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THE USSR
V/O"S ELKHOZPROMEXPORT” BARO-AKOBO (GAMSELLA) PROJECT
-AKOBO BASIIT STUDY (GAT BELLA) PROJECT CONSTRUCTION OF DALI OU THE AI7/ER0 RIVER AND DEVELOPMENT OF 10 THOUSAND HA OF IRRIGABLE LANDS IN THE BARO-AKOBO VALLEY IN SOCIALIST ETHIOPIA
DETAILED PROJECT REPORT
PART IX. MAIN PROVISIONS OF PROJECT REPORT (PRELIMINARY PROJECT REPORT)
BOOK I.I. EXPLANATORY NOTE (SECTIONS I...3)
PREPARED FOR THE PROVISIONAL MILITARY GOVERNMENT OF SOCIALIST ETHIOPIA
WATER RESOURCES DEVELOPMENT AUTHORITYComposition of the Mair. Provision^ of Project rEepcrt
Book 1.4.          Explanatory Note (sections 1-..3)
Hook 1*2. Bookie Book I.4- Bock 1.5 Book 2. Book 3. Book 4» Book 5*
Explanatory Note
(sections 4...6)
Explanatory' Note
(sections 7-*.14)
Explanatory Note
(sections 15-*-17)
Explanatory Note
(sections 18.. .21)
Nature ] Cond it ions
Cartographic Materials
Water          Management          Construetion Drawings
Agricultural construet ion Drawings
Estimate DocumentsExplanatory Note Composition
BOOK 1.1
Technical and Economic Indices.•
1.      Introduction..........................................................
2.       Project Backgrcaind_,l>ata*. 
•
Qharac'teristlos of Natural_C<md1 ti nna
-*■
BOOK 1.2
4. 
Irrigation Source and. Irrigation System.Locution
Justification. ............................................
5. 
Reservoir on the Alwero River................................................................................
6. 
Regulating Reservoir on the Alwero River..*
BOOK 1.J
7. 
Technical Scheme of the Irrigation System Under Design^—
8. 
Water Management Justification........
9. 
Irrigation Network and Its Structures..^.^.
10. 
Drainage and Escape Network.
11. 
Irrigation Methode and Technique..................................................................................
12. 
Levelling of Irrigated Lends...................................................................................................
13. 
Road Network  nd Ehibankments.......
a
14. 
Organization of Area and Agricultural Production................................................................... BOOK 1.4
15. 
Agricultural Construction.................................
16. 
Water Supply and Sewerage of the Projects Under Design..,..
17. 
Power Supply.
BOOK l.p
18. 
Environment Protection.
19. 
Organization of Technical Operation.
20. 
Basic Provisions of Construction Organization.................................................... ............ ..
21. 
Economics of Construction and Agricultural ProductionIcon.\:rs or doc.; i.L.
Toalniool and .Tootwoio Indiooo,•••••••
1,          introduction.,
2.          Projoot ?aaL®roand     Data...
3«          nhAYwiSorfAfrica of        Natural Conditions,
3.1.       lljyniogropbio Si fraction and      Roliof....
3.2.       Oldanto..
3.2.1.    Genuml Chara tordotioo......••••••••••«.................................•• 19
3.2.2.    Nninihll :oGiao..o....................... 0........................................ ..  22
3.2.3.   Air itertdlty,,.,.2J
3.2.4.    'totoi'-^urf'-'co Evaporation..••••.,•••................. ••«•.•••••• 23
3.2.5.    Ponporuturo itagtaa....,.•••••••••••••••••••♦•••••••• 31
3.2.6.    Rind............................................................................................    33
3.3,       liydmlo^................. . ..................................................................    34
3,3,1,  Thn Alvaro .Rivor Annual Runoff ante and ito Varia
bility..........................................................................................      34
3..%2, The Alvaro Rivor Annual Runoff Dlotrlbatiau,,••••<•• 33
3.3.3,    22io Alvoro Rivar Unslnaa Runoff,...................... •••••••••• 40
3.3.4,    Desies llydrogranho of tho Alvaro River Rainfall
Floods,,.,,..42
3.3.5,    Uinixn Runoff..•••.••••••••...•••••.•••••••••••«..•
3.3.6,    Sodlsont Runoff,.
3,4, ilicdnoarlne^JeolociooLl and ilydregooloeioal Canditianc,,,,,,
3.4.1.    Roaorvoir an '.bo Alvaro River........•••••••
3.4.2.    Seeulatine Reaorvoir on tho Alvaro River..•••••••„• 3.4.3/ Irrigation Systcn...
3.4.4*' ^ain Canal Hau to...,................
3.5,       Soil Roolonatlon Conditions.,,.
$7
W
33
70
77
3.5.1, 
Sail Cover.,,,..
3.5.2, 
Soil Rooloaation "aulng....
