin the linrf of the surface water divide, there is no ntenaqurfer How finftaw ar out flow) of grfkjndwar&r.
The basic equaiion* of waler bplance is:
Inflow = outflow +4S
'Afiere iS is change in storage
For the study area, the main inflow component 15 precipitation, but the outflow components are evapotranspiration and surface runoff assuming a* other components  such as  water abstract™  by  human fw other purposes  to be negligible. Besides  this, the change m storage. can be considered to be zero K the water balance 1$ made by taking waler year /or hydralogic year Hence, the value of AS roll be negfigibl^w zero smee the calculation n to
be made on annual basis.
---- LU I
Evapotfa"'5praiion (AETJ can be derived for the catchment in addiuon to ths. the
The surface runoff follows
The monthly minimum stream (low has been consitJeretj as4rjg Dedessa r/rlfittoa Project
Hydrogeolcgicai jnrestigatlofls
Rc = D/PA
Where
Rt" RWfflff ttwNiciftrtt
D = overland Row = 2,10579*6,874 <n*
P = annual pfetiprtat»ori =1452.9 mm = 1 452m
ii>r 2W
J
A = drainage area = 9,961,000.000 m  ■'drainage area a1 the r^ver gauging station. Bui Ihrs does not mean Iha1 the total drainage area of thg stud ied basin J Hence. Rc ■ E.105.796.674 m /1.4529 m < 9,961.000.000 m  = 0.1453
s
1
This Runoff coefficient is used lo estimate the surface runoff for the river basin ■’Dndessa Rivfi/J under study
In order 1o estimate the surface runoff of Oedessa area the mean annual precipitation
1452 9mm has been used
Hence the surface runoff tor the entire DedEssa River catchment becomes 0 1452 X
1.-52m X 10.293.303.358-08 ml = 2.170,141,264.31 m’. Thu* the surface runoff works 
our to 210.83mm This value is only aboul 14.51% of the total annual preaprtatlOn in lhe
fl 5ea Note lhat rhe total area of the studied river catchment at the out lei of the command
area is 10,293.303,358.08 m2
By  assuming, lhe comodence of groundwater basin with lhat of surface waler drvffe and also by  assuming lhat there is no artificial or natural mtra-basin subsurface or surface flow the grouridwale/ recharge of Dedessa riw catchment can he estimated as follows
GWf = P-(Sr *AETJ
Where GWf = Groundwater recharge
P = Annual precipdalicfi2 1452.9mm
AET - Actual £vapo-tran$p>ration
Sr = Surface runoff = 210.83mm
The  Aclual  Evapotranspiration,  (AET).  can  be  estimaied  based  on  afferent  methods-  one  or lhem is the empiocai Tore method Tore method is represented by the following formula °
Water Works Design & Supervision Enterprise
in ^soclaUos with Intercoottnent&l ConsulOnls and Technocrats Pvt Ltd.
14Arjg Mtosi Jrrlfa Upd haj«t
Hydrogeological tnvesdgadoas
2
AET -P -.J0 9 - IP'LJ ]
Where. P = annual mean precipitation io mm ■ 1452.5mm T = annual mean air temperature in  C - 20
L e 300 * 251 * 0 05T1 [mm] ■ 120dfflrm Hence far Dedessa nver catchment. AET - 544.57mm
Miy 2W7
J
Therefore, in order ro estimate grcvrfwater recharge for Dedessa River catchment IM value i‘AET - 94 J 57mmJ obtained by Jure method is used1 in ibe waler balancei rneJfrod of groundwater recharge eslimalion.
Hence. gr&Lndwaler recharge <n the Dedessa nver catchment becomes as Follows: GW* - P I Sr * AET.I - 1452.9mm - [944 57* 210.83) mm = 297.5mm
This vtfufl is about 20.43% of Che Idel annual precipitation in ihe area This high recharge rate may  be attributed possibly  to the relatively  better vegetation cover and to tM highly fractured rock prevailing rf> Lhe area
Finally, an average value from the two methods, the base flow analysis method (196.6mm) and the water balance meiJxxJ (29? 5mm). which i& 247 05 mm, has Io be used as annual groumwaler recharge of (he area Th.s value t$ about 17% of the tMal annual precipHabon
me areaArjaDedcjsa IrrlgaUrm Projwt Hydrojealogi ca! investigaUoas
4. WATER QUALITY
4.1Water sampfes
Mty 300?
Natural water interacts with CrrvirCrff-mcni. arid also it ;S affected by anthropogenic process changing  >is  chem*caL  physical  and  bictogical  constrtuents. The uWizaLiori of this wate requires  an  understanding  of  such  constituents.  Hence,  the  waler  should  mee1  certain qua-'.ty standard that is set manly based nn 4s purpose m order Io use 4. Some important physical and chemical parameters have been determined for 1he water of the study area to compare  dt  quality  with  certain  standards  set  by  different  Organization  such  as  WHO  tor specific water uses.
Waler   samples   from   different   sources,   have   been   taken   for   physicochemical   god microbiological    analysis    based    on    1he    aclualfexistrng    geology,    hydrogeology    and geomorphology of the area Accordingty. a total of Ihirte&n samples have been taken from springs and Wells, Fig 4 1 shows ihe location of the watar sqmpfe pomfs. Alt the samples have  been  subnutted  to  the  laboratory  of  WWDSE  for  analysis.  In  addition  to  lhe»  water samcJes  collected  during  the  field  work  previously  analyzed  water  quality  py  different instilutKjns have teen used for hydrogeorogical interpretation of the area
Among Che collected water Samples, four samples were taken from springs and nine were frcm boreholes. The numbers  of samples  have been determined based op vancus COKMtons  such as  geological and hydrogeological setup of the area and availably  of previously analyzed physicochemical and microbiological data in the area
Water Works Design fc Supervision Enterorlsr ’ “ «».»». MH ixomm c,Illu B Md lE£ M(ws
,
j
im
