- M i *               Acc -l?7
FEDERAL DEMOCRATIC REPURLIC OF ETHIOPIA
MINISTRY OF WATER RESOURCES
ARJO DEOESSA HYDRO POWER AND IRRIGATION PROJECT
AL FEASIBILITY REPORT
VOLUME-IV
OGICAL AND METEOROLOGICAL STUDIES
Jaie, 2119
Addis Ababa
TER WORKS DESIGN & SUPERVISION ENTERPRISE
IN ASSOCIATION WITH
INTERCONTINENTAL CONSULTANTS ANU TECHNOCRATS INDIA PVT
P O Box 2561. Addis Ababa Ethiopia
Tel (251)1 614501/631890 Fax (1251)1 61537IE-mail « u d s,c<;Ickxoin
* tV-' *■
zHYDROPOWER FEASIBILITY REPORT
ARJO-DEDESSA HYDROPOWER & IRRIGATION PROJECT
LIST OF VOLUMES SUBMITTED
VOLUME 1                 EXECUTIVE SUMMARY
VOLUME II                 MAIN FEASIBILITY REPORT
VOLUME III               GEOLOGICAL & GEOTECHNICAL STUDIES VOLUME IV               HYDROLOGICAL & METEOROLOGICAL STUDIES VOLUME V                DAM & APPURTENANT WORKS
VOLUME VI               HYDROPOWER STUDIES VOLUME VII              FEASIBILITY STAGE DRAWINGS
JArjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
TABLE OF CONTENTS
EXECUTIVE
1.0 INTRODUCTION1
1 1 EVOLUTION OF THE CONCEPT FOR POWER GENERATION .............
1.2     THE PRE-FEASIBILITY STUDY FOR IRRIGATION CUM HYDROPOWER PROJECT
June 2009
1.3
PRESENT
FEASIBILITY
STUDY
SUMMARYI
2
2
2
2.0 THE RIVER BASIN AND SUB BASIN4
2 1 THE NILE BASIN 4
2 2 THE DEDESSA CATCHMENT4
3.0 DATABASE6
3.1      CLIMATOLOGICAL DATA
3.2      RAINFALL 6
3.3      river discharge6
3 4 SEDIMENT DATA 6
4     ESTIMATION OF CROP REFERENCE EVAPOTRANSPIRATION7
4 1 CAUSATIVE CUMATE7
4.2      METEOROLOGICAL DATA7
4.2             1 Meteorological Observation Stations
42 2        Air Temperature
423         Air Humidity 
4 2 4 Wind Speed
4.2             5 Solar Radiation
4.3      PENMAN-MONTEITh EQUATION
5.0 RAINFALL ANALYSIS12
5.1      THE ANALYSIS 12
5 2    RAINFALL INTERNALAND EXTERNAL CONSISTENCY ............
5 3    ESTIMATION OF RAINFALL RELIABILITY LEVEL
5 4    ESTIMATION OF MAXIMUM RAINFALL FREQUENCIES
6.0 MONTHLY STREAMFLOW ANALYSIS 16
6
3
8
— ■■ 8
........................... 8
12
13
13
6.1      HYDROLOGICAL OBSERVATION STATIONS..................................................................................................................................... 16
6.2      EXTENSION OF RECORDS ................................................................................................................................................................. 16
6.3      SYNTHETIC FLOWS
7.0 ESTIMATION OF FLOODS FOR UNGAUGED CATCHMENTS22
7                1 RATIONAL METHOD.................................................................................................................................... 22
7.2             SCS METHOD 22
7                3 TRANSFERRING GAUGED DATA
7.4      ESTIMATION OF WEIGHTED AVERAGE
7 5 SYNDER METHOD OF CONSTRUCTING SYNTHETIC HYDROGRAPH ...
8.0 FLOOD FREQUENCY ANALYSIS24
8 1 INTRODUCTION
16
8
2
CHOICE
OF
DISTRIBUTION
9 0 DESIGN FLOODS AND FLOOD POUTING 27
9 1 SPILLWAY DESIGN FLOOD
91.1           The PMF Inflow Hydrograph
912 Routing of the PMF Hydrograph through the Reservoir 9                2 COFFERDAM DESIGN FLOOD 28
9 3 THE CROSS DRAINAGE WORKS DESIGN FLOOD
23
. 23
. 23
24
24
27
27
23
28
II
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10.0       SEDIMENTATION AND WATER QUALITY.............................................................................................................................. 31
10              1                ESTIMATION OF SEDIMENT YIELD.................................................. 31
102         distribution of sediment in the reservoir
31
10              3                WATER QUALITY ......................................................................................................................................................... 32
11.0       RESERVOIR SIMULATION CARRIED OUT FOR IRRIGATION FEASIBILITY...................................................................... 37
12.0       MODELING FOR IRRIGATION CUM HYDROPOWER GENERATION...................................................................................38
12 1        EVOLUTION ........................................................................................................................................................................................ 38
12 2        SIMULATIONS FOR OPTIMAL POWER GENERATION .
38
12 3        POWER EXPLORATIONS AT HIGHER LEVELS.............................................................................................................................. 38
12 4 INFERENCES.............................................................................................................................................................................................   *0
13.0         REDUCTION OF FLOWS IN DEDESSA SUB BASIN............................................................................................................. 44
14.0          MANDATORY DOWNSTREAM RELEASES..........................................................................................................................44
15.0          RECOMMENDATIONS............................................................................................................................................................ 44
REFERENCES............ .. ............................................................................................................................................................................. 46
____________________________________________________________________________________________ ______
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List of Tables
June 2009
Table  4  I  Table  Details  of  Meteorological  Observation  Stations  located  in  and  around  the  project  area  8
Fable 4 2 Types of Climatic Data available at the various Meteorological Observation Stations 
Table 4 3 Summaries of Meteorological Characteristics at Project Area Table 4 4     Summan of Estimated Mean ETo of Arjo Dedessa Project Area
....
9
.9
10
Table 5 I      Mean Monthly Rainfall ........................................................................................................................ 13
Table 5.2     Monthly Rainfalls Corresponding to Different Reliability Levels at Project Area Table 5.3     Maximum Annual 24-hr Rainfall
Table 5 4     Maximum Rainfall Magnitudes and Frequencies Table 6 I      Availability of Stream flow Data in the Region Table 6.2 Mean Monthly Flow (in Mm sec)
14
IT
15
I”
18
Table          6.3          Coefficient          of          V          ariation          of          Monthly          Discharges          18
Table 6 4     Summary of Regional monthly flow characteristics 
Table 6.5     Statistics of monthly flows at Arjo Dedessa dam site
Table 6.6      Reliability Level Vs Monthly Stream flows at Dam Site
Table 6 7      Monthly Flows at Dam Site All flows arc in Million Cubic Meters Table 8 1      Estimated Flood Quantiles Based on GEV Distribution
Table 8 2      Estimated Flood Quantiles Based on LLG Distribution Table 9 I Spillway Routing results (Irrigation Feasibility Phase)
T able 9 2 PMI Ii dr r iph Ordinate
Table 9 3 Cumulative Volume of Probable Maximum Hood
Table 10 I Relationships between water discharge and sediment load 33 Fable 10 2: Monthly Total Sediment Load at the Reservoir Site
Table 10 3   Accumulated Total Sediment Load at the Reservoir Site..
28
18
18
19
20
25
26
-1'
29
33
33
Table 10 4   Elevation-Area-Capacity Relationship at Arjo-Dedessa Irrigation cuin Power Reservoir Table 10 5   Distribution of Sediment in the Arjo Dedessa Reservoir (Area Increment Method) Table 10 6   Water quality results for sites on the Dedessa river
Table III Irrigation W ater Requirements for Various Scenarios Fable 12 I Firm Power at Various ERL conditions (1350 m amsl Minimum Table 12 2: FRI at 1376 m amsl Firm Power Generation
36
34
35
41
42
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In Association with Intercontinental Consultants and Technocrats Pvt. LtdArjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies EXECUTIVE SUMMARY
June 2009
The Dedessa sub basin is very important one. hydrologically for the Aboay River being major flow contributing sub basin Nearly  25 to 26% of the Abbay  flows  at the border is  due to Dedessa sub basin Draining an area of nearly 34 OOOkrrr it encompasses its tributaries like Wama Dabana and Angar all of which have been investigated for ambitious  irrigation and power projects by various study groups in the past This is because of the hydrological virtues associated with this sub oasm
The Rainfall With a variability of rainfall from 2013 mm in Dembi station to 1417 mm at Agaro stations the rainfall results in 1453 mm over the proposed Arjo dam and its catchment These rainfall estimates  in the study  have been made by  regionalization, followed by  rigorous statistical analysis  The data of the stations  at Jimma Deaessa. Bedelle Dembi and Agaro were included appropriately ana after consistency checks and such checks on the adequacy in quality  and length The above mean annual rainfall in the context of certain salient exceedance probability level years like 75% 80% and 90% are respectively 1148mm 1090mm and 951mm Being unimodal type of temporal distribution, bulk of the rainfall (63%) occurs in the block of 5 months (May to September) ana as such the proposed dam is to have season- to-season carry over
The Agro climatic  situation: The parameters  like monthly  mean temperature relative humidity wma speed and sunshine hours form the relevant inputs in the estimation of crop water requirements of irrigation development
The data of the stations Beaelle Dedessa and Jimma were found to be appropriate in representation and in quality for analysis by statistical techniques and hydrological methods On ascertaining these parameters they were usea in the estimation of the major input for crop water estimation namely "Reference Evapotranspiration - ETo " The estimates of these
parameters stand at the figures shown below at annual mean level
-  Mean Temperature
22 51°c
-  Relative Humidity
75 51%
-  Wind Speed
0 7lm/sec
-  Sunshine Hours
6 89hrs/day 
-  Reference Evapotranspiration (ETo)
1397mm/year
The Water Resources These could be established as a monthly time senes of 45 years from 1960 to 2005 because of good data base availability m Dedessa and the neighborhood sub basins The data of tne stations like Dedessa at Arjo upper Dedessa at Dembi Dabana near Abasina Gilgei Ghibe near Ascendabo and Gojeb near Shebe all formed a good data base for statistical analysis in estimating the above time senes of flows at th® nron^sed Ario dam s-to Tnc detailed mommy ume senes, tnougn avaiiaoie m tne sectoral report, tor ready appreciation the annual flow estimates are given below
Mean year
2477 Mm?
75% Exceedance probability year
1750 Mm
80% exceedance probability year
1635 Mm
90% exceedance probability year
1390 Mm3
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The historical time senes, since may not form a spectrum of hydrological inputs for the simulation study as recognized by the hydrological literature a synthetic series of length of
1000 years was generated by the robust and time tested single site multi season AR 1 type Thomas-Fierring model"
The simulations These were carried out at different assumptions and with different options
x  During  the  Irrigation  Feasibility  Study  simulations  were  carried  out  for  four  different irngation development scenarios for about 14 OOOha The simulation model was a tailor made type developed in MS Excel The MDDL was kept at two different levels like 1346 and 1350 mamsl as dictated by irrigation requirements The FRL was varied from 1350 89m to 1351 87m The synthetically generated flow time series of 1000 years formed the hydrological inputs to the simulation runs In all the runs, the irrigation was successful at tne appropriate norm viz 80% exceedance probability level, not only so the  irrigation  is  successful  even  in  stringent  years  of  90%  and  95%  exceedance probability   levels   Hence   no   ambiguity   anses   about   the   definite   success   of contemplated irrigation development
The dam though was  planned to be high and to possess  good water resources  was constrained to have a small live storage to cater to the need of irrigation imposed situations/constraints
Though not in the purview of the TOR of the Irrigation Feasibility Study the Consultants carried out further simulations for exploring possible power generation over and above the irrigation For this  the Consultants  developed another tailor made modei Fortran source coded termed
Arjosim'  Initially  a  couple  of  simulation  runs  were  carried  out  with  MDDL  at  1346  and subsequently at 1350m and FRl at 1953m and at 1956m At MDDL, two separate outlets were contemplated one for irrigation and another for power
The average Tail water level was kept at 1322 mamsi
A set of 8 simulation runs, with 4 different pattern of monthly releases indicated a so to say discouraging scenario The power generation could reach only up to 3MW at 97% exceedance level This stood at 5MW ano 7 MW in 65% ano 50% exceedance level
The exploratory simulations were to be earned out further with different FRls MDDLS and pattern of releases with mean Tail Water level at 1322 mamsl The model Arjosim was slightly recoded for the further runs Three domains were set for these simulations and a number of exploratory power generation runs were carried out The summary of the salient and optimal results of the domains aiong with tne nomenclature of these domains is as below
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i------------------------ -
r
Domain
No.
Power at 97%
Domain Nomenclature
FRL
exceedance level
I
(Firm Power)
1
MDDL at a lower level of 1346m and
1370m
11 22MW
assumed pattern of montnly releases
1372m
13 30MW
1374m
13 62MW
2
MDDL at lower level of 1346m but
1372m
16 49MW
releases based on decision support
1374m
17 20MW
1376m
17 90MW
1378m
19 50MW
3
MDDL for power at same level at
1370m
17 00MW
1350m as irrigation outlet (with
1372m
18 10MW
separate outlets) Decision support
1374m
18 95MW
based releases
1376m
20 00MW
At the end of the Irrigation Feasibility it was concluded that optimal firm Hydropower generation could te with FRL at 1376 m amsl and Hydrology  was  not a constraint However the constraints  due to geology  geotechnical aspects  environmental and social aspects  were required to be examined In that optimal scenario it was  founa tnat from simulations  the optimal power would be 20MW in the domain 3 case with MDDL at 1350 and FRL at 1376 which with a plant factor of 0 6 will lead to an installed capacity of 33 3 MW
The Tail Water Mean level in all the above cases was 1322 m amsl
x Next during the Pre-Feasibility Study for the combined Irrigation cum Hydropower Dam the simulations were up dated with Ms Excel Simulation Modeling with the 45 years monthly time series of inflows For this the decision support releases were set up for each month for Hydropower generation after satisfying the Irrigation needs on priority The Minimum operating pool for Hydropower was kept at 1350 m amsl The Irrigation out let was also kept at that level The tail water mean level was nowever brougnt down to 1317 m amsl from 1322 m amsi adopted dunng the Irrigation Feasibility study Here also the simulations indicated that the FRL at 1376 m amsl would be optimal The Firm power increased to 22 MW from 20 MW identified during tne end of Irrigation Feasibility study This is with minimum operating pool condition of 1350 m amsl and with tail water at 1317 m amsl
r During tne present Feasibility study for the Irrigation cum Hydropower project the simulations were rerun with different options ano assumptions First the simulations were earned out with minimum operating pool at 1350 m amsl with tail water at 1317 m amsl The firm power at 1376 FRL condition increased to 23 75 MW This was due to tne
? dat’ng t*v= • og'ca* !,p’'e
T he power imerit n it
simulated for this condition and tne results are as per Table 1 below
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Firm power at different FRLs (Minimum operating pool at 1350 m)
June 2009
I FRL (mamsl) 1356 1358 1360 1362 1364 1366 1368
Possible Firm
Power (MW)
Possible Installed Capacity by adopting
0 60 as Plant Factor (MW)
5 97                             995
I
■775                              12 90
10 75                           17 90
1325                            22 08
14 69                           24 48
16 47                           27 45
17 94                           29 90
1370
19 75
32 08
1372
20 95
34 91
1374
22 05
36 70
1376             23.75
40 00
Then finally during tne eno of this feasibility study the design considerations warranted the simulations to be redone for a minimum operating pool condition of 1353 m amsl instead of 1350 m amsl This simulation was performed for FRL 1376 m amsl with first priority for irrigation as in all runs This indicated a marginal increase in Firm power to 23 75 to 23 90 MW
Again after completing this Feasibility Report another exercise was carried out as 
Design considerations warranted the Minimum operating pool at 1346 40 m amsi The simulations are under completion by the time of completing this Executive Summary 
This does not show changes in the Firm Power at Higher FRLs But in tne lower FRL ranges some marginal increase is noted
Thus the simulations have been earned out with different options/alternatives as warranted by design considerations Now dunng detailed study for a particular FRL confirmed by Geological
A d  Des’dn
n
n rouos  the  f'nal  simulate1   runs  be  u^dena^^^  bv  more  detailed  S'm  H3hon
modeling
From Hydrological side at present the optimum FRL with 23 90 MW Firm power is identified
In all the simulation runs there is no indication of a major reduction in tne suo basin flow of Dedessa The present sub oasm flows going to Abbay is about 14 053Mm and this will oet reduced to 13 838Mm As sucn this reduction of 1 39% is a meager one because of the proposed Arjo Dedessa dam
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Floods: The approach was  to estimate the various  return period flood peaks  by  flood frequency analysis and to estimate such flood peak level corresponding to Probable Maximum flood level by  Hersnfiela technique coupled with synthetic  unit hydrograph developed by Snyder s method In the flood frequency analysis the Generalized Extreme Value distribution (GEV) as well as Log Logistic distribution were explored The results of the later were selected because of closer suitability to Dedessa suo-basin The flood peaks corresponding to salient return periods are as notified below
Return period (years) 2
5 10 20 50
100 1000
10 000
Flood peak (m3/sec) 394
500 575 654 771 871 1303 1948
The Probable Maximum flood had a peak of 3000m /sec For various peaks the respective
3
flood hydrographs  were developed based on the US Soil Conservation Services  (SCS) dimensionless hydrograpn development technique witn cue considerations of the shapes of observed nydrographs
Design Flood: During the irrigation Feasibility, for the design of the dam spillway the 10.000- year return period hydrograph was recommended, instead of the Probable Maximum flood hydrograpn This is because of aiming at economy in a situation, where the dam over topping and consequent failure will be confined to the irrigation command and the dam itself without loss of human lives at a large scale The smaller return period floods like 50 and 100 years return periods have been recommended for design of coffer dam. and cross drainage works in the command area The appropriate one needs to be adopted for design of eacn component on its merit
But however, in case the dam is to be raised up to 1376 m amsl, in addition to larger storage and height at the downstream the powerhouse will also be located. In that scenario adopting PMF will be appropriate
Flood routing: During the Irrigation feasibility the 10 000- year return period hydrograph when routed through the reservoir becomes attenuated Such attenuations for a couple of spillway 
lengths v/?re explored in the reservoir ^outing exercise ""he out^o/ pea^
g ''
peak of 1950m'/sec gets attenuated to 1165m7sec for a spillway length of 125m Sufficient fixation of MWL and free board nas been taken care of in the designs
But in the case of present position of a larger dam tne PMF was routed at FRL 1376 m amsl with a spillway of 125 meters. The outflow is about 1100 m 3/sec with a surcharge of 2 50
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meters above FRl of 1376 m amsl However this might have to be reoone depending upon the firmed up parameters of the dam by Geology and Design groups
Sedimentation: Suspended sediment concentrations had wide variations between 45mg/ht to 1670 mg/lit in the sediment observation in tne Dedessa sub basin.
Relationships connecting discharge (flows) and sediment load were developed in the region for tne stations in Guder Little Angar, Dabana and Abbay Rivers At site and regional approaches were developed to estimate the sediment load at the dam site using the flow data established Witn sediment density of 1.2gm/cc and with the assumption of bed ioad at 15% of the suspended load, the annual mean total sediment load at the dam site works out to be 0 775
Mm /year
The exercise by  “Area Incremental Method" of USBR was  carried out for distributing the sediment in tne reservoir storage The results indicated that, the volume of the reservoir gets reduced by 38 78Mm and 77 56Mm after 50 and 100 years of operation respectively The
3
3
3
new zero elevation is far below the proposed MDDL of 1350m provioeo at higher level due to
command area constraints At this levei tne dead storage provided is 874 67 Mm  which
3
is 
much more than the sediment accumulation of 77 56Mm  obtained after 100 years of operation
3
of the dam As such sediment interference with the operation of the dam is ruled out
Water  Quality:  The  quality of  Dedessa waters seems to have no adverse impact on the irrigation and crops proposed
Training Needs: The phase of development of various river basins is very encouraging At tnis planning stage there may not be encounters due to nydroiogical aspects When the basins become fully developed with various types of projects and with different objectives with trade off among them tne real time operation of tnese components of the basin system become very relevant. A judicial operation of a multi system will even off set expenditures on further projects Sucn appropriate judicial operations on real time during flood or drought syndromes have immense benefits for combating floods or tide over of droughts The various oasin authorities will have to possess a team of nydrologists involved in the real time operations of future multi systems in an integrated fashion The real time operations will have to be aided by modern soft ware decision support system, flood forecasting network ana telemetry for data collection ana transmission The personnel (hydrologists) to be involved in such future real time operations are to be identified and provided training in these aspects in advance perhaps in U S on India Conclusions: As such. Arjo Dedessa is a promising one with respect to irrigation and power development
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June 2009
The Feasibility Study for Arjo-Dedessa Irrigation Project had already been finalized based on a detailed study of the Meteorological and nydrological aspects The various aspects those were addressed are
♦   The data collection and processing for all relevant parameters of Meteorological and Hydroiogicai aspects
♦   Use of statistical bi-variate linear or non-linear models for consistency checks gap filling and extension of records
♦   Establishing the Water Resources monthly Time series for 44 years as tne Historical Time Series
♦   Generation of syntnetic Time Series on monthly basis using a AR1 type Stochastic Model
♦   Establishing the Time Series of all Agro-climatic parameters like, the Relative Humidity Sunshine Hours, Wind Speed, Monthly maximum, minimum and mean temperatures
♦   Establishing the Eto Time Series for crop water requirement.
♦   Establishing the Monthly Time Series of catchment as well as the command area rainfall ♦   Establishing tne annual one-day maximum rainfall series
♦   Estimation of the various Return Period Rainfall as well as River flows for Flood analysis for cofferdam. Command Area Flood Control and its Drainage
♦   Arriving at the shape of the design Hydrograph
♦   Evolution of the Probable Maximum Rainfall to develop PMF Hydrograph
♦    Running  of  an  Excel  based  simulation  model  for  various  control  levels using  the synthetically generated 1000-year long monthly time series
♦  Analysis of the sediment load on a regional oasis and establishing tne annual sediment load at the dam site then studying tne distribution of the sediment in tne live and dead storages of the reservoir oy USBR recommended “Area increment Method’
♦  Routing of the 100-year flood for deciding tne heignt of the cofferdam similar flood routing of tne 10000-year return period flood for deciding tne Maximum water Levei of the dam and the length of the Spillway
♦   Evolution of the Agricultural Drainage Duty
The Feasibility Study of the dam and appurtenant works had been piannea and designed Dasically for providing irrigation in a gross command area of about 17,825 ha located on both banks of river Dedessa downstream of tne dam Based or detailed Meteorological and Hydroiogicai Studies the values for design decision variables parameters and control levels 
haa Deen finalized as follows at the irrigation Feasibility level
Top level of dam crest
EL 1360 6 m
Full rxeservoir Lcvei
El. 1356 0 m
Maximum Water Level
EL 1358 6 m
MDDL
EL 1350 0 m
FSL of Canal on either side -
EL 1348 0 m
Gross storage
1341 6 Mm’
Live Storage
476 5 Mm'
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1.1 EVOLUTION OF THE CONCEPT FOR POWER GENERATION
June 2009
At the Feasibility level study of the Arjo Dedessa Irrigation Project it was confirmed by Simulation Studies that the contemplated Irrigation would be successful at 80% reliability This was for the given Hydrology and the reservoir geometry firmed jp during the above Feasibility study for Irrigation development. At the concluding stage of the above Feasibility study the concept of generation of Hydropower at the Arjo Dedessa dam triggered of for the following reasons
■   The water resource available at the aam site is 2477 10 Mm3 (as per iatest estimate in the  Pre-feasibility  study)  Whereas  the  maximum  consumptive  utilization  by  the Irrigation development is to a maximum of 200 Mm  only As such, the genuine question
3
arose namely “Why not the excess water over and above the irrigation requirement could be utilized for Hydropower generation at an optimal level9"
■   Raising the Full Reservoir Level (FRL) did not show any negative impact at least based on Topographic considerations in addition to support by nydrology to accommodate a larger  storage  for  Hydropower  generation  in  an  optimal  way,  along  witn  irrigation development
1.2    THE PRE-FEASIBILITY STUDY FOR IRRIGATION CUM HYDROPOWER PROJECT
The simulation runs were continued to explore the hydropower generation with tne reservoir neight as fixed for Irrigation Feasibility This indicated tnat after satisfying the irrigation the Hydropower generation with FRL at 1356 meters was a meager 6 MW at 97% exceedance level This discouraging scenario did not yield more than 7 MW and 8 MW even at 65 % and 50% exceedance levels As such it was inferred that there is no other alternative except raising the FRL of the dam to levels  even up to 1380 meters  to explore optimal Hydropower generation Some preliminary simulation runs were made to arrive at this conclusion during this stage
As such, to examine the combined feasibility of irrigation cum Hydropower generation the Pre- feasibility study for Meteorological and Hydrological aspects was unoenaken The inflow time series at the dam site was updated after a very careful review and consistency checks the other parameters connected with Meteoroiogical components have been reviewed and a set of screening levei simulations coupled with a firmed up simulation has been run using a tailor made Fortran source coded model, "Arjosim" and Ms Excel based firm up model
Tne preliminary simulation based on hydrological, topographical irrigation development downstream mandatory releases and reservoir losses constraints indicated that the FRl of the reservoir could be raised up to 1376 meters as an optimal alternative to generate a continuous n dropo .ve of about 23 "*5 MW .vh oh c'coarse with approp’ofa- — -- b ■ ■ --
r
installed capacity of 35 to 40 MW for firm power consideration The Irrigation interests were aiso safe guarded 100% in the firmed up final simulation runs
1.3    PRESENT FEASIBILITY STUDY
The Present feasibility study is for establishing the Irrigation cum Hydropower Feasibility on the Meteorological and Hydrological domains. The study warranted the analysis particularly on
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simulation runs for the power potential assessment, recasting tne inflow time series at the dam site and redoing the flood routing for the present optimal FRL of 1376 meters which are the main new activities  For tne increased height of the dam the earlier adopted 10000-year Return Period criteria needs to be changed to PMF criteria in view of higher height and storage and the location of the powerhouse in the just downstream The revised analysis on these was also to be undertaken.
The other aspects on the Meteorological aspects Agro-climatic aspects Return Period Floods Flood Frequency analysis and sedimentation studies did not call for mucn changes from the irrigation Feasibility Study except a limited data jp dating
On the review of Previous studies maae on the AbDay basin and particularly on the Dedessa Sub basin, a very exhaustive presentation had Deen made in the Irrigation Feasibility Study However since it stands approved already and above all, as it does not require any up dating this particular section is not presented in this Report.
For tnose aspects which have been already approved in the Irrigation feasibility level and which stand without any changes for the present Feasibility for irrigation cum Hydropower only a orief description ana presentation are made in this report. However for the aspects which have changed because of converting the Irrigation Feasibility to irrigation cum Hydropower Feasibility have Deen dealt with in detail
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2.0 THE RIVER BASIN AND SUB BASIN
2.1THE NILE BASIN
June 2009
Having a length of 6 825 km the Nile River takes the rank of number one with respect to
length, in the world. It drains a total drainage area of 2 96 M Km witn its annual total flow of
2
about 84 Bm   As one could appreciate,
J
the discharge per Km2  is small when compared to
other large rivers of the world From the Lake Victoria to the Mediterranean Sea. the river crosses very many different areas associated with different climate, relief and geology The main sources of the river are the equatorial lake plateau and the Ethiopian Highlands The three major tributaries, which emanate from the Ethiopian Highlands are from south to the nortn tne Baro Akobo the Blue Nile, familiarly known as Abbay and the Tekeze -Atbara System
The Abbay Basin is perhaps, the most important basin in Ethiopia. It accounts for about 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 km2 The Aobay nas an average annual run off of about 50 B m! The rivers of Aobay contribute on an average 62% of Nile river flows in Aswan dam
Two features dominate tne climate of the Abbay Basin, namely it's near equatorial location and in altitude range between 590 m amsl and 4000 m amsl These influence result in rich variety of local climates, ranging from hot/desen like along the Sudan border to the temperate type on the high plateau with depiction of cold in the nigh mountains The Basin can generally be described as temperate at higher elevation and tropical at iower elevations There are mainly 3 rainy seasons The main one (kiremt) lasts generally from June to September during which the southwest winds bring rains from the Atlantic Ocean About 70% to even up to 90% of the rainfall occurs during this season This season obviously is associated with minimum levels of sunshine low variations in daily temperature and high relative humidity A dry season (Bega; lasts from October to January during which clear skies are associated with maximum sunsh:ne hours hign daily temperature variation and low relative humidity Finally the minor rainy season (Belg; lasts from February to May. during which southeast winos bring the small rains from the Indian Ocean. The temperature range is very high in this season. The precise timing ano duration of tnese seasons vary considerably depending upon location within Aobay Basin and to some lesser extent year to year as well
Generally speaking the iow altitude depicts the pattern of 11 5 to even 12 5 hours of sunsnine and the temperature varying only for a small range from 3°C to 7°C through out the year
The mean annual rainfall over tne entire oasir. could be reckoned at 1400 millimeters where as the mean evapotranspiration is about 1300 millimeter With respect to the hydrographic scenario the Basin is dominated by Abbay River, which rises in the center of the catchment and develoDS its course in a clock wise SDinal It collects tributaries all alona its 992
journey up to Sudan ooraer
2.2    THE DEDESSA CATCHMENT
The Dedessa River is the largest tributary of the Aobay in terms of tne volume of water contribution to the total flow of Aobay at the Sudan border Draining nearly an area of 34 000 square kilometers, tne Dedessa River originates in the Mt.Venmo and Mt Wache ranges flowing in an easterly direction for about 75 Kilo meters then turning rather sharply to the nonh
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until it reaches the Abbay River. The major tributaries of the Dedessa River are the Wama entering from tne east, the Dabana from the west, and the Angar from the east
Deoessa Catchment is situated in the southwest part of Abbay Basin The catchment area at a gauging station near Arjo town is 9 981 km The catchment area at the proposed dam site is 
2
5632 64 km 2 The climate of the Dedessa Catchment results from its location and elevation (1220 to 3012 meters) The catchment is characterized by mountainous highly rugged and dissected topograpny with deep slopes The lowest part of the catchment is characterized by valley floor with flat to gentle slopes
Most of the rainfall in the Dedessa Catchment is concentrated in the June to September period with virtual drought from November through Feoruary Annual totals average from less than 150 centimeters to more than 200 centimeters The Dedessa catchment, besides reflecting a markeo rainfall increase with higher elevation, also receives heavier annual quantities than most of the catchments in the Abbay basin Examination of the rainfall records from this area shows that this is due to a longer (May through October) rainy season rather than heavier maximum monthly quantities
Tne mean annual flow of Dedessa River at Arjo station is about 3.800 million m  having its maximum flow in August and September (52 percent of the annual) and minimum flow in February and March (less than 1 5 percent of the annual)
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3.0 DATA BASE
June 2009
For the study towards the development of the Dedessa sub basin, the data on climate river flows and sedimentation become relevant with respect to Hydrological Modeling ano Water Resources  Planning The database stands  established up to 2004 from 1960 thus forming Time Series of 44 years length at required time resolution levels Statistically this much sample length is adequate However, for up dating the data, necessary up to date data are under collection for effective utilization in tne detailed design phase
3.1     CLIMATOLOGICAL DATA
The climatological data like sunshine duration relative humidity wino speeds temperature in the resolution levels of monthly means of daily means monthly mean of daily maximum and monthly  mean of daily  minimum, become very  important parameters  with respect to tne proposed command area development. These, in association with command area rainfall form the basic inputs for the estimation of the crop water requirement exercise. A vivid analysis had been carried out for the irrigation feasibility
3.2     RAINFALL
The rainfall requires critical analysis for the dam site and tne upstream for appreciating and developing floods eitner as a full hydrograph or in tne form of flood peak rate expected at different Exceedance probability levels (return periods) The rainfall data needs to be analyzed in its various forms like maximum of observed 1 day/2 day or 3 to 15 days values or as a time series of oDserved annual maximum 1 day rainfall or as monthly I fortnightly totals as per analysis at different stages The analysis has to under take the gambit of short duration rainfall intensities as well, in connection with design of drainages, and return period rainfall peaks for tne design of flood control works in the downstream of the dam in and in 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 ieveis  forms  the fore runner for establishing water resources  availability  for performing simulation whether as basic historical time series or indirectly through synthetically generated time series (mostly generated by a stochastic generation scheme) wnere as the same flow data has to be analyzed in a different form as discharge (flow rates instead of flow volumes) with respect to flood analysis
3.4     SEDIMENT DATA
The sediment data is obviously required to plan the size of the storages for apportioning the active and inactive storage spaces and for determining the revised geometry of the storage
certain des gn life 'revised e'e.at’O  — a^ea - capacity r.-ato-' ,p as ‘ . e.
relation is used in the simulation modeling The water quality is another aspect, wnich needs to be addressed in Hydrological study along witn low flow analysis for mandatory downstream releases closely associated with the concerns of environmental and ecological aspects
With such appreciation of the framework of hydrological studies and modeling the database was established during the irrigation feasibility study
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4 ESTIMATION OF CROP REFERENCE EVAPOTRANSPIRATION 4.1    CAUSATIVE CLIMATE
June 2009
The climate of the Arjo Dedessa catchment results from its location and elevation (1300 to 3012 meters) The list of stations for observations of meteorological data along with length of records ano availability of data types is given in Table 4 1
Climatic data for the project area such as temperature, relative numidity sunshine hours wind speed and rainfall have been collected ano reviewed Consistency tests, data rectification and other adjustments  have been performed as  necessary: data gaps  have been filled using interpolation and correlations methods as appropriate
The FAO Penman-Monteith method is  maintained as  the soie standard method for the computation of crop reference evapotranspiration (ET ) from meteorological data The monthly 
0
ET0 is determined from temperature humidity, wind-speed and sunsnme hours data collected at Bahir Dar station The ET0 calculation has  been carried out by  means  of a computer modeling
The FAO Penman-Monteith equation determines the evapotranspiration from the hypothetical grass reference surface and provides a standard to which evapotranspiration for various crops growing in the Arjo-Dedessa project command area can be related The methods  for calculating evapotranspiration from meteorological data require various  climatological and physical parameters Some of the data are measured directly in Bahir Dar meteorological station Other parameters are reiatea to commonly measured aata and can be derived with the help of a direct or empirical relationship
The meteorological factors determining evapotranspiration are weather parameters which provide energy for vaporization and remove water vapor from the evaporating surface The principal weatner parameters to consider are presented below The data obtained from the Bedele Dedessa and Jimma stations were assumed directly applicable to the Irrigation development with application of appropriate information transfer mechanisms
4.2    METEOROLOGICAL DATA
4.2.1 Meteorological Observation Stations
Five meteorological observation stations are located in and around the Arjo-Deaessa Irrigation Project area These meteorological data are obtained from the National Meteorological Services Agency (NMSA) Out of these Jimma is Class 1 station that include observations of rainfall temperature relative humidity sunshine duration wind speed and evaporation Beoele and Deaessa are also Class 1 stations but do not include sunshine duration In addition Agaro and Dembi are Class 3 stations that include observations of rainfall ana temperature The longest
f
f
r^Toro hat covers 50 yea s os n^e*eor?ioc 23! data is availab’e at j
n-
rainfall and temperature data since 1952
The details like location, altitude year of establishment along with their class are available in TaDle 4 1 The types of meteorological aata available at these stations along with the length of data are given in Table 4 2
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Climatological data obtained from Bedele. Dedessa and Jimma stations were found to be the most reliable and relevant for use in the analysis of rainfall for the irrigation command Bedele is geographically the closest station to the command area Dedessa station and the command area are located at the same elevation (i.e both 1330 m a s I). Jimma station (whicn is Class I) has tne longest record of all the stations within the neighborhood of tne command area so as to be index station in extrapolating and interpolating missing and short-term climatic data relevant to the Arjo Dedessa catchment and commano area
4.2.2 Air Temperature
in the project farm area, the mean monthly temperature variations throughout the year are minor oemg 20 0°C in December to 25 4°C in March The mean monthly temperatures of the command area is given in Table 4.3 and graphically illustrated by Figure 4 1
4.2.3 Air Humidity
Mean humidity values vary between 56.63 percent in March to 88 63 percent in September The mean monthly humidity of the command area is given in Table 4 3 and graphically illustrated Dy Figure 4 2 Data of humidity have been used in estimating evapotranspiration rates from reference crops
4.2.4 Wind Speed
Mean wind speed values vary in the range of 0 48 meter per second in November and 0 8 meter per second in April The mean monthly wino speeds of the commano area are given in Table 4 3 and graphically illustrated by Figure 4 3
4.2.5 Solar Radiation