16Fig. 4.1 A map lowing wiUr umpla poinls in Arpo- 0fld*8-M p<o#*ctArjo Dedessa Irricatlon Project
HydrosftDtDftcal investigations
May am?
4.2 Sampling techniques and analysis
A   tola’   of   thirteen   samples   have   been   collected
(ram  different  sources  One  duplicate
sample is collecled from spnng m order to see the reproducibility of the laboratory results
Malural water is sampled m view of carrying out various analyses on it In order to undertake water quality  analyses  water samples  have been collected for physicochemical analysis  The raitected water samples  ware from ground water (sorings  and Wells) sources. The samples have been taken with one liter capacity  plastic  bodies. In order to compare some physicochemical parameters, some physical parameters  such as  TDS (Total Dissolved Solids], Temperalure and PH have been measured at field in order to compare the result w-1h Ihat of Laboratory.
4.3 Pictorial representations d water quality analysis
4,3.1 Piper diagram
The P'per diagram plols  1he major ions  as  percentages  of milli-equivalents  in two base triangles. The Piper Inlmear diagram for water samples <n Ago- Dedessa is available at Fig 4 2. The total cations and the total anions are se1 equal to 100% and the data points m the two mangles  are projected onio an adjacent grid. This  plo1 reveals  useful properties  and relationships  for large sample groups. The main purpose of the Piper diagram is  to show clustering of dala points to indicate samples that have similar compositions.
The Piper diagram can be used to plot all samples m the open deiabase or selected sample groups  m addition, the symbols  representing the sample values  can be customized according to shape and color. Other oplions  include individual multiplication factors  for each seeded ion to prevent data point accumulation along a base line The highlighted sample points  indicate samples  that are selected in the database and are also highlighted on all other Open graphical displays. According to the water samples  ptplted in Pip&r irihnear diagram tor Arjo-Dedessa area, samples  can be categorized based on their clustering as Ad-01. Ad-10, AD’12 and AD-13 as  one category, AD-02. AD-03, AD-04. AO-05. AQ-09 and AD-11 as  second category. AD-07 and AD-OS as  third category, and finally  AD-06 as fourth category  However, d we refine further the water type based on the chemical composition, they can be categorized in to five categories
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt. LtdArjO Ordtssa Irrlgadcn Project
Hyttr&geotoEical liwesdi ations
•    Na- HCO3 type (SampteAD-Ot. AD-07. AD-08, AD-W, AD-12 end AD-13}
•    Ca- HCO3 type (Samples AD’ 05 and AD- 11)
•    Ca- Mg- HCO3 type (AD-O3, AD- 06 and AO- 09)
•    Ca- Mg- Na- HCO3 type (Sample AD- 04)
•    Ca- Na- HCO3 type (Sample AD-06)
May 2007
The eaten io anion rato also varies for the different samples mdicatmy various conditions of rock‘■waler interaction.
4.3,2  Schooller diagrams
These semi-logarithmic  diagrams  were developed to represent major ton analyses  m meq/l aM te demonstrate dtffererM nydrochemical waler types  an the same diagram This  type of graphical representation has  the advantage that ixilfke the tritinear diagrams, actual sample ooncerlratHins  are displayed and compared The SchoeUer diagram in AquaChem can be
uses  io  plot  all  samples  in  the  open  database  or  selected  sample  groups  only  Up  to  10
dihcrenl parameters  can be included along the x-axis  and the symbols  representing the sample points  can be customized according to shape and color. The highlighted lines indicate specific  samples  LhaL are selected in the database and are also highlighted on all other open graphical displays The Schoeller diagram far the water samples of Ar?o
--■r
shaped curve: where as waler of different types show differently shaped curves Accordingly, two major types of water can be identified from the graph: Calcium bicartonalA
4 3.3 Stiff diagrami
30
-
A&f*
SO*
■' a>i:
Afr*J
*
■J
<1
x
■ 35
o ■ £___________________________________________
Ab
-£
-d—"3?7“ 
* » -l w “
,™ j
Ci
m ap shifwrnfl Pipe'
N*-KHCC3
trifjnear tfiagrtm
samptt* rfl Arro- Dftrtssa art JCgncwlffatan
AO-C’
AE^S2
*
—»• -
AD-E3
AD-04
AO-O5
AE-OB
ADO7
AC1-06
AD-QS AQ-1Q JMMl AD-12
ft-gi 4.3 A map shrtng ScfloeHer
far water sample in Arjo-Detiessa areaM
Ci
Cl
->
Hr-
X.
-CC3
■■• HCS3
:*
Sa
SC*
V-2
1ix
50*
M3
Ti
K
CM
K
*
1
003
a
—z "S"
A£>o*
w
SJ
V.             ncca
Ca
L         53*
i          CM
for ^for sample* n ArjO- D^esa P^tWl area (CwetnL
f
JI!Cl
Hi
"v
wC03
Ci
Mfl
X
T
io-t
coa
K
•o             *
«o
V 1 AD- H
Na -
C*
Mg
fl
iV           Cl
w*
■JF
HCC3
K
_ ■"
•r 1
504
C03
40
™ AD- T3         “
*3
i
■Arjo tJedessa Irrigation Project
Hydrogeological Investigations 4,4 AgriculturaUirrigation water quality
May zoo?
Agricuhu ra? suitability  of wat&r depends  on crop type, di male, sori type, and amount ol irrigation water use. {Davis  1966). The main parameters  to be analyzed to evaluate ffrigafon water quality  are Boron, Sodium h azard. and S aNnlty. These parameters  a fled donls  either directly  (e g. by  causing an adverse physiological effects) or indirectly  (e g by hmrling pi'ant root nutrient ar moisture uptake}. Salinity  is  best estimated based on Electrical Conductivity  (EC) value. Other direct indicator of salinity  is  Total Dissolved Solids  (TDS) The two parameters, TDS & EC are related by the following equation:
TDS  (mg/L)  a   640  x  EC  (dS/m),  where  mg/L  =  milligram  per  litre.  d$;m  =  tied  Siemens  per meter
According   1q    U   S.   Department   of   AgricuHure   water   with   an   EC   greater   than   4dS/m   is considered as saline.
Sodium hazard is  assessed by  lhe so-called Sodium Adsorplton Ratio (SAR). It is  caused by  sodic  water. Sodrc  waler is  water that has  htqh sodium ooncenirali-on relative to the concentration of calcium and magnesium. Water is  said 10 he sodic  if its  SAR is  greater lhan 12 SAR is calculated as follows-
SAR= [N»*jNb.5(Csa+
+ Mg J
Jt
Where,   lhe   concentration   of   each   cation   is   expressed   in   meq/L,   If   the   concentration   Is expressed in mmolriilre. SAR = [Na’Jf V [Cb * + Mg *)
42
According   IO   Todd   (19B0   and   reference.   there   in),   the   water   qualify   evaluate   (or     |frigaliQC based on SAR and EC are as shown m Table 4.1
Table Al SAR and EC values m terms of imgaton water sortability
Water cIMS                    E i&fttenl                          Good
F“
* H>                             10- 15
Pdcw
I S*R
“--------- —------ -J
Water class
IsS-'m ■ ifl ,.fcCm
DouOUu
750
20QQ"
MM-MXKT '             *30M
In  order  io  evaluate  water  qualily  for  irrigation  from saio.1, and Soa um haa a ,
,
(or  Arjc-Dedessa  area,  lhe  parameters  have  been S-hcwn in Table 4-2
meas,J'M a a caiculalea and
„
are
t.
Water Works Design 4 Supervision Eriternrtse mw im.TO.ru,,,., c™,im
-- - - - - - - - ■
• JArjo Dedeua lrrt£atioa Project
Hydrogeological Investigations
Table 4.2 SAR and EC vaJueS f<K surface and groundwater in Arjo-Dedessa area
M*y 2007
E#T" sbM
_____ __
____________________ - _
i           ad-i
__ -----
*0-1
J     --- uM. Il'
■ JMJJ I - IS 1 mHj *n-H A
AM                           AM
l£l*M5 "    aD-iCt
ao-h
I **ia
1-----
-
—
--------------- — 4J'D DO*
4 Ml        4M
*96
4tB
—“
2660
665-
SIS
3560
3i&0 .
sap
M*           0?
16
■a a .
ILLj
21 0                  i‘e_,
Acc&rdmg Io SAR values  obtamed for the waler samples. AD-01. AD-07. AO-lO, AD-12 and AD-13 are all sodic  water and AD-OS is  slightly  sodic, where as, the remaining water samples  are an non sodic. From Irrigation waler quality  point of wew, ihey  range from excellent quality to poor quafity.
But from salinity  point of view, fhfl quality  vanes  from excellent lo unsuitable; i from A18 us'cm to 4450 jisfcm. In other wards, it can be sa>d the salinity  ranges  from medium salinity Io very  high salmily. Fig. 4.5 shows  values  of TDS and EC for different water samples  in lhe prefect area
Figure 4-5 Eledncal conductivity (EC) in usfcm and Total Dissolved Solids (TDS) in mg?L lor water samples <n Arjo-Dedessa area
Th.s graph clearly indicates the extent of sahnily for diUeranl water sa
of for the EC and the TDS. Contour map of the TDS iS available al
area For description one th* waler samples mav he based on their Elecinc conductivity and FDS vaillBe a
_______________________
• *       '9 4 b for lhe project Categories
«v „
0   samcles (A0 M
Waterworks Design &
- ——
24Arjo DM«sa rrrijflllflii Project
Bydrogeotoflcal Investigations
Mar
AM3 AJ>04. AD-05 and AD-06) have taw salinity, four samples  (AD-07, AD-03, AD-12 and AC-13) have high salinity ; and two semptes [ACMJ1 and AD-1D) are ewiramety saline Thu qualitative descr-pbon doesn't follow I he standard procedure of waler quality classifcatori based on TDS andtar EC. bul if *s  simply  for the sake of description Waler Samples  coded as  AD-Ok  AD-10, AD-12 and AD-13 are ell from springs; all olher water samples  are from boreholes  (drslad shallow Wells). Hence, d is  possible Lo conclude thal even if they  are aH from groundwaler, Ihey  are from different aquifers. The more salme waler (having high IDS values] are mainly  from waalherecf basement rocks  [granite and graMic  pegmalne], and deep'Sealed volcanic  aquifers, especially  al&ng fauR 'mes  (eg. Ihermal spnngsk
25Fjg. 4-5 4 map showing ttw cCknfDur for Total Dis*ofved SoNct* (TDS ■ mg^U fof A^o-DwfesM Pro^cfirM
I
IDedHtt I ntfJKkn Project
J^dr&gEtiJagicil tn irestiitfitions
5 PIEZOMETERS OBSERVATION WELLS ANO WELL FILED
S.f Distribution of Plezometers/Observaffon Walls
May 2007
tn order Io monitor grouncfwafer quaMy and quantity of the area both before and alter lhe OOftstnjction of the eJam under invesiiqalpon. .1 total of Fourteen Psezomalers^Observation wells    nave    been    proposed    and    lhair    sdes    have    been    located    The    geographic CWfigui^bonWKtributton    of    the    pezometersjObservation    wells    is    selected    based    on geology,  hytfrogeofogy.  topography,,  groundwater  4low  direction,  ale  ol  ’he  area  Since  the depth  of  the  p<ezc*neters  lo  be  constructed  rarely  mCMdS  100  rvetersh   PVC  casing  -s recommendable.  In  some  cases  tha  existing  wall  depth  at  Iba  immediate  down  stream  of the proposed dam axis are SO - 70 meters depth
Tabla 5 t shows the geographical coordinates of the proposed piezometers
Table 5 1 Locations of the Proposed Piezomelers
Gnc^raphkal caordteJln [LTTM]       f
5»f Na       Pr#zom#1«f
coda
_____ -I. _ —__ —____J.-
Eilltngi
AiNluds (mJ
1
(2 P,C?
24I2&J
23522U
Hodtin^
945079
S4J443
9*9563
1332
134$
3
l%’3
13M
4               P*3-4                     2323&B                     945622
5               f’.c-S                      23/107
■ 345
139!
4 Pia-6
T P^J
72M92
233190
1374
__ J_ :__________ _______ _.,_
.*