Mean sunshine duration is 8 3 hours in December and is reauced to 3 7 hours during July The mean monthly sunshine durations of the command area are given in Table 4 3 and graphically illustrated by Figure 4 4 Data of sunshine hours have been used in estimating evapotranspiration rates from reference crops
4.3    PENMAN-MONTEITH EQUATION
From the original Penman-Monteith equation and tne equations of the aerodynamic and canopy resistance the FAO has established the Penman-Monteith equation Using this the Eto was estabiisnea as a Time series
Table 4.1: Tabie Details of Meteorological Observation Stations located in ano around the
project area
I S.No
Station
Name
Latitude
North
Longitude
East
Altitude
Period
Deg. Min
Deg.
(m)
1
Agaro
07       51
36
36        1700
1980-2004 11
2
Bedelie
08       27
36
20        2005
1967-2004
|3
Dedessa
09       33
36
06        1300
1971-2004
4
Dembi
08       04
36
37        1950
1954-2004
5
Jimma
07       40
36
50        1725
1952-2004
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Table 4.2: Types of
Climatic D
ata available at th
e vari
ous 
Meteorological Observation
Stations
No |   Station name
Yrs
RF       Tm
RH
WS
SD 1 hr 1 day Rday
Class
1      Deaessa
30
XX
X
X
1
2      Bedele
28
XX
X
X
1
3          Dembi
20
XX
3
4      Agaro
21
XX
3
5      Jimma
50
XX
X
X
X       X       X       X|
1
I
Yrs     refer to rainfall series RF      monthly rainfall
Tm      average temperature RH      relative humidity yvs    wind speed
SD      sunshine duration
1 hr    maximum 1-hour rainfall 1 day  maximum 1-day rainfall Rday  number of ram aays
Table 4.3: Summaries of Meteorological Characteristics at Project Area
Jan Feb March April May June July Aug Sept Oct Nov Dec
Montnly Mean Temperature in oC
Average
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
0 048 0 044  0.036  0 065  0 071
0 029
0 028  0 031  0 027  0 038 0 0544 0 066
i Skew
0 071  -0 58  0 067 -3 628 -3 23
0 117
0 275  0 007   0 93   0 353 -0 118  -0 02
Mm
195   20 44  23 63  16 26 15 89
20 96
19 99  19 88  21 06  20 19 19 081 16 92
Max
24 6    24 9   27.37  27 72  26 19
23 41
22 72  22 34   23 2   24 25 25 051 22 88
Relative 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 65 23
65 8
61 77  72 23  82 49 74 24 67 667 55 37
Max
77 3   71 68 64 08  82 17 86 18
90 3
98 1   97 53  95 67 94 73 93 187 85 13
Wind Speed (m/s)
Average
0 62     08      1 0     1 08   1 04
0 86
0 62    0 51     0 5     0 51    0 48   0 51
Sunshine Hours (hrs/aay)
Average
8 155 7 638 7 452  7 287 7 624
6 061
3 703 4 059  6 164  7 855 8 3245 8 306
CV
0 125 0 166 0.145  0 165 0 157
C 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
iv .iH             C 35  T 
2 2u4 5 -»23           2 277    1 5    2 222  5 775 3 1121 3 w *
Max      10    9 919 9 744  9 44   10 15  8 12   5 445   6 2     9 12   10 08 10 201 11 02
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Table 4.4: Summary of Estimatea Mean ETo of Arjo Dedessa
Project
Area
Jan    Feb     March April   May    June   July
Aug
Sept
Oct
Nov
Dec
Daily Estimated ETo (mm/day)
Average     3.7     4 11     4 62    4 51     4 33     3 58     2.96
3 11
3 81
4 03
3 79
3 44
CV       0 05    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
-3 11
0 88 I
Min       3 23    3 38     3 99     3 44     3 35    2 97    2 58
2 44
2 88
35
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 '
Monthly Estimated ETo
(mm/monthj
Average    115     115      143      135     134      107     91 8
96 5
114
125
114
107 |
CV       0 05    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
-3 11
0 88
Min       100     94 8     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 (mm/day)
(form average values 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
Estimated Eto (mm/month)
(form average values of data)
I
Average     114     114      142      134     133      107      92
96
113
124
114
107 “I
1
Note: Total annual ETo = 1397 mm
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Fig 4.1
June 2009 Fig 4.2
Distribution of Monthly Mean Temperature over Command Area
JO GO r------------------ - ---------------------- --------------------------
Fig 4.3
Fig 4.4
Variation of Monthly Mean Wind speed
Over Command Area
Fig 4.5
Monthly ETo Variation over the
command area
—♦— Series 1
M onth
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5.0 RAINFALL ANALYSIS
5.1  THE ANALYSIS
During the Feasibility Study for the
irrigation Project very elaborate
Rainfall analysis had been
cameo out and got approved Now with data up dating there is no variation in the earlier study results However a brief presentation of the salient results is presented in this section
The rainfall data ootained from Bedele, Dedessa and Jimma stations were founa to be tne most reliable and relevant for use in the analysis of rainfall for the Arjo Dedessa irrigation project
Bedele is geographically the closest station to tne command area Dedessa station and the command area are located at the same elevation (i e both 1330 m asl) Jimma station (which is Class I) nas the longest record of all the stations within the neighborhood of tne command area
so as to be index station in extrapolating and interpolating missing and shortage of rainfall data relevant to the Arjo Dedessa catchment and command area
The rainfall in the Arjo Dedessa Catchment as well as in it's surrounding is uni-modai type
Most of the rainfall is concentrated in the May to September covering with virtual drought from November througn Marcn The five wettest months cover 63 percent of the total annual rainfall The dry season being from November to February (four months) has a total rainfall of about
7% of the mean annual rainfall
The mean monthly rainfall for stations in the project area is given in Table 5 1 and their pattern is  graphically  illustrated in Figure 5 1 The length of rainfall data collected from Jimma is relatively more reliable compared to tne data set collected from other stations because of its long record length and shorter time interval of ODservation Dedessa and Bedele stations also provide more relevant rainfall data that can be adopted for the command area since Bedele is close to the project area and Dedessa station is located within the same climatic zone as tnat of the project area
The annual rainfall at salient dependability levels is as below which is based on Regiona' Analysis
Mean Year
1453 millimeters
75% year
1148 millimeters
80% year
1090 millimeters
90% year
853 millimeters
The monthly rainfall for various exceedance probability levels are shown in the Table 5 2
5.2    RAINFALL INTERNAL AND EXTERNAL CONSISTENCY
Though a good database had been established for rainfall considering the data of the tnree stations namely Dedessa Jimma and Bedeie it is customary in Hydro-meteorological studies 
ini.      the corioiStency witn
analysis.
The trend in the annual rainfall pattern is a relevant aspect with respect to the behavior of the rainfall and to compare such behavior with those of otner relevant stations involved in the study with a view to firm up external consistency Accordingly a 3-year moving average analysis was taken up for each of the 3 stations
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Similarly, an analysis with respect to the cross correlation structure among the 3 stations was carried out. Then, the single mass curve analysis was taken jp for each of these 3 stations 
These did not indicate any abnormality to reject this data set As such, these rainfall data were
used in its different forms for various spectrums of the analysis
5.3     ESTIMATION OF RAINFALL RELIABILITY LEVEL
Using the rainfall for irrigation water requirement for the commana area requires the estimates 
of the magnitude and reliability level of rainfall corresponding to various rainfall time intervals 
Annual, monthly and half monthly intervals were chosen durations for analysis
Rainfall reliability  level and magnitude can be analyzed by  making use of theoretical distributions  In this  study  the Extreme Value Type III (minimum) distribution was  utilized The distribution is  also known as  the Weibull distribution or as  Gumbel’s  Limited distribution of the Smallest Value Since detailed discussions  were presented in the earlier Feasibility  Study  the results obtained only are presented in the Table 5.2
5.4     ESTIMATION OF MAXIMUM RAINFALL FREQUENCIES
For internal drains and smaller control works the needs for various return period rainfalls and with different durations were found to be necessary In general maximum rainfall magnitudes of intensity corresponding to various return periods (or probaoility levels) can be estimated by applying the following form
It = lm[1+CVK(T)J 
(5 1)
Where
It = rainfall intensity corresponding to return period of T years (mm), Im = mean of annual maximum intensity of rainfall (mm/hr)
CV = coefficient of variation of annual intensity of rainfall, K(Tj = frequency factor
For Extreme Value Type I ^or Gumbel s) Distribution,
K(T) = -0 779 {0 577 * In ln[T/{(T -1}]}
The maximum annual 24-hour rainfall series is given in the Table 5 3 Table 5.1: Mean Monthly Rainfall
(5 2)
Description     Jan   Feb   March April May   June   July   Aug    Sep   Oct     Nov  Dec   Total
Dedessa
3
6
26      49    158
274
312
277
209
104
28
8
1454
Dcucic
13
23
c5     « U3  239
z.3 i
510
3u3
wz
i
iz
1_ .
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
182
103
68
36
1502
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Table 5.2 Monthly Rainfalls Corresponding to Different Reliability Levels at Project Area Reliability
Level Jan Feb Mar April May      June July    Aug   Sept Oct Nov Dec         Annual
(%)
55    10 8 12 2 40 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 I 65       6 92 7 4 30 8 45 3   124    184    204    200    194   71 76 14 2 4 74     1253 | 70          5 5 03 25 8 38 6  111    169    197    190    184  61 82 12 2 3 43     1202 75        3 042 63 20 7 3.5  97 9   154    190    178    174   51 68 1042 16       1148 80       0 990 1615 5 238   84 2   138    183    166    164  41 138 830 92       1090 35      0      0 9 97 15 2      69 4   120    177    152    152  29 86 7 36 0          1025 90      0     0 3 87 4 84      52 9   99 7    170    135    138   17 29 6 02 0          951 95      0 0 0 0                     32.7    737   163    113    119   1 974 4 82 0          853
Avg 15 3 18 4 53.6 69.5 180.8 243.0 245.9 238.3 228.6 115.5 31.4 12.7 1453 Table 5 3 Maximum Annual 24-hr Rainfall
Year
(mm/d)
Year
(mm/d)
Year
(mm/d)
1967
47.1
1980
45 6
1993
50 1
1968
47 0
1981
1994
57 8
1969
64 0
1983
50 0
1995
61 0 I
1970
57.C
1984
51 7
1996
60 1 I
1971
70 0
1985
62 2
1997
104 5
1972
45 2
1986
64 6
1998
635
1973
35 9
1987
58 4
1999
630
1974
51 8
1988
53 2
2000
47 9
1975
36 4
1989
46 8
2001
69 0
1976
47 1
1990
49 5
2002
57 0 |
1978
1991
87 8
2003
1979
45 0
1992
51 6
2004
39 1
Average   54.14 CV       0.306
Skew     2E-04
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Table 5.4 Maximum Rainfall Magnitudes and Frequencies
June 2009
Return Peiod (T)
Frequency
Factor (K)
Rainfall Magnitude (mm)
24-hr
1-hr
2
-0 16
51
27
5
0.72
66
35
I
10
1 30
76
40
15
1.64
82
43
20
1 86
85
44
25
2 04
88
46
30
2.20
91
48
40
2.40
94
49
50
__________
Fig 5.1
Temporal Variation of Rainfall over the Project
Area
300 00
“          250 00
* 2 200 00
.= 0
2.61
98
51
a | 150 00
Z | 100 00
o 50 00
0 00
□ Series i
Month
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6.0 MONTHLY STREAMFLOW ANALYSIS
6.1 HYDROLOGICAL OBSERVATION STATIONS
June 2009
Hydrometric stations on the Dedessa River and the neighboring rivers within the Abbay oasin and the Omo-Ghioe basin had also been identified The hydrological data were obtained from the Hydrology Department of the Ministry of Water Resources (MoWR)
There are two hydrological observation stations located on tne Dedessa River These are Dedessa near Arjo town (Station No. 114001) and Dedessa near Dembi town (Station No
114014) Station 114001 with catchment area of 9981 Km2 is located aoout 44 km downstream
of the proposed dam site and has become operational since 1960 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 The catchment at the proposed dam site is 5632 64
Km2
Besides the two nydrological observation stations located on the main Dedessa River several hydrological observation stations  are located on its  tributaries  In addition, hydrological observation stations  on the neighboring Daoana near Aoasina (Station No 114005) (Gilgel Ghibe near Assendabo (Station No 091008), and Gojeb near Shebe (Station No 091012) have been found to be relevant to the study
The list of nydroiogical observation stations for which data have been collected along with otner details like their location and catcnment area is available in Table 6 1
6.2    EXTENSION OF RECORDS
Stream flow gauging stations have been installed on the Deaessa River near Arjo town (Station 14001) since 1960 and near Dembi town (Station 14014; since 1985 Before the stream flow analysis data obtained from Station 114001 (Dedessa near Arjo) and Station 114014 (Dedessa near   Dembi)   was   checked   for   temporal   and   spatial   homogeneity   The   investigation   of nomogeneity was concentrated mainly on the outliers of the monthly data series of the record Extremely high or low values of each series that nas occurred at time T (i) in eacn month M (i) was cneckeo against the records of the month M (i-1) and M (i-H) that has occurred at tne same year T (i) so as to judge whether the relation is still more or less the same as that of the other years Whenever the outliers were rejected by this test, again another test was performed with otner data senes of Station 114005 (Dabana near Abasina) Station 91008 (Gilgel Ghibe near Assendabo) and Station 91012 (Gojeb near Sheoe) for the same period T (i)
The data were checked for its  consistency  before it was  used for different analysis  The investigation concentrated mainly on the outliers of tne monthly and daily data senes Extremely hign or low values that occurred at a given time were cneckeo against records of other near by rivers isuch as Daoana) If the outliers were found to be inconsistent with others then they were lepiacea Dy new values tnai were generaiea oy regionally from Oata set ociaineu . ,.n otner stations
6.3    SYNTHETIC FLOWS
It was realized that the specific sequence of historic events was a random occurrence that would certainly never occur again in the same way To get some idea about other possible
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sequence  within  the  population,  in  order  to  improve  reservoir  design,  generating  a  long  stream flow series is a highly accepted procedure by hydrologists
The  stream  flow  record  length  at  the  gauging  station  near  by  the  dam  site  is  only  for  a  few years  It  would  be  possible  to  get  better  information  from  the  synthetic  flows  Synthetic  series can  fulfill  its  purpose  if  there  are  long  records  at  a  gauged  location  on  a  stream  When  the stream flow records are short, as that of the situation at the project area, synthetic flows that are based  on  statistics  of  a  single  site  cannot  give  satisfactory  result  These  short  samples  contain large   sampling   errors:   and   these   errors   are   also   preserved   in   the   long   synthetic   series Basically  synthetic  flows  do  not  improve  poor  records,  but  they  can  improve  the  quality  of  the reservoir designs by producing sequences of high or low flows (or large range) that do not exist in the original record
In such a situation where available records are short, rationalization approach would provide a
better result Statistics derived from other catchments in the region can significantly improve the required estimates
In order to suggest some procedures  in the application of rationalization approach to synthetic flows and obtain the necessary regional statistics required it was necessary to choose the form of the model intended to be used Accordingly  the best known the Thomas-Feirring monthly model was chosen This is an AR1 type model A Time Series of 1000-year monthly flows were generated
6.4  THE RESULTS
Mean monthly  discharges  coefficient of variation of monthly  flows  summary  of regional monthly flow characteristics statistics of monthly flows at Arjo Dedessa Dam Site are shown by Tables  6 2. 63 64 65 respectively  The monthly  stream flows  at different reliability  levels  are available at Table 6 6 The monthly Time senes of Flows at Dam site are provided in the TaDie 67
The Flows at the dam site at annual level are as below
Mean Annual Flows
•    Annual Flows at 75% Exceedance uevel
• Annual Flows at 80% Exceeoance Level
■ Annual Flows at 90% Exceedance Level
2477 10 Mm 3
1750  00  Mm3
1635 00 Mm 3
1390 00 Mm 3
Table 6 1 Availability of Stream flow Data in the Region
I SI No
St.
No
5 14001
Station name and Location Lat
Nonh
Long
East
Area
2
(Km )
Flow
3
(Mm /yr)
—’ — — - — —   —          ' J ~
— 
o 41
-T 1
*7 — o
- J *—■             - - -J *       - -•--
Runoff 1
(mm)
o *7 *■*
J
2      114014        Upper Dedessa near Dembi    8 02       36 28      1806        1221          676
3 114005 Dabana near Abasina
Gilgel Gibhe near
9 02       36 03      2281        1870          820
4
091008
Asendabo
7 45
37 11
2966
1211
408
5
091012
Gojeb near Snebe
7 25
36 23
3494
1803
516
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Table 6 2 Mean Monthly Flow (in Mm /sec)
St. No    Jan  Feb  March April May   June
July
Aug
Sep
Oct
Nov
Dec
Annual
114001  41 9  26 7    26     33 5 63 6      216
646
1050
902
526
148
80 7
3761
114014  12 2    95    11 5  16 9 36 4     1124
228 9
306 9
262 8
154 3
48 4
20 5
1221
114005  35 4  198     16 3  17 0 35 1     107 0
258 8
433 0
473 4
3139
103 3
56 6
1870
091008   14 7  135     12.2  15 9 33 9     100 3
216 5
319.2
277 8
137
60 2
24 5|
1211
901012  31 3 22 1     22.1  31 3 86 4     169 2
323 7
415 6
400 9
202.3
82 8
46 5|
1803
Table 6 3 Coefficient of Variation of Monthly Discharges
St. No    Jan Feb    March April    May    June  July    Aug     Sep     Oct     Nov    Dec 114001  0 51 0 57    0 66    0 68    0 62    0 45    0.35      03      0 33    0 67    0 62    0 59 114014  0 47 0 5      0 48    0 56    0 69    0 53    0 29    0 27    0 30    0 56    0 81     0 53 114005 0 28 0 42    0 33    0 43    0 60    0 47     020     0 16    0 25    0 44    0 30    0 34 091008  0 46 0 58   0 78    0 45    0 43    0 36    0 22     028    0 27    0 61     0 79    0 58 I 901012  0 79 0 36   0 34    0 43    0 63    0 44    0 31     0 26    0 34    0 49    0 54    0 70
Table 6 4 Summary of Regional monthly flow charactenstics
Param Year Jan Feb
cv      194   0 51    0 68 Skew   151    1 80    1 66
Mar  April  May  June  July
0595 0.58 0 61 0 47 0 33
1 503 0 86 1 65 1 05 0 12
Aug Sep I Oct Nov Dec
0 29 0 32 0 58 0 66 0 57
07 0 59 0 94 2 19 2 02
R       194   0 38    0.57   0 527 0 45 0 49 0 66 0 53   0 56   0 51    0 5  0 56   0 51
B      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
Table 6 5 Statistics of monthly flows at Ago Dedessa dam site
3
(in Million m )
Param     Jan Feb   Mar Apr May       Jun     Jul      Aug Sep         Oct (Nov Dec          Annual A verage 26 41 17 53 18 54 23 29 50 82 163 07 436 36 676 24 568 23 328 05 118 18 50 38 2477.10
Stdev 12 81 9 72 11 8216 41 29 69 70 67
Skew 0 626 0 7431 0670 9371 629 0 891
Max 59 09 40 3 46 01 68 61 144 9 366 1
Min 6 806 3 4621 7754 586 9 685 38 71
143 2  189 6  179 2   180 5  89 35 27 17   619.3
0 126  0 037  0 254   0 585   1 866 0 96     0 498
751 5   1043   905 1    661    400 8 120 1    4089
143 8 296 2 195 6 49 32 12 69 4 808 1124
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Table 6 6       ReliaDility Level Vs Monthly Stream flows at Dam Site (in Mm3)
Reliability
^^_Junej009_
Level
JanFeb Mar Apr May Jun Jul [Aug Sep Oct INov IDec Annual
(%)
55 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
60
19 0 11 6 13 0 17 4 34 7 122.3 348 4 542 6 454 6 216 6
69 9 33 2
2019
65
17 9 10 6 12 0 15 6 32 0 113 5 325 3 516 7 429 0 194 7
64 5 31 1
1924
70
16 9    9 6 11 0 13 8 29 5 104 9 301 3 490 8 403 3 173 1
59 6 29 2
1828
75
16 0    8 7 10 1 11.9 27 1
96 4 276 0 464 5 376 9 151 6
55 0 27 4
1750
80
15 0    7 8    9 2 10 1 24 9
87 8 248 5 437.3 349 4 129.7
50 9 25 7
1635
85
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
90
13 3    6 1    7 4    6 0 20 4
69 5 181 2 376 4 286 7
82 5    43 5 22 6
1390*
95
12 5    52     65      35 18 2
59 0 132 1 337 9 246.0
54 4    40 2 21 2
1224
Avg 26 41 17 5318 54 23 29 50 82163 07436 36676 24 568 23328 05118 18 50 38 2477.10
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Tabic (> :        Monthly Flows al Dani Site All flows arc in Million Cubic Meiers
SI. No | Year Sept Oct
1      1961-62          900 0          661
Nov
Jan
34 68
Feb
18 98
Mar
1947
12 28
Apr
5 07
30 86
May
21 39
111 6
June      July
2      1962-63          700 8
3      1963-64          622 8
512 2
223 9
291 8
64 92
1118
307
12 3
24 32
157 2
235 3
397 6
429 5
Aug Annual
560 6 3169 19
826 3 2990 73
17 86
24 21     41 69     167 0
670 0
4      1964-65          705 4        621 4
11 28
34 56
21 07
1965-66          410 3        573 5       194 6
39 61    53 61
47 41
6
5J
J 1966-67          726 3        49 32       25 38
Dec
101 4
31 95
97 23
42 03
90 12
11 62
22 72
7 64
33 05
42 41
6 81
18 95
16 1
40 3
5 36
15 57    14 73
19.24
38 17
122 1
134 3
82 14
117.13
532 7
547 5
452 6
784.4
6336
2792 85
3080 29
654 6 2828 26
764 7 I 2173 77
7      1967-68          719 5        634.8
8      1968 69         399 62       222 2
9      1969-70          565 3        174 2
10     1970-71          673 2        121.1
11     1971-72          568 4        450 3
■ -------- ----------
400 8
77 51
53 81
1102
120 1
34 45
26 41
35 46
12 57
13 26
17 23
.-
304 88
468 52
30 4    29 71
46 01
28 69     55 55
20 38     5 35
22.1     1044 31 3     18 92
9 25
7 45
24 21
9 02
25 78
2865 91
2642 04
2351 67
2439 27
-
184 8
-----------
71 09
60 15
29 98
37 0
27 9
33 52
41 9
47 94
1343
2740 58
12
13
14
15
16
1972-73          430 7        125 4
15 44 |  7 12
3 22
1973-74          839 1
1974-75          195 6
354 5 90 45
83 73 72 32
21 79 10 31
1844 12 23
23 04 15 29
9 89
12 9
16 13
4 59
6 56
16 76
34 36
40 6
42 79
82 96
253 9
209 3
175 5
85 61
181 5
607 0
593 4
525 6
512 9
156 2
409 5
296 64
857.0
635 7
708 6
746 2
633 0
1741 2
770 6 2810 85
455 86 1341 53
1975-76 388 82 216 2
1976-77 486 03 270 25
75 42
94 23
107 87
84 85
20 95
71 15
35 19
43 99
50 34
39 59
190 0
11396
142 45
163 0
128 21
370 8
569 82        191643
26 37 17 5
20 74 13 76
1846
23 97
424 27
651 99      2268 31
17 1977-78 556 11 309 22
18 1978-79 437 42 243 22
14 52
18 85
16 56
333 72
512 84       2103 37
37 71
10 27
7 81
35 18
94 19
19     1979-80         395 11       217 38    | 77 08
33 55
18 15
12 14
6 82
12 84
16 69     35 15  I 11347 25 58     40 74  [38 71
340 6
293 95
497 5 1812 13
454 03 1679 54
20 1980-81 745 0 233 5 62 71
21 1981-82 540 6 3152 19 85
22 1982 83 414 6 455 6 107 4
23 1983 84 668 2 617 6 282 5
52 8
7 14
53 96
47 75
27 57
35 71
19 2
29 73
19 63
180 3
412 8
451 6
633 0 2349 89
571 2 2209 06
25 9     20 13
23 4
8 15
13 95 34 68
16 88 39 8
6 85 t 21 69
111 5   j 361 4
687 0        2317 57
69 26      23 01    1061
134 7
449 2      4012        2692 97
24     1984 85         544 46
299 55 1 —--- ----
I 106 21
46 24
25 02    16 73
17 69
23 0     48 44  I 156 35
405 06    625 64       2314 39
25     1985-86         545 16      299 94     106 35      46 3
25 05  i 16 75
17 72    23 03      48 5     156 56 1405 59    626 45       2317 4
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SI. No            Year I    Sept          Oct          Nov 26     1986-87         656 38      361 13     128 05
Dec
i
Jan      Feb
30 16   20 17
Mar
21.33
Apr
27 72
27     1987-88         623 96      343 29
28 67 , 19 17
20 28
24 94
26 36
28
29
30
31
32
33
1988 89 767 6
1989 90 651 3
1990-91          669 7
422 32
3150
280 5
121 72
149 74
65 15
46 23
120 76
99 78
107 6
107 75
36 44
55 74
52 99
65 19
70 31
23 01
52 57
41 9
36 17
46 91
82 8
35 27 23 58
31 93 19 11
23 19
32 42
44 03
163     12 32
10 51    18 94
1991-92 619 06 340 59
1992-93 338 1 482 9
28 44    19 02
20 12    26 15
25 4     17 72
1993-94          377 8
243 8
303 88
93 56
23 32 1245
25 38 16 97
16 74
10 62
39 56
11 34
June      July
188 5    488 34
179 19 464 21
220 44 571 08
114 4     219 3
113 8     517 4
177 78   460 57
2269     383 1 160.1     341 3
34     1994-95         552 32
35     1995-96         291 05
17 95
23 33
158 61
29 25    18 44
26 36
36     1996 97          358 00       225 1       71 87
49 76      32 26   21 41
22 58
21 96
29 33
May
58 39
55 51
68 29 31 91 44 17 55 07 79 86 45 32 49 14 107 7
271 3
410 92
462 2
37     1997 98         680 44       378 29
38     1998-99         610 23      339 31
39    ■1999-00        750 64      417 38
131 98
118 36
145 6
58 65
52 61
64 71
28 93 19 2
35 59 23 62
20 25
24 91
26 3
32 36
61 59
55.24
67 95
199 43
178 86
220 02
519 13
Aug Annual
754 26 |   2790 17
717 Oj   2652 35
882 06      3262 93
1043 0 > 2628 63 964 2 2717 08 711 37 2631 5
698 7       2450 66 736 3       2106 12 634 68      2347 84
515 2 |    1956 26 797 75      2388 21
465 56
572 69
482 05
715 44
880 06
740 77
630 3
2759 14
29 96    19 88
20 97
27.23
2977 71
2941 57
40     2000 01          631 83       351 32     122 55
54 47    | 50 8      37 86
45 32
41 35
41 2001 02 546 29 300 56 106 57
42 I2002-03 597 57 328 77 11657
43     2003 04           533 1         293 3         104
46 39
50 75
25.1     16 78
17 75
23 07
57 19
97 36
48 6
53 16
47 43
2185 2
50.82
0.02
185 19
291 4
156 88
27 46
18 36
1942
25 24
45 27      24 49
16 38    17 32
22 52
171 61
153 09
7011 9
163.07
0.07
473 1
406 43
444 58
396 61
18764
436 36
0.18
627 75
686 67
612 59
2827 66
2322 17
2540 16
2266 1
iTotal               24434
MEAN            568 23
14106 5081 7
328 05 118.18
2166.3    1135 8  753.94
50.38
0 02
26.41
17.53
797.13 1001.4
18 54 23 29
Ratio to Mean annual
■j
0 23
0.13 1
0 05
0 01
0.01
0.01      0.01 J_____
29078       106515 676 24      2477.1
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7.0 ESTIMATION OF FLOODS FOR UNGAUGED CATCHMENTS
In  the  hydrologic  analysis  for  dams,  weirs,  bridges  and  drainage  structures 
it  must
be
recognized  that  there  are  many  variable  factors  that  affect  floods  Some  of  the
factors 
that
need be recognized and considered on an individual site-by-site basis are
o Rainfall amount and storm distribution,
o Catchment area size, shape and orientation
o Ground cover:
o Type of soil:
o Slopes of terrain and stream (S),
o Antecedent moisture condition,
o Storage potential (over bank, ponds, wetlands, reservoirs, channel, etc.), and
c Land use
In general, three types of estimation of floods magnitudes (namely the Rational Metnod SCS method and Transferring Gauged Data method) can be applied for the project area These techniques  h3d to be used as  per specific  problem with respect to Cofferdam floods. Agricultural command area floods  and drainage aspects  More elaborations  on these approaches have been presented in the Irrigation Feasibility Study.
7.1     RATIONAL METHOD
The Rational Method can be applied to small catchments if they do not exceed 12 8 km2 (or 5 square mile; at the most (Gray. 1971). The consequences of applying the Rational Method to larger catcnments 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 catcnments  This  is  because of its  relative simplicity  The vast majority  of catchments producing floods  imposed on the command drainage system lie within the validity  of the Rational Method ano it has Deen used as the principal method of estimating design discharges of dykes, culverts, drainage channels, etc
7.2    SCS METHOD
A relationship between accumulated rainfall ano accumulated runoff was derived by SCS (Soil Conservation Service) The SCS runoff equation is  therefore a method of estimating direct runoff from 24-hour or 1-day storm rainfall. The equation is
2
Q = (P - la) /(P-la) + S
(7 1)
Where
Q = accumulated direct runoff, mm
P = accumulated ramrail (potential maximum runorf), mm
la  =  initial  abstraction  including  surface  storage,  inception,  ano  infiltration  prior  to runoff, mm
S = potential maximum retention, mm
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Gauged data may  be transferred to an ungauged site of interest provided such data are nearby (i.e. within the same hydrologic region, and there are no major tributaries or diversions between the gage and the site of interest) These procedures  make use of the constants obtained in developing the regression equations  These procedures  are adopted from the work of Admasu (1989) as follows.
Qu = Qg (Au/Ag)070
(7.2)
where
3
Qu = mean annual daily maximum flow at ungauged site (m /s)
Qg = mean annual daily maximum flow at nearby gauged site (m /s)
Au = ungauged site catchment area (km ),
2
Ag = gauged site catchment area (km )
The estimated daily (or the 24-hr) annual maximum flood could be converted into a momentary peak as
3
2
Qp = Cf Qu
(7.3)
Here Cf is factor estimated as Cf = 1 ♦ 0 5/Tc (where, Tc is time of concentration)
7.4   ESTIMATION OF WEIGHTED AVERAGE
In general, the Rational method. SCS method and Transferring Gaugec  Data are recommended for relatively small, medium and large catchments  respectively  However it is very  important to establish a smooth pattern of transition from small to medium and from medium to large catchments
Accordingly, the recommended weighted average estimate of peak flood can be given as
Qw = W, Q, + W  Q  + W .Q
2z           33
(7.4)
Where
Qt  Q , and Q
2                    3  are mean annual momentary peaks estimated by Rational, SCS and
Transferring Gauged Data methods, respectively
W,.W and W3 are weighing factors of mean momentary peak estimates by Rational
2
SCS and Transferring Gauged Data methods respectively
ano
W, = 12 5/(12 5+Au)
W  = (Au/Ag)
3
070
(7 5)
(7 6)
W- = 1 - (W- + W .'
Where Ag and Au are gauged and ungauged site catchment areas respectively
7.5    SYNDER METHOD OF CONSTRUCTING SYNTHETIC HYDROGRAPH The Synder method has been used extensively to provide a means of generating a syntnetic unit hydrograph The elaboration on this important tool for constructing synthetic unit hydrographs has been made in the Irrigation Feasibility already
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8.0 FLOOD FREQUENCY ANALYSIS
8.1 INTRODUCTION
In  flood  frequency  analysis,  the  objective  is  to
estimate
a
flood  ma
gnitude
c
orresponding
to
any  required  return  period  of  occurrence  The
resulting
rel
ationship
betwee
n
magnitude  a
na
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 qunatile) is expected to be exceeded.
A reliaDle estimate of the entire Q-T relationship cannot be obtained from small samples of at- site data. The benefits  of rationalization in flood frequency analysis  have been recognized at least since the work  of Dalrymple (1960). Nowadays, the rationalization approach to flood frequency analysis (particularly the index-flood method) is becoming more popular
An essential prerequisite for the index-flood method is the standardization of the flood data from sites with different flood magnitudes The most common practice used also in this study is to standardize data by division by an estimate of the at-site mean, thus
Xi = Qi/Qm
(8 1)
Where Xi is tne itn standardized flow, Qi is the iin annual maximum flow Qm is the average value of at-site annual maximum flow series
Then the quantile QT is estimated as
Qt=
Qiti.Xt
(8 2)
Thus, the mean annual flood is  the index-flood The parameters  of the distribution of X are obtained from the combined set of regional data In this  study, two distributions  have been
□sea for flood frequency analysis These distributions are
(a; Generalized Extreme Value (GEV) distribution (Jenkinson, 1969)
(b) Log-Logistic (LLG) distribution (Ahmed et al., 1988j
The results obtained by the above two methods are shown m the Table 8 1 and 8 2 respectively
8.2   CHOICE OF DISTRIBUTION
Robustness  as  criteria has  received widespread attention for cnoice of distribution for an annual maximum flood (AMF) Robustness  is  assumed to test whether a distribution ano method of parameter estimation, considered jointly, are insensitive to departures  from assumptions made in their use In this regard LLG/PWM has been found to De more robust than GEV/PWM (Admasu
Often, a compromise has to be reacnea between flexibility and sensitivity to outliers One may need to compromise on some Kind of mid-way solution The compromise could be to use a tnree-parameter distribution such as GEV and LLG However, for this purpose LLG has Deen found to be more attractive than GEV
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In addition, LLG is less sensitive (compared to GEV) to changes in the small values of the annual maximum floods  Therefore, LLG/PWM is  better than GEV/PWM for modeling AM samples that display a dogleg shape when plotted on probability paper
In general, LLG/PWM has been found to be more appropriate for modeling annual maximum floods  (AMF) compared to other distributions  Therefore LLG/PWM has  been applied for estimating design floods required for the project
Thus, based on probability  weighted moments  method and using LLG distribution, on a regional flood frequency  approach, the return period floods  have been arrived at for the proposed dam site The momentary peak discharges ar various levels of probability of
exceeaance (return Periods; are summarized below:
10 year return period flood peak
20 year return period flood peak
> 50 year return period flood peak
575 m 3/sec
654 m 3/sec
771 m 3/sec
100 year return period flood peak
500 year return period flood peak
871 m 3/sec 1155 m 3/sec 
'r
r
1000 year return period flood peak 
1303 m 3/sec
10000 year return period flood peak 1
948 m 3/sec
Table 8 1 Estimated Flood Quantiles Based on GEV Distribution
T           xt       Mean Max. Daily Discharge                   Momentary Peax
Growt
Return h Gauging
period factor Site (1)
Wama                                             Wama Gauging      at       Dam  Gauging Gauging      at         Dam Site (2)  Junction   site    Site (1)   Site (2) Junction      site
33
(years) (ratio) (m /s) (m /s)
3
(m /s)
33
(m /s) (m /s) (m/s) (m /s) (m /s)
33
2          0 95      670        214        238       354       788        272    264            392
5          1 23      869        278         309       460      1022       353        342        509
10        1 42     1001        320        356       530      1178       406        395        586
20         1 60     1129       361         402       597      1329       458        445        661
50         1 83     1296       414        459       686      1526       526        509        759
100       2.01      1422       455         505       752      1674       577        559        833
200        2 19     1549       495         550       819      1822       629        609        907
500        2 43     1716       549        610       908      2020       697         676        1005
1000      2 61      1844       589        655       975      2170        749        726       1080
2000       2 79     1972       631         700      1043    2321        801         776        1155
5000       3 03     2143       685        761      1134 1    2522        870        842        1255
i nnnn      n m I
-79-         oqo            « 703     2r”5        Q -> *7             oae
Average      1        707        226        251      374      832        287        278        414
Note The analysis is based on regional flood frequency analysis based on General Extreme Value (GEV) distribution with parameters estimated by probability weighted moments method
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Table 8.2 Estimated Flood Quantiles Based on LLG Di st n button
June 2009
T                Xt
Return    Growth period    factor
Mean Max. Daily Discharge
Momentary Peak
Gauging      Gauging    Wama at    Dam  Gauging Gauging Wama at        Dam
Site (1)        Site (2)     Junction     site    Site (1)    Site (2)
Junction
5t
site
— (years)      (ratio)
3                     (m3/s)        (m3/s)      (m3/s)
(m /s)
------  ------ (m /s)       (m /s) ;    (m /s)      (rrT/s)
2J
2 0 95
5            1.21
10           1.39
20           1 58
50           1 86
100          2 1
200          2.38
500          2.79
1000 3 15
2000 3 55
672             215            238         356
854             273            304         452
982             314            349         519
1118            357            397         591
1317            421            467         697
1488            476            527         787
1680            537            597         889
1972            630            700        1043
2225            711            791        1177
2511             803            891        1329
791          273           264         394
1005        347           336         500
1156        399           386         575
1315        454           439         654
1550        535           517         771
1751        604           584         871 I 1977        682           662         984
2320        800           776        1155
2619        903           876        1303
2956       1020         987        1471 |
5000         4 17          2947            942           1047       1559      3468       1196        1159       1726 10000       4 71          3326           1063          1182       1760      3915       1350        1309       1948
Average                       707            226           251         374 J    832         287          278        414
Note:  The  analysis  is  based on  regional  flood frequency analysis  based on Log-Logistic (LLG) distribution with parameters estimated by probability weighted moments method
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9.0 DESIGN FLOODS AND FLOOD ROUTING
9.1 SPILLWAY DESIGN FLOOD
June 2009
3
Earlier in the feasibility study for irrigation development, the spillway design criteria was based on a 10000-year return period flood as arrived at based on recommendations of section 8 It was decided so for two reasons as below:
I The dam was not a large dam. having a heignt of only 36 meters and nad a gross 
storage of 1341 M mJ
II The dam is located where failure may prooably be confined to the irrigation command
and the dam itself. As such, no excessive loss of human life was anticipated
The flood hydrograph peak was 1948 M m The full design flood hydrograph was convoluted based on U.S Soil Conservation Services  (SCS) recommendations  in the form of a dimensioniess nydrograph.
The 10000-year return period hydrograph was routed througn the reservoir when the reservoir is  at FRL (1356 m amsl) Different lengths  of spillway  were assumed and the routing was repeated for each spillway length. The Storage Indication Method (Modified Pul's Method) was adopted for flood routing, which is a recognized one in the Hydrological literature The 10000- year nao produced the out flows and surcnarges over the FRL as shown in the Table 9.1 for different spillway lengths
However the justifications put forth for adopting tne 10000-year return period flood hydrograph for spillway may not be applicable in the Irrigation cum Hydropower scenario Now the dam is oroposed to have a FRL of 1376 m amsl, which will bring the he«ght of the dam to 56 to 61 meters above the Riverbed level No more, the dam could be classified as a small dam The gross  storage  at  the  FRL  will  be  3679  M  m  ’  As  per  recommended  standards  the  dam spillway  is  to  be  designed  for  full  Probable  Maximum  Flood  Condition  (PMF)  The  criteria  of 10000-year flood or half PMF, if adopted may lead to higher risk level to the dam, irrigation command  and  aoove  all  to  the  Power  House.  Further  when  developments  take  piace  the downstream  area  will  invite  a  sudden  increase  in  human  settlements  Hence  adopting  such lower  criteria  is  unsafe  in  tne  changed  scenario  of  Irrigation  cum  Hydropower  development
The  PMF  is  recommended  as  such  if  the  neight  is  finally  increased  to  have  FRL  at  1376
Pending the Geological and Design confirmation, the above cnterion is  decided If however the above considerations fix up a lower FRL, the design flood criteria is to be again revened bacK to 10.000- year Return period Flood
9.1.1 The PMF Inflow Hydrograph
Prooable maximum flood is defined as the most severe flood considered reasonably possible to occur It is customarily obtained hv using unit hvclrogi’achs and rain^H inform q
PMF Hydrograph though not adopted for Irrigation feasibility was generated in tne course of this present study The generation was with a combined approach of Hershfield technique ano the U S Soil Conservation services Procedures The detailed description had been made about tnese procedures in the Irrigation feasibility Report In the course of the present study the PMF hydrograph was reviewed in detail for firming up its shape on tne oasis of the shapes of some large flood hydrographs at the gauging site downstream This exercise was to give a
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more  firm  up  shape  to  the  PMF  design  Flood
Hydrograph  The  firmed  up  flood
hydrograph
is 
shown  in  the  Table  9  2  with  a  peak  of  3000
cumecs  The  volume  of  the  flood
hydrograph
is 
shown in the Table 9 3
9.1.2 Routing of the PMF Hydrograph through th
e Reservoir.
The nydrograph was routed through the reservoir with small adjustments in the shape <urther The PMF Hydrograph was impinged on the reservoir when the reservoir is at FRL (1376 m amsl) The Storage Indication Method (Modified Pul s Method) was adopted for sucn flood
routing The spillway lengths and respective outflows and the surcharge above FRL are shown
in the Table 9.4
It is recommended to adopt a spillway of 125 meters long as effective linear waterway
However,  in  case  the  FRL  is  changed  to  any  other  level  based  on  Geological  and  Design considerations, the entire routing studies will have to be revised according to that new FRL
9.2  COFFERDAM DESIGN FLOOD
The cofferdam inflow design floods  Hydrographs  had been generated already  in the course of tne Irrigation feasibility  study  The return period flood peaks  as  arrived at in section 8 and the U S Soil Conservation Services  recommendations  were jointly  usea for such generation of return period flood hydrograpns  Such Hydrographs  had been developed even during the Irrigation feasibility  study  phase for 10 20. 50 and 100-year return period levels  The 50-year and 100-year return period Hydrographs  were routed through the cofferdam to decide the safe height of tne cofferdam for the above return period conditions These results are as below
=> At 50-year Return Period Condition the cofferdam needs to be raised up to
1335 m amsl.
=> At 100-year Return Period Condition the cofferdam needs to be raised up to
1338 m amsl
However the cofferdam flood routing studies will not face any changes even if the FRl  is  fixed at any levei based on Geological and Design considerations
9.3    THE CROSS DRAINAGE WORKS DESIGN FLOOD
Seven relatively large catchments cross the irrigation command area from the left and right bank directions The mean floods generated and the unit run off rates was also estimated for these crossing points during tne Irrigation feasibility phase These require no change now