r*
PjuuB
P*y9
P -iO
iB
Z25779
220119 ------ - ----------|
2i?5?7
951745
: M4 575
952070
M7I33
lJEfl
1324
954 Ml
S517D7
■ 341
1319
h                %z!l
12              P.q-r2
fa               P^IS
I ■' ___________L
217135
961437
212716
211854
713336
&S2444
95Wfl7
$51120
The oonslrudton d these piezometers shall follow |hfi tijiivi ^
irio >i-cir
a
1332
i'iiM
1323
I32Q
pfcxxsdijres aith
Ste^peulf-C condiluXis iuch as hyrjrogealpgicar sei up b|eq
pfopottd fMzoflidef* 15 salable on Uia rnfl
p  ho
L      wn in Fig 54
9b 3™1|,; Oc atioft of 1he
Witti Works DcslfiJi &
---------- ------
37
J — JArJ» Dedessa irfigadoa Project
HydrugcologlcaJ Investigations
5.2 Future well field
May 2007
The potential acruifers for groundwater storage in IM area are basatbc lava flows win minor safes- including rhyotte and ignimbrite, and alluviaJ deposits in the river valley d Oedessa
This tan be vcrrficd by existing borehotes data in the area For examprefc BorehOte data m Agaro area show this situation.
Well held sites  on which detail geophysical'investigation shall be undertaken have been kfenlihed based on geological, hydrogeological and geomorphological settingfor approaches  Test wells  drilling and construction shall follow lhe detail geophysical investigation.■Arjti DciSes-sa Irrigation froJecE
Dydrogeol apical investigations
6.        WATER LOGGING ANO DRAINAGE
6.1 Topographic feaiures and soil characteristics
The undulating and rolling  topography in upper part of the project area gradually acqui es ganrla  ^pe  of  RaL  land  «(he  botlom  valley  at  Dedeasa.  especially  lhe  few  part  where  tbo command  area  becomes  almost  flat.  This  A  al  'and  »S  covered  with  sediments  njmly  ot colluvial'delluv^al  and  ai.'uv^l  uri<|.n  This  sediment  is  underlam  mainly  by  hasemed  rocks. The  I  cpcgraphy  and  land  chsractensttasoi  the  command  area  can  be  said  to  tai  under level  (0-  1%).  nearly  level  (1-2%  slope},  very  gentle  (2-  4%  slope  I.  and  gentle  (4-  6% stope),  categories  as  about  35%  ol  (he  command  area falls under hrs! two  categories and about  23%  d  the  command  area  falls  under  lhe  last  two  categories.  Though  lhe  command area  is  plain,  it  has  a  rolling  lopography  and  mere  are  several  small  hills  dispersed  in  the conmanc There are rising hills also on the ouler boundaries of the command area on ooth birJci cf river DtdtSM
Tne mater pan of lhe area is comprised nt vertisol (47% of the command areal that has very taw pdntlsaWly  Next Lo vertisols  are camb*spls  and Itrvisols  covering 15% and 8 69% of the ares  respectively  Hence, this  soil type hinders  the infiltration of (ha most incoming ramfari during rainy  season On onu hand this  helps  to restrain the rise of the groundwater table ihrougl reducing infiltration on lhe other hand the plain nature of the land wouldn't allow the surface run of! l.o flow out easily.
6 2 Existing groundwater lable
Groundwater level m the prqecl area varies from 2 to 2Dm b.g I
In tb  command area the
a
groundwater tabto is 2 molars beta* surface dunng rainy season except in f6w ftxCepl mojl cases of surface water logging. During dry season 1he groundwaier iable was four d
,
than 5 meters befow natural ground surface. The rise of the groundwater (able can ha due CO different nalural conditions arwJ man made aclhnlieq th* .
- application of irfiqation practice is the =wr human interferences lor ij£e of groundwater i^hi»
imgation (drip, torrow etc) lhal is practiced and the crops propD5ed to ... deLftffl.fle (he Orient to which II may aifect (he use in groundwater level at the
■
.
1 D,e method of
Water Works Design & Supervise
JB AssOriadoaArje Brute sei Jirijratkio Prsjcd
Hydrogeological lumtigations
6.3 Future groundwater table and recharge from irrigation
M1J 2007
Whenever there <s a major irrigation project wlh continued and intensive irrigation adivrty. 1here ri always an apprehension of rise of groundwater table. <f ITie ris# of the groundwater table Is significant, and n continues unabated, it may cause -serious- adverse impact cn lhe fertility of "he iand. Same of the factors that affect lhe rise of groundwater arc
*    Topographic features
*    Land characteristics
*    Natural drainage system
*    Intensity and amount of rainfall
*    EMisting groundwater table
« Soil characteristics
*    Crops and its waler req^emeni
*    Seepage and Other losses from canal system
*    Surface drainage system implemented an»d ils effectiveness
The estimated annual crop water requirem&nl al primary canal head, for various crops to tie Cultivated m lhe command area of rhe proposed Aijo- Dedessa project comprises four s&l of values  categorized under two phases  each phase having two rotations. This  has  been sftewn m Table 6.1.
Table fi. 1 Annual gross crop water requirement al primary canal head
Ser. No               Phase J---------------
RoEaElort
GCWR (mm)
1I
_____________
I
907 40
2
II
1086.14"
3
<
II
■ ------------ ——____ —____
1
.
1311 47
II
II
1423.234
J
in o*der to assess gioundwaler recharge from irrigation water th& v.
c . me maximum value rtf th a
Gross C rt)R Water R equipment (GCWR) in 1 he second p haso o f,
&
-    * flCGnd r;j-?^||‘in— ih=iF
1423 234 mrtVyr nas been used. Therefore, ihe gnjvndwafor recha^e frurn t . of ir-rigalian has been estimated under pws mam siiurations, as fallows 
*
& aPP,italHJn
Water Works Design   Supervision EntTroriV-------- ------------------