Table 9.1: Spillway Routing results (Irrigation Feasibility Phase) Spillway Length     Out Flow in               Surcharge above FRL of
In meters               Cumecs
50
800
1356 mamsl in meters
3 75
100
1069                                 2 87
150
1246
2 42
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Table 9.2: PMF Hydrograph Ordinates
June 2009
Time hours         Hydrograph Time         Hydrograph
Ordinates
| In cumecs
hours
Ordinates
In cumecs
Time
hours
Hydrograph
Ordinates
In cumecs
0 00
152.80
67 50            2024 19               135 00               365 31
4.50
195.21
72 00            1740 69               139 50               339 39
9 00
365.31
76.50            1542.24               144 00               311 04
13.50
605 88
81 00            1343 79               148 50               282 69
1800
946 89       | 85 50
J
1202.40
153 00               285 74
22.50
1372.14
_______________
90.00 1060.29 157.50 254 34
27 00
1854.09
94 50
946.89                162.00
243 00
31 50
2336 85
99 00
828.63
36 00
2672.05
103.50
747.63
40.50                2903 85
108 00
662.58
45 00
3000 00       112.50            600 88
I
49 50
2932.00       117 00            520 83
54.50
r
58 50
130 50           401.76
__________ L_
Table 9.3: Cumulative Volume of Prooable Maximum Flood
2762 00 121 50 464 13
2280 15
2535 30       126 00           430.11
63 00
-I
Time
(hrs)
Cum. Volume
(%)
J ~ Time
(hrs)
Cum. Volume      Time
j(Mm3)     ]_ (%)
(hrs)
Cum. Volume
(Mm3) (%)
000      0 000       0 00      103 50    687 8       89 5      207 00     765 3        99 6
4 50      0 440       0 06      108 00    698 7       90 9   I 211 50      765 8        99 6
9 00      2.936       0.38      112 50    708 3       92 2      216 00     766 1        99 7
13 50     9 389        1 22      117.00    716.4       93 2      220 50     766.5        99 7
18 00 21 87 2.85 121.50 723.2 94 1 225 00 766 8 99 8 ’
22.50 42.15 5 48
27 00 71 51 9 31
126 00 729 1 94 9 229 50 767 1 99 8
130.50 734 4 95 6 234 00 767 3 99 8
31 50     110 5       14 4      135 00    739 0       96 2      238 50     767 5        99 9
36 00     157 6       20 5      139.50    743 0       96 7      243 00     767 7        99 9
40 50      2104        27 4      144 00    746 5       97 1      247 50     767 9        99 9
45 00     266 4        34 7      148 50    749 3       97 5      252 00     768 1          99 9 I 49 50     322 6       42.0      153 00    751 7       97 8      256 50     768 2       100 0 I 54 00     376 4       49 0      157 50    753 6       98 1      261 00     768 3       100 0
58 50      426 4         55 5        162 00     ?55 5         98 l       265 50
*nn n
63 00 471.6 61 4
67 50 511 8 66 6
72 00 546 4 71 1
76 50 576 0 75 0
81 00 601 7 78 3
166 50    757 2       98 5      270 00     768 5       100 0
171 00    758 6       98.7      274 50     768 5       100 0
175 50    759 9       98 9
180 00    761 0       99 0
184 50    762.0       99 2
I
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Time
(hrs)
Cum. Volume
Time 1 Cum. Volume      Time      Cum. Volume
(Mm3)~P (%)
(hrs) | (Mm3) I (%)         (hrs)
(Mm3) f (%)
85 50 623 9 81 2
90 00 643.4 83.7
189 00 762 9 99 3
193.50 763 6 99 4
94 50
660 4      85 9
198.00   764 3
99 4
99 00
675.1       87 9
202 50   764 8
99 5
Table 9.4 Results of Reservoir Routing (For Irrigation cum Hydropower Stage)
Spillway Length in
meters
Out Flow in
cumecs
Surcharge aoove FRL I
1376 mamsl in meters
50
716
3.50
hoo-
986
2 78
125
1100
2 50
150
1165
2.30
175
1214
2 15
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10.0 SEDIMENTATION AND WATER QUALITY
10.1    ESTIMATION OF SEDIMENT YIELD
June 2009
In the Feasibility study for Irrigation project, suspended sediment data from Stations 14001 14014 and 14005 were obtained. Suspended concentration rates varying between 45 mg/lt to 1670 mg/lt were observed from Dedessa river
Relationships Detween water discharge and sediment loads at various sites in the region are presented in Table 10 1 At-site and regional approach had Deen used to estimate sediment rates from the estimated stream flows at the dam site Accordingly, the following relationship had Deen derived.
Gs = 0 078Q15
(10 1)
Where
Gs = sediment load (in gm)
Q = monthly mean discharge (in lt/s/km ).
2
Careful assessment regarding reservoir sedimentation will be required in the site as the life of the storage created Dy a dam is dependant of the sedimentation situation. Accordingly reservoir planning will include assessment of tne probable rate of sedimentation in order to predict the useful life of the proposed reservoir
In estimating reservoir sedimentation, materials originating as bed load were assumed to have a density of 1 4 gm/cc ano material carried in suspension assumed to have a aensity of 1.2 gm/cc The bed load at the dam sues was assumed to De 15 percent of the suspended load Monthly total sediment load (suspended and Ded load) and accumulated total sediment load at the reservoir site is given by Table 10 2 and 10 3. respectively The reservoir elevation area capacity relationships are shown in the Table 10 4 The same is depicted pictorially in Figure 10 1
10 2 DISTRIBUTION OF SEDIMENT IN THE RESERVOIR
So far tne sediment load likeiy to deposit in tne reservoir has been estimated But estimating the sediment inflow to tne reservoir is not enough as how hign tne sediment will accumulate in the reservoir is also important. Accordingly Area-Increment method had Deen used for this purpose The method is expressed as.
(10.2)
Where
Vs = Ao(H - Ho) + Vo
Vs — s^dimon* vni*
Vo = sediment below the new zero elevation
H = original reservoir depth from the stream bed level
Ho -height to which the reservoir is completely filled with sediment, i e height of tne new zero elevation
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The results so obtained from the analysis of distribution of sediment in the Arjo-Dedessa Reservoir are given in Table 10.5 However the sediment is found to have no interference with the operation of the reservoir
10.3 WATER QUALITY
The water quality status of the Dedessa River is evaluated using the data collected from MoWR dataoase Abbay River Basin Master Plan Study Report (1998) The samples were taken as part of the supporting measurement for the aquatic study and appear to represent the only available data on water quality within the catchment Table 10 6 shows water quality measurements taken for Dedessa at two sites. The samples snowr. in Taole 10 6 were taken after the start of the rainy season and presumably all tributaries of the river exnibited adequate water quality at the time of sampling
Total Dissolved Solids (TDS) 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  water  is  soft  in  nature  and  has  low  salinity  Moreover  the  low conductivity is sign of low fertility of the water with regard to aquatic life Electrical conductivity (EC) measurements were very low at all tne sampleo sites EC is the ability of the water to conduct electric current and directly related to the amount of cations and anions in the water pH
The pH value is the measure of the concentration of hydrogen (Hrj ano hydroxyl (OH-) ions in the water It is to determine the acidity or alkalinity of the substance
Sodium and Potassium
The Na’ and K* reading expressed in terms of Sodium Adsorption Ratio (SAR) is the useful parameter for the evaluation of the water body for irrigation purpose For irrigation water it is important to measure the sodium adsorption ratio as follows
SAR = Na’____________ [(Ca^ + Mg~)/]05
(111)
The nigher the SAR value of the water the less suitable will be for irrigation purposes The maximum computed value among the readings is 0 29 which are less tnan 10 This illustrates tnat the water is very much suitable for irrigation purpose and Hydropower generation purposes
Chloride
The chloride concentration of the rivers is very low (1 0 to 2 0 ma'h at tim«c nf samoiinc Hence the parameter was in conformity with tne standard set by EPA (250mg/l ror aquatic species)
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Table 10.1 Relationships between water discharge and sediment load
June 2009
No
Station
Area
(km2)
Module
10 t'yr
Loss Vales of C in:
3
t/km /y Qs =C.(Qw)’
2
5
3005     Guder at Guder                                          524         77          90        0 025
4007     Little Angar near Gutin 4005     Dabana near Abasma 4002    Anagar near Meqemte 6002    Abbay at Sudan Border
Arjo Dedessa Dam site
1975       176          89        0 096
2881       453        157        0 059
4674       702        150        0 061
172254 335170      1946        0 165
5278       776         147       0.078
l
Table 10.2 Monthly Total Sediment Load at the Reservoir Site (in 1000 m )
3
Jan Feb March April May June July Aug Sep Oct Nov Dec Annual
Avg    2 48 1 33  1.14   1 71 4 51  27 2
131 1 248 5 211 5
Stddev 1 71 1 01   1 11   1 72  4 2   17 6 62 72 98 19 92 6 CV    3 63 4 01   5.15   5 31 4 91  3 42  2.526 2 086 2.311
720 7 19 29 6 87
99 01 14 7 4 95 4 349 4 024 3 8
Skew  7 36 6 29   8 83   7 54  114  7.48
3 696 0 678 3 509 7 051 10 92 8 77
Table 10 3 Accumulated Total Sediment Loan at the Reservoir Site (in Mm )
3
Years Jan Feb March      April   May   June      July   Aug   Sep     Oct   Nov   Dec  Annual
25    0 06 0.03    0 03
0 04
0 11
0 68
3.28
6.2
5 29
3.00
0 48
0 17   19.39
50    0 12 0 07    0.06
0 09
0.23
1 36
6.6
12.4
106
60
0 96
0 34   38.78
75    0 19 0 10    0 09
0 13
0 34
2 04
98
18 6
15 9
90
1 45
0 52   58.17
100   0 25 0 13    0.11
0 17
0 45
2.72
13.1
24 8
21.1
12 0
1 93
0 69   77 56
125   0.31 0 17    0 14
0.21
0 56
3.40
16 4
31 1
26 4
15 0
2 41
0 86   96.95
150   0 37 0 20    0 17
0 26
0 68
4 08
19 7
37.3
31 7
18 0
2 89
1 03   116.3
175   0 43 0 23    0 20
0 30
0 79
4.76
22 9
43 5
37 0
21 0
3 38
1 20   135.7
200   0 50 0 27    0 23
0 34
0 90
5 44
26 2
49 7
42 3
24 0
3 86
1 37   155 1
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Table 10.4: Elevation-Area-Capacity Relationship at Arjo-Dedessa Irrigation cum Power Reservoir
Elevetion        Area         Volume     Elevetion        Area          Volume
(m asl)
(km )
2
(Mm )
3
(m asl)
(km )
2
(Mm )
3
1320
0 54
00
1356
87 85
1341 2
1321
0 99
0.8
1357
90 75
1430 5
1322
2.39
2.5
1358
94 18
1522 9
1323
3.78
5.5
1359
97 23
16186
1324
5 11
100
1360
100 54
1717.5
1325
6 64
15 9
1361
103 64
1819 6
1326
8 03
23.2
1362
106 39
1924 6
1327
9.46
31.9
1363
109 00
2032 3
1328
10.87
42.1
1364
111 91
2142.8
1329
12.67
53.9
1365
115 05
2256 3
1330
14 40
674
1366
11768
2372 6
1331
15 89
82.5
1367
120.20
2491 6
1332
17 74
99 4
1368
122 76
2613 0
1333
19 46
118 0
1369
125 28
2737 1
1334
23 59
139 5
1370
127 69
2863 5
1335
26 66
164 6
1371
130.25
2992 5
1336
29 05
192 5
1372
133 03
3124 2
1337
31.73
222.9
1373
135 45
3258 4
1338
34 24
255 8
1374
138 08
3395 2
1339
36 62
291.3
1375
142 38
3535 4
1340
39 45
329 3
1376
145 27
3679 2
1341
41 97
370 0
1377
148 00
3825 8
1342
44 25
413.1
1378
150 75
3975 2
1343
47 05
458 8
1379
153 73
4127 5
1344
49 95
507.3
1380
156 02
4282.3
1345           53.11           558 8           1381           159 09         4439 9
1346           56.31           613.5           1382          162 13         460C 5
1347           59 15          671 2           1383          166 96         4765 0
1348           61 56          738 8           1384          173 01         4935 0
1349           63 97          808 7           1385          178 58         5110 8
1350           67 88          874 7           1386          183 38         5291 8
1351           70 62          943.9           1387          188 10         5477 5
1352           74 35         1016 4          1388          193 28         5668 2
1353           77 88         1092 5          1389          197 36         5863 6 1254            pi 2 3               11^2 "          1390          201 96         6CZ0 2 1355           84 51          1255 0
_________
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Elev
(m
asl)
~~1
2
Original
area
(Mm )
2
jution of Sediment in the Arjo Dedessa Reservoir (Area Increment Method)
50 y
Oiiginal
capacity
i Mm )
ears sediment load
Ho = 2 03 m
Ao = 1.52 Mm2
Sediment
Depth
volume
Revised
area
Revised
capacity
3
3             (Mm2)       (Mm3)
(m)        (Mm ) 4567
100 years sediment load
Ho = 3 42 m
Ao = 3.15 Mm2
Original  Original               Sediment  Revised    Revised Elev       aiea     capacity  Depth    volume       area       capacity
(m asl) (Mm ) (Mm ) (m) (Mm ) (Mm ) (Mm )
23
323
3
1234567
1346 56 76 i 29 8
1343    48 13     ■166 4
1340    39 92      331 8
1337    32 17        224
1334 24 93 140 7
1331 18 24 79 64
1328    12 19       :8 24
1325    6911         136
1322     2619       2 322
27           38 7         55 24        591 1
24           34 2         46 61         432 2
21           296         38 41        302 2
18          25 1         30 66        198 9
15          20 5         23 41         120 2 12            16           16 72         6367 9           11 4         10.68        26 82 6           6 88         5 395        6 724 3           2.33
1346     56 76      629 8        27          77 4         53 61         552 4 1343     48 13      466 4        24            68          44 98         398 4
1340     39 92       331 8        21          58 6         36 78         273 3
1337      32 17        224          18          49 1         29 03         174 8
1334      24 93       140 7        15          39 7         21 78           101
1331      18 24      79 64        12          30 2         15 09          49 4
1328      12 19      38 24         9           20 8         9 046         17 44
1325      6911         136          6           11 4         3 765         2 239
1322      2 619      2 322         3           1 92
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Table 10.6 Water quality results for sites on the Dedessa river
June 2009
r
Sampling
at Bedeie          at Gimbi
bridge              bridge         Comment
Sample date Elevation (m asl)
TDS (gm/l)
EC (Ds/cm)
pH
Na”
K"
Ca** (mg/l)
Mg” (mg/l)
Cl' (mg/l)
SAR
13/08/96            14/08/96 1300                 1200
20                      20
60                      50
6.74                  6 97
33                     30 1.9                     2.5 64                     9 6
2.43                    1.4
10                     20
0.29                   0.25
I
N
N
N
N
N
N
N
N
N
i
Figure 10.1 (Original Elevation-Area-Capacity Curve)
Elevation-Area-Capacity Curve for Arjo Didessa Reservoir
Area (Sq Km)
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11.0 RESERVOIR SIMULATION CARRIED OUT FOR IRRIGATION FEASIBILITY
June 2009
ElaDorate simulations had been carried out during the irrigation feasibility study The various inputs to tne simulation model are as below
•    Historical monthly flows Time Series of 44 years
•    Synthetically generated monthly flows Time Series of 1000 years generated by AR 1 model
•    ApproDriate monthly Irrigation Requirements (Vide Table 11.1)
•    Evaporation and seepage losses
•    Downstream mandatory releases for environmental stipulations
•    Revised elevation-area-capacity curve of the reservoir expected after 50 years of operation
A precise tailor made model was developed in MS Excel base With the control levels of 1350 mamsl and 1356 mamsl as Minimum Draw Down and Full reservoir levels the simulation runs established about 90 % success of the contemplated irrigation
However during the present feasibility for Irrigation cum Hydropower generation, a new set of simulation models are required to be processed for the changed scenario
Table 111: Irrigation Water Requirements for Various Scenarios
(Mcum)
Phase I
Phase II
Month
Roti
Rot2
Roti
Rot2
Sep
8 38
8.43
12.43
12 45
Oct
10.41
10 69
1319
13 72
Nov
2.89
2 90
3 16
3.29
Dec
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
18 49
22.15
22 99
26 41
Apr          4 98           5.21           5 09           5 30
May         2.01           2.01           2.01           2.01
Jun         21 64         21 64         32.42         32 42
Jul I     5 97           5 97           8 95           8.95
Aug 6 89 6 89 10 33 10 33 Total 134.93 148.43 179.22 194 49
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12.0 MODELING FOR IRRIGATION CUM HYDROPOWER GENERATION
12.1   EVOLUTION
As discussed in the Introduction, on the establishment of Irrigation Feasibility it was decided to go for Hydropower generation along with Irrigation development because of availability ot considerable water resources and a favorable topography to explore the proposal tor a dam with considerable higher heights  As  such a Pre-feasibility  level study  was  taken up ano completed in February 2008
The modeling for the combined development of irrigation and hydropower was different »n this case from conventional projects  If the project had a single purpose of either Irrigation development or Hydropower development, obviously the modeling would be straightforward In such cases, some of the appropriate models from hydrological literature couid be used Even in case of twin objective projects, the problem becomes simple if the irrigation releases pass tnrougn the power turbines, in which case the irrigation releases are advantageously utilized for power generation.
But in the present situation of the proposed Arjo Dedessa the modeling becomes  not so straightforward The irrigation releases need to be made on first priority: at the same time it can not be passed through the turbines, as the irrigation command is situated much above the River bed level because of topographic constraints As such, two sets of separate out lets are to be established one dedicated for irrigation and the other for hydropower releases  This situation in a way constrains the hydropower generation, as it has to sacrifice the irrigation releases For such a situation, readily available simulation models in the hydrological literature may not be able to cope up However the Consultants with ricn experience in nandling sucn situations by simulation developed a tailor made simulation model
12.2   SIMULATIONS FOR OPTIMAL POWER GENERATION
The simulations runs were carried out with the irrigation feasibility FRl of 1356 m amsl This indicated that with the above contemplated FRl, the Irrigation development was successful at 80% reliability levei, not only so, such development was successful even in stringent years like 90% and 95% of exceedance probability levels Hence no ambiguity was coming forth with respect to success of Irrigation development over an area of about 17 000 nectares However with respect to the Hydropower generation, after fully satisfying irrigation could go up to only about 5 5 MV\/ Hence it was decided that to obtain a reasonably higher power it becomes necessary to try Full reservoir levels at higher zones above 1370 m amsl
At the end of the Feasibility study for the irrigation Project such a conclusion was arrived at The Tail water level was at 1322 m amsl in the above simulations
12 3 POWER EXPLORATIONS AT HIGHER LEVELS
Subsequently  at tne end of the Feasibility  study  for irrigation tne simulation model was sligntly modified /recoded and compiled to cater to simulation runs for higher/raised levels and to various  patterns  of power releases For tne sake of hydropower potential assessment a large number of alternative runs of the model were exercised in 3 different domains These are,
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■   Domain 1: Keeping the power outlet at a lower level of 1346 meters and increasing the FRL in stages with combination of release patterns This is with a view to utilize the water storea in the reservoir above the actually required MDDL of 1346 meters and the Irrigation MDDL of 1350 meters That is. the idle water with respect to Irrigation stored between 1346 meters and 1350 meters could also be used for power generation
■   Domain 2: Keeping the power outlet at the lower level of 1346 meters as above and increasing the FRL in stages but with model inbuilt decision support based power releases
■   Domain 3: Keeping the power outlet at the same level as that of the Irrigation outlet (1350 meters), and increasing the FRL in stages with model inbuilt decision support based power releases
o In the Domain 1 case a set of 12 different simulation runs was attempted within the FRL range of 1370 meters to 1380 meters
In the Domain 2. there were 10 different simulation runs.
In the Domain 3. there were 8 runs of tne simulation. The results are as below
Domain
No.
r
Domain Nomenclature
FRL
Power at 97%
exceedance level
(Firm Power)
h _ MDDL at a lower ievei of 1346m 1370m 11 22MW
1 and assumed pattern of monthly             1372m                  13 30MW
]
]
]
I
releases
1374m
13 62MW
MDDL at lower level of 1346m. but
1372m
16 49MW
releases based on decision support
1374m
17 20MW
1376m
17.90MW
1378m
19 50MW
3
MDDL for power at same level at
1370m
17 00MW
1350m as irrigation outlet (with
1372m
18 10MW
I    separate outlets). Decision support
1374m
18.95MW
J
1
1
1
1
1
L
based releases
1376m                  20.00MW
Thus at a FRL of 1376 meters, the firm power generation goes jp to 20 00 MW There was also an indication that above 1376 meters the reservoir is not opening up to accommodate higher incremental volume per unit raise in the FRL. As such, tne increase in FRL further may not be producing power commensurate witn the cost element Further even after raising the FRL up to 1382 meters the surplus in very good years could not be fully arrested and the Hydrology oecomes a constraint aDove FRL of 1376 mamsl As such, at this level it is found ’jiai the FRl ai 1^76 meters seems io oe opumai As such, nyaiotogy permits t. ic .ais.ng or the dam FRL to 1376 m amsl ano generation of about 20 MW firm power round tne year (97 % Exceedance probability level), which with a plant factor of 0 6 may result at the installed capacity of 33 MW This emerging picture is of coarse after satisfying irrigation almost at 100% reliability
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However even for raising up to this level, tne Geological/Geo-techmcal support needs to be established. Since the detailed geological investigations are to be completed some geological or design constraints may crop up to raise the FRL to 1376 m amsl. At this time the Tail Water level was at 1322 m amsl
Then during the Pre-Feasibility Study tne simulations were rerun because of change in the Tail Water level from 1322 mamsl to 1317 mamsl. The simulations were rerun again for the FRL of 1376 mamsl Because of lowering of the Tail Water ievei, tne Firm power increased to about 23 75 MW for the Domain 3 conditions which is optimal
During tne present Feasibility Study, with updating of the inflows the simulations were rerun for various FRL conditions The Tail water level was at 1317 m amsl and the minimum operating pool was  at 1350 m amsl Considering the aspects  other than Hydrology  ano for facing different constraints and possible reductions in FRL from 1376 m amsl, a son of Firm up Simulations  were carried out by  an Ms  Excel based model for a spectrum of FRL The simulations were carried out for FRLs at 1356, 1358, 1360, 1362, 1364 1366. 1368 and 1370 Tms is to aid the Design group to come out with an appropriate FRL cased on the constraints other than Hydrology The FRLs, tne Firm Power, the possible installed capacity at a plant factor of 0 6 are presented in the Table 12 1. In all the cases the Minimum operating pool is well above 1350 m amsl.
The input hydrological time series up dated during this study is given in the TaDle 6.7 The simulation starts at the end of the fair weather season in September The starting level as such is Kept at FRL 1376 meters The Irrigation developments requirements had already been precisely estimated in the course of the Feasibility study for Irrigation development for inputting in the simulation The reservoir live storage has been segmented into 6 different zones At any stage depending upon tne starting zone of the reservoir, the power release ruie was inbuilt in the modei The tail water level was kept around 1317 meters On firming up tne exact height of tne dam the tail water rating will be firmed up using software “Hec Ras" of the US Army Corps of Engineers
Subsequently  in the course of this  present Feasibility  study  the design considerations warranted revising the simulations with minimum operating pool at 1353 m amsl instead of at 1350 m amsl This was again carried out for the FRL 1376 m amsl with minimum operating pool at 1353 m amsl. This marginally increases the firm power to 23 75 to 23 90 MW As a sample 2 -years simulation out puts are shown in the Table 12 2
In the Annexure volume at B-7 tne entire 44-year simulation abstracts are provided At the end of this present Feasibility and just after finalizing this report the Design considerations warranted to rerun the simulations with the Minimum operating pool at 1346 40 m amsl. which is under progress There is an indication that because of this there is not any change in the Firm Dower at higher FRL conditions and that there could be marpinal increase in lower FRL ranges However a detailed final simulation is pianneo in tne detailed stuuy wnen tne Geoiogy and Design Groups take a unique decision about tne FRl
12.4 INFERENCES
By the foregoing discussions it is found that with identified optimal FRL 1376 meters and the MDDL at 1353 meters the Irrigation development contemplated is completely successful and
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in addition, generation of continuous Hydropower of 23 90 MW as firm power is also possible However, for facing some constraints other than Hydrology, the firm power generated at various levels (FRLs) from 1356 to 1374 is also established and provided in the Table 12 1 (for  Minimum  operating  pool  at  1350  m  amsl)  However  depending  upon  Geological Investigation  results  and  consequent  changes  in  heignt  of  the  dam  ano  tne  location  ot minimum operating pool, the simulations are to be firmed up The simulation out puts shown in the Annexure B-7 and Table 12.2 are for minimum operating pooi at 1353 m amsl Table 12.1: Firm Power at Various FRL conditions (1350 m amsl Minimum operating
pool)
FRL (mamsl)
Possible Firm
Power (MW)
Possible Installed Capacity by adopting 0.60 as Plant Factor (MW)
1356
597
9 95
1358
775
12 90
1360
10 75
17 90
1362
13 25
22 08
1364
1469
24 48
1366
16 47
27 45
1368
17 94
29 90
1370
19.75
32 08
' 1372
20 95
34 91
1374
22.05
36.70
1376
23.75
40.00
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Table 12.2: FRL t 1376 m amsl Firm Power Generation
June 2009
FRl at 1376 mamsl
Firm Power Generation
1353
mamsl minimum
operating
Year and
Starling
Inflow
Storage 1
Irrigation
Storage 2
Reservoir
Power St
orage 3 Mea
n
Head
pool
Power
Energy
Surplus
End
Month
Storage
requireme
nt
Zone
release Mcum
I evel
Mcum
Mcum
Mcum
Mcum
Mcum
Mcum
m
m
MW
GWhr
Mcum
Storage Mcum
1961 62
2789
900
3689
12
3677
surpls
142
3535
1376
59
23 79
17 13
746
2789
SEP
1961-62 Oct
2789
661
3450
14
3436
surpls
142
3294
1376
59
23 79
17.13
505
2789
1961 62
2789
292
3081
3
3078
surpls
142
2936
1376
59
23 79
17 13
147
2789
Nov
1961-62
2789
101
2890
16
2874
syrplus
142
2732
1376
59
23 79
17 13
0
2732
Dec
1961-62 Jan
2732
35
2767
29
2738
2
148
2590
1374
57
23 96
17 25
0
2590
1961 62
2590
19
2609
35
2574
2
148
2426
1374
57
23 96
17 25
0
2426
Feb
1961 62
2426
19
2445
26
2419
2
148
2271
1374
57
23 96
17 25
0
2271
Mar
1961-62 Apr
2271
5
2276
5
2271
2
148
2123
1374
57
23 96
17 25
1961 62
2123
21
2144
0
2
2123
2142
3
159
1983
1370
53
23 93
May
17 23
0
1983
1961-62 Jun
1983
157
2140
32
2108
3
159
1949
1961 62 jul
1949
1370
398
53
2347
23 93
9
17 23
2338
0
3
1849
159
2179
1370
53
1961-62
217'
561
23 93
2740
17 23
10
0
2730
3
2179
159
2571
Aug
1370
53
23 93
17 23
0
2571
Mean
245’
149 7
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Table 12 2 Contd
Year and           Stinting       Inflow Storage 1  Irrigation Storage 2  Reservoir  Power     Storage 3 Mean  Head   Power   Energy    Surplus       Fnd Month
St age
requirement             Zone         release
Level
Storage
Mcum       Mcum Mcum       Mcum Mcum
Mcum     Mcum       m        m        MW       GWhr     Mcum            Mcum
1962-63 Sep
2571
900
3471
12
3459
2
148
3311
1374
57     23 96
17 25
522
2789
1962-63 Oct
2789
512
3301
14
3287
1
142
3145
1376
59     23 79
17 13
356
2789
1962-63 Nov
2789
65
2854
3
2851
1
142
2709
1376
59     23 79
17 13
0
2709
1962-63 Dec
2709
32
2741
16
2725
2
148
2577
1374
57     23 96
17 25
0
2577
1962-63 Jan
2577
23
2600
29
2571
2
148
2423
1374
57     23 96
17 25
0
2423
1962 63 Feb
2423
12
2435
35
2400
2
148
2252
1374
57    23 96
17 25
0
2252
1962-63 Mar
2252
12
2264
26
2238
3
159
2079
1370
53    23 93
17 23
0
1962-63 Apr
2079
31
2110
5
2105
2079
3
159
1946
1370
53    23 93
17 23
1962-63 May
1946
112
2058
2
0
2056
1946
3
159
1897
1370
53    23 93
1962 63 Jun
1897
235
2132
17.23
32
0
2100
1897
3
159
1941
1370
1962-63 Jul
1941
430
2371
53    23 93
9
17 23
2362
0
1941
3
159
2203
1962-63 Aug
1370
2203
826
3029
53    23 93
10
17 23
3019
0
3
2203
159
2860
Mean
2348
1370
53    23 93
17 23
71
2789
152 5
55 33    23 92
206 7
949
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13.0 REDUCTION OF FLOWS IN DEDESSA SUB BASIN
In  all  the  cases  of  simulation  runs,  there  is  no  detrimental  effect  on
the  downst
ream
flows  of
Dedessa  sub  basin  The  maximum  consumptive  utilization  is  only  for
irrigation,
which
is  only 
194  49Mm3   annually,  as  the  additional  releases  made  for  power  are  not  consumptive  uses The  power  releases  go  back  to  River  Dedessa.  just  in  the  downstream  Thus,  a  net  reduction in  tne  sub  basin  flows  will  be  up  to  a  quantum  of  195  Mm3   even  without  accounting  for  any irrigation  regenerated  flows  The  sub  basin  of  Dedessa  contributes  at  its  end  annually  to Abbay  a  quantum  of  14  033Mm3    (BCEOM  Master  Plan  Study)  This  will  get  reduced  to 13,838Mm3    because   of   the   proposed   Arjo   Dedessa   project,   which   is   only   a   negligible reduction  of  1.39%.  As  such,  the  Arjo  Dedessa  Dam  proposal  is  not  going  to  jeopardize  the overall developments of the sub basin considering various identified projects of the sub basin
14.0 MANDATORY DOWNSTREAM RELEASES
Mandatory  downstream releases  are to be made from the dam for ecological and Environmental angles  This  a continuous  discharge of 2.5 cumecs  based on low flows  time Series analysis Since this a Hydropower dam. tne releases at any time will be more than tms minimum requirement. As such the mandatory minimum releases are more than assured
15.0 RECOMMENDATIONS
I  Once  the  dam  is  operational,  in  addition  to  its  own  contemplated  development,  it  will spread  its  positive  impacts  on  tne  downstream  with  regulated  power  releases  That  is  the downstream   area   is   going   to   enjoy   tne   regulated   releases   The   present   somewhat unfavorable  Hydrology  of  the  downstream  areas  will  become  a  hydrology  with  positive impacts  The  situation  will  become  like  the  TK95  dam  and  the  Humera  irrigation  project  in the  Tekeze  basin  As  such,  immediately,  a  suitable  irrigation  project  needs  to  be  identified in   the   downstream   for   availing   the   opportunity   of   utilizing   the   regulated   releases   of hydropower  from  Arjo  Dedessa  dam  In  the  downstream,  a  simple  Darrage  or  weir  or  a small  dam,  which  will  produce  the  benefits  equivalent  to  a  big  dam,  could  divert  tne waters
II.   It   is   very   heartening   development   that   the   water   resources   exploitation   for   optimal utilization  towards  economic  stability  is  getting  the  major  thrust  in  Ethiopia  With  phase  of activities,  soon  the  rich  river  basins  will  be  impounded  in  different  storages  associated with  a  number  of  runoff  the  river  schemes  either  for  irrigation  or  power  or  in  a  multi objective  sense  As  such,  in  the  present  scenario,  the  hydrological  planning  and  design are  in  the  usage  However  when  the  basins  in  the  near  future  become  stuffed  with i,'.an>  projects  then,  the  real  time  operation  of  those  projects  ..i"  be  tn?  Ju;  .
Judicial operation of 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 optimization
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models) Such a scenario of real time operation will nave to be backed up by flood
June 2009
forecasting networks, advance prediction of seasonal rainfall, adequate telemetry (for transfer of data), dedicated computers, telecommunication soft ware in addition to subject matter (hydrology/simulation) software. The personnel heading such operations in a basin and those working in such a team need to be trained in the above mentioned aspect so as to undertake operation which has immerse advantages Hence, it is recommended that experts on Hydrology and Hydrological modeling should be identified for undergoing such trainings in Institutions/universities in appropriate countries Though there could De many such institutes, the consultant feels for such multi system operation, adequate expertise is available in countries like U.S.A and India, where many institutions Universities, River basin authorities, and research stations could be identified for offering such trainings. Such trained personnel, with expertise in hydrology will be able to head future river basin authorities for optimal real time operation of the systems
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REFERENCES
June 2009
Admasu Gebeyehu, 1988. Regional Analysis on Some Aspects of Stream flow Characteristics in Ethiopia. (Unpublished Draft Report) August 1988.
Admasu Gebeyehu 1989: Regional flood Frequency Analysis PhD thesis. Royal Institute of Technology, Bulletin No TRITA-VBI-148 Stockholm. Sweden
BCEOM, 1999 Abbay River Bain Integrated Development Master Plan Project Phase 2 Data Collection, Site Investigation Survey and Analysis Section II. Sectoral Studies Volume III. Water Resources Part I - Climatology and Part II - Hydrology BCEOM - French Engineering Consultants - in association with ISL and BRGM
ERA (Ethiopian Roads Authority), 2002: Drainage Design Manual Hydrology
Fiddes D 1977: Flood estimation for small East African rural catchments. Proceeding Institution of Civil Engineers, Part 2, 63, 21-34 (1977)
Gray. D M Editor in Chief, 1971 Handbook on the Principles of Hydrology
Haan, C T 1977 Statistical Methods in Hydrology The Iowa State University Press Ames Hersfield D M 1961. Estimating the probable maximum precipitation. ASCE. J Hya Div 87
No Hy 5 99-116
Matalas N.C . 1963 ProbaDility Distribution of Low Flows Statistical Studies in Hydrology Geoi. Survey Prof Paper 434-A
Shaw Elizabeth M 1988 Hydrology in Practice International Van Nostrand Reinhold USBR (United States Department of the Interior Bureau of 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 for Etniopia. Final Report. Volume III Annex A Hydrology & Hydrogeology. Addis Ababa.
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List of Annexes
Annex A. Results obtained from the Meteorological Analysis 
Al     Estimated Mean Temperature at Arjo Dedessa Project Area i in oC)
A2   Estimated Minimum Temperature at Arjo Dedessa Project Area (in oC)
A3   Estimated Maximum Temperature at Arjo Dedessa Project Area (in°C)
A4  Estimated  Relative  Humidity  at  Arjo  Dedessa  Project  Area  (in  percent)
A5 Estimated Mean Daily Sunshine Duration at Arjo Dedessa Project Area
A6  Estimated  Mean  Dail)  ETo  of  Arjo  Dedessa  Project  Area
A7  Estimated  Mean  Monthly  ETo  of  Arjo  Dedessa  Project  Area
AS Estimated Mean Monthly Rainfall at Arjo Dedessa Project Area
A9 Estimated Mean Half-Monthly Ramfal at the Project Area (in mm)
Annex B Results obtained from the Hy drological Analysis 
BI Regional monthly coefficient of variations (CV) of monthly flows
B2           Regional           monthly           coefficient           of           skewness           of           monthly           flows B3 Regional monthly coefficient of correlations (R) for monthly flows
B4 Standardized probability weighted moments arrived for Synthetic flow generation
2
2
4
14
B5 Mean Monthly Total (Suspended and Bed) Sediment Load............................................................................................... 15
Bo             Eleveauon-Area-Capacity             Relationships             of             Arjo             Dedessa             Reservoir
B7 Simulation Run Extracts For Irrigation and Hydropower Generation at Arjo Dedessa Dam
Annex C Standards ....................................................................................... .........................................  39
CI Commonly used values of runoff coefficients 
C2 Runoff coefficient for perv ious surfaces by selected hydrologic soil C3 SCS Curve Numbers tor Various Conditions 
C4 Reservoir Flood Standards 
17
39
39
.40
42
C5          Ranos          of          tne          basic          dimensionless          hydrograph          of          the          SCS          43
C6 Guidelines for Interpretations of U ater Quality for Irrigation
\nnex D Meteorological Data
DI      Details of Meteorological Observation Stations (Raw Data Collection) D2.    Ty pes of Climatic Data av ailaoic at the various Meteorological
D3 Mean Monthly Rainfall at Bedele Station D4 Mean Monthl) Rainfall al Jimma Station
4a
45
45
45
46
47
D5   Mean Month!) Rainfall at Dedessa Station....................................................................................................................... 49
D6   Mean Temperature at Bedele Station (Raw Data before gap filling) D7   Relative Humidity at Bedele Station (in%) (Raw Data before gap fillingi DH    Wind Speed at Jimma Station (Raw Data before gap filling)
D9     Sunshine Duration at Bedele Station (Raw aata collected) Annex E Hydrological Data
......................................... 55
El List of Selected Hvdrologicai Observation Stations 
Annex E2 Mean Month!) Stream flow at Dedessan near Arjo Station
E3 Mean Monthl) Stream flow at Dedessan near Dembi Station
E4 .Annual Maximum Floods.......................................................................................................... 59
E5 Measured Sediment Concentration at Relevant Gauging Stations 
Annex F Routing of PMF Hydro graph o............................................... Annex G: Arjo Coffer Dam Out Flow Routings 
60
50
52
53
54
55
. 56
58
62
................ 68
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ANNEXES
Annex A: Results obtained from the Meteorological Analysis A1 Estimated Mean Temperature at Arjo-Dedessa Project Area (in oC)
June2009
Year Jan Feb March April May June July Aug Sept Oct Nov Dec
1961    22 2       21 8      24 7      24 0      23 2     21 5     20.7     20 2    21 6     22 0     21 9     19 7
1962    20 0       21 8      24 9      22 5     23 2     21 0     20 0     20 0    21 3    22 1     20 2     19 0
1963    21 7       23 2      24 3      16 3      15.9    21 6    21 1     20 8    21 4     21 7     24 6     21 3
1964    21 7       22 9      254      24 6      23 7     21.5     20 4     20 4    21 4     22 0     21 5    20 8
1965    21 5       21 8      24 8      24 8      23.5     21 6     21 3    20 8    21 5     22 4     23 2     20 5
1966    22 7       23.6      25 3      24 8     24 1     21 7    21 4    20 8    21 5     22 3     22.0     18 8
1967    195       22 5     25 1      24 8     23 7     21.2     20 7     20 5    21 3    21 1     23 0     18 7
1968    199       22 4      23 6      24 5     24 1     21 6    21 6    21 1     21 2     21 4     21 2     196
1969    22 4       23 2     25 1      24 6      24 0     22 0     20 7     20 7    21 5     21 7     21 2     16 9
1970   21 5       22.9      25 0      24 9     24 3     22 0    21 4     20.8    21 6     22 8     19 8     18 2
1971    21 6       20 4      23 9      24 7     23.7     21 1    21 0     19 9    21 1     22 4     21 7     18 2
1972   21 5       23 1      24.2      24 9     23.2     21 0     21 8    21 3    21 6     22 3     22 8    20.2
1973   22 7       22 6      25 8      26 8     24 1     21 8    21 3     20 8    21 5     21 7     21 7     17 4
1974   21 2       23 3      25 3      23.9     23 9    21 8     20 8     21 3    21.3     21.2     19 1     19 0
1975   21 0       23 6      25 9      24 8     23 7     21 7    20.5     20.2    21 3     21 9     20 4     18 9
1976   20 6       23 9      24 8      24 3     23 1     21 0    21 0     20 8    21 6     22 4     22 5     197
1977   23 0       23 5      24 9      25 3     24 4     21 4    21 0     21 3    21 9     23.5     23 0     20 9
1978   21 1       22 8     26 1      25 6     23 8     21 9    20 9     21.2    21 1     22 3     20 9    20 4
1979   22 2       23 5      24 7      24 2     24 2     21 9    21 3    21 6     22 0     22 3     21 6    20 9 198G   22 3      24 1      26 1      25 8     24 4     22 3    21.1     20 8     22.0     22 0     22 0     19 5 1981   22 4       22 6      26 2     25 1      24 7    22 3    20 6    21 1     21.5     22 0     21 6     192 1982   22 7       22 3      23 8      24 9     23 5     21 9    21 2     20 7    21 6     21 8     23 0    20 6 1983   20 3       23 6     26 1      25 6     25 0     22.8    22.3     21 8    21 7     22 4     22 3     186 ; 1984   20 6       20 6      25 4      26 2     24 5     21 9    20 9     20 7    21 1     20 2     23 4     20 6 1985   21 5       22 9      25 7     25 1      24 0     21 7    20 6    20 4     21 5     21 5     22 1     197 , 1986   21 5       24 7      23 9      24 6     24 6     22 0    21 3    21 1     21 2     21 7     22 0    20 4 | 1987   21 8       23 0      25 4     25 1      24 2    22 6    22 2     21 6    21 9     23 1     22 7    20 2 1988   22 4       24 5     25 1      25 8     25 3     22 5    21 3    21 6     21 9     22 5     20 6     18 8 1989   21 3       22.3      24 6      24 5     23.3    21 9    21 3    21.6    21 7     22 0     21 9    21 6 | 1990   21 0       21 9      24 8     25 1      186     22 4    21 4    21 4    21 9    22.1     22 4    20.9
1991    23 0      23 6     25 1      25 1     24 6     22 6    21 3    20 8    22 0    21 4     21 4     18 2
1992   22 1       24 1      25 2      25 2     24 6     22 3    21 1    21 3    21 8    22 7     21 8    21 3
1993    22 6       23 5      24.3      25 6     24 4     22 7    21 4    21 4     21 8    22 9     21 7     19 6
1994   21 6       24 2      26 8      24 9     24 3     22 3    21 1    21 5    21 8    22 0     23 3     20 0
1995   22 3       24 5      26 4      26 5     25 3     23 1    21 9    22 1     22 3    23 0     23 3     22 2 |
1996
22 6
24 1
26 3      25 9
24 7
21 9
21 7
21 8
22 4
22 4
22 0
20 2
1997
4
22 4
^5 9      25 5
24 4
2j1
22 3
3
23 2
<.4 J
25 ’
1998
24 6
24 9
27 4      27 7
26 2
23 4
22 4
22 3
23 1
24 2
22.0
19 1 ,
1999
( 21 9
22 8
26 2      26 3
24 9
22 8
21 6
21 3
22 9
23 5
21 0
19 8 |
2000
21 6
22 9
26 6      26 6
25 5
22 6
21 9
21 8
23 0
24 0
23 5
20 S |
2001
23 0
24 3
26 0      26 4
25 5
23 0
22.0
22.2
23 0
24 2
23 6
21 6
2002
I 23 2
23 6
26 9      25 9
25 8
22 8
22 7
22 2
22 8
23 3
23 1
22 7
2003
21 9
24 5
26 4      25 7
25 8
23 2
22 0
22 2