4
la
*w> litKeudMitit CombIu^
T J™ 
recJ,n««r»is Pn, Lw
31Arjo Dedttti Irrigation Project Kydro^eolagical Investigations
May 2)007
1.    According  tn  groundwa
ter
recharge  e
stimati
on
made  m
this  report,  bul  I  he
iQlat
annual  preci  Relation  id
the
awe,  only 
17%
-s 
going  for
recharging  :he  groundw
ater
if   1he   same   scenario
i>
considered,
the
an
nual   grou
ndwater   recharge   from
the
application of irrigation in the command area becomes  241.95 mm This  value is  a crude eslimslipn Since uanous  factors  among which 1he irrigation merhod ten affetls the groundwater recharge
2.    Akrng  wrih  other  crops,  cullivalion  of  paddy  has  been  proposed  in  the  command area Paddy r$ 1ho only crop 1hat requires conslanl standwig water in I he field for ils growlh  and  d  evelopment.  Thus  paddy  cvRivalioh  results  into  percdglion  loss,  and only  that  quantity  of  waler  which  is  lost  through  percolation  has  1he  chance  and tendency  of  reaching  groundwater  It  may  be  noted  that  aboul  330  mm  of  waler  is estimated  Co  be  tost  through  percolation,  and  only  this  quantity  of  water  has  thd scope  of  reaching  groundwater,  which  may  add  to  the  rise  of  the  groundwater  The intensity  of  paddy  r$  only  30%  in  phase-  1,  which  will  increase  finally  to  45%  m phase-  It.  Coos-denng  lhe  entire  command  on  average  the  annual  contributions  of irrigation   waler   to   the   groundwater   would   be   99mm   in   lhe   Phase-   I.   which   will increase to 148.5 mm under phase* II.
Regarding other crops, they  are all dry  .rrigated ,.e„ no standing water is  required. The irrigation water applied 1o 1he field in case of all other crops except paddy will be contained 8S soil moisture w-ir.n the r«n zone. Very  small amount gi water, which will be l0SI below
the  rout  z  one,  w  ill  reach  the  groundwater  Giber  losses  wiH  be  in  form  of
f     fUnQ^
SUf 3re
Wtfch wiH be iaton care by surface drainage System As such (he addition to qf 'irto Mtsa Irrieawoi
Table 6.2 Estimation of wetted area hw Arjo- Dedessa Irrigation canal
Avirage
* 
a J—
waned
ptrimater
(mifflj
' »<W~| Lett
Total             Jm'
Cirvjl caBigory
i
l
Total Area
?
(m )
1           Min can*
Left _______ so.rao.uo
7
■*460_B_ 3.00 131.696 05
?
3 ST.ro. tal ’
No
Secondary canal Tetwi«y can*
8.7.1.15
Z7S&
10.211 .
2.79S
Right
42 800 00 49.37D.W
47.1W.0t)
]■    i.K
I
1.02
199 *&*0°
239.100.00 H"
Rlflhl
"278.W w .
137.96*00
203.453 0°
621.061*0°
243 W2.00 L——--------------
aaSiSSM*
iwn*oi’-«*"**’****"
Talrie 6.3
c®Ml
1
No
Command {ring)
|
’ 1 "Right Bank 2      Lift
ar&3
ge loss from urwm*v ^-1- —                     -
—
2
Wetted area of Csa* (m )________________ |
Mam canal 573 63M i’/j
&econcrary 
canal
137.989 00
Tertiary 
canal
- 2637453.00
loss (mm)
’ ““480,073.00
131,096 05 243 0B2 OO
-
-----------------------I
Total wetted area (m }
s
"621.0BtOO ' 836,651 05 1
T
4 T(
TS* w*1 lrTI 1 Total
7*0 512-00  ■ ■ •   *
1n9.fl8iOS           W.MS.pO             Jj«T,732.0S
Z3.32OJSM-1 . 6,400,aD9.7J [
■’ J
In the seepage loss  calculation from the Main canal, only  75%, of the total area has  been conskierad The duration of the seepage toss  is  considered to be eight months  (October - May) and twenty four hours a day for the main canal; where as for six months of twenty four hours  for secondary  and ternary  canal The command area on which the seepage loss  has been averaged out «5 the gross command area, i.e , 17.825 hectares (178. 250. 000 m ?) i.e the total seepage loss  of 40,330,960.60 mJ is  spread in the gross  command afes which gave an average seepage loss of 2Z6 26mm from the irrigation canal
-------- Water Works Design & Supervision Enterprise
Is Association with iDterMMlieiml Cmultants and Technocrats Pvt ltd,
33Arjn-Dadcssa Irrt^nana P7d J«l
Hydregeelegtea! invesd^aUons
Ha? ^nT
Tnaretere, lhe total annual groundwater recharge from rhe application of rnga'n.'becomes rhe 5UH df the MJM0* <«* fromthfl canals  (225$6 mm I and from the picHy  irrigated f 1-4-B.5 mm) Ihal i$ 374,76 mm.
AHhough detail aquifer and soil sampling and analysis  is  required lr> comfl up win actua ro&ull pftlHpfltHty, jI3 value has  been eslimated tab* 35% i n r ha command a f*a b y considering a range from day  1& send safe Thu parameter will be used Lo asltmate groundwater fevtJ nse due Io the application of irrigation
Finally, by  Knowing rho groundwater recharge from lhe application of mqalion, and the porosily  ol the aquifer end the kH malenals  above it, the extent of the groundwater level nse due tQ 1M spplication of irrigation has  bMO eslrmn'ed under different Ksnanoa as fafcws:
Scenario I. No groundwater flows out Ol the catchment (stagnant condition)
Annuel groundwater recharge from application of irrigation, GR = 241 GSmm
Effective porosity oi aquifer (sano)« command area, r, - 0.35 (35%)
Groundwater level use due 1o application pf irngatior,
GWLr = GRfok =24v95mnV0.35 = 0.591 m.
However, n should be nwed 1had groundwater is  always  m a dynamic  conation; hence, ihe Stagnant groundwater cpnditipn never prevails  in lite area. Therefore. the stated value ol groundwater level rise |0 59lei) will never happen
Scenario   JI:   Groundwater   flow!   Out   of   the   catchment   (dynamic   system)
Annual groundwater recharge from apphtaifon of inrigatkjn. GR = 241 %mm
Effecuve porosity of aquifer (sand) m command area n, a 0.35 [35%)
According  to  b*9e  flow  HpnUM  melhod.  lhe  ratio  cf  groundwater  pullfow  from  lhe    entire nver Moment to 1he groundwater recharge of ertfihmerf fion precipitation IS 79 50...
Hence, ihe regaining 20 42% tf lhe groundwater recharge conlribule^ to groundwater lev  i nse Similady. if we apply such dynamicity to foa groundwater recharge fr(Jm ™<. 3 will irngaiFJn w-aiesr apphtdlon. rhe groundwater CXJtficrw from rhe irrigation appbcalten becomes ig? 54 mrY
Water Varfcl Oesl^n A Supcrvlsioji
foAsnclatlDO wtt talffWltinUl Consultary aa(j TeehQacttl3 P„ , |d
—
34AtJd-Dctf«sa Irrigation Project
Hydrogeological Jnvesilgatioits
May 24W7
e
1Q7Q.74mm=- 107m.
Scenario IV; (Scenario III under dynamic  condition). This  Scenario assumes  that ground water is continuous flowing out of the catchment Hence, only 20 4 2% (76 S3 mm|
□f  the  groundwater  recharge  from  Irrigation  water  will  contribute  to  the  groundwater  level nse Therefore, the groundwater lever rise under this Scenario becomes GWLr = GR/n, =
76.53 mmTO.35 = 2j 8,65mm - 0.219m.
In conclusion. the assumption of stagnant groundwaler condition Scenarios  (sccnarro I and III}, over estimalw the groundwaler level nse due Io the application of irrigation Because it assumes  stati&'or stagnant groundwater condition that is  not lhe case in realty  s,n _ groundwater is usually in a dynamic condition The second Soenano (Scenario II) fe|,es
Heoca, if we reduce this, amount from lhe recharge due Io the application of irrigation meniKined above (241.95mm). the net recharge thart contributes  Io th® groundwater level rise becomes only 49.4mm. Therefore. under this scenario the groundwater tevel rise due "o the application of irrigation will be
Groundwater  Eevel  rise  due  to  application  of  irrigation,  GWLr  =  GR/nf   =  49.4  mm/0.35  ■ 0.141m.
Scenario III According 1o 1h® paddy  cultivation and seepage toss  from canals  the annual groundwater recharge from the application of imgalion es 374.76 mm as mentioned before It this  i$ the case, the groundwater level nse due to the application of irrigation under stagnant groundwater condition becomes:
Groundwater level n$e due to application of irrigation. GWLr = GR/n  =374 74 mm/0.35 “
groundwater recharge estimation from imgation water appl^tion ea ja|c - ,
preapilanon However, groundwale.' recharge from irrigate ^jter from paddy fffgrfcfl and canal loss should be higher than from scenario underestimates the groundwaler recharge Therefore aCr
rn-ai irom vpiH?-aiiDn particularly
t
h* piLaiMjn Meno® ihic 
investigation.   the   Scenano   that   works   oest   is   Scenario   IV.   Henrs   ih-   Cordin9   this 
«            .■
level n$e cfue 10 the application of imgatran water will be 0.519 m However, '1 h®* t0 noted that the Oxisling soil jn ^)e
' tne af|nual groufi
|,,
C w a oruwater
loam 5*lls 35 re
area is mainly day and 7 aied from sail survey (sampling and analysis) under the same project
Waterworks Design & Supervision Enterprise
In AssDctatMtt With tntertCntlneout CoisuIimu and Technocrats PvL Ltd.
“ 35Dedcssi Irrigntlqu Frujwl
Hjdro^cologieal LgvcstlgattaiLS
May 2007
Thesollhas        UiWrege        fttftulfa        DondudMtyofO        rjM0056m^.i.B.0.4S2        ifl/titf-This vahjs is very small inhibiting 1he Infiltration of any vfller f preci prl alien or irrigation} to GtftjnchwfSf   Men«,   ine   crmfritaxlion   uf   groundwater   radwgs   from   Uw   appUcahtxi   gf irrigation  should  be  less  ihamhe  amount  slated  here.  TtW*fan.  the  groundwater  level  rise due 10 lha applicabcm of Irrigation cannot <«Mt HilSmtyw
Arother factor iha1 can reduCS rhe conlnbutinn of irrigation applicalKin to grounuwJJter recharge is  lb* presence of number of Creeks  that are transversal to the trend of the command area and Dedessa flivcr. Some infiltrated water from the irrigation ipptiaflpn wul co me out as re^eneratico through the creeks before reaching lhe groundwater tabic Profile across seme c/eeks and Ded&ssa river in the command area is available in Fig. 6.1 (a, bB c, d and e) The lines along which the profiles have bean lakan are also shown in the map Fig
Although lhere is w well documented wefl cc*mple<K5fl data in the command area, the depth to gmundwatef in ihe area is  below 5 meters  during dry  seasons  except *n some creeks such as Chuli area (eastern pad of command area) where the waler tab!* is abOb| 2 meters telcw ground Surface. Only  few boreholes  and their data exist in thB Dertts^a Rhw uglloy of prcjecl area since it to inhaaiad mainly Lhnougn msettlemsfitB only 2- 4 yE?irs .l£)..
Hence,  construct  gf  colour  map  deling  daplb  10    groundwaler  is  TiarJIy  possible  under MCh data Hmtafanflfrwe tMy » entirely coreiwctecf for emergency purgesI
I
I
I
I
I
I
I0 02               wiS II
0 51
wiWL
<^5Z
in DSEL
- - UJC9EI
n 01EI
0ZW£ uffzaZR ^*;
■*" “Wr
nw^'uay^y ff
U^S
«T“5
IFrom Pp»: 2191B4O91. 943954,006
To Poor 22641 ?.470 954446.014
rFrom Po«: 223707.657. 939756.863
To Pos; 23016J.8WL 953187,677
1400 m
UlSiib
1325 m
1366 m
2.5 kffr
5.0 km
lfl.O kin
12-5 km
14.99 kmFinn Ph,; ti0789-844, Ot, 2206.14?I
A map showing lines nt profiles th the command areaA^d-IMbhi Irrtfittott Pro jed
Hydropeijtoglcal investigations
7. SALINITY AND SODICITY
May 2DO7