22.7
23 0
23 5
20 6
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt. LtdArjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
A2 Estimated Minimum Temperature at Arjo Dedessa Project Area (in oC)
Year
1961
1962
1963
Jan Feb Marchj April May j June July
97 105 138 14 7 14 9 14.6 14 7
88 10 5 139 138 15.0 14 3 142
95 112 136 9.9 10 3 14.7 15 0
Aug , Sept |
143 145
Octj
130
Nov      Dec
10 3       80
14 2 14 4 130 95 77
147 144 12.8 11 6 86
1964     95      11 1     14 2      150     15 3    14.6   14 5    144     144      130      10 1       8 5
1965     94       106      139     15.1    15 1     14 7   15 1     14 7    14 5     13 2
10 9      8 3
1966 99 114 14.2 15 1 155 14 8 15.2 147 14.5
1967 85 109 14 1 15 1 153 14 4 14 7 14 5 14 3
132
10 3       76
12 5     10.8       76
1968     87       108      132      150      155     147    15 3    14 9    14 3     126      100       8 0
1969     98       112      14 0      150     15.5    14 9   14 7    14 6    14 5     12 8      100       69
1971      95        99       134     15 1     15.3    14 3
1970     94      11 1     14 0      152      157    14 9    15.2    14 7    14 5     13 5       93        74
14 9    14 1    14.2     132       102       74
1972     94       112      135      15.2    14.9    14.3     154    15 1  14.6       13.2      108       8.2
1973
1974
1975
1976
99       109      14 4     16 3    15 5    14 8   15 1
9.3      11 3     14.2     14 6     154    14 8    14 8
92      11 4     14.5     15 1     15.3    14 8    146
14 7    14 5     12.8      102       7 1
15 1    14 3     126       9 0        77
14 3    14 4     12.9      9.6        77
1977    10 1     11 4     14.0      154      158     146     14 9    151     148      13.9     10.8       85
90      11 6      139      14 8    14.9    14 3    14 9    14 7    14 5     13.2     10.6       80
1978
1979
1980
1981
9.7      11 4      138      14 8    15.6    14 9    15 1
9.2      11 0     14 6     15.6     153    14.9    14.8    150     14.2     13.2      9.8        83
15.3    148      13.2
130
10.2 85
10 3 7.9
1982     99       108     13 3     15.2    15.1     14 9    15 1    147     14.5     12.9     10 8       84
9 8      109      14 7     15.3    16 0     151     14 6    14 9    14.5     13.0     10.2       7.8
98      11 7     14.6      157     15.8    15.1    150     14.7    148
1983 89 11 4 146 156 16 1 15.5 15 8 15.5 14.6 13.2 10 5 76
1984 90 100 14.2 16 0 158 14 9 14 8 14.6 14.2 11 9 110 84
1985 94 11 1 14.4 15.3 15.5 14 8 146 14 4 14.5 12.7 104 80
1986 94 12 0 134 150 158 150 15 1 14 9 14 3 12 8 10 3 8 3
1987 95 11 1 14.2 15.3 156 154 15 8 153 148 136 107 8 2
1988
1989
1993 99 11.4 136 156 157 154 15.2 15.2 14 7 13.5 102 7.9
1994 95 11 7 150 15.2 15.7 15.2 15 0 15.2 147 130 11 0 8 1
9 3      108      138      14 9     150    14 9    15 1    15.3  14.6
92       106      13 9     15.3     120    15.2    15.2    15.2  14.8
10 1     11 4     14 0     15.3     159     154     15.1    14 7    14 8
97 11 6 14.1 154 158 15.1 15.0 15.1 14 7
98      11.9     14 0     15.7     16.3    15.3    15.1    15 3    14 8     13.3
1990
1991
1992
130
130
126
9.7 7.6
10 3 88
106 8 5
10 1 74
13.4      10 3       86
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
98       119      14 8     16.2    16.3    15.7    15.5    15.6  15.0       136       11 0       90
99       11 6      147      15.8     16 0     149     154     15.4    15.1     13.3      104       8.2
102      108     15.1     15.6     15.8    157     15.8    15.8  15.6       14.2
108     12.1     15.3     16.9     16.9    15.9    15.9    158   15.6 96       11 0      147      16.0    16.1     15.5    15.4    151     15 4
14 3
139
9.5    11.1     149      16.2     164    15.4    15.6    154   15.5       14.2
10 1      118      14 6     16 1     16.5     156     15 6    15.7    15.5
10.2     114      150      15 8     16.6     155     16 1    157     154
9.6       118      14.8      157      167     158     15.6    157   15.3 106     11 7      147      16.2     16.5    15.5    15.3    157     15.2
14 3
138
118 9.3
10 3 78
9.9        8.0
11 1       84
111        88
109 9.2
136 110 84
134 109 8 8
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo-Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
A3 Estimated Maximum Temperature at Arjo Dedessa Project Area (in °C)
June 2009
Year
Jan
Feb
Marcn]
April
May I June
July
Aug ' Sept
Oct
Nov
Dec
1961
347
330
35.6
336
31 7    28 6
267
26 1     24 4
30 9
33 5
31 4 |
1962
31 2
33 0
35 8
31 6
31 8    27 9
25 8
25 8    24 2
31 1
30 9
30 4
1963
33 9
352
34 9
22 8
21 7     28 8
27 2
26 9    24 2
30 6
37 6
34 0
1964
33 9
34 7
36 6
34 4
32 4    28 6
26 3
26 4    24 2
31 0
32 9
33 3
1965
33 6
33 1
35 7
34 7
32 1     28 8
27 5
26 9    24 3
31 5
35 5
32.8
1966
35 4
35 8
36 5
34 7
32 9    28 9
27 6
26 9    24 4
31 4
33 6
30 1
I 1967
30 4
34 1
362
34.7
32 4    282
267
26 5    24 1
29 6
35 1
29 9
1968
31 1
33 9
34 0
34 3
32 9    28 8
27 8
27 3    24 0
30 1
32 4
31 3
1969
35 0
352
36 1
344
32 8    29.2
26 7
26 7    24 3
30 6
32 4
27 0
1970
33 6
34 6
36 0
34 8
33.3     292
27.6
26 9    24 4
32 1
30 2
29 1
1971
337
31 0
34 5
34 6
32 4    28 0
27 0
25 7    23 9
31 5
33.1
29 1
1972
336
35 0
34 8
34 8
31 7    27 9
28 1
27 5    24 5
31 4
34 9
32.3
1973
35 4
34 2
37 1
37.5
32 9    29 0
27.5
26 9    24 4
30 5
33 1
27 8
1974
33 1
35.3
36 5
33.5
32 7    28 9
26 8
276     24 1
29 9
29 2
30 3
1975
328
35 7
37.3
34.8
32 4    28 9
26 5
26 1     24 2
30 8
31.2
30.2
1976
32 2
36 2
35 7
34 1
31 5    27 9
27 0
26 9     24 4
31 5
34 5
31 5
1977
35 9
35 6
35 9
35 4
33 4     28 5
27 1
27 6    24 8
33 0
35.2
33 4
1978
32 9
34 5
37 5
35.9
32 5    29 2
27 0
27.4    23 9
31 4
31.9
32.6
1979
34 7
35 5
35 6
33 9
33 1     29 1
27 5
27 9    24 9
31 4
33 1
33 4
1980
34 8
36 5
37 5
36 1
33 4    29 6
27.3
26 9     24 9
30 9
336
31.2
1981
35 0
342
37 8
35.1
33 8    29 6
26 6
272     24 4
30 9
33 1
30 6 I
1982
35 4
33 7
34 3
34 8
32.1     29.2
27 4
26 8    24 4
30 7
35 2
32 9
1983
31 7
35 7
376
35 8
34 2    30 4
28 8
28 2    24 6
31 5
34 1
29.8
1984
322
31 2
36.5
367
33 5    29 1
270
26 7    23 9
28 4
35 8
33.0
1985
33 6
346
370
35.2
32 8    28 9
26 5
26 4    24 3
30 3
33 8
31 4
1986
336
37 5
34 5
344
336     29 3
27 5
27 3    24.0
30 5
336
32.6
1987
340
348
36.5
35 1
33 1     30 1
286
27.9    24 8
32.5
347
32 3
1988
350
37.2
36 1
36.1
346     29 9
27 5
27 9    24 8
31 7
31 5
30 1
1989
332
338
35 4
34.2
31 9    29.1
27.5
27 9    24 6
30.9
33.5
34 5
1990
32.8
332
35 7
35 2
254     29 8
276
27 7     24 8
31 1
34 3
33 4
1991
359
35 8
36 1
35 2
337     30 1
27 5
26 9     24 9
30 1
32 7
29 1
1992
34 5
36 5
36 3
35 3
33 6    296
272
27 5     24 7
32 0
33 3
34 0
1993
35 3
35 5
350
35 9
33 4    30 1
27 6
27 7    24 7
32 2
33.2
31 3
1994
33 7
36 7
386
34 8
33 3    29 7
27 3
27 8     24 7
31 0
35 7
31 9
1995
34 8
37.2
38 0
37 2
346     30 8
28 2
28 5    25 3
32 3
356
35 5
1996
35 3
36 5
37 9
36 3
33 8    292
28 0
28.2    25 4
31.5
33 7
32 3
1997
36 5
339
38 8
35 7
33 4    308
28 7
28.9    26 3
33 8
38 3
36 6
1998
384
377
394
38 8
35 8    31 1
28 9
28 9    26 1
34 1
33.6
305 1
1999
34 2
34 5
37 8
36.8
34 1     30 4
27 9
276     25 9
33 0
32.1
31 6
2000
33.7
347
38.2
37 3
34 8    30 1
28 3
282     26 0
33 7
36 0
33.2
2001
35 9
36.8
374
37 0
34 9    30 5
28 4
28 7    26 0
34 1
36.2
34 6
2002
36 2
35.7
38.7
36.2
352     30 3
29 3
28 7    25.8
32.8
35.3
36 2
2003
342
37.1
38.0
36 0
35.3     30 8
284
28 7    25 7
32.3
35.9
33 0
2004
37.8
36.6
37 8
37.2
35.0    30 4
27 8
286     25.5
31 8
355
34.8
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4
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo-Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
A4 Estimated Relative Humidity at Arjo Dedessa Project Area (in percent)
June 2009
Year      Jan    |Feb     iMarch,   April     May  ^une      July    Aug    Sept |   Oct     Nov    Dec
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
67          52         46         70         71        78       87       87       82        82        68       72
77          69         64         73         86        85       94       94        96        95        88        84
65          72         63         82         84        85       89       91        89        83        87       85
71          66         57         63         75        82       88       88       92        84        73       75
67          52         50         68         69        78       83       85       84        82        86       74
65          68         58         71         73        78       86       90       85        84        80       69
65          50         57         66         76       81        91        89       92        85        89       73
55         66         54         68         75       81        88       85       89       81        76       72
72         68         64         69         75        82        88       89       88        80        77       65
71          62         64         69         74        79        86       92       89        86        72       66
60          48         50         64         76       81        87       90       87        87        82       76
64          65         56         70         74        79       89       85        86        80        83       75
65          59         57         68         76       81        62       88       89        83       77       63
54         49         53         58         78       81        90       90       93        83        72       63
52          59        51         70         74        83        86       93        90        84       73       66
55         55         57         68         79       81        92       91        91        91        93       82
72         66         58         57         66       81        89       88        87        86        82       74
58         61         58
75        77        87       86        84        84        75       55
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
68         65        61         64         70        77        84       85       86        79       69       67 59         55         53         68         76       81        86       87        85        79       75       65 54         46         56         63         72        76        88       88        83        82       77       64 67         62         55         65         75        80        88       90        90        87        86       79 66         63        61         70         79        78        85       89       89        88       82       72 59         49         47         61         76        80       88       88        86        74        82       75
68         50        51         67         78        80       90       89        87       81        77       70
58         60         57         69         73        85       87       87        88        82       73       72
59         56        63         69         79       81        83       39       86        85       79       75
72         64         49         62         75        82       90       91        93        87       73       66 63         61         60         75         73        79       91       88       91        84       82       85
67          70         62         68         77       81        90       90       91        80       80       71
68         69         60         80         74        83       90       91        89        82       75       75
68         67         54         69         79        84       90       94        88       89       84       79
69         63         56         75         80       85       89       89        90       86        82       69
57         53         55         67         78        86       86       98        89        75       80       72
60         58         57         72         79        90       98       90       92        84       81        79
72         43         63         73         80        63       89       88       87       81        69       70 73         53        53         72         76       81        86       89       87        88       89       80
74         66         62         64         79       66       74       74       93        92       78       67
61          48         53         65         76        80       90       89       89       92        73       68
55         48         45         67         77       81        89       72        89       93        84       74
67         57         58         69        81        90       91       92        89       88        82       75
71          56        62         64        71       81        85       88       87        84       78       79
71          60         60         66         65        78       90       89       90       84       77       73 66         59         55         70         76       81        87       89       89       91        78       78
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5June 2009
A5:     Estimated Mean Daily Sunshine Duration at Arjo Dedessa Project Ar
Year
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Aug  i Sept | oct 62       9 1       9 2
1
8 9       74
20       6.3        65       76       7 5 38        58        80      9 1       8 3
3 0       68       9 1       9 0      10 0
5.5       79        74       84       8 1
3 8       60       9.2       98       8 3
5.2      8 3        85       76        90
3.2      5.7       6.5      10 1      8 3
4 1       6.2        79       8 3       8 3
47        7.5       7.9       8 3       8 3
4 1       6.2        79       83        83
48        80        88       99        77
4 1       7.2        95       95       9.0
4 8       5.8        86       0 1       8.3
1.6      4.1       7.5       8.4       9.2
4 1       5.2        66       67       8.1
4.1       6 3       6.9       8.2       8 3
3.8       5.5        68       8 9      7 1
3.8       4.2       5.8       7.8       7.5
39        5.9       7.9       7 8       86
4.5       2.6       6 5       96        79
3.7       67        7 5       66       7 3
3.6       56        66       84       8.2
4.3       7.0      10 1       86       8 1
3.1       5.8        76       87       7 8
4.0       4 1       7.4       94       8.2
4.2       7.4        76       8.3      110
4.9       5.5       8 5      10.2     9 1
5.1      6.3       8.3       82       6.6
3.9       59        95       8.9       9.2
6.2       9 1       9.2       8 9       74
2.0       6.3       6.5       7.6       7.5 38       5 8       8 0       9.1       8.3
3.0      6 8       9 1       90      10 0
5.5       7.9       74
84       8 1
2001      8.2
2002      9.2
2003      8 5
2004
3.8       6 0       9.2       98       8 3
5.2       8 3       8 5       76        90
3.2       57       6 5      10 1      8.3
4 1       6.2        79       83       8.3
4.7       7 5        79       8 3       83
76        7.5        7.3        76       6.1       3.7      4.1       6.2       7 9       8 3       83
8.8        74        9.4        8 3       64        54      4.8       8.0       8.8       9 9       77 89         85         84       10 1      7.3       3.2      4.1       7.2       9.5       9.5       9 0
4.8       5 8        86      0.1       8 3
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In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological FeaslbllityStu^es
A6 Estimated Mean Daily ETo of Arjo Dedessa Project Area (in mm/day)
June 2009
“Jan Feb March’ AprilJ May ]June
July , Aug]SeptT Oct
3 73 3 93 4 49 4 26 3 73 3 64 3 04 3 54 4 43 4.27 3 86 3 24
3 23 3.75 4 66 4 32 4 43 3 49 263 2.5 3 72 3 63 3 48 3 19
3 48 372 4.66 3 44 3 36 3 11 2 71 3 3 63 3 98 4 22 3 56
3 95       4 18     4.65      4 66     4 52     3 45     272      2.79
3 84       4 13      4 83      4.25      4 43     2 97      3.1
3 43
3 87 4 25 3 86 3 82
4 13 3 88 3 92 3 45
3.68       422       4 47      4 73     4.35
34       3 07       3
37      4.31     4 09     3 35
3 45       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       45       4 64      4 1      371      2.63      2.9
3.59     3 59    4 06      34
3 06
4 01      4 45      5.06      4 58      4 76     4 01     3.21     3.22
3 71      4 06       4 5       4 43      4 28     3.56     2.91
4 24     3 49     2.93     3 01
3 72
4 06
369
3.94 3.7 3 19
4 04 3.58 3 28
3 66        39       4 49      4 49
4       3 75     3 29
3.86       4 34       4.5
5 03
4 34     3.55     3.39
3 28
3 09
4 17    4 23      4 2     3 34
3 81 4 3 4 87 4 92 4.91 3 84 2.81
3 58 4 18 4.53 4 24 4 61 3.51 3.3
3.97    4 32    4.01
3.29     3.62    4 07     1 95
3 34
3.35
3 82 427 4.66 4 34 4 09 33 2.73 2.44 3.2 3.87 3 64 3 49
3.73 4 38 4 65 4 75 4 02 3 68 2 93 3 06 3.5 3.69 3.48 3.38
3.4        3 85     4 34      4 49      424      3.46      2.9
3.1      3 78     3 87     3.86     3 52
3 85       362       4 64        47        4.39     3.57
2 58
3 04     3.53     3 74     3 79
3 36       3.89     4 18      4 37     4 08     3 38     2.64     3.07      3.3       3.5
329        3 63     4.21      4 39     4.32     3 56     2.93     3.05      3.7      3 98
3 78      4.25      3.99      4 13     4.42     3 53     2.91      3.2      2.88     364
3 64
3 66
3.23
3 34
3 44
3.6        374      463       4 32     4 13     3.77
2.98     2 98    3.87     3 86
3 54      4 14     4.55      4 76     4.15
406
3.43
3 14
271
3.03    3.61
37
4.01      3.3
3 49      3.3
3 82     3.32
3 58 4 31 4 73 5.02 4.08 3.55
3 73 4 04 4 59 4 36 3.93 3.53
3.11    3 87     4 3     3 98     3 46
2.81     3.63     3.86
343 3 94 4 31 4 03 4 22 304 2.85 3.08 3.22
3 67 4 14 4 31 4 74 3.83 35 3.27 3.16 4 06
3 76        42
5 04       4 82     4.58     3.78     2.71     3 34    3 59
3 72 4 18 4 42 4 39 4 64 3 83 2.97 3.38 3 77
3 82 3 38 4 31 3.57 3.35 3.25 2 92 3.07 3.69
3 82
4
4 17
4 06
3 88    3.32
4 01    3 46
3.83     3 96
4 02 3 48
3 74 3 24
379       4 05     4 43      4 31      3 82     3.72     3 06    3.59    4 49
4.37 3 92 3 67
4 22 3 84 3 11
3 42 3.94 4 71 4 62 465 363 2.73 2.59
3 54 3.75 4 68 4.29 4 25 321 2.72 3.04
3 78
37       3 61     3 38
3.67    4 09    3 91      3.4
3.94       4.3       4 79      4 65     4 55      35      2.75     2 83    3.91    4 26    4 06     3 75
3 92      4 34      4 96      4 34     4 53
2 98     3 11    3.52    4.21
3 68 429 4.57 4.88
3.77 4 43 4 95 4 46
4 37
3 35     3.09    3.03
4.65     4.07     3.23    346
3 91      4 33       4.8       4.93     4.24     3.85    2.66     2.96
377
4 41
374
3.94 3 92 3 59
4 31 4 09 3.46
4 32 3.9 3 85
3.83 4 12 3 36
368       4 07     4.67      4.57      4.36     3.63
2.98     3 11
3.83    4 11      37       3.42
4 03 4 45 524 4.79 4.86
3 78 4.21 4.66 4 64 4 42
3 31 3 35 4.19 4 16 392 3.5
2.98 3.16 3 84 4 19 3 92 3 57
4
4 39     4 75      5 13     4 59
3.46      3.4     4.29
3 75 4 49 4.92 4.82 5.06
3 84 4.28 4 58 4.51 4 83
4 15
365
3.71
3 88
2.85     3.16
4 08
4 34 4.24 3.54
4 47 4 19 3 63
3.6      3 22    3.35
3.72    421      2 06     3.61
Water Works Design & Supervision Enterprise
8
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
A 7 Estimated Mean Monthly ETo of Arjo Dedessa Project Area
June 2009
Year
Jan
Feb Marcn
April
May £June I July
Aug
Sept
Oct
Nov
Dec
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
116
100
108
122
119
114
107
109
115
124
110     139
105    144
104    145
117 144
116 150
118 138
124 148
114     140
114    140
124    157
128
130
103
140
128
142
133
139
133
137
116    109   94 2
137    105   81 6
104   93.2     84
140 104 84 3
137 89 962
135 102 95 1
143 118 97 7
127 111 81 4
133 107 90 1
148 120 99 4
110
77 4
92 9
86 6
106
93 1
103
89 9
94 8
99 7
133
132
116
100
112
109
116
124
111
127
108
112
122
112
124
132
120
134
125
111
122
125
104
127
116
118
123
111
122
111
107
99
110
119
107
104
107
105
99
102
1971
1972
1973
1974
113
120
118
111
109    139
122    140
120    151
117 140
135
151
148
127
132 105 90 8
135 106 105
152 115 87.2
143 105 102
93.2
102
959
102
111
125
119
109
124
131
134
126
113
126
120
586
102
104
104
104
1975
118
120    144
130
127     99    84 7
757
96
120
109
108
1976
116
123    144
143
125    111   90 8
94 8
105
115
104
105
1977
105
108    135
135
132    104     90
96
113
120
116
109
1978
119
101    144
141
136    107     80
94 2
106
116
114
100
1979
104
109    130
131
126    101   81 9
95 3
989
109
109
104
1980
102
102    130
132
134    107   90.9
94 5
111
123
110
107
1981
117
119    124
124
137    106   90 1
992
86 5
113
120
102
1982
112
105    144
129
128    113   92.3
92.5
116
120
105
102
1983
110
116    141
143
129    122    106
94
108
115
115
103
1984
111
121    146
151
127    107   97 4
96.6
116
133
120
107
1985
116
113    142
131
122    106   84 1
87 1
109
120
116
103
1986
106
110    134
121
131    91 3   88.2
956
96.5
118
120
107
1987
114
116    134
142
119    105    101
98
122
124
115
123
1988
117
118    156
145
142    113   84 2
103
108
129
121
108
1989
115
117    137
132
144    115     92
105
113
126
112
100
1990
118
94 8    133
107
104   97 4   90 6
95
111
136
117
114
1991
117
113    137
129
118    112   94 8
111
135
131
115
96 4
1992
106
110    146
139
144    109   84 5
80 3
113
115
108
105
1993
110
105    145
129
132    964   84 4
94 3
110
127
117
105
1994
122
120    149
139
141    105    852
87.8
117
132
122
116
1995
122
121    154
130
140   89 4   964
109
126
122
118
111
1996
114
120    142
147
135    101   95 8
94
113
134
123
107
1997
117
124    153
134
144    122    100
107
132
134
117
119
1998
121
121     149
148
132    115   82.6
91 9
112
119
124
104
1999
114
114     145
137
135    109   92 4
963
115
127
111
106
2000
125
124     162
144
151    125    103
104
126
129
118
109
2001
117
118    144
139
137     110   92.4
98
115
130
118
111
2002
124
123    147
154
142    111    107
106
129
135
127
110
2003
116
126    153
145
157     117   88.2
98
122
139
126
112
2004
119
120    142
135
150     108    100
104
112
130
61 7
112
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.
Annual 1403 1308 1303 1420 1410 1408 1444 1358 1369 1466 1366 1466 1464 1346 1332 1375 1362 1359
1299 I 1343 1338 1358 1401 1432 1349 1320 1412 1443 1408 1318 1411 1360 1355 1437 1439 1425 1505 1419 1402 1518 1429 1515 1498
1393
9Arjo-Dedessa Hydropower & Irrigation Project
^eieorol
ogicalj^Hy dr o logical Feasibility Studies
June 2009
A8
Estimated Mean Monthly Rainfall at Arjo Dedessa Project Area
(in mm)
Year
Jan  Feb   March   April    May]  June | July [  Aug    Sept    Oct[    Nov   Dec
Annual
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1978
1979
1980
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
156    0       96 3     21 7     172     172     140     220     220    111 5    151   0 12       1320
0    57 6    0 75     36 4    93 8     169     186     207     192    90 97   21 7   14 5       1070
37 7  35 9    53 7      140     121     144     159     212     165    56 39   7 39      0          1132
29 2   30     51 3     21 2     149     154     249      162     256    107 2   4 44   4 04       1217
11 3  0 32     207      30 8     142     193     180     135     262    188 2   32.3   14 1       1210
156  11 1      15      89 1      53      166     186     157     170    49 48     69    9 24       990.6
0    9 97    5 66     29 4     236      155     186     233     143    58 82   12 2   5 77       1075
38 7  7 98    31 8     5 14     287     205     242      168     212    72 78    462   16 7       1292
23 5  55.1    21.1      60 4     116     124     189     159     141    131 3    115   12.5       1045 23 7  16.2    90 3     55.8     154     154     192     215     273    88.66     36    5.37       1303
3     3 5     66 5      103     122     154     206     206     181    1226    0 58   12.5       1181
15.6  8 89      17       256     97 5     202     235      159     154    64 94   31 2   12.5       1024
156   178    57 3      118      164     100     136     176     246    49 87    287      0         1110
15 6   823    27 6     35.6     149     213     296     270      177    113 9   57.2     0         1362
15.6    0      31 6     69.8     234     249     443      198     230    8.716   26 8   5 77       1514
2 79    0       12 3      105     257     341     242     212     315     48.2     32 5    377       1607
0     392    46 9     56 4    37.5 ’   315     274     244     191    103 8   35 9   0 46       1345
2 89  17.2     886      79 9     123     282     488      328     183    1164    42 3   34 3       1785
14 1  42 7    74 3     15 3     335     325     177     297     343    259.9    15 4   3 87       1903
25 6  26 7    76 3      108     245     284     316     332     297    189 3   61 3   47 1       2008
8 77  37 8    50 4     83 3     906     438     228     319     241    73.89    334   3 12       1607
26 4  7.91    68.2     74 4     139     106     364     309     222    98.59     35      13        1464
24 8  32 8     106      105     222     225     267     291     250    104 7   53.6   15 8       1697
1 04   31      69.5      100     213     313     217      347     166    1494    2.03      0          1609
11 2  1 15    20 1      53 9     127     227     255     228     279    8 467    137      0          1223
0    22 9    75.5      109     222      195     229     310     279    86 46    11.2   22.3       1563
45 5  19 1     162      71.7     338     225     245      197     215    74 57    446   7 56       1645
396  0.97    566      139     293     314     205     291     234     213     40 4   2.54       1830
13     84     81 1      15.2     162     280     264     272     239    235 9   67.2   1 04       1638 31.7 2.91      15       92.3     393     427     257     239     309    197 3   8 89   42 1       2014
0       0      3.69      105     195     345     222     260     274      255     344   7.39       1702 0      32     65 5     60 3     327     346     298     292     312    206 3    19 9  24 1        1983
177  2.19    39 7     42 2     106     252     274      153     224    59 11    1 84  53 1       1226
584  53.5     117      121     58.9     358     232     300     155    51 59   11.5   1 86       1466
4 96   2.1     61 2     51.5     150     353     326     243     249    193 9   40 7   13 1        1689
Average
CV
Skew
Max
Min
75.3  18 4    53 6     69.5    180 8  243.0  245.9  238.3  228.6   115.5   31 4   12 7
0.85  0 96    0 68     0.55    0.49    0.37    0.31    0.25    0.24   0.591    0.9    1 13
0 62  0 78    0 74      0.1     0.62    0.38    1 44    0.07    0 17   0.635   2.31   1 48
45.5 57 6 161.7 139 9 392.7 437 6 487 6 346.6 343 1 259 9 150 7 53 1
00 0.0 0.8 5.1 37 5 100.3 136.2 135.3 141.3 8 5 06 00
—
1452.9
0.209
0.26
2014.5
990.6
Water Works Design & Supervision Enterprise
10
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.r
" ArjoDe'dessa Hydropower& Irrigation Project "
L L-
Meteorological & Hydrological Feasibility Studies
A9 Estimated Mean Half Monthly Rainfal al the Project Area (in mm)
June 2009
1.1
1.2    2.1    2.2    3.1    3.2    4.1    4.2    5.1     5.2     6.1    6.2     7.1     7.2    8.1     82    9.1    9.2     10     10 11.1 11          12.1    12
Total
Year
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1978
1979
1980
1983
1984 1985 1986 1987 1988 1989 1990 1991 1992
7 8    779     0       0    224   73 9     0    21 7  75 2  96 97   112  60 8   68 4   71 7   110   110   132   87 7   110   1 92 75 7     75    0 12     0 0       0     57 3  0 29    0    0 75  1.27 35 1    31     62 8   81 4  87 4    82 5   104   121  86 1   76 5   115   76 8  14 2    0    21 7   103   4 25
26 1  11 6  14 7  21.2  37 6 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 3 92        0       0
2.1   27 1   7 27  22 7  236   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
11    0 27  032     0    4 62    16   30 4  0 46  42.1  99 86  622   131    63 4    116   61 4  73 9  125   137   104   84 3 26 8 5 48      3 17    11
78    7 79  4 31  684     0      15    365   52 6  25 5  27 53  78 1  87 9    872     99    89 7  67 2  94 2  75 8  25 7  23 8 61 3 7 69        0     9 24
0       0     997     0       0    5 66  25 4  4 04   140  96 39  962   58 9   91 6   94 2   108   125   78 8  64 1  57 1   1 73 12 2      0       0     577
30 6  8 12  226   5 72  19 9   119  029   4 85   188  98 87   102   103   1195   123   101   67 5  102   110   44 4  28 3     0     4 62  4 62   12.1
0     23 5  477    74    0 69  20.4  5 14   552  67 5  48 89  808   43 3   75 2    113   62 1  96 9  92 5  48 8  86 9  44 4 11 5      0     606   6 46
23 7     0     103   5 89  57 9   324  32.2   235  78 8  74 81    72   81 8   102 9 89 1   51 9  163   198  74 2  40 1  48 6 32 3 98         2 89  248
3       0      35      0     56 4 10 1   124   90 9  49 1  73 14  87 8   66     797    127   71 2  134   84 8  96 5    72    50 5 0 58      0     6 06  6 46 78    7 79  8 89    0     0 46  16 5  11 6   14    57 2  40 35  99 6  102     145    90 3  85 5   736  97 2    57   40 4  24 5 156 156       6 06  6 46
78     779  889   8 89  277   29 6  28 6  89 8  64 2  100 3  41 6  58 7   65 6   70 6    99    76 5   138   109  26 3  23 5 11 9 169         0       0
78    7 79  7 98  0 25  187   8 89  20 7  14 9  54 3  94 53  89 7   123   168 1  128   134   136   89 9  86 7  78 7  35 2 44 2     13      0       0
7 8   7 79     0       0    4 73   269  17 3  52 5  53 9  180 3   138   111   232 6  211   51 8  147   66 7   163  7 16  1 56 152 11 6      4 96  081
03     249     0       0      15   10 8  57 5  47 8   121   136 6   168   173    94 1    148   82 6   130   160   155   37 2    11   24 9 7 58    36 9  0 81
0       0     2 75  36 4  152   31 7  28 1  28 3  1 24  36 22   195   119   147 6  127    110   134   114  77 1    85    18 9 28 2 7 68     0 23  0 23 0     2 89     0     172   48 1  40 5  6 93  72 9   192   104 3   158   124   224 5   263   215   112   116   66 8  81 4    35 31 2       11    34 3     0
94    4 73  2 66    40     57     173  098   14 3   145   190 2   172   154    75 1    102   175   122   179   164   155   104 15 4      0       0     3 87 186   7 03    26     07    43 9  32 5  65 3  42 7   148  96 74   182   102   208 4   107   186   145   194   104   91 5  97 8 29 5 31 8      198   27 3
0     8 77   13.1  24 7  21 6  28 8     0      833  60 3   30 3    253   185   123 1   105   108   211   98 1   143   53 4  20 4 32 4 1 03      3 12     0 14 2  12 2     0     7 91  37 6  30 6  1.27  73 2  89 9  49 04   133  93 1   195 1   169   179   131   144   77 9  97 3  1 27 10 5 24 5     12.7  0 29
0     24 8   17 7  152   25 2  80 6  3 34  102    152  70 12  82.1   143   161 3   106   159   131   102   148   81 4  23 3 29 24 6         1 15  14 7
1320
1070
1132
1217
1210
990.6 1075
1292
1045
1303
1181
1024
1110
1362
1514
1607
1345 1785 1903 2008 1607 1464 1697
Water Works Design & Supervision Enterprise
11
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
Annexure A9 contd. (in mm)
June 2009
1.1 1.2 2.1 2.2 3.1 3.2 4.1           4.2     5.1     5.2     6 1     6.2     7.1     7.2    8.1    8.2      9 1      9.2      10       10    11.1 11 12.1 12
Year
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
0 1 04 6 64 24 4 3 06 66 A 63 6    36 6   93 7  119 7  86 2    227    79 7    137   149   197     104    61 9    83 9    65 5   1 39 0 65     0       0
11 2 0         0 1 15 1 3 18 8 29 2        24 7     55    71 64   105    122   109 7   145   116   111     166     112    7 24    1 23  9 52 4 16     0      0
0      0    5 6 17 3 0 75 5 0 52          109    116   105 9  63 4    131   1239    105   177   133     125     154    40 8    45 7        5 95 5 3 1 96 20 4
9 2 36 3 4 09 15 78 8 82 9 26 6        45 1    146   192 4   159   66 1   84 7    160   100   96 6   93 2    122    58 2    164      8 48 36 1 0 69 6 87
2 1 37 5 0 0 97 28 1 28 5 72 8 66 6 71 7 221 5 152 161 78 6 127 165 126 148 85 8 119 94 2 25 3 15 1 0 06 2 48
11 2 1 84 1 94 6 46 24 6 56 5 8 89    6 33   69 7  92 18   142    138   141 7   122   131   142     118     121    92 9    143   62 3 4 92     0    1 04
28 3 3 35 0 2 91          0     15    19   73 3    227    166    209    217    992     158   141   98 2    146     162     148    48 9           8 89 0 26 6 15 5
0      0      0      0 2 31 1 39 28 4      76 2   76 9   1186   215     129    994     123   149   112     139     135     168    87 1   25 2 9 15 2 89 4 5
0      0 23 7 8 3 1 24 64 3 36 9         23 3   96 3  230 8   122    224   118.2   180   126   165     187     124    96 4     110      7 27 12 7 14 4 9 75
12 5 5 19 0 2 19 8 37 31 3 37 7         4 49    198   86 64   139    114   156 4   118  51.7   102    95 4    129    35 3    23 8           0 1 84 3 29 49 8
2 3 84 17 8 35 7 39 2 77.6 68 8       52 3   20 3  38 67   165    193   127 5   105   133   166    85 9   69 1    23 7    27 9        6 64 4 91 1 4 0 46
0 2 4 76 1.4 0 7 10.6 506 9 7        41 8   28 5  121 9   148    204   256.7  69 6  91 1   152     132     117     168    25 7      11 3 29 4 9 24 3 88
Average CV
Skew
Max
Min
7 5 7 8 8 8 9 6 20 6 33 0 22 7 46 7 78 2 102 6 119 8 123.2 122 0 123 9 117 121 8 120 0 108 5 73 7 41 8 19 7 11 8 6 1 66 1 18 1 28 1 48 1 21 1 03 0 74 0 95 0 72 0 68 0 511 0 46 041 0 425 031 0 36 0 29 03 0 32 0 58 0 86 0 94 1 26 1 57 1 5 1.27 1.82 2 47 1 27 0 95 0 83 0 95 0 63 0 94 0 84 041 0 57 1 039 1 64 0 36 0 47 0 72 0 1 0 63 1 11 1 42 2 61 2 15 2 9 30 6 37 5 57 3 40 0 78 8 82 9 72 8 133 1 226 7 230 8 252 9 226 8 256 7 263 1 216 210 9 198 4 164 1 168 3 143 0 75 7 75 0 36 9 49 8
00000000000800
0.5     1.2    27 5    133    43.3    55.2   69 6  51 7  67 2    66 7    48 8     7 2      1 2                  00 00 00 00
Total
1609
1223
1563
1645
1830
1638
2014
1702
1983
1226
1466
1689
1452.9
0.209
0.26
2014.5
990.6
Water Works Design & Supervision Enterprise
12
in Association with Intercontinental Consultants and Technocrats Pvt. LtdArjo-Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
Annex B: Results obtained from the Hydrological Analysis
B 7 Regional monthly coefficient of variations (CV) of monthly flows
June 2009
Station
Year
Jan
Feb Mar April\May\june July' Aug Sep Oct Nov Dec
114001
114014
114005
114004
114003
91008
91012
35
20
23
22
21
38
35
0 51 0 57 066 0 68 0.62 0 45 0 35 0.3 0 33 0 67 0 62 0 59
0 47 046 0 48 0 56 069 0.53 0.27 0 33 0.28 0 56 0 81 0 53
0.28 041 0.33 0 43 06 047 02 0 16 0.25 044 0 3 0 34
033       042     0 45    0.55  0 56   043    0.57    0 38      0 43    0 64   0 35    0 33
0 51      0 83     0.57    0 71   066   0 58   0 35     025      0.36    0.56   046     0 55
0 68       1.3       0.7      06    0.61    0 46   0.29    0 32      0.28     064     1       0 86
0.61 0 49 0.76 049 0.57 042 0 3 0 29 0 32 0 52 08 0 59
B2 Regional monthly coefficient of skewness of monthly flows
Station
Year
Jan
Feb
Mar \April\May
June
July
Aug
Sep
Oct\ Nov
Dec
114001
114014
114005
91008
91012
35
20
23
38
35
0 63 0.74 1 07 0 94 1 63 0.89 0 13 0 04 0.25 0 99 1.37 0 96
1 35 0.31 0 47 0 81 0 85 1 03 -0 5 0 93 0 89 0 67 2 6 1 98
0.33 1 48 0.59 -0 1 2.18 1 54 0 07 0 45 0 81 0 42 0 52 1 09
2.73 0.29 3.26 0.77 1 14 0 81 0 17 1 14 1 13 0.77 3 14 2.85
3 17 4 94 1.22 1 5 2.34 1 15 0 43 0.94 0.05 1 6 2.86 2.79
B3 Regional monthly coefficient of correlations (R) for monthly flows
Station
Year
Jan      Feb     Mar April May[June\ July\ Aug               Sep Oct       Nov    Dec
[
114001
114014
114005
114004
114003
91008
91012
35
20
23
22
21
38
35
-0.1       083     0 89 0 59 0.3          0 78 0 45       0 53      0 44    0 45   0 74    0 78
0 36 0 5 0 77 0.56 0.62 0.81 0.46 0 54 0.28 -0 04 065 0 78
084 0.5 0.35 0.3 0 64 0.38 0.48 0 68 0 8 0 83 0.25 0 16
08 052 0.21 0.52 0 6 0 58 0.58 0 69 0 61 0 77 0 37 0 14
084       0.3      0.18    0.52 045 073 0 68             0 66      0 58    0 82   0 56     0.1
027      0 33     0 37 0 27 0.53 0.59 0 54              0 55      0 46    0 45   0 77    0 62
0 12     0 83     0 72    0 48 0 41 0 72 0 53           0 41      0 48    0 31   0 44    0 65
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84 Standardized probability weighted moments arrived for Synthetic flow generation
June 2009
I
T ....
Station              Name of Station
1 114001 Dedessa near Arjo
Upper Dedessa near
4    91008 Gilgei Ghibe
Location        Area
Record                  PWMs
Deg N. 1 Deg E. (km2)   uengtft.N   I
m102
2 114014 Dembi
8 02 36 28
1806
15
0 420504
0 262951
3 114005 Dabana near Abasma
8 41 36 25 9981 29 0 40739 0 243171
7 45 37 11 2966 37 0 400025 0 240847
9 02 36 03
2881
18
0 414042
0 253945
5    91012 Gojeb near Shebe
Angar Gutin near
6 114007 Neqemte
7 114004 Wama near Neqemte
8 114003 Siffa near Neqemte
9 115008 Aleltu at Nejo
10 101001 SoratMetu
7 25 36 23      3494        34
1975        20
8 53 36 47 844 21
8 52 35 45 951 20
9 30 35.3 155 7
8 19 35 36 1622 17
11 91013 Ghibe-Limu near Limu 8 35 37 13 663 10
12 91001 Great Ghibe near Abetti 8 14 37 15 15460 19
L
-------------
0 408619
0421145 0 419805 0 416527
0 400261
0 401323
0 425296
0 424754
L
Weightea Average
255     0.411964
0 248091
0 2540331
0 254029
0 251324
0 247582
0 244658
0 261749
0 260656
O.25O375
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Meteorological & Hydrological Feasibility Studies 05 Mean Monthly Total (Suspended and Bed) Sediment Load
June 2009
3
at Arjo Dedessa Dam Site (in 1000 m )
[Year
Jan    Feb    March     April    May   June    July   Aug    Sep    Oct     Nov    Dec    Annual
----------------- ---------------
I 1961
2 11    1 75      1.27       5 73    3 11    33 4     315     523     476     372    32 3
15 3      1781
1962
1963     1 3    0 47      0 39        1 6     113     40 8     129    403     264    50 4    16 5    14 3      932.5
2 56   0 94     0 81       1 07    3.18     224      114    216     319     189    6 92    241       878 9
1964    1 78   1 32     0 71       1 07    2 34    23 6     262     370     322     387     197    3 74
1397
1965 2.37 0 72 034 1 91 0 79 14 3 182 263 135 227 40 1 127 880.6
1966 3 54 3 13 2 54 3 86 2 88 22 4 190 277 338 102 40 8 9 14 995.4
1967 0 64 0 57 0 57 0 49 3 18 224 140 356 333 352 71 4 20 1 1300
1968 5 73 2 22 0 52 0.22 2.26 2.27 123 265 299 102 104 2 97 815.6
1969 2 07 1 92 3 22 1 42 371 46.1 224 427 205 102 5 13 1 78 1024
1970
1971
1972
1973
1974
1979
1 09 0 75 04 0.23 1 72 33 8 216 246 205 102 16 1 2 85 826.7
1 25 0 36 0 18 0.22 2.25 25.5 178 315 228 154 36 9 6 64 948.3
2 17 0 88 0 45 1.2 244 8 09 171 342 146 199 8 2 18 704.9
0 7 02 005 008 7 04 26 9 123 246 425 105 11 8 3.05 949.6
1 22 0 35 028 0 13 5.51 29 119 360 205 102 8 23 1 94 833.7
1 91 1 29 0 65 0.59 1 79 943 88 9 179 115 28 6 5 63 1.64
0 39 0.3 0 15 3.41 17.2 82 8 211 365 352 54 6 6 55 5 39
.434.5
1980
1098
1982
1983
1984
269 0 96 0.83 045 1 74 267 140 223 138 157 15.5 5 58 711.7
1 61 1 03 1 09 061 2 18 12.3 97 7 300 296 339 29 6 8.32 1089
1985
1986
1 33 0.35 02
0.2 0.06 0 02
0 14 0 82 16 7 138 127 87.3 9 39 15 5 5 24 402.1
02 2 87 14 5 65 216 188 28 2 4 31 1 71 520.8
0 38   0 15      0 33       0 26    0.23    8.21     68 3     78      151    21 9    15 5
524        349
1987
0.23   0 07      022       0 38     1.23    22 4     91 7    301     132    53 1    13.3   3.28
618.6
1988
1989 2 38 063 0 48 1 08 0 76 84 30 4 80 1 284 102 6 96 8 52 525.4
1990 2 24 0 95 1 08 2 82 1.53 12 9 44 246 205 102 15 5 5 24 639.8
1 44   0 78      0 52        0.1      1 24    32 4     94 8    246     205     102    17.3   1 31      703.4
1992
1993
1994
1995
1996
2001
2002
2003
0 64 062 0.26 0.5 245 13.3 49 1 179 99 4 172 13 8 3.72 534.7
1 56 084 0.64 2 37 663 38 5 107 308 119 57 7 15.5 2.94 660.6
1 36 0 48 0 31 0 32 268 22 89.2 335 194 12 5 3 37 1.24 662.4
0 48 023 0.29 045 1 31 4 63 224 987 78 2 12.5 2.75 5 24 227
1 78 087 0.71 093 107 51.2 145 189 109 102 15 5 4.9 631.5
4 72 2 83 3 15 2 55 9.1 57 5 150 261 250 129 21 1 7 29 899.3
6 01 2 66 2.37 3 01 1 78 152 69 5 105 103 20 1 7 82 4 61 341.1
244 1.28 2.43 3.88 1 89 8 37 123 123 205 102 15 5 524
2 16 1 43 09 0 84 3 08 19.2 87 1 119 122 90.2 107 5 24
594.5
2004
461.9
Water Works Design & Supervision Enterprise
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Meteorological & Hydrological Feasibility Studies
86           Eleveation-Area-Capacity Relationships of Arjo Dedessa Reservoir
June 2009
Elevetion
(m as!)
Area
(km2)
Volume
(Mm3)
Elevetion
(m asl)
Area
(*" )
Volume
2
1320             0 54               0.0
1321             0 99               0.8
1322             2 39               2.5
1323             3 78               55
1324             5.11              100
1325 6 64 15 9
1326 8 03 23 2
1327 9 46 31 9
1328 10 87 42.1
1329 12 67 539
1330            14 40             67 4
1331            15 89             82 5
1332            17.74             994
1333            19 46            118 0
1334            23 59            139 5
1335            26.66            1646
1336 29 05 192.5
1337 31 73 222.9
1338 34 24 255 8
1339 36 62 291.3
1340 39 45 329 3
1341            41 97            370 0
1342            44 25            413 1
1343            47 05            458 8
1356            87.85           1341 2
1357            90 75           1430.5
1358            94 18           1522 9
1359            97.23            16186
1360 100 54 1717 5
1361 103 64 18196
1362 106 39 1924 6
1363 109 00 2032.3
1364 111 91 2142 8
1365            11505           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 13545 3258.4
1374 138.08 3395.2
1375 142.38 35354
1376 145.27 3679 2
1377 148 00 38258
1378 150.75 3975.2
1379 153.73 4127 5
1344            49 95            507 3            1380           156 02          4282 3
1345 53 11 558 8
1346 56 31 6135
1347 59 15 671 2
1348 61 56 738 8
1349 6397 808 7
1350 67 88 874 7
1381 159 09 4439 9
1382 162.13 4600.5
1383 166 96 4765 0
1384 173 01 49350
1385 178 58 5110 8
1386 183.38 5291 8
1351            70 62            943 9            1387           188 10          5477 5
1352            74 35           10164           1388           193 28          5668 2
1353            77 88           1092 5           1389           197 36           58636
1354            81 28          1172 1           1390           201 96          6063.2
1355            84.51           1255.0
Water Works Design & Supervision Enterprise
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16Arjo Dedessa Hydropower & irrigation rrujcui Meteorological & Hydrological Feasibility Studies
B7
June 2009
Year and
Starting
Storage Inflow Storage 1
Irrigation
requirement
Month        Mcum     Mcum     Mcum        Mcum
1961-62 SFP 2586 900 3486 12 1961 62 Ocl 2586 661 3247 14
1961-62 Nov        2586       292         2878                  3
1961 62 Dec        2586       101         2687                16
1961 62 Jan         2529         35         2564                29
1961-62 Feb         2387         19         2406                35
1961 62 Mar 2223 19 2242 26 1961-62 Apr 2068 5 2073 5 1961-62 May 1920 21 1941 2 1961-62 Jun 1791 157 1948 32 1961 62 jul 1768 398 2166 9 1961-62 Aug 2009 561 2570 10
Storage 2 Mcum
3474
Reservoir
Zone
surpls 
17 13
17 13
17 13
17 13
Mean
1962 63 Sep
1962-63 Oct 2586 512 3098 14
1962-63 Nov         2586         65         2651                  3
1962 63 Dec         2506         32         2538                16
1962 63 Jan         2374         23         2397                29
1962-63 Feb         2220         12         2232                35
1962 63 Mar 2049 12 2061 26
1962-63 Apr 1887 31 1918 5
1962-63 May 1754 112 1866 2
1962 63 Jun 1705 235 1940 32
1962-63 Jul 1749 430 2179 9
2253 25
2412       900         3312                12
Storage 3 Mcum ..
3332 3091 2733 2529 2387 2223 2068 1920 1791 1768 2009 2412
Mean Level m
1376 1376 1376 1376 1374 1374 1374 1374 1374 1374 1374 1374
Fnergy
GWhr
3233 surpls 
2875
2671
2535
2371
2216
2068
1939
1916
2157
2560
surpls 
syrplus
Surplus Mcum
746 505 147 -57 199
-363 -518 -666 -795 -818
577 -174
End Storage Mcum
2586 2586 2586
2529
2387
2223
2068
1920
1791
1768
2009
2412
1962-63 Aug         2022       826         2848 Mean             2154 167
10
3300 surplus 3084
2648 2522 2368 2197 2035 1913 1864 1908 2170 2838
2
2
2
2
2
2
2
2
1
1
2
2
2
2
3
3
3
2
1
Power release
Mcum 142 142 142 142 148 148 148 148 148 148 148 148
146
142 142 142 148 148 148 148 159 159 159 148 142
148 75
3158
2942
2506
2374
2220
2049
1887
1754
1705
1749
2022
2696
1376
1376
1376
1374
1374
1374
1374
1370
1370
1370
1374
1376
Power MW
23 79
23 79
23 79
23 79
23 96
23 96
23 96
23 96
23 96
23 96
23 96
23 96
23.90
23 79
23 79
23 79
23 96
23 96
23 96
23 96
23 93
23 93
23 93
23 96
23 79
17 25
17 25
17 25
17 25
17 25
17 25
17.25
17.25
206.52
17 13
17 13
17 13
17 25
17 25
17 25
17 25
17 23 17 23 1723 17 25 17 13
Note 1
23 90        206 47
572
356
80
212
366
537
699
832
881
837
564
110
2586
2586
2506
2374
2220
2049
1887
1754
1705
1749
2022
2586
The Releases in any monlh is aimed at Target Power of 24 MW
Head m
59 59 59 59 57 57 57 57 57 57 57
57
57.i667
59 59 59 57 57 57 57 53 53 53 57 59
56 67
efee        S
i^. < K J ®-_ _'
n 3ny mon,t1 ,or powe’IS based on the
The Reservoir is divided into 6 zones
............... ■
is e storage between 1356 and 1362 mamsl and 7
is storage between 1372 and 1376 mamsl, Zone 4 is the storage between 1
c
™,wu"
mamsl
362 aa| nd 1368
_
operating pool of 1353 mamsl and 1356 mamsl Th 1
?One 'S 1he S,orage between m
mamsl.
' minimum
------- is gioss storageArjo-Dedessa Hydropower & Irrigation Project ---------------------- —-                  —- __________ ________ ________ Meteorological & Hydrological Feasibility Studies
_________ June 2009
Annexure B 7 contd
Year and
Starting
Storage Inflow
Month          Mcum     Mcum 1963-64 Sep          2586        623 1963-64 Oct           2586        224 1963-64 Nov          2586        112 1963-64 Dec          2586          97 1963-64 Jan          2525            8 1963-64 Feb          2356         24
1963-64 Mar          2197          18
1963-64 Apr          2041          24
1963-64 May          1912          42
1963-64 Jun           1793        167
1 963-64 Jul           1769        670
1963-64 Aug          2282        784
Mean                2268.25
1964-65 Sep 2586 705 1964-65 Oct 2586 621 1964-65 Nov 2586 307 1964 65 Dec 2586 42 1964-65 Jan 2470 33 1964-65 Feb 2326 16 1964-65 Mar 2159 11 1964-65 apr 1996 35 1964-65 May 1867 21 1964-65 Jun 1727 122
Storage 1
Mcum         Mcum       2 Mcum       Zone 3209                12        3197
1
2810                14        2796
1
2698                  3        2695
1
2683                16        2667
1
2533                29        2504
2
2380                35        2345               2
2215                26        2189               2
2065                  5        2060               2
1954                  2        1952               3
1960                32        1928               3
2439                  9        2430               2 3066                10        3056               1
Irrigation
requirement Storage Reservoir
Storage
3291                 12        3279               1      147 33
3207                14        3193
2893
2628
2503
2342
3 2890 16 2612 29 2474
1
1
1
2
2170                 26        2144                2
35        2307                2
2031 5 2026
1888 2 1886
1964-65 Jul
1964-65 Aug          2034        634 Mean               2215.083
1658        533
1849
2191
32 9
2668                 10        2658               1
1817
2182
Q3
3
u
3
2
Power i elease
Mcum 142 142 142 142 148 148 148 148 159 1  1 4 589 142 142
142 142 142 148 148 148 159 159 159 148 142
148 25
Storage 3 Mcum
3055 2654 2553 2525 2356 2197 2041 1912 1793 1769 2282 2914 3137 3051 "2748
2470 2326 2159 1996 1867 1727 1658 2034 2516
Mean Level m
1376 1376 1376 1376 1374 1374 1374 1374 1370 1370 1374 1376 1376 1376 1376 1376 1374 1374 1374 1370 1370 1370 1374 1376
I lead      Power m         MW
59 23 79352
59 23 79352
59 23 79352
59 23 79352
57 23 95824
57 23 95824
57 23 95824
57  23  95824
S3 23 93268 53 2393268
57 23 95824 59 23 79352
57.17 23.88535
59 23 79352
59 23 79352
59 23 79352
59 23 79352
57 23 95824
57 23 95824
57 23 95824
53 23 93268
53 23 93268
53 23 93268
57 23 95824
59 23 79352 56 83 23 88432
Energy GWhr
17 13133 17 13133 1713133
17 13133
17 24993
17 24993
17 24993
17 24993
17 23153
17 23153
17 24993
17 13133
206.3694
17 13133
17 13133
17 13133
17 13133
17 24993
17 24993
17 24993
17 23153
17 23153
17 23153
17 24993
17 13133 206 351
Surplus Mcum
469 68
-33 -61
-230 -389 -545 -674 -793 -817 -304
328 551 465 162
-116 -260 -427 -590 -719 -859 -928 -552
-70
M      E   cu   nd  m 2586
2586
2586
2525
2356
2197
2041
1912
1793
1769
2282
2586 2586 2586 2586
2470
2326
2159
1996
1867
1727
1658
2034
2516
Wafor Wnobx
o n.Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Year and
Month
Starting
Storage
Mcum
Inflow
Mcum
Stoiage 1
Mcum
Irrigation requirement   Storage
2 Mcum
Mcum
Reservoir
Zone
Power
release
Mcum
Storage 3
Mcum
Mean
Level m
Head
m
Power
MW
Energy
GWhr
Surplus
Mcum
End
Storage
Mcum
2926
12
59
23 79352
17 13133
3160
14
59
23 79352
17 13133
2781
3
2778
1965-66 Sep          2516        410                                                2914                1          142          2772         1376                                                                  186         2586
1965-66 Oct           2586        574                                                3146               1           142          3004         1376                                                                  418         2586
1965-66 Nov          2586        195                                                                                    142          2636         1376                                                                   50         2586
1
59
23 79352
17 13133
2681
16
2665
1
59
23 79352
17 13133
2565
29
2536
2
57
23 95824
17 24993
2428
35
2393
2
57
23 95824
17 24993
2285
26
2259
2
57
23 95824
17 24993
2165
5
2160
2
148
2012
1374
57
23 95824
17 24993
2059
2
2057
2
148
1909
1374
57
23 95824
17 24993
2043
32
2011
3
159
1852
1370
53
2393268
17 23153
2400
9
2391
2
148
2243
1374
2898
10
2888
1965-67 Dec 2586 95 142 2523 1376
1965-66 Jan           2523          42                                                                                     148          2388         1374
1965-66 Feb          2388          40                                                                                    148          2245         1374
1965-66 Mar          2245          40                                                                                    148         2111         1374
1965-66 Apr           2111          54
1965-66 May          2012          47
1965-66 jun            1909        134
1965-66 Jul            1852        548
1965-66 Aug          2243        655
Mean               2296 417                                                                                              146 42
1
142
2746
1376
-63         2523
-198         2388
-341          2245
-475         2111
-574         2012
-677         1909
-734         1853
57   23 95824     17 24993          -343         2243
59   23 79352     17 13133           160         2586
57 50    23 88532    206 3878
Starting
Year and       Storage     Inflow Month          Mcum      Mcum
Irrigation
Power
End
Storage 1
requirement
Mcum
Mcum
Storage Reservoir release Storage 3 Mean Head Power Energy Surplus Storage
2 Mcum Zone Mcum Mcum Level m m MW GWhr Mcum Mcum
3312
12
2635
14
2504
3
2365
16
2349
2
2208
29
2179
2
2036
35
2001
3
1858
26
1832
3
1385
5
1380
4
1223
2
1221
4
1127
32
1095
4
1372
9
1363
4
1966-67 Sep 2586 726 3300 1 142 3158 1376 59 23 79352 17 13133 572 2586
1966-67 Oct           2586          49                                                2621                1           142          2479         1376           59    23 79352    17 13133         -107         2479
1966 67 Nov          2479          25                                                2501                2          148          2353         1374           57    23 95824    17 24993          -233         2353
1966-67 Dec          2353          12                                                                                     148         2201         1374           57    23 95824    17 24993          -385        2201
1966-67 Jan          2201            7                                                                                     148         2031         1374           57   23 95824    17 24993          -555        2031
1966-67 Feb          2031            5                                                                                     159          1842         1370           53   23 93268    17 23153         -744         1842
1966-67 Mar          1842          16                                                                                     159          1673         1370           53   23 93268    17 23153          -913         1370
1966-676 Apr         1370          15                                                                                     176         1204         1365           48   23 99232    17 27447        -1382         1204
1966-67 May          1204          19                                                                                     176          1045         1365           48   23 99232     17 27447       -1541         1045
1966-67 jun            1045          82                                                                                     176            919         1365           48   23 99232     17 27447       -1667           919
1966 67 Jul              919        453                                                                                     176          1187         1365           48    23 99232    17 27447       -1399         1187
1966-67 Aug          1187        764                                                                                     159         1782         1370           53    23 93268    17 23153         -804         1782
1951
10
1941
3
Mean               1816 917
159 08  «•
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53 33    23 93576     206 8049
19Ado Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Year and
Month
Starting
Storage
Mcum
Inflow
Mcum
Storage 1
Mcum
Irrigation
requirement
Mcum
Storage
2 Mcum
Reservoir
Zone
Power
release
Mcum
Storage 3
Mcum
Mean
Level m
Head
m
Power
MW
Energy
GWhr
Surplus
Mcum
End
Storage
Mcum
1967 68 Oct           2342        685          3027                 14       3013               1          142         2871         1376           59    23 79352    17 13133           285         2586
1967-68 Sep          1782        720         2502                 12
2490               2          148          2342         1374          57    23 95824    17 24993          -244         2342
1967-68 Nov 2586 401 2987 3 2984 1 142 2842 1376 59 23 79352 17 13133 256 2596
1967-68 Dec          2586        120         2706                 16       2690               1          142          2548         1376           59    23 79352    17 13133            -38         2548
1967-68 Jan           2548          19         2567                 29        2538               2          148          2390         1374           57    23 95824    17 24993         -196         2390
1967-68 Feb
2390
13
2403
35
2368
2
148
2220
1374
57
23 95824
17 24993
■366
2220
1967-68 Mar
2220
13
2233
26
2207
2
148
2059
1374
57
23 95824
17 24993
-527
2059
1967-68 Apr
2059
17
2076
5
2071
2
148
1923
1374
57
23 95824
17 24993
-663
1923
1967-68 May
1923
38
1961
2
1959
3
159
1800
1370
53
23 93268
17 23153
-786
1800
1967-68 jun
1800
117
1917
32
1885
3
159
1726
1370
53
23 93268
17 23153
-860
1726
1967-68 Jul
1726
305
2031
9
2022
3
159
1863
1370
53
23 93268
17 23153
-723
1863
1967-68 Aug
1863
469
2332
10
2322
2
148
2174
1374
57
23 95824
17 24993
-412
2174
Mean
2152 083
149.25
56.5
23.91067
206.5882
-2586
1968-69 Sep
2174
400
2574
12
2562
2
148
2414
1374
57
23 95824
17 24993
-172
2414
1968-69 Oct
2414
222
2636
14
2622
1
142
2480
1376
59
23 79352
17.13133
-106
2480
1968-69 Nov
2480
78
2558
3
2555
2
148
2407
1374
57
23 95824
17 24993
-179
2407
1968-69 Dec
2407
34
2441
16
2425
2
148
2277
1374
57
23 95824
17 24993
-309
2277
1968-69 Jan
2277
30
2307
29
2278
2
148
2130
1374
57
23 95824
17 24993
-456
2130
1968-69 Feb
2130
30
2160
35
2125
2
148
1977
1374
57
23 95824
17 24993
-609
1977
1968-69 Mar
1977
46
2023
26
1997
3
159
1838
1370
53
23 93268
17 23153
-748
1838
1968-69 Apr
1838
29
1867
5
1862
3
159
1703
1370
53
23 93268
17 23153
-883
1703
1968-69 May
1703
56
1759
2
1757
3
159
1598
1370
53
23 93268
17 23153
-988
1598
1968 69jun
1598
254
1852
32
1820
3
159
1661
1370
53
23 93268
17 23153
-925
1661
1968-69 Jul
1661
607
2268
9
2259
2
148
2111
1374
57
23 95824
17 24993
-475
2111
1968-69 Aug
2111
857
2968
10
2958
1
142
2816
1376
59
23 79352
1713133
230
Mean
2064 167
2586
150 67
56 00
23 92227
206 6884
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd
20"^“Deawsa Hyaro*p  wer&^rrigauon Project
Meteorological & Hydrological Fe^hmtv studies
O
June 2009
Starting
Year and Month
1969-70  Sep 1969 70- Oct 1969-70- Nov 1969 70- Dec 1969 70- Jan 1969-70-Feb 1969-70- Mar 1969-70- Apr 1969-70- May 1969-70- Jun 1969-70- Jul 1969-70- Aug
Mean
1970-71 Sep 1970-71 Oct 1970-71 Nov 1970-71 Dec 1970-71 Jan 1970 71 Feb 1970-71 Mar 1970-71 Apr 1970-71 May 1970-71 Jun 1970-71 Jul 1970-71 Aug Mean
Storage Mcum
2586 2586 2586 2495 2357 2200 2022 1846 1706 1579 1597 2022
2131 833
2506 2586 2551 2516 2387 2232 2059 1893 1738 1618 1602 1971
2138 25
Inflow Mcum
565 174
54 26 20
5 9
24 34
209 593 636 673 121 110
35 22 10
7 9
41 175 526 709
Storage 1 Mcum
3151 2760 2640 2521 2377 2205 2031 1870 1740 1788 2190 2658 3179 2707 2661 2551 2409 2242 2066 1902 1779 1793 2128 2680
Irrigation requirement
Mcum 12 14
3 16 29 35 26
5 2 32
9 10
Storage Reservoir
2 Mcum 3139 2746 2637 2505 2348 2170 2005 1865 1738 1756 2181 2648
Zone
1
1
1
2
2
2
3
3
3
3
3
1
Power release
Mcum 142 142
Storage 3 Mcum
2997 2604
142  M            2495
148 148 148 159 159 159 159 159 142
150.58
142 142 142 148 148 148 147 159 159 159 148 142
148 67
2357
2200
2022
1846
1706
1579
1597
2022
2506
12 3167
14 2693
3
2658
16        2535
29
35
26
5 2 32
9
10
2380
2207
2040
1897
1777
1761
2119
2670
1
1
1
2
2
2
2
3
3
3
2
1
3025
2551
2516
2387
2232
2059
1893
1738
1618
1602
1971
2528
Mean Level m
1376 1376 1376 1374 1374 1374 1370 1370 1370 1370 1370 1376
1373.00
1376 1376 1376 1374 1374 1374 1374 1370 1370 1370 1374 1376
1373 67
Head m
59 59 59 57 57 57 53 53 53 53 53 59
56.00 59 59 59 57 57 57 57 53 53 53 57 59
56 67
Power MW
23 79352
23 79352
23 79352
23 95824
23 95824
23 95824
23 93268
23 93268
23 93268
23 93268
23 93268
23 79352
23.89
23 79352
23 79352
23 79352
23 95824
23 95824
23 95824
23 79636
23 93268
23 93268
23 93268
23 95824
23 79352 23 88
Energy GWhr
17 13133
17 13133
17 13133
17 24993
17 24993
17 24993
17 23153
17.23153
17 23153
17 23153
17 23153
17 13133 20643
17 13133
17 13133
17 13133
17 24993
17 24993
17 24993
17 13338
17 23153
17 23153
17 23153
17 24993
17 13133 206 35
Surplus Mcum
411 18 91
-229 -386 -564 -740 -880
-1007 -989 -564
-80 439
•35 -70
-199 354
-527 -693 -848
968 -984 -615
58
End Storage
Mcum 2586 2586 2495
2357
2200
2022
1846
1706
1579
1597
2022
2506
2586
2551
2516
2387
2232
2059
1893
1738
1618
1602
1971
2586
21
Consonants and Technocrats Pvt Ltd■
Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Year and
Month
1971-72 Sep
Starting Storage
Mcum
2586
Inflow   I
Irrigation
Storage 1 requirement Storage Reservoir
Powei
release Storage 3 Mean
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum       Mcum
Level m
Head
m
Power
MW
Energy
GWhr
Surplus
Mcum
End
Storage
Mcum
568
3154
12
3142
1
1971-72 Oct
2586
450
3036
14
3022
1
1971-72 Nov
2586
185
2771
3
2768
1
142
2626
1376
1971-72 Dec
2586
60
2646
16
2630
1
142
2488
1376
1971-72 Jan
2488
31
2519
29
2490
2
148
2342
1374
1971-72 Feb
2342
19
2361
35
2326
2
148
2178
1374
1971-72 Mar
2178
13
2191
26
2165
2
148
2017
1374
1971-72 Apr
2017
26
2043
5
2038
2
1971-72 May
1890
43
1933
2
1931
3
1971-72 Jun
1772
86
1858
32
1826
3
1971-72 Jul
1667
513
2180
9
2171
2
1971-72 Aug
2023
746
2769
10
2759
1
Mean
222675
142         3000        1376          59   23 79352    17 13133         414        2586
142         2880        1376          59   23 79352    17 13133         294        2586
59   23 79352    17 13133           40        2586
59   23 79352    17 13133          -98        2488
57   23 95824    17 24993        -244        2342
57   23 95824    17 24993        -408        2178
57    2395824    17 24993        -569        2017
148         1890        1374          57   23 95824    17 24993        -696        1890
159        1772        1370          53   23 93268   17 23153        -814        1772
159         1667        1370          53   23 93268   17 23153        -919        1667
148         2023        1374          57   23 95824   17 24993        -563        2023
142         2617        1376          59   23 79352   17 13133           31        2586
147 33                     1374 17     57 17         23 89       206 37
Year and
Starting
Storage
Inflow
Irrigation
Power
Storage 1 requirement    Storage Reservoir
release Stqjage 3
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum 1
Mean
Level m
Head
m
Power
End
Energy Surplus Storage
Month
Mcum
1972-73 Sep
2586
430
3016
12
3004
1
142
2862
1376
5
1972-73 Oct
2586
125
2711
14
2697
1
142
2555
1376
5
1972-73 Novp
2555
71
2626
3
2623
1
142
2481
1376
MW          GWhr       Mcum      Mcum 9   23 79352    17 13133         276        2586
9   23 79352    17 13133          -31        2555
59   23 79352   17 13133        -105        2481
1972-73 Dec
2481
30
2511
16
2495
2
148
2347
1374
57   23 95824    17 24993
-239
2347
1972-73 Jan
2347
15
2362
29
2333
2
148
2185
1374
57   23 95824   17 24993
-401
2185
1972-73 Feb
2185
7
2192
35
2157
2
148
2009
1374
57   23 95824    17 24993
-577
2009
1972-73 Mar
2009
3
2012
26
1986
3
159
1827
1370
53   23 93268   17 23153
-759
1827
1972-73 Apr
1827
5
1832
5
1827
3
159
1668
1370
53   23 93268   17 23153
-918
1668
1972-73 May
1668
83
1751
2
1749
3
159
1590
1370
53   23 93268    17 23153
-996
1590
1972-73 Jun
1590
187
1777
32
1745
3
159
1586
1370
53
23 93268   17 23153
-1000
1586
1972-73 Jul
1586
156
1742
9
1733
3
159
1574
1370
53
23 93268    17 23153
-1012
1574
1972-73 Aug
1574
633
2207
10
2197
2
148
2049
1374
57
23 95824    17 24993
-537
2049
Mean
2082 833
151 08
1372 83
55 83
23 91        206 55
Water Works Design & Supervision Enterprise
22
In Association witb Intercontinental Consultants and Technocrats Pvt LtdStarting
Irrigation
Powei
Year and Month
1973 74 Sep 1973-74 Oct 1973-74 Nov 1973-74 Dec 1973-74 Jan 1973-74 Feb 1973-74 Mar 1973-74 Apr 1973-74 May 1973 74 Jun 1973-74 Jul 1973-74 Aug Mean
Year and
Storage  Inflow Storage 1    requirement  Storage Reservoir     release   Storage 3 Mean           Head      Power
Mcum    Mcum Mcum Mcum
2 Mcum Zone            Mcum Mcum I evel m m
MW
Energy Surplus GWhr Mcum
End
Storage
Mcum
2049
839
2888
12
2876
1
142
2734
1376
59    23 794    17.13133
148
2586
2586
355
2941
14
2927
1
142
2785
1376
59    23 794    17 13133
199
2586
2586
90
2676
3
2673
1
142
2531
1376
59    23 794     17 13133
-55
2531
2531
37
2568
16
2552
2
148
2404
1374
57    23 958    17 24993
-182
2404
2404
22
2426
29
2397
2
148
2249
1374
57    23 958    17 24993
-337
2249
2249
10
2259
35
2224
2
148
2076
1374
57    23 958    17 24993
-510
2076
2076
10
2086
26
2060
2
148
1912
1374
57    23 958    17 24993
-674
1912
1912
7
1919
5
1914
3
159
1755
1370
53     23 933    17 23153
-831
1755
1755
71
1826
2
1824
3
159
1665
1370
53     23 933    17 23153
-921
1665
190
1855
32
1823
3
1665
159
1664
1370
53     23 933    17 23153
1664
410
2074
9
2065
2
922
1664
148
1917
1374
1917
771
2688
57     23 958    17 24993
10
2678
-669
1
142
1917
2536
1376
2116 167
59    23 794    17 13133
148 75
-50
2536
56 667       23 90        206 47
Month 1974-75 Sep 1974-75 Oct 1974 75 Nov 1974-75 Dec 1974-75 Jan 1974-75Feb 1974-75 Mar 1974-75 Apr 1974-75 May 1974 75 Jun 1974-75 Jul 1974-75 Aug Mean
Starting Storage
Mcum 2536 2578 2506 2427 2291 2132 1961 1789 1642 1516 1439 1568
2032 083
Irrigation
Inflow Storage 1 requirement Storage Reservoir Mcum     Mcum         Mcum       2 Mcum       Zone
196          2732                12        2720                1
84          2662                14        2648                1
72          2578                  3        2575                2
28          2455                16        2439                2
18          2309                29        2280                2
12          2144                35        2109                2
13          1974                26        1948                3
17          1806                  5        1801                3
35         1677                   2         1675               3
114          1630                32        1598               3
297          1736                   9        1727                3
456          2024                 10        2014                3
Power
release Storage 3 Mean
Mcum Mcum Level m
142          2578         1376 142          2506         1376
148          2427         1374
148         2291         1374
148          2132         1374
148          1961         1374
159          1789         1370
159          1642         1370
159          1516         1370
159          1439         1370
159          1568         1370
Head m
59
Power MW
23 794
End
Energy Surplus Storage
GWhr Mcum Mcum
17 13133
8         2578
59    23 794
57    23 958
57    23 958
57    23 958
17 13133            -80         2506
17 24993
-159
2427
17 24993
-295
2291
17 24993
-454
159 152 50
1855         1370
«<
57    23 958    17 24993          -625         1961
53    23 933    17 23153          -797          1789
53     23 933     17 23153         -944          1642
53     23 933     17 23153        -1070          1516
53     23 933
53     23 933
53     23 933
55 33       23 92     206 6516
23
2132
17 23153
-1147
1439
17 23153
-1018
17 23153
1568
-731
1855
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Il
1
ArJoJtedessa  Hydropower 4 IrrigatlonVroJect
Meteorological & Hydrological Feasibility Studies
June 2009
Starling
Storage
Irrigation
Power
End
Year and
Inflow
Storage 1
requirement
Storage
Reservoir
release
Storage 3
Mean
Head
Power
Energy
Surplus
Storage
Month
Mcum
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum
Level m
m
MW
GWhr
Mcum
Mcum
1975-76 Sep
1855
389
2244
12
2232
2
148
2084
1374
57
23 958
17 24993
-502
2084
1975-76 Oct
2084
216
2300
14
2286
2
148
2138
1374
57
23 958
17 24993
-448
2138
1975-76 Nov
2138
75
2213
3
2210
3
148
2062
1374
57
23 958
17 24993
524
2062
1975-76 Dec
2062
33
2095
16
2079
2
148
1931
1374
57
23 958
17 24993
-655
1931
1975-76 Jan
1931
23
1954
29
1925
3
159
1766
1370
53
23 933
17 23153
-820
1766
1975-76 Feb
1766
15
1781
35
1746
3
159
1587
1370
53
23 933
17 23153
-999
1587
1975-76 Mai
1587
16
1603
26
1577
3
159
1418
1370
53
23 933
17 23153
-1168
1418
1975-76 Apr
1418
21
1439
5
1434
4
176
1258
1365
48
23 992
17 27447
-1328
1258
1975-76 May
1258
44
1302
2
1300
4
176
1124
1365
48
23 992
17 27447
-1462
1124
1975-76Jun
1124
142
1266
32
1234
4
176
1058
1365
48
23 992
17 27447
-1528
1058
1975-76 Jul
1058
371
1429
9
1420
4
176
1244
1365
48
23 992
17 27447
-1342
1244
1975 76 Aug
1244
570
1814
10
1804
3
159
1645
1370
53
23 933
17 23153
-941
1872
Mean
1627 083
161 00
52 67
23 96
207 0237
Starling
Irrigation
Power
End
Year and
Month
Storage Inflow Storage 1 requirement Storage Reservoir release Storage 3 Mean Head Power Energy Surplus Storage
Mcum Mcum Mcum Mcum 2 Mcum Zone Mcum Mcum Level m m MW GWhr Mcum Mcum
1976-77 Sep
1872
486
2358
12
2346
2
148
2198
1374
57    23 958
17 24993
-388
2198
1976-770ctp
2198
270
2468
14
2454
3
159
2295
1370
53    23 933
17 23153
291
2295
1976-77 Nov
2295
94
2389
3
2386
2
148
2238
1374
57    23 958
17 24993
-348
2238
1976-77 Dec
2238
42
2280
16
2264
2
148
2116
1374
57    23 958
17 24993
1976-77 Jan
2116
26
2142
-470
2116
29
2113
2
148
1965
1374
57    23 958
1976-77 Feb
1965
17 24993
17
1982
-621
35
1965
1947
3
159
1788
1370
53    23 933
1976-77 Mar
1788
18
17 23153
1806
-798
26
1780
1788
3
159
1621
1976-77 Apr
1370
1621
23
1644
53    23 933
17 23153
5
-965
1621
1639
3
159
1480
1976-77 May
1480
1370
50
53    23 933
1530
17 23153
2
-1106
1528
1480
3
159
1976-77 Jun
1369
1369
1370
163
1532
53    23 933
17 23153
32
-1217
1500
4
1369
1976-77 Jul
176
1324
1324
424
1365
1748
48    23 992
17 27447
9
1739
-1262
1324
1976-77 Aug
3
1580
159
651
1580
1370
2231
10
53    23 933
17 23153
2221
2
-1006
148
2073
1580
Mean
1820 5
1374
57    23 958
17 24993
155 83
-513
2073
54 25      23 95
206 9133
Water Works Design & Supervision Enterprise
In Association with intercontinental Consultants and Technocrats Pvt. Ltd
24Arjo\)edessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
Year and
Starling
Storage
h ngation Inflow Storage 1 requirement
June 2009
Power
Storage Reservoir release Storage 3 Mean Head IPower
End
Energy Surplus Storage
Month         Mcum     Mcum     Mcum         Mcum      2 Mcum      Zone       Mcum      Mcum Level m           m         MW         GWhr       Mcum      Mcum
1977-78 Sep 2073 556 2629 1977-78 Oct 2475 309 2784 1977-78 Nov 2586 102 2688 1977-78 Dec 2543 48 2591 1977-78 Jan 2427 21 2448
1977-78 Feb 2271 14 2285
1977-78 Mar 2102 15 2117
1977-78 Apr          1943
1977-78May          1798
1977-78 Jun         1677        1
1977-78 Jul           1614        3
1977 78 Aug         1780       5
Mean                2107 42
Starting
12        2617 14        2770
3        2685 16        2575 29        2419 35       2250 26       2091
5       1957 2        1836
32        1773
9        1939
10       2283
1
142
2475
1376
59    23 794
17 13133
-111
2475
1
142
2628
1376
59    23 794
17 13133
42
2586
1
142
2543
1376
59   23 794
17 13133
-43
2543
2
148
2427
1374
57    23 958
17 24993
-159
2427
2
148
2271
ii
1374
57    23 958
17 24993
-315
2271
2
148
2102
1374
57    23 958
17 24993
-484
2102
2
148
1943
1374
57    23 958
17 24993
-643
1943
19
1962
3
159
1798
1370
53    23 933
17 23153
-788
1798
40
1838
3
159
1677
1370
53    23 933
17 23153
-909
1677
28
1805
3
159
1614
1370
53    23 933
17 23153
-972
1614
34
1948
3
159
1780
1370
53    23 933
17 23153
-806
1780
13
2293
2
148
2135
1374
57     23958
17 24993
-451
2135
150 17
56 17     23 91
206 5698
Irrigation
Power
End
37
2572
12
2560
2
148
2412
1374
57    23 958
17 24993
-174
2412
43
2655
14
2641
1
142
2499
1376
59   23 794
17 13133
-87
2499
85
2584
3
2581
2
148
2433
1374
57    23 958
17 24993
-153
2433
38
2471
16
2455
2
148
2307
1374
57    23 958
17 24993
-279
2307
10
2317
29
2288
2
148
2140
1374
57    23 958
Year and      Storage    Inflow   Storage 1 requirement   Storage Reservoir i   release Storage 3      Mean I     Head Power          Energy Surplus Storage
Month         Mcum      Mcum      Mcum         Mcum       2 Mcum      Zone       Mcum       Mcum Level m            m         MW        GWhr       Mcum I    Mcum
1978-79 Sep 2135 4 19A8-790ct 2412 2
1978-79 Nov         2499
1978-79 Dec          2433
1978-79Jan           2307
1978-79 Feb 1978-79 Mar
1978-79 Apr
17 24993
-446
2140
2140
8
2148
35
2113
2
148
1965
1374
57    23 958   17 24993
621
1965
1965
7
1972
26
1946
3
159
1787
1370
53    23 933   17 23153
-799
1787
1787
17
1804
5
1799
3
159
1640
1370
53    23 933   17.23153
-946
1640
1978-79 May
1640
35
1675
2
1673
3
159
1514
1370
53    23 933   17 23153
-1072
1514
1978-79 Jun
1514
94
1608
32
1576
3
159
1417
1370
53    23 933   17 23153
-1169
1417
1978-79 Jul
1417
341
1758
9
1749
3
159
1590
1370
53    23 933    17 23153
-996
1590
1978-79 Aug
1590
498
2088
10
2078
2
148
1930
1374
57    23 958   17 24993
656
Mean
1986 583
1930
152 083
55 50      23 93   206 7886
Water Works Design & Supervision Enterprise
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In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Meteorological & Hydrological Feasibility Studies
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Year and
Starting
Storage Inflow
Storage 1
Irrigation requirement  Storage
Energy      Surplus
End
Storage
Month          Mcum      Mcum 1979-80 Sep          1930        395 1979-80 Oct           2165        217 1979-80 Nov          2220          77 1979-80 Dec          2146          34 1979-80 Jan           2016          18
1979-80 Feb 1846 1979-80 Mar 1664 1979-80 Apr 1492 1979 80 May 1365 1979-80 Jun 1222
0         1127
1979 80 Aug          1236
Mean                1702417
Mcum Mcum 2 Mcum 2325 12 2313 2382 14 2368 2297 3 2294 2180 16 2164 2034 29 2005
1823 1651 1504 1398 1303 1412 1680
148
Power
Reservoir   release   Storage 3 Zone        Mcum       Mcum
2          148         2165 2          148         2220 2          148         2146
2
3 3 3
4 4 4
2016
1374
159
1846
1370
12
1858
35
159
1664
1370
13
1677
26
159
1492
1370
GWhr        Mcum       Mcum
17 24993         -421         2165
17 24993         -366         2222
17 24993         -440         2146
17 24993         -570         2016
17 23153         -740         1846
17 23153         -922         1664
17 23153       -1094         1492
17
1509
5
176
1328
1365
17 27447
-1258
1365
35
1400
2
176
1222
1365
17 27447
-1364
1222
113
1335
32
176
1127
1365
17 27447
-1459
1127
294
1421
9
4
176         1236
17 27447
-1350
1236
454
1690
10
Starting
Storage Inflow Storage 1
Irrigation
requirement
3          159 161
Power
1521
Mean       Head      Power Level m        m          MW
1374          57    23 958
1374          57    23 958
1374          57    23 958
57    23 958
53    23 933
53    23 933
53    23 933
48    23 992
48    23 992
48    23 992
1365          48    23 992
1370          53    23 933
17 23153
-1065
1521
52 67      23 96   207 0237
Year and
Head     Power      Energy     Surplus
End
Stoiage
Month          Mcum      Mcum      Mcum         Mcum 1980 81 Sep          1521        745          2266                 12 1980-81 Oct           2106        236          2342                 14
1980-81 Nov          2180          63          2243                   3
1980-81 Dec          2092          53          2145                 16
1980-81 Jan           1981
1980-81 Feb 1841 1980-81 Mar 1675 1980-81 Apr 1520 1980-81 May 1382 1980-81 Jun 1245 1980-81 Jul 1076 1980-81 Aug 1304
Storage   Reservoir     release :Storage 3     Mean 2 Mcum       Zone        Mcum       Mcum     Level m
2254                2          148          2106         1374
2328               2          148       ” 2180         1374
2240
2
2129
2
48
2029
29
2000
3
148 2092 1374
148 1981 1374
159 1841 1370
28
1869
35
1834
3
159
1675
1370
30
1705
26
1679
3
159
1520
1370
26
1546
5
1541
3
159
1382
1370
41
1423
2
1421
4
176
1245
1365
39
1284
32
1252
4
176
1076
1365
413
1489
9
176
1304
1365
633
1937
10
Mean
1660 25
1480               4
1927                3          159 159 58
1768         1370
m          MW         GWhr        Mcum       Mcum 57    23 958    17.24993         -480         2106
57    23 958    17 24993         -406         2180
57    23 958    17 24993         -494         2092
57    23 958    17 24993         -605         1981
53    23 933    17 23153         -745         1841
53    23.933    17 23153         -911         1675
53    23 933    17 23153       -1066         1520
53    23 933    17 23153       -1204         1382
48    23 992    17 27447       -1341         1245
48    23 992    17 27447       -1510         1076
48    23 992    17 27447       -1282         1304
53    23 933    17 23153         -818         1768
53 08      23 96    206 9808
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*
Year and
Starting
Storage Inflow
Irrigation
Storage 1 requirement Storage Reservoir
June 2009
Power
release Storage 3 Mean Head Power Energy Surplus
End
Storage
Month          Mcum      Mcum      Mcum         Mcum       2 Mcum       Zone       Mcum       Mcum     level m         m          MW         GWhr       Mcum      Mcum
1981-82 Sep           1768       5                                                                                                        2149        1374          57    23 958   17 24993        -437        2149
41
2309
12
2297
2
148
15
2464
14
2450
2
148
57    23 958   17 24993
-284
2302
20
2322
3
2319
2
148
57    23 958   17 24993
-415
2171
7
2178
2178
2
148
57    23 958   17 24993
-556
2030
36
2066
159
1981-82 Oct           2149        3                                                                                                       2302        1374
1981-82 Nov           2302                                                                                                                 2171        1374
1981-82 Dec           2171                                                                                                                 2030        1374
1981 82 Jan           2030                                                                                                                 1889        1374
1981-82Feb 1889 1714 1370
29
2037
2
148
57    23 958   17 24993
-697
1889
19
1908
35
1873
3
53    23 933   17 23153
-872
1714
20
1981-82 Mai            1714                                                                                                                 1549        1370          53    23 933   17 23153      -1037        1549
1981-82 Apr            1549                                                                                                                 1399        1370          53    23 933   17 23153      -1187        1399
1981-82 May          1399                                                                                                                  1256        1365          48    23 992   17 27447       -1330        1256
1981-82 Jun           1256                                                                                                                  1228        1365          48    23 992   17 27447      -1358        1228
1981-82 Jul            1228                                                                                                                  1512        1370          53    23 933   17 23153      -1074        1512
1981-82 Aug           1512                                                                                                                  1925        1374          57    23 958   17 24993        -661         1925
1734
26
1708
3
159
14
1563
5
1558
3
159
35
1434
2
1432
4
176
180
1436
32
1404
4
176
452
1680
9
1671
3
159
571
2083
10
2073
2
148
Mean
156 33
54 17      23 96   206 9747
Year and Month
1982-83 Sep 1982-83 Oct 1982-83 Nov 1982-83 Dec 1982-83 Jan 1982-83 Feb 1982-83 Mar 1982-83 Apr 1982-83 May 1982-83 Jun 1982 83 Jul 1982-83 Aug Mean
1747 25
Starling Storage
Mcum 1925 2180 2480 2436 2326 2175 2012 1850 1703 1582 1503 1696
1989
Irrigation
Powei
Head IPower
End
Energy Surplus Storage
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
m          MW        GWhr       Mcum      Mcum
415
2340
12
2328
2
148
57   23 958
17 24993
-406
2180
456
2636
14
2622
1
142
59   23 794
17 13133
-106
2480
107
2587
3
2584
2
148
57   23 958
17 24993
-150
2436
54
2490
16
2474
2
148
57   23 958
17 24993
-260
2325
26
2352
29
2323
2
148
57   23 958
17 24993
-411
2175
20
2195
35
2160
2
148
57   23 958
17 24993
-574
2012
23
2035
26
2009
3
159
53   23 933
17 23153
-736
1850
17
1867
5
1862
3
159
53    23 933
17 23153
-883
1703
40
1743
2
1741
3
159
53    23 933
17 23153
-1004
1582
112
1694
32
1662
3
159
Inflow Storage 1 requirement Storage Reservoir release Storage 3                  Mean
Mcum I L evel m 2180 1374 2480 1376
2436        1374
2326        1374
2175        1374
2012        1374
1850        1370
1703        1370
1582        1370
1503        1370
1696        1370
2225        1374
53    23 933
17 23153
-1083
1503
361
1864
9
1855
3
159
53    23 933
17 23153
-890
1696
687
2383
10
2373
2
148
57    23 958
17 24993
-361
2225
152 08
56      23 93
206 7886
_____________________________________ _  _             __ ____ I* _
__________________________
Waler Works Design & Supervision Enterprise
In Association with intercontinental Consultants and Technocrats Pvt. Ltd
27Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Year and
Starling
Storage Inflow
Irrigation
Storage 1
requirement
Storage   Reservoir
Power
release Storage 3 Mean Head Power Energy Surplus
End
Storage
Month          Mcum      Mcum
Mcum
Mcum
2 Mcum       Zone        Mcum       Mcum     Level m       m          MW         GWhr       Mcum      Mcum
2893
1983 84 Sep          2225        668                                               2881                1         142         2739        1376          59    23 794    17 13133          153        2586
12
1983-84 Oct           2586        618                                                3190               1          142         3048        1376          59    23 794    17 13133
1983-84 Nov          2586        283                                               2866               1          142         2724         1376          59    23 794    17 13133
1983 84 Dec          2586          69                                               2639               1          142         2497         1376          59    23 794    17 13133
1983-84 Jan           2497          23                                               2491                2          148         2343        1374          57    23 958   17 24993
1983-84 Feb           2343          11                                                2319               2          148         2171         1374          57    23 958   17.24993
3204
14
462
2586
2869
3
138
2586
2655
16
-89
2497
2520
29
-243
2343
2354
35
-415
2171
2179
26
1374
-581
2005
2012
5
159
1848
1370
-738
1848
1870
2
1983-84 Mar          2171            8                                                2153               2
1983-84 Apr           2005            7                                               2007               3
1983-84 May          1848          22                                                1868               3
1983 84 Jun           1709        135                                                1812               3
148
2005
159
1709
1370
-877
1709
1844
32
159
1653
1370
1983-84 Jul 1653 449 2102
1983 84 Aug 1945 401 2346
9 2093 2
10 2336 2
148
1945
1374
148
2188
1374
Mean                   2179 5                                                                                              148 75
57    23 958    17 24993
53    23 933   17 23153
53    23 933   17 23153
53    23 933   17.23153        -933        1653
57    23 958    17 24993        -641         1945
57    23 958   17 24993        -398        2188
56 67      23 90   206 4696
End
Year and
Starting
Storage Inflow
Irrigation
Power
Storage 1
requirement
Storage   Reservoir
i elease I Storage 3    Mean      Head     Power      Energy     Sur
Month          Mcum      Mcum
Mcum
Mcum
2 Mcum       Zone        Mcum       Mcum     Level m       m          MW         GWhr       Mc
plus
um
Storage
Mcum
1984-85 sep 1945 544 2477 2 148 2329 1374 57 23 958 17 24993
1984-85 Oct            2329        300                                                2615               1          142         2473        1376          59    23 794    17 13133
1984-85 Nov           2473        106                                                2576               2          148         2428        1374          57    23 958   17 24993
1984-85 Dec           2428          46                                                2458               2          148          2310        1374          57    23 958   17 24993
1984-85 Jan           2310          25                                                2306               2          148         2158        1374          57    23 958    17 24993
1984-85 Feb           2158          17                                                                                     148         1992        1374          57    23 958   17 24993
2489
12
-257
2329
2629
14
-113
2473
2579
3
-158
2428
2474
16
-276
2310
2335
29
-428
2158
2175
35
2140
2
-594
1992
1984-85 Mar           1992          18
1984 85 Apr            1825          23
1984-85 May          1684          48
1984-85 Jun           1571         156
1984-85 Jul             1536        405
1984-85 Aug           1773        626
Mean 2002 152 08
2010
26
1984
3
159
1825
1370
1370
1732
2
159
1571
1370
53    23 933   17 23153
53    23 933   17 23153
53    23 933    17 23153
53    23 933    17 23153
53    23 933   17 23153
57    23 958    17 24993
55 50 23 93 206 7886
-761
1825
1848
5
1843
3
159
1684
-902
1684
1730
3
•1015
1571
1727
32
1695
3
159
1536
1370
-1050
1536
1941
9
1932
3
159
1773
1370
-813
1773
2399
10
2389
2
148
2241
1374
-345
2241
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt LtdArjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
Year and
Starting
Storage Inflow
Irrigation
Storage 1
requirement
Storage   Reservoir
Power
release Storage 3 Mean Head Power Energy Surplus
End
Storage
Month          Mcum      Mcum
Mcum
Mcum
2 Mcum      Zone       Mcum       Mcum     Level m       m          MW         GWhr        Mcum      Mcum
2786
12
1985-86 Sep          2241        545                                               2774                1         142         2632         1376          59    23 794    17 13133            46        2586
1985-86 Oct           2586        300                                               2872               1          142         2730        1376          59    23 794    17 13133          144        2586
1985-86 Nov          2586        106                                               2689               1          142         2547         1376          59   23 794    17 13133
1985 86 Dec          2547          46                                               2577               2          148         2429        1374          57    23 958    17 24993
1985-86 Jan           2429          25                                               2425               2          148         2277        1374          57    23 958    17 24993
1985-86Feb           2277          17                                               2259               2          148     •• 2111         1374          57    23 958    17 24993
2886
14
2692
3
-39
2547
2593
16
-157
2329
2454
29
-309
2277
2294
35
-475
2111
2129
26
-631
1955
1978
5
-772
1814
1863
2
-884
1702
1859
32
1985-86 Mar          2111          18                                               2103               2
1985-86 Apr           1955          23                                               1973               3
1985-86 May         1814          49                                               1861               3
1985-86 Jun           1702        157                                               1827               3
148
1955
1374
159
1814
1370
159
1702
1370
159
1668
1370
1985-86 Jul 1668 406 2074
1985-86 Aug 1917 626 2543
9 2065 2
10 2533 2
148
1917
1374
148
2385
1374
Mean
2152 75
Starting
Storage Inflow
Irrigation
14925
Power
57    23 958    17 24993
53    23 933    17 23153
53    23 933    17 23153
53    23 933    17 23153        -918        1668