Salinity of soils/water can be defined in terms &f electrical conductivity Particularly for soils il i$ Mie electrical conductivity of the ssluralion extract. However, sodicily is defined in terms of  e  xchangeable  sodium  percentage.  Salinity  may  be  categorized  in  to  two  based  on  *ts sources,  primary  (inherenlj  salinity  and  secondary  salinity.  Primary  {inherent  i  saFirflty  is derived  Irom  the  weathering/degradation  of  primary  rocks/mmerats  ft  usually  occurs  when evaporation  exceeds  precipitation.  Where  as  secondary  salinity  is  derived  from  the  upward movement  of  sails  from  saline  groundwater  through  capillary  size  under  the  situation  of  in adequate  leaching.  This  situation  happens  mainly  under  shallow  groundwater  Mass  flow  to lhe  sail  surface  Ifwough  capillary  nse  is  known  to  cease  when  the  water  table  ?s  below  2 meters  in  a  day  and  sihy  clay;  where  as  the  same  value  is  1.6  meters  in  coarse  textured sml.
Water  and  serf  salinity  occur  due  to  d-flerent  reasons.  Among  (ham  are  over  irrigation  trial causes groundwater level rise due 1o in appropriate prevision of drainage and/or crop water requirement  calculation,  poor  method  of  irrigation,  capillary  rise  of  groundwater  du«  Io naturally  high  groundwater  tevef  below  surface,  etc.  When  such  ra.aed  groundwater  level is sheeted  to  evaporation  loss,  the  chemical  constituents  of  the  water  will  be  left  over  and becomes  concentrated  on  the  surface  leading  to  soil  and/or  waler  salinity  Th®  |eflr   njng  Qf some  exisL<ng  nutrients  in  soil  is  also  the  potential  source  of  salinity  of  water  and  soil  m irrigation.  In  order  to  assess  lhe  possibility  of  salinity  for  lhe  propel  area  n  the  future  d have  been  collected  and  have  been  evaluated.  Among  lhem  are  the  existing  rot  nd quality    {physicochemical    characteristics    of    groundwater),    and    sod    chemistry    On Parameters  that  have  been  given  emphasis  here  <s  the  meteorological  parameters  itT cause h^h evapotranspiration. However, lhe high rate or precipitation (rainfall) "n
can cowheraci lhe problem by leaching the highly soluble lyi-, such aMcbonaiesahs.
Ths dislrtxlfon of .-elabveiy saline water js sporadic in the area H is
d,ed
Wphaie,
basernenl   (crystalline   >   rocks   and   thermal   springs.   CoM   grrjundwate   aSS°Cia,e£l     wi,h
vokanx: rocks m the area has very few TtS; and hence, very lDlv Toial Dissolved Solids of lite project area is available at Fig 15
3r '9inBled from
7- A map showing
Water Works Design it Supervision Enterprise           "
In Asswladite wit* InimoBtiBenttl Coasultacu and Technocrats Py
L L(dArjo&sjpsia rrflfukn Project
Bydrogeitiftglcal investlgatioiis
flay mat
Hance. 1ha huwti soil/wate/ safrnriy  during 1hfl design period of the project can be M*iiralled naluralty  [through high prcCipilaltoo and topography  of lha area) or artificially Ihrough appropriate irrigation water rbanagemartf.
torWo^Desig^SupeT^^---- - - . . .
Ip ftxKcfedOu WIW UnTOrtHttil OOMttilitte aim
“’“Scrats PtL Ltd,
■if)A-rJa lirdfiua [rfijatloo Project
Hydrogeological Investigations
May 2W
8.  EXSITING AND FUTURE PROSPECT OF GROUNDWATER
8.1 Existing groundwater development
Presently,  the  majority  of  lhe  Woredas*  capital  lawn  and  the  rural  community  m  the  river catchment    are    supplied    potable    W    from    groundwater,    either    through    borehole construction  or  from  spring  develocxnert  with  the  exception  of  Sadete  low  that  get  wafer from Dabana River through te* treatment of raw water. The yield of groundwater from some volcan.c lava how shows very promising result both for current and future water supply from groundwater for different purposes. Can be mentioned as examples are boreholes (or Agard town where the yteld is about SOlit/sec from a Single borehole Furthermore, the aquifer in this particular area has multilayer system attributing to a confined aquifer
Here. rf <5 vital to discuss Agaro town as an example. The town is entirely supplied water from groundwater through borahotes. There are three new boreholes  and 1wo aid boreholes. Among these boreholes, four boreholes are currently functional, one from the old and three of tee new borehctes
In addition to this, the Quaternary sediments m the river valley are the potential aquifers for groundwaler development particularly shallow groundwater
Other  Woreda  towns  teal  are  suppted  potable  water  from  ground  water  are  Ar|O   Alnago Galira and Atnago
8.2 Future groundwater prospect
The exiting gectogical. meteorological. hydrogeological and geomorp^oluyi^i it
in the river catchment indicate there are areas thai can be devafooed m
n r Jni °f groundwater for various waler supply purposes Accordingly, potental well fjAlri <,..=<■ u
T1
IBS ^ve been identifi pfi
in order to develop groundwater. These identified well field sues have Io b on geophysical investigations and test well drilling before being entirety
likely limitation in the future groundwater development in lhe area « . . J 3
hot iho quaniit* h
quality (relatwery Ngh iron concentration). The map of potential grounds» future development is avertable at Fig. 8.1
'
a 12 r dfeas for
The ”*
faier Works Design & Supervision Enterprise             ———
j B Association with Intercontinental Consultants aoj Tettnocrau Py L
t
W4 /rup
0
ter porwrtttafJ a-fpj-i fof fufw* tfevp/iiprt?w?f «r.tYi MHM
**»i®AUTHOR
TITLF-
call no.
EDITION
VOLUME
CAre. NO.