57    23 958    17 24993        -669        1917
57    23 958    17.24993        -201         2385
56 50     23 91    206 5882
End
Year and
Storage 1
requirement
Storage   Reservoir
release Storage 3       Mean      Head     Power      Energy I    Surplus I
Storage
Month          Mcum      Mcum
Mcum
Mcum
2 Mcum       Zone        Mcum       Mcum     I evel m        m          MW         GWhr       Mcum      Mcum
3041
12
1986-87 Sep          2385        656                                                3029                1         142          2887         1376          59    23 794    17 13133         301        2586
2947
14
1376
2714
3
1986-87 Oct           2586        361                                                2933               1
1986-87NOV           2586        128                                                2711               1
1986-87 Dec           2569          56                                                2609               1
1986-87 Jan           2467          30
1986 87 Feb           2320          20
142
2791
142
2569
1376
2625
16
142
2467
1376
2497
29
2468
2
148
2320
1374
2340
35
2305
2
148
2157
1374
59 23 794 17 13133 205 2586
59    23 794    17 13133          -17        2569
59    23 794    17 13133        -119        2467
57    23 958    17 24993        -266        2320
57    23 958    17 24993         -429        2157
2178
26
2152
2
2032
5
2027
3
1926
2
1924
3
1954
32
2251
9
1986-87 Mar           2157          21                                                                                     148         2004         1374          57    23 958    17 24993        -582        2004
1986-87 Apr           2004          28                                                                                     159          1868         1370          53    23 933    17 23153         -718        1868
1986-87May           1868          58                                                                                     159         1765         1370          53    23 933    17 23153        -821         1765
1986-87 Jun           1765        189
1986-87 Jul            1763        488
1986-87 Aug          2094        754          2848                 10        2838               1           142          2696         1376          59    23 794    17 13133          110        2586
1922
3
159
1763
1370
53    23 933    17 23153
-823
1763
2242
2
148
2094
1374
57    23 958    17 24993
-492
2094
Mean               2213 667                                                                                               148 25
56 83      23 88     206 351
Water Works Design & Supervision Enterprise
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In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Starting
Iri igation
Power
End
Year and       Storage     Inflow Storage 1 requirement !      Storage Reservoir     release Storage 3        Mean       Head      Power       Energy      Surplus    Storage
Month
Mcum
Mcum
Mcum
Mcum
1987-88 Sep
2586
624
3210
12
1987 88 Oct
2586
343
2929
14
2 Mcum       7one        Mcum       Mcum     I evel m        m          MW         GWhr        Mcum       Mcum 3198                1          142          3056         1376           59    23 794    17 13133           470         2586
2915               1           142          2773         1376           59    23 794    17 13133          187         2586
1987-88 Nov
2586
122
2708
3
2705               1
132
2573
1376
1987-88 Dec
2573
53
2626
16
2610
2
148
2462
1374
57
23 958
17 24993
1987-88 Jan
2462
29
2491
29
2462
2
148
2314
1374
57
23 958
17 24993
1987-88 Feb
2314
19
2333
35
2298
2
148
2150
1374
57
23 958
17 24993
1987 88 Mar
2150
20
2170
26
2144
2
148
1996
1374
57
23 958
17 24993
1987-88 Apt
1996
26
2022
5
2017
3
159
1858
1370
53
23 933
17 23153
1987 88 May
1858
56
1914
2
1912
3
159 k
1753
1370
53
23 933
17 23153
1987-88 Jun
1753
179
1932
32
1900
3
159
1741
1370
53
23 933
17 23153
1987-88 Jul
1741
464
2205
9
2196
2
148
2048
1374
57
23 958
17 24993
1987-88 Aug
2048
717
2765
10
2755
1
142
2613
1376
59    22 118      15 9249           -13         2573
-124         2462
-272         2314
-436         2150
-590         1996
-728         1858
-833         1753
845        1741
-538         2048
27         2586
End
59
23 794
17 13133
Mean 2221 083 147 92
Power
56 67
23 76
205 2632
Starting
Irrigation
Year and
Storage
Inflow
Storage 1
requirement
Month
Mcum
Mcum
Mcum
Mcum
1988 89 Sep
2586
767
3353
12
1988-89 Oct
2586
422
3008
14
1988-89 Nov
2586
150
2736
3
1988-89 Dec
2586
65
2651
16
2635
1
1988-89 Jan
2493
35
2528
29
2499
2
1988-89 Feb
2351
24
2375
35
2340
2
148
2192
1374
1988-89 Mar
2192
25
2217
26
2191
2
148
2043
1374
1988 89 Apr
2043
32
2075
5
2070
2
148
1922
1374
1988 89 May
1922
68
1990
2
1988
3
159
1829
1370
1988-89 Jun
1829
220
2049
32
2017
3
2420
2
Storage   Reservoir   release   Storage 3     Mean       Head     Power      Energy      Surplus    Storage 2 Mcum       Zone        Mcum       Mcum     Level m        m          MW         GWhr        Mcum       Mcum
3341               1           142          3199        1376           59    23 794    17 13133          613         2586
2994               1           142       ” 2852         1376           59    23 794    17 13133          266         2586
2733               1           142         2591         1376           59    23 794    17 13133              5         2586
142          2493        1376           59    23 794    17 13133           -93         2493
148         2351         1374           57    23 958    17 24993         -235        2351
57    23 958    17 24993         -394         2192
57    23 958    17 24993         -543         2043
57    23 958    17 24993         -664         1922
53    23 933    17 23153         -757         1829
53    23 933    17 23153         -728         1858
57    23 958    17 24993         -314         2272
159
1858
1370
1988-89 Jul            1858        571           2429                   9
148
2272
1374
3144
1
142
1988-89 Aug          2272        882          3154                 10
Mean 2275 333 147 33
3002
1376
Water Works Design & Supervision Enterprise
59    23 794    17 13133          416         2586 57 17      23 89   206 3694
30
in Association with Intercontinental Consultants and Technocrats Pvt Ltd.ArjoDedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
k
to
Year and
Month         Mcum      Mcum      Mcum 1989-90 Sep          2586        651          3237 1989 90 Oct           2586        315          2901 1989-90 Nov          2586          65          2651 1989-90 Dec          2506          70          2576 1989 90 Jan          2312          32         2344 1989 90 Feb          2167          19          2186 1989 90 Mar          2003          23          2026 1989-90 Apr          1841          44          1885 1989-90 May         1721          32          1753
1989-90 Jun          1592        114          1706
1989-90 Jul           1515        219          1734
1989 90 Aug          1566      1043          2609
Mean                2081 75
Starling
Storage Inflow Storage 1
Irrigation
requirement   Storage    Reservoir Mcum        2 Mcum       Zone
12         3225                1
14         2887                1
3         2648                1
16         2560                2
29         2315                2
35        2151                2
26         2000                3
5         1880                3
2        1751                3
32        1674                3
9        1725                3
10        2599                1
June 2009
Power
release   Storage 3     Mean       Head Mcum       Mcum      l.evel m        m
142          3083         1376           59
End
142          2745         1376           59    23 794     17  13133
142          2506         1376           59    23 794     17  13133
148          2412         1374           57    23 958     17  24993
148          2167         1374           57    23 958     17  24993
148          2003         1374           57    23.958     17  24993
Power
MW
23 794
Energy GWhr
17  13133
159         1841         1370           53
159         1721         1370           53    23 933     17  23153
159          1592         1370           53    23 933     17  23153
159          1515         1370           53    23 933     17  23153
159          1566         1370           53    23 933     17  23153
23 933     17  23153
142
150 58
2457         1376           59    23 794
56 00      23 89
1713133
206 4328
Surplus Mcum
497 159 -80
-174 -419 -583 -745 -865 -994
•1071 -1020
-129
Year and
Month
1990-91
1990 91
1990-91
1990 91
1990-91
Starling
Storage
Mcum
Sep
Oct
Nov
Dec
Jan
Inflow
Mcum
Storage 1
Mcum
Irrigation
requirement
Mcum
Reservoir
Power
release
1990-91 Feb 1990-91 Mar 1990 91 Apr 1990 91 May 1990-9Uun 1990-91 Jul 1990-91 Aug Mean
2457
2586
2586
2487
2346
2185 2014 1840 1695 1578 1501 1850
2093 75
3127
2867
2632
2510
2362
2197
2025
1859
1739
1692
2018
2814
12 14
3 16 29 35 26
5 2 32
9
10
Storage 2 Mcum
3115 2853 2629 2494 2333 2162 1999 1854 1737 1660 2009 2804
Mcum
Storage 3 Mcum
2973 2711 2487 2346 2185 2014 1840 1695 1578 1501 1850 2662
Mean Level m
1376 1376 1376 1374 1374 1374 1370 1370 1370 1370 1370 1376
Head m
59
Power
MW
23 794
59    23 794    17  13133
Energy GWhr
17 13133
59 23 794
57 23 958
57 23 958 17 24993
57 23 958 17 24993
17 13133
17 24993
56 00
53    23 933
53    23 933
53    23 933
53    23 933
53    23 933
59 23 794
23 89
17 23153
1 17 7 22 33115533
17 23153
17 23153
17 13133
206 4328
Surplus Mcum
387 125 -99
-240 -401 -572 -746 -891
-1008
■1085 -736
76
Storage Mcum
2586 2586
2506
2412
2167
2003
1841
1721
1592
1515
1566
2457
S  E to nr dage Mcum
2586 2586
2487
2346
2185
2014
1840
1695 1578 1501 1850
2586Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Starling
Irrigation
Power
End
Year and       Storage     Inflow   Storage 1  requirement   Storage  Reservoir   release   Storage 3    Mean      Head     Power      Energy     Surplus   Storage
Month          Mcum      Mcum 1991-92 Sep           2586        619 1991-92 Oct            2586        341 1991-92 Nov           2586        121 1991-92 Dec           2562          53 1991-92 Jan           2457          28
1991 92 Feb           2308          19
1991-92 Mar           2144          20
1991-92 Apr            1990          26
1991-92 May           1852          55
1991-92 Jun            1746        178
1991-92 Jul             1733        461
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum
I evel m
m
MW
GWhr
Mcum
Mcum
3205
12
3193
1
142
3051
1376
59
23 794
17 13133
465
2586
2927
14
2913
1
142
2771
1376
59
23 794
17 13133
185
2586
2707
3
2704
1
142
2562
1376
59
23 794
17 13133
-24
2562
2615
16
2599
1
142
2457
1376
59
23 794
17 13133
-129
2457
2485
29
2456
2
148
2308
1374
57
23 958
17 24993
-278
2308
2327
35
2292
2
148
2144
1374
57
23 958
17 24993
-442
2144
2164
26
2138
2
148
1990
1374
57
23 958
17 24993
-596
1990
2016
5
2011
3
159
1852
1370
53
23 933
17 23153
-734
1852
1907
2
1905
3
159
1746
1370
53
23 933
17.23153
-840
1746
1924
32
1892
3
159
1733
1370
53
23 933
17 23153
-853
1733
2194
9
2185
2
148
2037
1374
57
23 958
17 24993
-549
2037
1991-92 Aug Mean
711
2748
10
2738
1
142
2596
1376
59
23 794
17.13133
10
2586
Year and Month
1992-93 Sep 1992-93 Oct 1992-93 Nov 1992 93 Dec 1992-93 Jan 1992-93 Feb 1992-93 Mar 1992-93 Apr 1992-93 May 1992 93 Jun 1992-93 Jul 1992-93 Aug Mean
2037 2215 583
Starting Storage
Mcum 2586 2586 2586 2541 2419 2267 2102 1945 1821 1740 1776 2002
2197 583
Inflow Mcum
338 483 100
42 25 18 17 40 80
227 383 699
Storage 1
Irrigation
requirement Storage Reservoir
14825
Power
release I Storage 3 Mean
56 83      23 88     206 351
End
Head Power Energy Surplus Storage
Mcum
Mcum
2 Mcum
7one
Mcum
Mcum
Level m
m
MW
GWhr
Mcum
Mcum
2924
12
2912
1
142
2770
1376
59
23 794
17 13133
184
2586
3069
14
3055
1
142
2913
1376
59
23 794
17 13133
327
2586
2686
3
2683
1
142
2541
1376
59
23 794
17 13133
-45
2541
2583
16
2567
2
148
2419
1374
57
23 958
17 24993
-167
2419
2444
29
2415
2
148
2267
1374
57
23 958
17 24993
-319
2267
2285
35
2250
2
148
2102
1374
57
23 958
17 24993
-484
2102
2119
26
2093
2
148
1945
1374
57
23 958
17 24993
-641
1945
1985
5
1980
3
159
1821
1370
53
23 933
17 23153
-765
1821
1901
2
1899
3
159
1740
1370
53
23 933
17 23153
-846
1740
1967
32
1935
3
159
1776
1370
53
23 933
17 23153
-810
1776
2159
9
2150
2
148
2002
1374
57
23 958
17 24993
584
2002
2701
10
2691
1
142
2549
1376
59
23 794
17 13133
-37
2549
14875
56 67
23 90
206 4696Arjo ueaessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Starting
Irrigation
Power
Year and      Storage     Inflow   Storage 1 requirement I  Storage Reservoir release Storage 3           Mean Head Power
End
Energy Surplus Storage
Month          Mcum      Mcum      Mcum         Mcum       -2 Mcum      Zone        Mcum       Mcum Level m            m          MW         GWhr       Mcum Mcum
1993-94 Sep
2549
378
2927
12
2915
1
142
2773
1376
59
23 794
17 13133
187
2586
1993-94 Oct
2586
244
2830
14
2816
1
142
2674
1376
59
23 794
17 13133
88
2586
1993-94 Nov
2586
108
2694
3
2691
1
142
2549
1376
59
23 794
17 13133
-37
2549
1993-94 Dec
2549
36
2585
16
2569
2
148
2421
1374
57
23 958
17 24993
-165
2321
1993-94 Jan
2421
23
2444
29
2415
2
148
ei2267
1374
57
23 958
17 24993
-319
2267
1993-94 Feb
2267
12
2279
35
2244
2
148
2096
1374
57
23 958
17 24993
-490
2096
1993-94 Mar
2096
11
2107
26
2081
2
148
1933
1374
57
23 958
17 24993
-653
1933
1993-94 Apr
1933
11
1944
5
1939
3
159
1780
1370
53
23 933
17 23153
-806
1780
1993-94 May
1780
45
1825
2
1823
3
159
1664
1370
53
23 933
17 23153
-922
1664
1993-94 Jun
1664
160
1824
32
1792
3
159
1633
1370
53
23 933
17 23153
-953
1633
1993 94 Jul
1633
340
1973
9
1964
3
159
1805
1370
53
23 933
17 23153
-781
1805
1993-94 Aug
1805
736
2541
10
2531
2
148
2383
1374
57
23 958
17.24993
203
2383
Mean
2155 75
150 17
56 17
23909
206 5698
Starting
Irrigation
Power
End
Year and       Storage    Inflow   Storage 1   lequirement  Storage   Reservoir   release ! Storage 3    Mean      Head     Powei      Energy     Surplus   Storage Month          Mcum      Mcum      Mcum          Mcum       2 Mcum       Zone        Mcum       Mcum     Level m       m          MW         GWhr       Mcum      Mcum
1994-95 Sep 2383 552 2935 12 2923 1 142 2781 1376 59 23 794 17 13133 195 2586 1994-95 Oct 2586 304 2890 14 2876 1 142 2734 1376 59 23 794 17 13133 148 2586
1994-95 Nov          2586        108          2694
3        2691               1           142         2549        1376          59    23 794   17 13133          -37        2549
1994-95 Dec          2549          47           2596                 16        2580               2          148         2432        1374          57    23 958   17 24993        -154        2432
1994 95 Jan           2432          25          2457                 29        2428               2          148         2280        1374          57    23 958   17 24993        -306        2280
1994-95 Feb           2280          17          2297                 35        2262               2          148         2114        1374          57    23 958   17 24993        -472        2114
1994-95 Mar           2114          18          2132                 26        2106               2          148         1958        1374          57    23 958   17 24993        -628        1958
1994 95 Apr           1958          23          1981                   5        1976               3          159         1817        1370          53    23 933   17 23153        -769        1817
1994 95 May          1817          49          1866                   2        1864                3          159         1705        1370          53    23 933   17 23153        -881        1705
1994-95 Jun
1705
159
1864
32
1832
3
159
1673
1370
53
23 933i 17 23153
-913
1673
1994-95 Jul
1673
411
2084
9
2075
2
148
1927
1374
57
23 956I 17 24993
-659
1927
1994-95 Aug
1927
635
2562
10
2552
2
148
2404
1374
57
23 958 17 24993
-182
2404
Mean
2167 5
149 25
56 5C)
23 9^I 206 5882
Water Works Design & Supervision Enterprise
33
In Association witb Intercontinental Consultants and Technocrats Pvt Ltd.Arjo-Dedessa Hydropower &. Irrigation Project
Meteorological & Hydrological Feasibility Studies
u
June 2009
Starting
Year and Storage
Month          Mcum
Irrigation
Power
End
Inflow
Storage 1
requirement
Storage
Reservoir
Mcum
Mcum
Mcum
2 Mcum
Zone
release Stoiage 3 Mean Head Power Energy Surplus Storage
Mcum Mcum level m m MW GWhr Mcum Mcum
543
2946
12
2934
1
94
2680
14
2666
1
36
2560
3
2557
2
83
2492
16
2476
2
29
2357
29
2328
2
1995-96 Sep 2403 142 2792 1376 59 23 877 17 19166 206 2586
1995 96 Oct 2566 142 2524 1376 59 23 794 17 13133 62 2524
1995 96 Nov           2524                                                                                                    148         2409        1374          57    23 958    17 24993        -177        2409
1995-96 Dec           2409                                                                                                   148         2328        1374          57    23 958   17 24993        -258        2328
1995-96 Jan            2328                                                                                                   148         2180        1374          57    23 958   17 24993        -406        2180
1995-96 Feb 2180
1995-96 Mar 2015
1995 96 Apr 1856
1995 96 May 1714
1995-96Jun            1661
1995-96 Jul            1741
1995-96 Aug           2046
18
2198
35
2163
2
148
2015
1374
26
2041
26
2015
3
159
1856
1370
22
1878
5
1873
3
159
1714
1370
108
1822
2
1820
3
159
1661
1370
271
1932
32
1900
3
159
1741
1370
462
2203
9
2194
2
148
2046
1374
515
2561
10
2551
2
148
2403
1374
Mean
2121 92
Starting Storage
57    23 958   17 24993       -571        2015
53    23 933    17 23153        -730        1856
53    23 933   17 23153       -872        1714
53    23 933   17 23153        -925       1661
53    23 933   17 23153       -845       1741
57    23 958   17 24993        -540        2046
57    23 958    17 24993       -183        2403
56 00      23 93   206 7487
In igalion
150 67
Power
Year and
Inflow
Storage 1
requirement
Storage
Reservoir
Month          Mcum
1996 97 Sep           2403
1996-97 Oct            2586
1996-97 Nov           2586
1996-97 Dec 2513 1996-97 Jan 2399 1996-97 Feb 2254 1996-97 Mar 2092
1996-97Apr            1941
1996-97 May           1806
1996-97 Jun            1707
1996-97 Jul             1715
1996-97 Aug           2077
Mean 2173 25
Mcum
Mcum
Mcum
2 Mcum
Zone
358
2761
12
2749
1
225
2811
14
2797
1
release :Storage 3    Mean      Head Mcum       Mcum     Level m       m
142 2607 1376 59 142 2655 1376 59
Power     Energy     Surplus
End
Storage
MW GWhr Mcum Mcum
23 794 17 13133 21 2586
23 794 17 13133 69 2586
72
2658
3
2655
1
142         2513        1376          59   23 794    17 13133          -73       2513
50
2563
16
2547
2
32
2431
29
2402
2
21
2275
35
2240
2
23
2115
26
2089
2
148      •• 2399        1374          57
148         2254        1374          57
148         2092        1374          57
148         1941         1374          57
23 958   17 24993       -187        2399
23 958   17 24993       -332        2254
23 958   17 24993       -494        2092
23 958 17 24993 645 1941
29
1970
5
1965
3
159
1806
1370
62
1868
2
1866
3
159
1707
1370
199
1906
32
1874
3
159
1715
1370
519
2234
9
2225
2
148
2077
1374
798
2875
10
2865
1
142
2723
1376
148 75
53    23 933   17 23153        -780        1806
53    23 933   17 23153        -879        1707
53    23 933   17 23153       -871        1715
57    23 958   17 24993        -509        2077
59   23 794   17 13133          137       2586
56 67      23 90   206 46964I
W•
I
Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Starting
Irrigation
Power
End
Year and       Storage     Inflow    Storage 1 irequirement   Storage Reservoir     release Storage 3       Mean      Head     Power         Energy JSurplus   Storage
Month
Mcum
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum I
_evel m
m
MW
GWhr
Mcum
Mcum
1997-98 Sep
2586
610
3196
12
3184
1
142
3042
1376
59
23 794
17 13133
456
2586
1997-98 Oct
2586
339
2925
14
2911
1
142
2769
1376
59
23 794
17 13133
183
2586
1997-98 Nov
2586
118
2704
3
2701
1
142
2559
1376
59
23 794
17 13133
-27
2559
1997-98 Dec
2559
53
2612
16
2596
1
142
2454
1376
59
23 794
17 13133
-132
2454
1997-98 Jan
2454
36
2490
29
2461
2
148
2313
1374
57
23 958
17 24993
-273
2313
1997-98 Feb
2313
24
2337
35
2302
2
148
2154
1374
57
23 958
17 24993
-432
2154
1997 98 Mar
2154
25
2179
26
2153
2
148
2005
1374
57
23 958
17 24993
-581
2005
1997-98 Apr
2005
32
2037
5
2032
2
148
1884
1374
57
23 958
17 24993
-702
1884
1997-98 May
1884
68
1952
2
1950
3
159
1791
1370
53
23 933
17 23153
-795
1791
1997-98 Jun
1791
220
2011
32
1979
3
159
1820
1370
53
23 933
17 23153
-766
1820
1997-98 Jul
1820
573
2393
9
2384
2
148
2236
1374
57
23 958
17 24993
-350
2236
1997-98 Aug
2236
880
3116
10
3106
1
142
2964
1376
59
23 794
17 13133
378
2586
Mean
2247 83
147 33
57 17
23 89
206 3694
Starting
Irrigation
Power
End
Year and       Storage     Inflow   Storage 1   requirement  Storage   Reservoir   release   Storage 3    Mean      Head     Power      Energy     Surplus   Storage
Month
Mcum
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum
Level m
m
MW
GWhr
Mcum
Mcum
1998-99 Sep
2586
610
3196
12
3184
1
142
3042
1376
59
23 794
17 13133
456
2586
1998-99 Oct
2586
339
2925
14
2911
1
142
2769
1376
59
23 794
17 13133
183
2586
1998-99 Nov
2586
118
2704
3
2701
1
142
2559
1376
59
23 794
17 13133
-27
2559
1998-99 Dec
2559
53
2612
16
2596
1
142
2454
1376
59
23 794
17 13133
-132
2454
1998-99 Jan
2454
35
2489
29
2460
2
148
2312
1374
57
23 958
17 24993
-274
2312
1998 99Feb
2312
24
2336
35
2301
2
148
2153
1374
57
23 958
17 24993
-433
2153
1998-99 Mar
2153
25
2178
26
2152
2
148
2004
1374
57
23 958
17 24993
-582
2004
1998 99 Apr
2004
32
2036
5
2031
3
159
1872
1370
53
23 933
17 23153
-714
1872
1998-99 May
1872
68
1940
2
1938
3
159
1779
1370
53
23 933
17 23153
-807
1779
1998 99 Jun
1779
220
1999
32
1967
3
159
1808
1370
53
23 933
17 23153
-778
1808
1998-99 Jul
1808
573
2381
9
2372
2
148
2224
1374
57
23 958
17 24993
-362
2224
1998 99 Aug
2224
880
3104
10
3094
1
142
2952
1376
59
23 794
17 13133
366
2586
Mean
2243 58
148 25
Water Works Design & Supervision Enterprise
56 83      23 88     206 351
35
In Association with Intercontinental Consultants and Technocrats Pvt. LtdArjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
••
June 2009
Starling
Irrigation
Power
End
Year and      Storage    Inflow   Storage 1 requirement   Storage Reservoir     release Storage 3       Mean      Head     Power       Fnergy Surplus Storage
Month         Mcum     Mcum      Mcum         Mcum       2 Mcum      Zone        Mcum       Mcum Level m            m          MW          GWhr         Mcum      Mcum
1999-00 Sep
2586
751
3337
12
3325
1
142
3183
1376
59
23 794
17 13133
597
2586
1999-00 Oct
2586
417
3003
14
2989
1
142
2847
1376
59
23 794
17 13133
261
2586
1999-00 Nov
2586
146
2732
3
2729
1
142
2587
1376
59
23 794
17 13133
1
2586
1999 00 Dec
2586
65
2651
16
2635
1
142
2493
1376
59
23 794
17 13133
-93
2493
1999 00 Jan
2493
30
2523
29
2494
2
148
2346
1374
57
23 958
17 24993
-240
2346
1999-00 Feb
2346
20
2366
35
2331
2
148
2183
1374
57
23 958
17 24993
-403
2183
1999-00 Mar
2183
21
2204
26
2178
2
148
2030
1374
57
23 958
17 24993
-556
2030
1999-00 Apr
2030
27
2057
5
2052
2
148
1904
1374
57
23 958
17 24993
-682
1904
1999-00 May
1904
57
1961
2
1959
3
159
1800
1370
53
23 933
17 23153
-786
1800
1999 00 Jun
1800
185
1985
32
1953
3
159
1794
1370
53
23 933
17 23153
-792
1794
1999-00 Jul
1794
482
2276
9
2267
2
148
2119
1374
57
23 958
17 24993
-467
2119
1999-00 Aug
2119
740
2859
10
2849
1
142
2707
1376
59
23 794
17 13133
121
2586
Mean
2251 08
147 33
57 17
23 89
206 3694
Starting
Irrigation
Power
End
Year and      Storage    Inflow   Storage 1  requirement  Storage   Reservoir   release   Storage 3    Mean       Head     Power       Energy      Surplus    Storage
Month
Mcum
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Mcum
Level m
m
MW
GWhr
Mcum
Mcum
2000-01 Sep
2586
632
3218
12
3206
1
142
3064
1376
59
23 794
17 13133
478
2586
2000-01 Oct
2586
351
2937
14
2923
1
142
2781
1376
59
23 794
17 13133
195
2586
2000-01 Nov
2586
123
2709
3
2706
1
142
2564
1376
59
23 794
17 13133
-22
2564
2000-01 Dec
2564
54
2618
16
2602
2
148
2454
1374
57
23 958
17 24993
-132
2454
2000-01 Jan
2454
51
2505
29
2476
2
148
2328
1374
57
23 958
17 24993
-258
2328
2000-01 Feb
2328
38
2366
35
2331
2
148
2183
1374
57
23 958
17 24993
-403
2183
2000-01 Mar
2183
45
2228
26
2202
2
148
2054
1374
57
23 958
17 24993
-532
2054
2000-01 Apr
2054
41
2095
5
2090
2
148
1942
1374
57
23 958
17 24993
-644
1942
2000-01 May
1942
97
2039
2
2037
3
159
1878
1370
53
23 933
17 23153
708
2000 01 Jun
1878
291
2169
1878
32
2137
2
148
1989
1374
57
23 958
17 24993
-597
2000-01 Jul
1989
473
2462
1989
9
2453
2
148
2305
1374
57
23 958
17 24993
2000-01 Aug
2305
630
2935
-281
10
2305
2925
1
142
2783
1376
59
23 794
Mean                2287 92                                                                                               146 92
17 13133
197
2586
57 33      23 90     206 5064
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June 2009
Starting
Irrigation
Power
End
Year and      Storage Inflow Storage 1 requirement Storage Reservoir release Storage 3 Mean
Head Power Energy Surplus Storage
Month         Mcum Mcum           Mcum         Mcum       2 Mcum       Zone       Mcum Mcum Level m                   m          MW        GWhr Mcum Mcum
2001-02 Sep 2586 546 3132 12 3120 1 142 2978 1376 59 23 794 17 1313 392 2586
2001-02 Oct 2586 301 2887 14 2873 1 142 2731 1376 59 23 794 17 1313 145 2586
2001-02 Nov          2586        108          2694
3       2691                1          142         2549        1376           59 23 794        17 1313           -37         2549
2001-02 Dec
2549
47
2596
16
2580
2
148
2432
1374
57 23 958        17 2499
-154
2432
2001-02 Jan
2432
25
2457
29
2428
2
148
2280
1374
57 23 958 17 2499
-306
2280
2001-02 Feb
2280
17
2297
35
2262
2
148
2114
1374
57 23 958        17 2499
-472
2114
2001-02 Mar
2114
18
2132
26
2106
2
148
..1958
1374
57 23 958 17 2499
-628
1958
2001-02 Apr
1958
23
1981
5
1976
3
159
1817
1370
53 23 933 17 2315
-769
1817
2001-02 May
1817
49
1866
2
1864
3
159
1705
1370
53 23 933 17 2315
-881
1705
2001-02 Jun
1705
159
1864
32
1832
3
159
1673
1370
53 23 933 17 2315
-913
1673
2001-02 Jul
1673
411
2084
9
2075
2
148
1927
1374
57 23 958 17 2499
-659
1927
2001-02 Aug
1927
634
2561
10
2551
2
148
2403
1374
57 23 958 17 2499
-183
2403
Mean                2184 42                                                                                             149 25
56 50      23 91    206 588
Starting
Irrigation
Power
End
Year and      Storage     Inflow   Storage 1 i requirement  Storage Reservoir release Storage 3            Mean       Head Power Energy Surplus Storage
Month         Mcum      Mcum      Mcum         Mcum       2 Mcum       Zone        Mcum       Mcum Level m             m          MW        GWhr I     Mcum      Mcum
2002-03 Sep
2403
598
3001
12
2989
1
142
2847
1376
59 2 3 794 17 1 313
261
2586
2002-03 Oct
2586
329
2915
14
2901
1
142
2759
1376
59 23 794 17 1313
173
2586
2002-03 Nov
2586
117
2703
3
2700
1
142
2558
1376
59 23 794 17 1313
-28
2558
2002-03 Dec
2558
51
2609
16
2593
1
142
2451
1376
59 23 794 17 1313
-135
2451
2002-03 Jan
2451
27
2478
29
2449
2
148
2301
1374
57 23 958 17 2499
-285
2301
2002-03 Feb
2301
18
2319
35
2284
2
148
2136
1374
57 23 958 17 2499
-450
2136
2002-03 Mar
2136
19
2155
26
2129
2
148
1981
1374
57 23 958 17 2499
-605
1981
2002-03 Apr
1981
25
2006
5
2001
3
159
1842
1370
53 23 933 17 2315
-744
1842
2002-03 May
1842
53
1895
2
1893
3
159
1734
1370
53 23 933 17 2315
852
1734
2002 03 Jun
1734
172
1906
32
1874
3
159
1715
1370
53 23 933 17 2315
-871
2002-03 Jul
1715
445
2160
1715
9
2151
2
148
2003
1374
57 23 958        17 2499
2002-03 Aug
2003
-583
689
2003
2692
10
2682
1
142
2540
1376
59 23 794 17 1313
Mean
2191 33
-46
2540
148 25
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June 2009
Starting
Irrigation
Power
End
Year and
Storage Mcum
Inflow
Storage 1
requirement
Storage Res
ervoir
release Mcum
Storage 3
Mean
Head
Month
Mcum
Mcum
Mcum
2 Mcum
Zone
Mcum
Level m
m
Power MW
Energy
GWhr
Suiplus Mcum
Storage Mcum
2003-04 Sep
2540
533
3073
12
3061
1
142
2919
1376
59
23 794
17 1313
333
2586
2003-04 Oct
2586
293
2879
14
2865
1
142
2723
1376
59
23 794
17 1313
137
2586
2003-04 Nov
2586
104
2690
3
2687
1
142
2545
1376
59
23 794
17 1313
-41
2545
2003-04 Dec
2545
45
2590
16
2574
2
148
2426
1374
57
23 958
17 2499
-160
2426
2003-04 Jan
2426
24
2450
29
2421
2
148
2273
1374
57
23 958
17 2499
-313
2273
2003-04 Feb
2273
16
2289
35
2254
2
148
2106
1374
57
23 958
17 2499
-480
2106
2003-04 Mar
2106
17
2123
26
2097
2
148
1949
1374
57
23 958
17 2499
-637
1949
2003 04 Apr
1949
23
1972
5
1967
3
159
1808
1370
53
23 933
17 2315
-778
1808
2003-04 May
1808
47
1855
2
1853
3
159
1694
1370
53
23 933
17 2315
-892
1694
2003 04Jun
1694
153
1847
32
1815
3
159
1656
1370
53
23 933
17 2315
-930
1656
2003-04 Jul
1656
397
2053
9
2044
2
148
1896
1374
57
23 958
17 2499
-690
1896
2003-04 Aug
1896
612
2508
10
2498
2
148
2350
1374
57
23 958
17 2499
-236
2350
Mean
2172 08
149 25
56 50
23 91
206 588
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Annex C. Standards
C1 Commonly used values of runoff coefficients
June 2009
Class
Description of catchment
Runoff
percentage
A            Flat, cultivated and blck cotton soils
B            Flat, partly cultivated stiff soils
C            Average catchment
D            Hills and plains with little cultivation
E Very hilly and steep with little or no cultivation
10
15
20
35
45
C2 Runoff coefficient for pervious surfaces by selected hydrologic soil
groupings and slope ranges
Terrain Type
Soil Type
A
B
C
D
Flat, <2%
0 04 - 0.09             0.07-0 12
Rolling, 2 - 6%                   0.09-0.14              0.12-0.17
Mountain, 6-15%                0 13-0.18              0.18-0.24
Escarpment, >15%            0.18-0.22             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 - 0 40           0 38 - 0.48
Note Where A, 8, C. ano D are defined as shown in C3
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C3               SCS Curve Numbers for Various Conditions Cover Description
June 2009
c'urve
nu mbers for
hy
drologic
B
soil group
cD
■«
Cover type
Fallow Bare soil
Crop residue
cover (CR)
Pasture, grassland, or range- continuous forage for grazing'
Meadow-continuous   grass, protected from grazing
Brush-weed-grass  mixture  with brush the major element3
Woods-grass combination5
Woods6
Farms—buildings,   lanes,  driveways, and surrounding lots
Arid and semi-arid rangelandse
Hydrologi
c
A
b
condition
Poor 76 85 90 93
Good 74 83 88 90
77            86            91            94
-
Poor Fair Good
Poor Fair Good Poor Fair Good Poor Fair Good
Hyd
concf
Mixture of grass, weeds, and iow-
Poor
68            79            86            89
49            69            79            84
39           61            74            80
35            59            72            79
48            67            77            83
35            56            70            77
304                48            65            73
57            73            82            86 43            65            76            82 32            58            72            79 45            66            77            83 36            60            73            79 30*           55            70            77 59            74            82            86
A              B                         CJ   D
—
80
87
93
growing brush, with brush the minor
Fair
—
71
81
89
element
Good
—
62
74
85
Mountain Drush mixture of small
Poor
—
66
74
79
trees and brush
Fair
—
48
57
63
Good
—
30
41
48
Small trees with grass understory
Poor
—
75
85
89
Fair
—
58
73
80
Good
—
41
61
71
Brush with grass understory
Poor
—
67
80
85
Fair
—
—
51
63
70
Good
35
47
Desert shrub brush
55
Poor
63
77
85
88
Fair
55
72
81
Good
86
49
68
79
84
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C3:_____ con tin ued)
2 Average runoff condition, and la = 0.2S
Poor < 50% ground cover or heavily grazed with no mulch
Fair 50 to 75% ground cover and not neavily grazed
Good: > 75% ground cover and lightly or only occasionally grazed Poor < 50% ground cover
Fair 50 to 75% ground cover
Good: > 75% ground cover
* Actual curve number is less than 30; use CN = 30 for runoff computations
June 2009
CNs shown were computed for areas with 50% grass (pasture) cover Other combinations of conditions may be computed from CNs for woods and pasture
6   Poor Forest litter small trees, and brush are destroyed by heavy grazing or regular burning
Fair       Woods grazed but not burned, and some forest litter covers the soil Good     Woods protected from grazing, litter and brush adequately cover soil
7   Poor < 30 % ground cover (litter, grass, and brush overstory) Fair 30 to 70 % ground cover
Soil Groups
Good: > 70 % ground cover
Group A Sand, loamy sand.or sandy loam. Soils having a low runoff potential due to high infiltration rates. These soils primarily consist of deep, well-drained sanas and gravels
Group B: Silt loam or loam Soils having a moderately low runoff potential due to moderate infiltration rates. These soils primarily consist of moderately deep to deep moderately well to well drained soils with moderately fine to moderately coarse textures
Group C: Sandy clay loam. Soils having a moderately high runoff potential due to slow infiltration rates. These soils primarily consist of soils in which a layer exists near the surface that impedes the downward movement of water or soils with moderately fine to fine texture
Group D Clay loam, silty clay loam, sandy clay, silty clay or clay Soils having a hign runoff potential due to very slow infiltration rates These soils primarily consist of clays with high swelling potential, soils with permanently-high water taoles, soils with a clay pan or clay layer at or near the surface, and shallow soils over nearly impervious parent material.
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C4 Reservoir Flood Standards
2009
Dam design flood inflow
c ategory of reservoir        Initial
General
condition
Min. standard,
Rare
overtopping
Wind speed,
Min. wave
surcharge
Spilling
long
term av 
A. Breach endangers in     Daily
Larger of 0 5
PMF or 10,000
Average
annual max
lives in commentary     inflow        PMF               year flood              hourly wind
B  Breach may 
endanger lives not in
Larger of
0 5 PMF or Larger of 0 3
a community, 10,000 year
extensive drainage      Full           flood
PMF or 1,000
Wave
surcharge
allowance >06
year flood             m
C  Breach with negligible risk to life and causing limited damage
Full
Larger of 0 3 PMF or 1,000 year flood
Larger of 0.2 PMF or 150 year flood ’
Av Annual max hourly wind. Wave surcharge allowance >04 m
Note For the purpose of PMF the ordinates of the computed PMF
hydrograph are multiplied by the proportion indicated.
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C5 Ratios of the basic dimensionless hydrograph of the SCS
June 2009
T/Tp             Qi/Qp
Ti/Tp             Qi/Qp
Ti/Tp              Qi/Qp
00
0 05            0 008
0.1              0015
0.15            0 043
0.2             0 075
0.25            0 11
0.3              0.16
0.35             0.22
04               028
0 45             0 36
0.5              0.43
0.55             0.52
06               0.6
065             0.69
07              0.77
0.75             0 83
0.8              0.89
085             0 93
09              0.97
0.95             0.99
11
1.05             0.99
1.1              0.98
1.15             0.95
1.2              0 92
1.25             0.88
1 3              0 84
1 35             0 80
1 4              0 75
1 45             0.71
1.50             0.66
1.55             0.61
1.6              0.56
1.7              0.49
1.8              0 42
1.9              0.37
2.0              0.32
2.1              0.28
2.2              0.24
23              0.21
2.4              0.18 2.5              0.16
2.6 0 13
2.7 0 11
2.8 0 098
2.9 0 088
3 0 075
3.2 0 056
3.5 0.036
3.7 0.027
4 0.018
4.2 0 014
4.5 0.009
4.7 0 007
5 0 004
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C6 Guidelines for Interpretations of Water Quality for Irrigation
June 2009
Water parameter
Symbol
Unit1
Usual range in irri water
gation
SALINITY
Salt Content
Electrical Conductivity
ECW
dS/m
0-3
dS/m
(or)
1
Total Dissolved Solids
TDS
mg/l
0 - 2000
mg/l
Cations ano Anions
Calcium
Ca”
me/l
0-20
me/l
Magnesium
Mg”
me/l
0-5
me/l
Sodium
Na*
me/l
0-40
me/l
Chloride
er
me/l
0-30
me/l
NUTRIENTS'
-------------- 1
Potassium
K’
mg/l
0-2
mg/l
MISCELLANEOUS
V
1
Acid/Basicity
pH
1-14
6.0-8 5
Sodium Adsorption Ratio1
SAR
(me/l) , *
1
0-15
Source.   FAO,   1994   Water   Quality   for   Agnculture   Irrigation   and   Drainage   Paper   No   Rev   1, Reprinted, 1994
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Annex D Meteorological Data
D1 Details of Meteorological Observation Stations (Raw Data Collection)
June 2009
Station Name
Q Mr,
□ .NO.
Latitude
North
Mir,
Longitude East
Deg. Min.
Altitude
(m)
Period
Class
1
________________ Agaro
07          51          36          36             2030          1980-2004                 1
2              Arjo                             08          45         36          30             2565          1972-2004                 3
3              Bedelle                        08          27         36          20             2030          1967-2004                 1
4               Dedessa                     09          23         36          06             1200          1971-2004                 1
5              Demoi                         08          04          36          27             1950          1954-2004                 3
6              Gimbi                          09          10         35          47             1970          1978-2004                 1
7              Jimma                         07          40         36          50             1725           1952-2004                 1
8              Kone                           08          41          36          47             2000           1979-2004                 4
9              Meko                           08          41          36          02             2000           1980-1989                 4
10            Nekemte                     09          05         36          28             2080           1971-2004                 1
11            Wama
08 s         59         36          40             1450           1980-1987
3
D2: Types of Climatic Data available at the various Meteorological
Observation Stations
S.No.
Station Name
Altitude
(m)
'Yrs
RF
TM
RH   I WS
SD
EP
1        Agaro                            2030            25             X                  X              X              X                X                  X
2        Arjo                               2565            33             X                  X
3        Beaelle                         2030            38             X                  X               X                                X             X
4         Dedessa                       1200            34             X                  X               X             X                                     X
5         Dembi                           1950           51             X                  X
6        Gimbi
1970            27             X                  X               X              X                X
7        Jimma                           1725            53             X                  X               X              X               X             X
8         Kone                             2000            26             X
9         Meko                             2000            10             X
10       Nekemte                       2080            34             X                  X               X              X               X
11        Wama
1450             8              X                  X
Yrs refer to rainfall series
RF        monthly rainfall
Tm average temperature
RH        relative numidity
WS       wind speed
SD         sunshine duration
1 hr maximum 1-hour rainfall
1 day     maximum 1-aay rainfall Rday     number of rain days
* Data length refers to Rainfall and Temperature data.
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D3: Mean Monthly Rainfall at Bedele Station
June 2009
Year
I"’ '
Jan FeD iMarchlApril
May
June July    Jau£
0        0       152      33     181      221     212     381
0      100       1        55      163       0       323     380
67      59      81      198     210     250     275     368
54      50       89      258     258     266     432     280
20       1       41       53      246     334     311     234
0       20       42      178     116     263     337     287
0       19       10      51      337     269     322     403
68      13       55        9       497     355     351     292 44     101      37      105     202     215     327     276 41       29      156      97        0       267     333     373
5        7       115     179     204     267      310      303
0        0        29       44      169     350     408     276
0        0         0       208     285      174     236     304
0        8        48       62      237     369     499     468
0        0        45       66     291      275     469    211 2       34       80     141     243     222     218     357 17       2        33      106     225      281       250     258 0       17      102     130     257     292     257     318
48      34     208      83      317     232     290     203
53       2        50      142     340     307     221     304
13      15       87       57      203     332     314     327
28       3        13      147    431      441      319     242
0        0         4       123     256     420     186     273
0       33       87       72      322      390     297     329
16       4        63       38      169     298     296     202
7       66       84      131      37      320     278     258
6        3        46       81      248     447     299     268
0
Annual
1980
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1978
1979
1980
1983
1984
1993
1994
1995
1996
1997
1998
1999 2000 2001 2002 2003 2004
380 167 253
324 137 35
22       1539
286      98
7
0
1897
455 326 56 25 2101
287 110 122 26 1788
444      186       0
7        2322
248 102 21
368      126       8
245     228       20
472      154      62
281 204 41
267      113       0
363      86        50
306      197      99
10 1790
29 2171
0
9
1796
1993
72       1926
242
9
200 183
276 21
353 77
25
1• 17 10
0
0
0
5
0
0
1655
1706
2293
1637
1680
1484
128 70 45
232 309 38
291 245 59
324     328
8
24 1837
13 1670
4 2001
1 1942
39 2321
286 242 29
370 211 29
8
1827
253 63
197 52
3
13
14 2155
46 1450
3
1446
273      168      62
15       1917
Average     18       23        65       105      239
291       310      303       302       156        41          12
CV        1 28     1 28    0 77     0.58     0.434   0 312    0 242    0.21    0 266    0 563    1 256     1 114
Skew      1 05      1 6      1 09
0  68    0 098    -0 91    0 837    0 56    0 345    0.375    2 913     1 172
Max        68       101      208      258       497
Min
0
0
0
9
0
447 499 468 472 328 253 46
0         186       202      128         9           0            0
1864
0.14
0.18
2322
1446
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D4 Mean Monthly Rainfall at Jimma Station
June 2009
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Year Jan Feb March [April {May June July Aug Sep_tjjct_--------------------------- Nov-----Dec
June 2009
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
9 81 110 237 237 225 189 263
33 28 87 153 213 274 255 155
8 27 74 193 115 163 181 216
35       22       135     203     175     183    231      91
65        49         69       178     274     237    122     276
103      22         97       93      174     223    248     307
30        1         84       72      214     575    136     102
0         1         39       194     238     154    266      159
16       13       86       117     341     299    312     161
69        5        11        90      137     242     150     235
29 61 87 111 12 272 187 151
51 28 46 131 162 128 216 219
164 17
177 11
141 54
245 24
3
0
18       11
30
93
96
40
Annual
1534
1415
1298
1476
148      337      243       36        2034
200      201        47
131      198
1
255 244 47
183 163 76
1
2
25
4
1713
1546
1622
1772
165 80
239 92
8
30
138 1330
15 1285
210      133       67
33 49 88 133 172 219 208 210
0 86 0 71 0.48 0 43 0 39 0.34 0 24 0 26
0 95 0 68 0 55 041 041 2.53 0 11 0 12
105 140 199 301 341 575 312 344
182        103
68
89
36
1482
1502
Avg
CV
Skew
Max
0.26 0 67 0.96 1 06 0.13
0 04 1 10 1 32 1 74 0.83
1            7                                12       114       96         91
299 337
58 11
243
1
170        2034
0
1169
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D5 Mean Monthly Rainfall at Dedessa Station (in mm)
—
Year
1971
1972
1973
1976
1977
1978
1979
1980
1981
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
Feb March April May June July Aug Sept Oct
Annual 1679
1222 1128 1278 1695 1306 1695 1284 1691 2101 1880 1216
1251
4          0          0          0        84      197     153      207       171       183        65          6 0          8         26        95      141     224     307      264       170       132        15          0 0          0          1         79
0          0         34        19       81       112     265      241       177        89          10          5
21         4         79        60       239     311     380      380       370         0           12          0
13         0         13       154      184     203     277      247       147         0          60          0
0          0         13        14      251      399     196      371       254       191         29          0
18         0          0         47       178     306     151      274       351       141         17         11
0          0          0        154     241     448     136      347       300       192        22          0 0         11        27        31       143     214     196      224       254       128        40         29 6         15        30        31        77      203     252      126       102        17          0           8 0         35        50         0         73      366     417      302       193        67          36          6 0          5          6         35       106     252     427      318       140       147        36          0
1069
1382
1032
1856
1299
1717
1494
1842
1296
865
1544
1470
Average
CV
Skew
Max
Min
3          6         26        49       158     274     312      277       209       1C4        28          8
1 91     1 87     1 28     0 88    0 51    0 29    0 37      025      0 38      0 64      0 76      2 05
2 18     2 78     2 75     0 94     -025     025     064      0 35      0 87     -0 04      0 59      3 66
21        48       160      154      275     448     625      442       380       241         68         76
0          0          0          0          0       112     136      126       102         0           0           0
1426
0.23
0.05
2101
784
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Mean Temperature at Bedele Station (Raw Data before gap filling) (in oC)
June 2009
Year         Jan     Feb     Mar
i--------
Apr    fMay ]” Jun      Jul   I Aug   ]Sep        Oct   | Nov |    Dec
1971
1972
1973
179      199     21 2    20 8    21 5    20 4      182      16 7     16 6      155      154      17 2
19 5    20 9     184     179     198      183
158      159
179      187     21 5    21 5     194     179      14 3     16 4     180     17 3      174     24 9
1974      177     198     193     202    18 7     182      16 9      157      172      17 1     179      170
1975      173      193     197     198    19 4     17.7     16 7     16 2     177      18 1     17 2
1976      179     18 1    19 1     188                 178      176      17.2     17.1      177      170      16 7
1977      182      190
16 8     16 0     16 1      197
1978 173 184 19.3 189 18 5 17 5 16 0 16 5
1979 21 0 20 5 197 195 79 166 173 173 17 5
1980
192    19 1      176      17.2      16 9     174      170      176      174
1981      173     175     17 1                 170
1982
1963                   75      19 1    20 1     176     174      178      18 3     187      190      194     20 8 1984                  21 4    21 2    22 0     197     180      16 9      173      174      186     18.9     196 1985     20 5     205     21 4     205      186     180      17.2     17 1     17 3     17.7      188      18 9 1986      199     20 6    20 8     209    21 4     18 1      174       178      177     18.2      187      184
1987      194     20 8    20 4
18 1      182      18.3     190
1988      197     20 3    20 8    21 6     196     18 1      170       173      175     18 3      182      179
1989      178     18 7    19 1     193     190     178      150       173      177      175      180      178
1990     18 1     187      195     20 2     193     18 5      174       174      17 8     182      18 9     19 1
1991     19 3     20 6    20 7    21 0    20 4     18 3                   174      182      184       187     20 0
1992     19 1     20 1    21 3    20 6    20 7     195      184       180      196      19 1     18 8     20 6
1993
1994      20 9    209     22 0    21 3     195                  178       177      18.2     190       196      19 5
1995     20 5     20 8    21 3    21 4     199     194      176      18 1     18 5     18 8      18 9     195
1996      192     21 0    20 6    20 7    19 1      184      178       180      18 3     18 3      18 5     187
1997      192      199     21 5     199     193     186      178       180      188
1998      139     21 2    21.2    23 2    21 0     19.3     18 1      18 3     18 9      192      18.6     192
1999      196     21 7    21 7    21 8    19 1      187      173       177      186      17 9      184      192
2000
177       179      18.5      189      186      189
2001      19 1    20 9     207     21.2     199     180      175      17 7      186      194      187      19.2
2002      192     21 1    21 6    21 8    21 2     18.5      183       175     18 1      18 1      186      18 9
2003     20 0     21 5    21.1    21 2    21 9     187      176      18 1      186       190      196      196
2004      208     21 0    22 1    21 5    20 8     183       178      18 1      186       187     19 1     196
Avenge
CV
Skew
Min
Max
18 7     19.7      20 6      20 6      19 6      18 0       17 3       17 4       17 9        180       183       18 9
0 08      0 13      0 05      0 05      0 06      0 12       0 05       0 04       0 05       0 05       0 06      0 09
-121      -3 96     -1 19     -0 08     0 00     -4 24      -2.06      -0 86     -0 58     -0 94      -1 35      1 44
13 9        75        17.1       184       17 0       79         14 3        15.7       160        15.5       15.4       159
20 9 21 7 22 1 23 2 21 9 20 4 184 18 3 19 6 19 4 19 7 24 9
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D7 Relative Humidity at Bedele Station (in%) (Raw Data oefore gap filling)
June 2009
Year
Jan
Feb      Mar
Apr
May
Sep
Oct
Dec
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
80
80
69
58
63        80        58        52        70
51        53        67        62        68
59        62        56        60        70
55        46        56        67        78
68        65        58        62        66
53        48        48        57        78 46        50        51        59        72 59        54        63        62        75
63
65        55
59        50        49        55        76
58
62        62        65        65        73 69        60        66        65        67 62        55        63        60        57 61        54        56        62        66
Jun
78
80
79
80
75
83
75
82
64
76
83
81
81
81
89
83
82
82
77
85
85
83
84
82
84
85
88
85
84
85
80
84
81
72
83
84
84
84
84
86
86
84
83
76
63
50
84
72
64
75
80
70
69
60
77
71
65
65
74
72
69
64
81
61
66
61
78
69
69
67
80
72
68
64
80
78
64
63
82
80
74
70
83
80
74
67
83
84
73
69
61
82
74
70
69
Average^ 60               57          58         61_____7O_ ^8_                               83           81__ 69[_63-------------------- 60
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D8 Wind Speed at Jimma Station (Raw Data before gap filling)
June 2009
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D9 Sunshine Duration at Bedele Station (Raw data collected)
(in hrs/day)
June 2009
Year
------
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
Jan      Feb      Mar
Apr      MaX
JunH    Jul
Aug 1 Sep
79        7.2        69        85        56         6         6 3         57         84
93       7 1        65        82        79       64         26         4.2        5 1
85        8.2        79        79        74         6          38         5 1        6.5
89        56        77        64       8.2       64         3.8        4 8         6
79       8 1        68        63       7 1       4 5        2 7         34         59
57        77       7 1       8.3       6 1        3.4        2.2        67
7.6        66        75       5 5
77        75        77        76         ■          24         3.4        58 88        66        77       6.6         •           •            •            •
•           •         79         •          •          *          3.7        4.3        67
7.2       9.2        75        68         7        6 1        4 1         46        8.4 75        7.7       64        87       6.4       6.7        2.9        3.3        4.7
8
79
96
8
62
95
9
7.6
5.4
58
6.4
8.8 95
8.2
Nov Dec
83       83 97       95 8 8        64
8 1       9 1        88       7.6       76       66         3.5
4.6        66
9         88         9        6 1       7 8        8
•*
•
5.5
• 82 7 5 9.1 84 6 1 56 3 1 69
79 86 7 3 88 96 57 2.9 36 6 1
7 5 79 6 57 74 4 3 4.2 4.5 3.5
87
84
62
84
79
67
84
98
83
87
8.3
9
7I 83
93 78 83 92 88 76 86 77
Average      8 2         7 6         7.5        7 3        7.6        6 1          3 7          4 1          6.2
7.9        8.3         8 3
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Annex E:       Hydrological Data
E1 List of Selected Hydrological Observation Stations
^June 2009
s.
No
—
Station
No.
Latitude, N
Longitude, E
Station Name
Deg.
Min.
Deg. I
L
Min.
Catch, i Area
2
(km )
Period
1
114001
Deaessa near Arjo
08
41
36
25
9981
1960-2004
2
114002
Angar near Nekemt
09
30
36
35
3742
1994-2004
3
114005
DaOana near Abasina
09
02
36
03
2881
1962-1984
4
114007
Angar near Gutin
29
1999-2003
5
114008
Yebc at Yebu
07
48
36
42
47
1979-2004
6
114009
Urgessa near Gembe
07
50
36
39
19
7
1979-2004
---------------- -I
114013
Dabana near Bunno Bedelle
08
24
36
17
47
1984-2003
8
114014
Dedessa near Dembi (Toba)
08
03
36
27
1&06
1985-2003
9
114016
Lotto near Nekemt
09
22
36
36
375
1997-2004
10
114019
Temssa near Agaro
07
51
36
35
47 5
1989-2004
11
113004
Melke near Guder
08
51
37
44
38
______________ 1998-2004     |
12
113038
indris near Guder
08
56
37
45
111
1986-2004
13
101006
Uka at Uka
08
10
35
22
52 5
1980-2004
14
091008
Gilgeignibe near AsenaaDo
07
45
37
11
2966
1967-2004
15
091012
Gojeb near Shebe
07
25
36
23
3577
1970-2004
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Annex E2 Mean Monthly Streamflow at Dedessan near Arjo Station
(Million m3) (Raw data before processing)
June 2009
Year
Jan |  Feo |   Mar [  Apr | May |  Jun       Jul
Aug
Sep
Oct
Nov [      Dec
I960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1054       1124               _ -
51 5    44 0    37 5    94 9    65 6      286      1176      1613       1503      1304      280        177 5 58 1    29 8      284-          -                              622        930       1170        855      107          55 9
38 1     193     179    42 7  147 1      324        672      1370       1040        374      184        170 3
38 2-                          549      230      1049      1301       1178      1337      205          73 6
55 4    25 3     164    47 8    27 8      168        834      1051         685        957      320        157 8
71 0    63 4    57 7   74 1     62 5-                   857      1086       1212 -             -
22 7    20 4
708      1268      1201      1260      459        210 4
96 0 52 9 21 4- - - - - 138 63 7
50 9 46 7 67 1 39 7 73.2 349 950 1421 944 291 89 46 2
34 1-
-             45.3      288        929 -             -
181          62 1
37 0    164     10.9    12.5    53 5      241         823      1175         949        752      304        105 3
524    29 8    196    35 7    56 4      118        803      1237         719        209      117          52 5
259     11 2      47       63  109 3      250-                                  1401        592      149          64 8
36 5    16 2    14 4     9 1    93 7      261        641      1278
24 5    21 9     11 5-
-
48 3    37 8     24 7-          -                     -
r               259    18 1    12.7
-
119 48 9
151 89 5
324 128 7
55 5     20 1-              124     80 1-           -
-                     -             22.9    46 4      130        533        825         619        262        94          44 0 180    15 3    100    68 6  190 9      504        914      1288       1244        393      103          92 5
80 0    43 4    43 3    35 4    53 7         53-
-
59 8    30 2    28 6     193    45 7      248        707        947         692       761       177          94 5 43 4    31 7    34 1    23 3    524      153        566      1139       1116     1231       265        121 3 38 5    16 7    11 9      95    28 6      185        703        665        521        131              -
12 0       54      2.6   11 8    624      169        438        927         842        260        79          45 0 176       95    16 1    13 8    12 8      119        452        491         732        222             -
130       59    124    17 3    36 7-           -
40 5 27 5 21 6 77 37 0 280 555
673 386 160 67 8
189-
-             23 3    20 4    33.5   27 1      121        273        499       1087-                   107       123 1
53 5    30 0    33 8    60 9    42 0      157        343
-
-                     ---
543      1143
38 1
24 5 239 13 8 20 7 56 5 161 368 824 564 806 164 73 4
42 5 27 9 24 4 54 7 105 2 312 600 1159 631 407 177 63 3
39 1 196 15 5 15.7 59 7 220 534 1221 858 156 68 36 9
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E2:           Continued)
June 2009
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep      lOct      ,Nov    bee
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
20 4   12.2    148    194    383       83       225       569       486       156       60
-         -         -            30 4 141 8     373       723      854       598 -           -
87 2
41 4    190
-
-
-
--
-
-
-                              242       135 7
85 1   59 5  66 1    57.2 128 3    401        740     1045     1005      674     215      111 7
99 0   57.2   55 3   634    46.2     175       457       591       578      211      115        83 9
56 4   36.2    562   74 3   48 0     120-
652-            -
-
523   40.2    30 3   28.7   65.2    202       526       639       643      538      140-
A vg
CV
Skew
Max
Min
46.2   28.7   26.0   33.2   66.5    223       654     1007       889      581      177        90.9 0.47   0.52   0.66  0.71   0.59   0.46      0.34      0.30      0.32     0.68    0.51        0.50
0.66   0.65   1.14   0.94   1.54   0.74      0.22    -0.16      0.43     0.73    1.26        1.00
99.0   63.4   67.1   94.9 190.9  503.5   1176.1 1612.8 1502.5 1337.4     459.2      210.4
12.0     5.4     2.6     6.3   12.8   53.2    225.0   491.1    485.9    130.8    59.9        36.9
Mean annual flow = 3821 Mm3)
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E3 39 Mean Monthly Stream flow at Dedessan near Demm Station
(Million m3) (gap filled senes)
June
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug        Sep       Oct
Nov
Dec
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
64       37      42      78   26 8       92          83        165        302       272     70 2        21 9 8 5       55       97      84      94        58        262        208        299         67     22 9        11 5
59       45       97      92    186     105        243        342        218       104    44 1        27 1
179     157    12 5      64    239     153        217       392        489       142     52 0        18 8
11 0       76       45   11 5      82       31        167       253        272       142     24 8        13 8
183       58      5 6   22.7      99       52        252        564        362       126     20 9          94
7.2       63     6.6   12 5   29 5       76        305        522        263       140      134           89 78    15.3    12 9     8.8    366       78        138       269        183       218     45.2       17 1
11.2 172 166 37 6 808 252 334 378 204 110 48 7 14 7
12.3     135    168   22 5    378     112        274       381        282         59     26 6        16 4
12 9   12 1    16 5   23 8   48.7       87        190       272        331       101     32 5        33 7
12 9       94    16.5   23 8   48.6       87        190       272        331       101     32.5        33 7
21.2     138    232   30 1    55.2     142        219       343        204       262      188       56 1
28 1     136    20 3   12 7   31.1      110        272       415        299       329     88 8       21 1
130       65      83      95   54.9     148        242       245        214       302     48 4        18 3
102       56       45      97   41.2     119        290        309        242       209     82 0       21 9
127       96     112   14 5    555     226        330       322        296       212     59 6        22 5
65       69       66     9.0      65       63        192        255        195         68     27 7        14 9
74       40      92   24 0      67       59       241        223        324         82     20 3         100
130    13.0    137   33 0   98 5     198        208        208        145         39     18 8       18 8
Average CV
Skew
Max
Min
12 2 9 47     11 5     169    36 4    112.4      232.4      3169           273     154 3        48 4         20 5
0 47 0 46     0 48    0 56    0 69    0 526         0.27     0 326          0 28     0 561       0 81          0 53
1 35 0.31      047    0 81     0 85    1 028       -0 47      0 927         0.89      0 668         2.6         1 98
28 1     17 2     23 2    37 6     98.5       252         334         564          489         329    187 9         56 1 5.9       3 7       4 2       6 4       6 5        31            83         165          145           39      13.4           8 9
Mean annual flow = 1255 Mm3)
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E4 Annual Maximum Floods
(in m3/s)
June 2009
Year
Dedessa
near Arjo
Upper
Dedessa
near Dem bi
Dabana
near
Abasma
Gilgel Gbibe near
Asendabo
Gojeb near Shebe
Angar near
neqemte
Angar near
Gutin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
633
1173
893
789
850
951
814
1165
781
634
896
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
267
467
264
434
449
247
196
257
180
314
341
238
202
248
151          132 198          272 130          176 330          127 151          231 167          110 205          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            188 185        258 186        241 284        217
214
140
249
177
288
138
297
314
184
150
203
226
132
245
366
164
164
261
164
150
282
132
193
199
439
236
335
361
209
247
256
157
271
252
128
141
73
55
124
107
134
105
125
142
. 136
142
149
178
172
109
106
79
181
128
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59Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility studies
E5 Measured Sediment Concentration at Relevant Gauging Stations
June 2009
No
Field
sample
No
Lab.No
River / Stream
Station
Date & Time
of Sampling
Time
(Sec)
G/height
(m)
Flow
3
(m /s)
Depth
(m)
Width
(m)
Sediment
Concen
(mg/l)
Remarks
AV
484         1                          Dedessa          Toba         15 Mar-90                     0 43
485         2
Dedessa          Toba         15 Mar-90
043
486         3                          Dedessa          Toba        15 Mar-90                    0 43
664         1                         Dedessa          Toba        21 Mar 90                     0 50
665 2
666 3
1057        1
1058        2
1059        3
1190        1
1191        2
1192        3
1223        1
1224        2
1225        3
2698 1
Dedessa          Toba         21 Mai-90
Dedessa          Toba        21-Mar-90
Dedessa          Toba          2-Jul-90
Dedessa          Toba          2-Jul-90
Dedessa          Toba          2-Jul-90
0.50
0 50
1 81
1.81
1.81
Dedessa          Toba        22 Dec-90       50        0 40
Dedessa          Toba        22 Dec-90       50         040
Dedessa          Toba        22 Dec 90        50         040
Dedessa          Toba        18 Sep-90
Dedessa          Toba        18-Sep-90
Dedessa          Toba        18 Sep-90
2 46
2 46
2 46
Dedessa          Toba        16-May-93       45        0.46
2699        2                          Dedessa          Toba        16-May 93       45         0 46
2700        3
Dedessa          Toba        16-May 93       40        0 46
2704        1                          Dedessa          Toba         12-Apr-93                     0 64
2705        2                          Dedessa          Toba         12-Apr-93                     0 64
2706        3                          Dedessa          Toba         12-Apr-93                     0 64
4 16          0 26               6.9 4 16          0.70             13 8 4 16          0 36             20 7
541          0 54               7.0
541          0 80             14.0
5.41          039               6 1
9 14          8 40               6.6
9 14          8 00             13 3 9 14          7 00             19 9
4.37          0 43               7.0
4 37          0 74             14 0
4 37          0 46             21 0
98 50
98 50
98 50
2 89              0 66        19.5 2 89              0 61           6 5
2 89              0 71         13.0
8 01
8 01
8 01
51 56
40.00
42 81
59.69
173 13
90 63
215 31
135 62
190 00
90 94
99 37
63.13
141 56
187 82
124 69
87.90
108 63
81 40
73 05     64 61
61 59
59 20Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
E5             i, continued)
No.
Field
sample
No
Lab.No
River /
Stream
Station
Date & Time
of Sampling
Time
(Sec)
G/height
Flow
3
(m /s)
Depth
(m)
Width
(m)
Sediment
Concen
(mg/l)
Remarks
AV
541 1 179/04 Dedessa Arjo 10 Aug-04 30 2 45
542 2 Dedessa Arjo 10-Aug 04 26 2 45
543         3
Dedessa           Arjo         10-Aug 04       28        2 45
544         1        180/04       Dedessa           Arjo         11-Aug 04       32        2 56
545 2 Dedessa Arjo 11-Aug-04 28 2 56
546         3
Dedessa           Arjo         11-Aug-04       27         256
559         1        185/04       Dedessa           Arjo          1 Sep-04        29        3 61
560 2
561 3
Dedessa Arjo 1-Sep-04 28 361
Dedessa Arjo 1-Sep-04 29 3.61
143.12 9 05ft 17 5
143 12 9.1ft 35 0
143 12 9 5ft 52 5
196.11        11ft          18 0
196 11        9 6ft         36 0
196 11        9 6ft         54 0
611 23       137ft         180
611 23 14 3ft 37 0
611.23 1 46ft 55.0
1417 50
1739 74
1740 74
1652 86
1718.12
1639 31
1360 22
1328 81
1438 44
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al & Hydrologica
l Feasibility Studies
June 2009
Annex F
Routing of
PMF Hydrograph
Time
Hydro
Hours
Cumecs
0 00
106 00
1 50
134 66
3 00
163 33
4 50
192 00
6 00
214 44
7 50
236 88
9 00
259 31
1050
339 50
12.00
41969
13 50
499 88
15 00
613.55
16 50
727 22
1800
840 89
19.50
982 65
21 00
1084 00
22.50
1134 00
24 00
= 1284 00
25 50
1374 00
27 00
1584 00
28 50
1694 00
30 00
1804 00
31.50
2044 00
33 00
2144 00
34 50
2274 00
36 00
2384 00
37 50
2494.00
39 00
2674 00
40.50
2764 00
42.00
2829.00
43 50
2861.00
45 00
3106 00
46.50
2871 34
48 00
2848 68
49 50
2826 00
51 00
2769 34
52.50
2710.68
54 00
2656 00
55 50
2552 00
57 00
2448 00
58 50
2344.00
60 00
2227.34
61.50
2110.68
63.00
1994 00
64.50
1946 00
66.00
1898 00
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Meteorological & Hydrological Fea
sibility Studies
June 2009
Time
Hydro
Hours
Cumecs
67.50
1850 00
69 00
1738 00
70 50
1626 00
72 00
1514 00
73 50
1459 34
75 00
1404 68
76.50
1350 00
78 00
1279 00
79 50
1208 00
81 00
1137.00
82.50
1090 00
84 00
1043 00
85.50
996 00
87 00
978 67
88.50
961 34
90 00
944 00
91 50
909 63
93 00
875.26
94 50
840 89
96 00
824 60
97 50
808 31
99 00
794.00
100 50
776.34
102 00
758 68
103.50
741 00
105 00
725 34
106 50
709.68
108 00
694 00
109 50
677 34
111 00
664.68
112.50
644 00
114 00
627 34
11550
610.34
11700
594 00
118 50
577.34
120 00
560 68
121.50
544.00
123 00
527.34
124 50
510 68
126.00
494 00
127 50
474.00
129 00
454.00
130 50
434 00
132 00
421 00
133 50
408.00
135.00
395 00
136 50
384 00
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63Arjo-Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Time
Hours
138 00
139 50
141 00
142 50
144 00
145 50
147 00
148 50
150 00
151 50
153 00
154 50
156 00
157 50
159 00
160 50
162 00
163 50
165 00
166 50
168 00
169 50
171 00
172.50
174 00
175 50
177 00
178 50
180 00
181 50
183.00
184 50
Hydro
Cumecs
374 00
364 00
350.67
337 34
324 00
314 00
304 00
294 00
277 40
260.60
244 00
224.00
204 00
184 00
168 39
154 66
137.00
136 00
135.00
134 00
133.00
132.00
131 00
130 00
129 00
128 00
11660 115.34
124
122.67 121.34
120 00
186 00
187 50
11867
117.34
189 00
116 00
190 50
115.00
192 00
114.00
193 50
113.00
195 00
111.00
196 50
109 00
198.00
107 00
199 50
106 90
201 00
106 50
202.50
106 00
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64Arjo-Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
Spillway of 125 meters tong
June 2009
HEAD(m)
Q=2 2*125*H power
Discharge in cumecs
0 00 0 00
0.25 34 38
0 50 97 23
075 17862
1.00
275 00
1.25
384 32
1.50
50521
1.75
63663
2.00
777 82
225
928.13
2.50
1087.03
2.75
1254 10
3.00
1428 94
3.25
1611.23
T=1 50 S/T+O/2 CURVE              Hours
Elevation
m
Storage
Mcum
0/2
Cumecs
S/T
Cumecs
1376 00
367920
000
681333 33
1376 25
3715 85
17.19
688120.37
1376 50
3752.50
48.62
694907 41
1376 75
3789 15
8931
701694.44
1377 00
3825.80
137.50
708481 48
1377 25
3863 15
192 16
715398.15
1377 50
3900 05
25261
722231 48
1377.75
3937.85
318 18
729231 48
1378 00
3975.20
388 91
736148 15
1378.25
4027 28
464 07
745792 59
1378.50
4089 36
543 52
757288 89
1378 75
4100 44
627 05
759340 74
1379 00
4127 50
714 47
764351 85
1379 25
4166 20
805 62
771518 52
1379 50
4204 90
900.34
778685 19
1379 75
424360
998 51
785851 85
1380 00
4282 30
1100 00
793018 52
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FLOOD ROUTING
June 2009
Time
Inflow
Mean
S/T-O/2
Hrs
Cumecs
Cumecs
Cumecs
0 00
106 00
0 00
1 50
134 66
120 33
695587 41
300
163 33
149 00
695601 55
4 50
192.00
177 67
695643 84
600
214 44
20322
695713 96
7 50
236 88
225 66
695808 49
9 00
259 31
248.10
695924 07
10 50
339 50
29941
696060 44
12.00
419 69
379 60
696245 88
13 50
499.88
459 79
696508 34
15.00
613.55
556 72
696846 91
16 50
727 22
670.39
697277 22
18.00
840 89
784 06
697814 72
19.50
982.65
911.77
698458.12
21.00
1084 00
1033.33
699220.04
22.50
1134 00
1109 00
700092 99
24 00
1284.00
1209 00
70.1030 31
25 50
1374 00
1329 00
702054.26
27.00
1584 00
1479.00
703182 09
28 50
1694 00
1639.00
704441 90
30 00
1804 00
1749 00
705841 68
31 50
2044 00
1924 00
707330 18
33.00
2144 00
2094 00
708969.22
34 50
2274 00
2209 00
710749.89
36 00
2384 00
2329 00
712615.84
37 50
2494 00
2439.00
714570.64
39 00
2674 00
2584 00
716600.43
40 50
2764.00
2719 00
718737.08
42.00
2829 00
2796 50
720968 90
43.50
2861 00
2845 00
723236 41
45 00
3106 00
2983 50
725509 42
46 50
2871 34
2988.67
727876 18
48 00
2848 68
2860 01
730201 86
49 50
2826 00
2837 34
732354 41
51 00
2769 34
2797 67
734441 16
52 50
2710.68
2740 01
736450 16
54 00
2656 00
2683.34
738371.32
55.50
2552.00
2604 00
740206 98
57 00
2448.00
2500 00
741936 14
58.50
2344.00
2396 00
743536 16
60 00
2227 34
2285 67
745009 05
61 50
2110 68
2169 01
746352 34
63 00
1994 00
2052.34
747562.13
64.50
1946.00
1970.00
748640.25
66 00
1898.00
1922 00
749622 36
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66Arjo-Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Time
Inflow
Mean
Hrs
Cumecs
Cumecs
67 50
1850 00
1874 00
69 00
1738 00
1794 00
70 50
1626 00
1682 00
72 00
1514 00
1570 00
73 50
1459.34
1486 67
75 00
1404 68
1432 01
76 50
1350.00
1377 34
78 00
1279 00
1314 50
79 50
1208 00
1243.50
81 00
1137 00
1172 50
82 50
1090.00
1113.50
84 00
1043 00
1066 50
85 50
996 00
1019 50
87 00
97867
987.34
88 50
961.34
970.01
90 00
944 00
952.67
91 50
90963
926 82
93.00
875.26
892.45
94 50
840.89
858 08
96 00
824 60
832 75
97 50
808 31
816 46
9900
794 00
801 16
100 50
776.34
785.17
102 00
758 68
767 51
103 50
741 00
749 84
105 00
725 34
733.17
106 50
709.68
71751
108 00
694.00
701 84
109 50
677 34
685 67
111.00
664 68
671.01
112 50
644 00
654 34
114 00
627 34
635.67
115 50
610.34
618.84
11700
594 00
602.17
118 50
577 34
58567
120 00
560.68
569.01
121 50
544 00
552.34
123 00
527.34
53567
124 50
510.68
519.01
126 00
494 00
502.34
127 50
474 00
484 00
129 00
454 00
464 00
130 50
434 00
444 00
132.00
421.00
427.50
S/T-O/2 Cumecs
750543 64 751404 94 752175 51
752825 04
753355 20
753795 89
754176 62 754498.21 754753 40 754935 07 755044 21 75509367 755096 10 755052.13
754977 05
754885 91
754778.92
754647 89 754484.77 754289 99 754072 90 753842.72 753600 62 753346 07 753077 60 752795 38 752500 60 752194.42 752896.26 752567.24
752228 .21
751877 33
751512 79
751136.59 750749 03 75035045 749940.84 749520 33
749089 07
748647 22
748194 90
747730.63
747252.91
74676: 94
Water Works Design & Supervision Enterprise
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67Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Routing of PMF Hydrograph//lnflow and Out Flow
hydrographs
Time in hours
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68Arjo-Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
June 2009
Annex G: Arjo Coffer Dam Outflow Routings
level (m)
Discharge
1324 5
1327
1330
1333
1336
1339
cumecs
0
4982
147 8
183 75
213 72
240
Inflow Hydrograpon
100 year return Period
Peak Direct Run Off 871 cumecs Baseflow-169 60 cumecs 
Time to PeaK=45 nours
0.80 times August Mean Discharge
Shape developed Dy USBR Dimensionless Hydrograph Peak of Flood Hydrograph=1040 60 cumecs
USBR Hydrograph
A                    Routing of 100-year Flood
HEAD(m; Discharge in cumecs 00
25             49.87 55            147 8 8.5          183.75
11.5          213 72 14 5               240
S/T+O/2 CURVE              T=1 OOhours
Elevation
Storage
0/2
S/T
m
Mcum
Cumecs
Cumecs
S/T+O/2
Cumecs
O
Cumecs
1324 5
12.95
0
3597.222
1327
3597.222
31.9
24935
0
8861.111
8886 046
1330
674
49 87
739
18722 22
1333
18796 12
118
147 8
91 875
32777 78
1336
32869 65
192 5
183 75
106 86
53472.22
1339
53579 08
291.3
213 72
120
8091667
81036 67
240
Water Works Design & Supervision Enterprise
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June 2009
Time
Inflow
Mean
S/T-O/2
Hrs
Cumecs
Cumecs
Cumecs
S/T+O/2 Out Flow Level
Cumecs Cumecs Meters
0
1696
27287 14
169 6            1331 81
1
17685
173.225
27117 54
2
184 11
180 48
27121 27
3
191 36
187 735
27132.22
4
198 6
194 98
27150 38
5
205 86
202 23
27175.72
6
213.11
209 485
27208.23
7
220 36
216735
27247 89
8
2276
223 98
27294 68
9
234 93
231 265
27348 58
10
254 77
244 85
2740961
11
274 61
264.69
27484 03
12
294 45
284 53
27578.05
13
314 29
304.37
27691 62
14
334 13
324.21
2782469
15
35397
344.05
27977.21
16
373 81
363 89
28149 13
17
393 65
383 73
283404
18
41349
403 57
28550 97
27290 77            169 4991           1331 811
27301 75            169 5271           1331 813
2731995             169 5736           1331 817
27345 36              1696385           1331 822
27377 95             169 7218           1331 829
27417 71             169 8233           1331 838
27464 63             169 9432           1331 848
27518 66             170 0812           1331 859
27579 85             170 2375           1331 872
27654 46            170 4281           1331 888
27748 72             170 6689           1331 908
27862.58             170 9597           1331 933
27995 99             171 3005          1331 961
28148 9            171 6911           1331 994
28321.26             172.1314             1332 03
28513 02             172 6212          1332 071
28724 13             173 1605           1332 116
28954 54            173.7491           1332 165
19
444 45
42897
28780.79
29209.76
174401             1332 22
20
475.35
459.9
29035 36
21
506 32
490 835
29320 13
22
537 22
521 77
29635 03
23
568 12
552.67
29979 98
24
607 09
587 605
30354.87
25
530 06
618 575
30763 64
26
661.03
645 545
31202.27
27
692.2
676.615
31666.67
28
720.46
706.33
32160.88
29
748 32
734 39
32683 47
30
776.36
762 34
33233.32
31
804 44
7904
33810.28
29495.26 175 1303 1332281
29810 96             175 9368           1332 348
30156 8             176.8202           1332 422
30532.65             177 7803          1332 502
30942 47            178 8271           1332 589
31382 22             179 9504           1332 683
31847 81             181 1398           1332 782
32343.29             182.4054           1332 888
32867.21             183 7438           1332 999
33417.86             184 5433           1333 079
3399566             185.3795           1333 163
34600 68            186 2551            1333251
32
832 56
818 5
34414 42
35232.92
187.17           1333 342
33
860 56
846 56
35045 75
34
888 62
874 59
35704 19
35
916 68
90265
36389 66
36
944 79
930 735
37102.16
37
955 43
950 11
37841 67
38
966.07
96075
38599 46
39
97671
971 39
39366 78
40
987 35
982.03
4014361
41
997 99
99267
4092994
42
1008 63
100331
4172576
43
1019 27
101395
42531 05
44
1029.91
1024 59
43345 8
45
10406
1035.255
44170
46
1032 84
1036.72
4500365
47
1025.06
1028.95
45837 56
35892.31 188 1243 1333438
36578.78             189 1177           1333.537
37292 31             190 1503          1333 641
38032.89            191 2221           1333 748
38791 78             192 3203           1333 858
39560.21             193 4324           1333 969
40338 17             194 5582           1334 082
41125 64             195 6978           1334 196
41922.61             196 8511           1334 311
42729.07             198 0182           1334 428
43545               199 199           1334 546
44370.39             200 3935           1334 666
4520526             201 6017           1334 787
46040 37             202.8102           1334 908
46866.51 204.0058 1335 028
Water Works Design & Supervision Enterprise
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70Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Time
Inflow
Mean
S/T-O/2
Hrs
Cumecs
Cumecs
Cumecs
48
1017 32
1021 19
46662.51
49
1009 72
1013 52
47478.51
50
1001 96
1005 84
48285 67
51
994 2
99808
49084
52
986 44
990 32
49873 42
53
97868
982 56
50653 95
54
970 8
974 74
51425 6
55
954 35
962 575
52188 32
56
937 9
946 125
52937 8
57
921 55
929 725
53669 91
58
905
913275
54384 94
59
888.55
896 775
55082 85
60
872.1
880 325
55763.61
61
855.65
863 875
56427.28
S/T+O/2 Out Flow Cumecs Cumecs
476837             205 1884
4849203             206 3582
49291 51              207 5152
50082 08             208 6592
50863 74             209 7904
51636 51             210 9088
52400 34             212 0142 53150 9             213 1003
53883 92 214 0118 54599 64 214 6968 55298 22 215 3654 55979 62 216 0176 56643.93 2166534 57291 15 217 2729
62
839.2
847 425
57073.88
57921 31
217.876
63
822 75
830975
57703.43
64
804 46
813.605
58315.94
65
786 07
795.265
58910.51
66
767 66
776.865
59486.2
67
749.27
758 465
60042.94
68
735 88
742 575
60580.78
69
712 49
724 185
61102.22
70
694 1
703295
61604 79
71
675 71
684 905
62086 01
72
657 36
666 535
62548 4
73
643 81
650.585
62991.99
74
630 26
637 035
63419.22
75
616 71
623485
63832 51
76
603 16
609 935
64231 87
77
58961
596 385
64617 3
78
576.06
582.835
64988 83
79
562 51
569.285
65346 47
80
548.96
555.735
65690.22
81
535 42
542.19
66020 12
82
525 74
530.58
66336 16
83
516 06
520 9
66640.3
84
506.38
511.22
66934 48
85
496.7
501.54
67218 71
86
487 02
491 86
67492 99
87
477.34
482 18
67757 35
88
467 66
472.5
68011 78
89
457 98
462 82
68256 29
90
448 32
453 15
68490.9
91
440 58
444 45
68715 62
92
432 84
436.71
68931 44
93
425.1
428 97
69139 32
94
417.36
421 23
69339 26
95
409.62
413.49
69531.29
96
401.88
40575
69715 39
58534 4             218 4628 59129.55             219 0324 59705 78             219 5839 60263 06             220 1173 60801 41              220 6326 61323 35             221 1321
61826 4             221 6136
62308 09             222 0746
62770 92              222 5176
63214 93             222.9426
63642 58 223 3519 64056.26 223.7478
64456             224 1304
64841 8             224 4997
65213 69             224 8556
65571 66             225 1983
65915.75             225 5276
66245.96             225 8436
66562.31 226 1464 66866 74 2264378
67161.2             226 7196 67445.7             226 9919
67720.25             227 2547
67984 85             227 5079
68239 53             227 7517
68484 28             227 9859
68719 11 228 2107
68944 05               228 426
69160 07             228 6328
69368 15             228 8319
69568 29             229 0235
69760 49             229 2074
69944 78             229 3838
70121 14             229 5526
994 14 „   99(101 ,- 09091 59   , 70200 0  -- water Works Design & Supervision Enterprise
223 7190
Level Meters
1335 146
1335 263
1335 379
1335 493
1335 607
1335 719
1335 829
1335 938
1336 033
1336 112
1336 188
1336 262
1336 335
1336 406
1336 474
1336 541
1336 606
1336 669
1336 73
1336 789
1336 846
1336 901
1336 954
1337 004 1337 053
1337 1
1337 145
1337 188
1337.231
1337 271
1337 31
1337 348
1337 384
1337 419
1337 452
1337 484
1337 515
1337 545
1337 574
1337 602
1337 629
1337 654
1337 679
1337 702
1337 725
1337 747
1337 768
1337 788
1337 807
-W3Z 826
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.Arjo Dedessa Hydropower & Irrigation Project Meteorological & Hydrological Feasibility Studies
June 2009
Time
Inflow
Mean
srr-o/2
Hrs
Cumecs
Cumecs
Cumecs
98
386 4
390.27
70059 89
99
378 64
382 52
70220 29
100
372.83
375 735
70372 8
101
367 02
369 925
70518 38
102
361.21
364 115
70658 02
103
355 4
358 305
70791 72
104
349 59
352 495
70919 48
105
343 78
346 685
71041 32
106
337 99
340 885
71157 24
107
332 16
335 075
71267 26
108
326 35
329 255
71371 36
109
320 71
32353
71469.55
110
316.67
318 69
71561 93
S/T+O/2 Out Flow Level Cumecs Cumecs Meters
70450 16             229 8675           1337 843
70602 81             230 0136             1337 86
70748 53            230 1531           1337 876
70888 3              2302869          1337 891
71022 13               230 415           1337 906
71150 02             230 5374             1337 92
71271 98            230 6541           1337 933
71388 01             230 7651           1337 946
71498 13             230 8705           1337 958
71602 33             230 9703           1337 969
71700 62 231 0644 1337 98 71793 08 231 1529 1337 99
71880 62             231 2366
111
311.83
314 25
71649 38
1338
112
306 99
309 41
71732.32
113
302.15
304 57
71810 34
114
297.31
299.73
7188345
115
292.47
294.89
71951 65
116
287.63
290 05
72014.95
117
282.83
285.23
72073.36
118
27963
281.23
721269
119
27643
278.03
72176.39
120
27323
274 83
72222.63
121
270 03
271 63
72265.63
122
266 83
268 43
72305.4
123
263.63
26523
72341.93
124
260 43
262.03
72375.22
125
257.23
258 83
72405.29
126
254.03
25563
72432 14
127
25083
25243
72455.76
128
247 63
249.23
72476.16
129
24443
246 03
72493.34
130
241.23
242 83
72507 32
131
238 03
239 63
72518.08
132
234.83
236.43
72525.63
133
231 63
23323
72529.98
134
228.43
230.03
72531 13
135
225.23
226.83
72529 08
136
222 03
22363
137
72523 84
218 83
220 43
72515 4
138
21563
217.23
139
72503 77
212.43
214 03
140
72488 96
209.23
141
210 83
72470 97
206 03
207 63
142
72449 8
202.83
204 43
143
72425.45
199.63
201 23
72397.92
71963 63            231 3161           1338 009
72041 73             231 3908           1338 017
72114 91             231 4609          1338 025
72183 18             231 5262          1338 033
72246.54             231.5869            1338 04
72305             231 6428          1338 046
72358 59             231 6941           1338 052
72408 13             231 7415          1338 057
72454 42             231 7858          1338 062
72497 46               231 827          1338 067
72537 26             231 8651           1338 071
72573 83             231 9001           1338 075
72607 16               231 932           1338 079
72637.25             231 9608           1338 082
72664 12             231 9865           1338 085
72687 77             232.0092           1338 088
72708 19             232 0287             1338 09
72725.39             232 0452           1338 092
72739 37             232.0586           1338 093
72750 15             232 0689            1338 095
72757 71             232 0761           1338 095
72762.06             232 0803           1338 096
72763.21             232 0814            1338.096
72761 16             232.0794            1338.096
72755 91 232 0744 1338 095 72747 47 232 0663 1338 094 72735 83 232 0552 1338.093
72721               232.041           1338 091 72702 99             232 0237            1338 089
72681 8             232 0035            1338 087 72657 43             231 9801            1338 08a 72629 88             231 9538            1338 084 72599 15             231 9243            1338 078
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.
72Arjo Dedessa Hydropower & Irrigation Project
Meteorological & Hydrological Feasibility Studies
Routing
As actual Reservoir Area Survey is yet to be completed it is better to go up to 1339 00 mamsi
0                  1696                1696 10               254 77         170 4281
20               475 35         175 1303
30               776 36         185.3795
40               987 35         195 6978
45               1040 6         201 6017
June 2009
50
1001 96
207 5152
60
872 1
216 6534
70
694 1
222 0746
80
548.96
225 8436
90
448 32
228426
100
372.83
230 1531
110
31667
231 2366
120
273.23
231 827
130
241.23
232.0689
140
209 23
232 0035
143
199.63
231 9243
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Cofferdam inflow and Routed Hydrographs
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Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt Ltd.
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Summery