Summery

Arjo-Dedessa Irrigation Project Summary

Arjo-Dedessa Irrigation Project Feasibility Study Summary

Project Location: Dedessa River, a major tributary of the Blue Nile (Abbay) in Ethiopia

Lead Organization: Ministry of Water Resources, Federal Democratic Republic of Ethiopia

Consultants: Water Works Design & Supervision Enterprise with Intercontinental Consultants and Technocrats Pvt. Ltd.

Report Date: May 2007

1. Project Overview

The Arjo-Dedessa Irrigation Project is a major development initiative in the Dedessa sub-basin of the Blue Nile (Abbay) River in Ethiopia. The project includes:

Construction of a dam and reservoir
Development of irrigation infrastructure for approximately 139,000 hectares
Potential hydropower generation components

2. Key Hydrological Characteristics

2.1 Dedessa River Basin

Catchment area at dam site: ~10,000 km²
Mean annual flow: 3,800 million m³ (at Arjo station)
Flow distribution:
- Peak flows (Aug-Sep): 52% of annual flow
- Minimum flows (Feb-Mar): <1.5% of annual flow

2.2 Climate and Rainfall

Uni-modal rainfall pattern (main rainy season June-September)
Mean annual rainfall: ~1,450 mm
Dry season: November-February (7% of annual rainfall)

Rainfall Reliability Levels
Reliability Level	Annual Rainfall (mm)
Mean year	1,453
75% year	1,148
80% year	1,090
95% year	853

3. Water Resources Analysis

3.1 Streamflow at Dam Site

Reliability Level	Annual Flow (Mm³)
Mean year	2,328
75% year	1,729
80% year	1,625
90% year	1,384
95% year	1,224

3.2 Evapotranspiration

Estimated using Penman-Monteith equation:

Total annual reference evapotranspiration (ET₀): 1,397 mm
Monthly ET₀ ranges from 91.8 mm (July) to 143 mm (March)

4. Flood Analysis

4.1 Flood Frequency

Return Period	Peak Discharge (m³/s)
10-year	575
20-year	654
50-year	771
100-year	871
500-year	1,155
1,000-year	1,303
10,000-year	1,948

4.2 Probable Maximum Flood (PMF)

Estimated PMF peak discharge: 3,690 m³/s
Total PMF volume: 768.5 million m³

5. Sedimentation Analysis

Estimated annual sediment load: 776,000 m³
Sediment distribution in reservoir modeled for 50, 100, and 150 years
Sediment relationship: Gs = 0.078 Q^1.5 (Gs in gm, Q in lt/s/km²)

6. Water Quality

Water quality analysis showed:

Low sodium hazard
Low to medium salinity hazard
Boron content: 0-0.2 ppm (tolerable for most sensitive crops)

7. Key Recommendations

Proposed dam with storage capacity to support irrigation for 139,000 hectares
Consideration of hydropower potential (estimated 299 MW capacity)
Need for training in hydrological monitoring and data analysis
Continued monitoring of sediment loads and water quality

Note: This summary covers Volume III (Water Resources) of the feasibility study report, focusing on meteorological and hydrological aspects. The complete report includes additional volumes covering topography, natural resources, agriculture, and socio-economic aspects.