Arjo Dedessa Hydropower & Irrigation Project Summary

Arjo Dedessa Hydropower & Irrigation Project - Summary

Project Overview

The Arjo Dedessa Hydropower and Irrigation Project is a major development initiative in Ethiopia, located in the Dedessa sub-basin of the Abbay (Blue Nile) River. The project combines irrigation and hydropower generation components.

        Key Project Details
        Location: Dedessa sub-basin, Ethiopia
Catchment Area: 5,632.64 km² at dam site
River: Dedessa River (major tributary of Abbay River)
Primary Objectives: Irrigation and Hydropower generation
Study Period: Final Feasibility Report completed June 2009

    

Hydrological Characteristics

Rainfall

Parameter	Value
Mean Annual Rainfall	1,453 mm
75% Exceedance Probability Year	1,148 mm
80% Exceedance Probability Year	1,090 mm
90% Exceedance Probability Year	853 mm

Rainfall is unimodal with 63% occurring from May to September.

River Flows

Parameter	Value (Mm³)
Mean Annual Flow	2,477.10
75% Exceedance Probability Year	1,750.00
80% Exceedance Probability Year	1,635.00
90% Exceedance Probability Year	1,390.00

Project Components

Irrigation Development

Gross command area: ~17,825 ha
Successful at 80% reliability level
Maximum consumptive use: ~200 Mm³ annually

Hydropower Generation

Optimal configuration identified:

Parameter	Value
Full Reservoir Level (FRL)	1,376 m amsl
Minimum Draw Down Level (MDDL)	1,353 m amsl
Firm Power (97% exceedance)	23.90 MW
Potential Installed Capacity (at 0.6 plant factor)	~40 MW
Tail Water Level	1,317 m amsl

Design Floods

Return Period (years)	Flood Peak (m³/sec)
2	394
10	575
50	771
100	871
1,000	1,303
10,000	1,948
Probable Maximum Flood (PMF)	3,000

Sedimentation

Annual mean total sediment load: 0.775 Mm³/year
Reservoir volume reduction after 50 years: 38.78 Mm³
Reservoir volume reduction after 100 years: 77.56 Mm³
No interference with dam operation expected

Key Findings

The Dedessa sub-basin contributes 25-26% of Abbay River flows at the border
Project will reduce sub-basin flows by only 1.39% (from 14,053 Mm³ to 13,838 Mm³)
Optimal FRL identified at 1,376 m amsl with firm power of 23.90 MW
Irrigation development is successful even at stringent 90% and 95% exceedance probability levels
Water quality is suitable for both irrigation and hydropower purposes

Recommendations

Develop downstream irrigation project to utilize regulated hydropower releases
Train personnel in hydrological modeling and real-time operation of multi-reservoir systems
Establish flood forecasting networks and telemetry systems