3.6, 
Evaluation of natural Conditions.,,.,............................ ,,.••••
30
1335
lable_L
Technical and economic Indicog
Indices
of mea sure
ment
Total
including
the 1st
stage
1. General Data
1.1. Total area
Ha           11,379              1,171
1.2, Irrigated area
Gross area
H
ir
11,146
1,138
Net area
w
10,025
1,020
including: new construction
n
10,025
1,020
1.3. Utilization of irrigated lands
- cotton
tt
5,325
740
- rice
n
2,034
-
- maize
w
1,347
185
- sorghum
if
1,334
185
- groundnut
n
2,893
281
- soya bean
w
1,864
185
- oesane
n
1,341
185
- haricot bean
if
533
-
- vegetables
rr
54
-
- crotolaria
n
2,525
279
.4, Number of state fains
farm
3
1
.5. Land-use efficiency
5 Jf
0.90
0.90
.6. Irrigation System efficiency
0.77
0.77
.7. Irrigation source
1.8. Water supply method
1.9. Irrigation method
- furrow and border-strip
- rectangular check flooding 1.10.Designed Irrigation modulus
ordinate (net;
- for dry season
ha
..b /•••       s u r f e           c e
g r a      v i t y
s u r       face
7,191             1,020
w                   2,834          -
l/s/ha
0.85
0.85
- for rainy season
it
0.43
- for rice (max.)
II
2.87
1.11.Open irrigation network
ha
10,025
1.12.Open drainage and escape network
n
10,025
1.13.Land-olearing works
•i
13,819
0.42
1,020
1,020
3,611
1.14.Total water consumption (gross) mln.m^/yoar 150.60
10.70Table 1. corn'd
"UnlT 3T
Quantli
y
Indices
measu
rement
Total
including the 1st
stage
1.15. Average irrigation rete, 
net/gross
- for dry season
nr
z- „
6.280
ha “
8,170
6,280 BtTTo
- for rainy season
?jTo
1.586
2?™
- for rice
"
1.4JW.
19,610
-
2. Hain Technical Indices
2,1. Discharge (gross) at the main 
canal head
- normal
m3/s
14.20
1.13
I
- maximum supply
ft
16.25
1.30
2.2. Irrigation network, total
kn
322.80
87.97
including: main oenal
it
25.30
18.7
including: in concrete-lined
channel
"
3.20
0.77
- farm canals
« 
27.50
1.86
- on-farm canals
• 122.10
15.84
- reotangular chock dual-purpose
ditches
"
147.90
-
2.3. Drainage and escape network in
earth channel
"
117.30
13.95
2.4. Gravel-paved roads
"
. 70.40
12.40
2.5. Dirt roads
"
253.20
25.30
2.6, Snbankments
2.7. Regulating Reservoir
” 10.90
seasonal control
- levels: FRL
« 
454.50
454.50
DSL
"
450.60
450.60
- storage: at FRL
mln.m-5
74.60
74.60
at DSL
"
17.30
17.30
- effective storage
* 
57.30
57.30
- water surface area
at    FRL
ha
2,210
2,210
et
DSL
n
- effective yield for irrigation mln.m3
865
150.60
865 150.60
2.8. Land levelling
thou, nrr1
Table 1. coat'd.
Unit of l
—*—
Quan tity
Indices
2.9. Electric power supply
-   source
v, - number of diesel powor plants
-   installed power
-   number end capacity of trans former substations
-   power consumption (annual) 2.10.Power supply and sewerage
- water supply source
- water consumption
- length of water supply network 
- sewage volume
measu
rement
Total
i Including the 1st stage
diese
l power plants
pcs 5 kW 2,01 pcs
3
0
12 
&r 27m
-Ln.kWh 8.1 underground
nr/day
1,625.0      408.0
- sewerage network length 2.11.Agricultural construction
- population
- population density in the residential area
- settlement area
including:
residential area
social projects
; production urea
- building density of settlements
- housing
including G-1 residences
km        30.40           5.03
mVdcy 731.30         266.10
kn         24.70           6,28
persons 6,100 PGroono
1,200
ha             135               130 ha         158.80        51.30
n             45.20           9.20
r»            21.90           7.30
n             13.60           8.80
% 18.50 18.50
thou.m 2 75.20 thou.m 2 59*10
7o«w
15.09
11.48
76.10
G-2 residences                          n          ■ftSs
1*24_
3.2o
i
|
G—3 realdGnces G-4 residences
n             5.30             1.78 7.10              11.80
it          -2^10 £.7o
0.59
5.§0
• average housing area per 1 person
3. Volumes of Hain Works
3.1. Earthwork
- excavation
- backfill end fill
person 12.30 12.50
thou.m-^     21,220.1        3,586.2 n          22,455.0        4,417.6V.Indices
Table 1, cont*d
Unit     ofj~ measure*, 
□ent
Total         Including the 1st
otage
3.2.     Concrete and reinforced-
ooncrete works
3.3.     Sand bed
3.4.     Crushed-stone bed
3.5.     Sand-gravel bed and gravel pa vement of motor roads
3.6.     Brickwork
3.7.    Stonework
Including: stone fill, masonry 
rookfill
3.8.    Metalwork mounting
3.9.     Equipment mounting 3.10.   Pipeline laying:
steel
reinforced concrete
concrete
JVC
3.11 .Reinforcement Installation 4. Construction Cost
3
thotunr
45.7
23.5
w
23.3
15.2
w
4*8
1.0
w
282.9
137.5
n
16.2
4.1
H
194.5
176.4
it
28.9
10.8
n
165.6
165.6
t
639.4
236.5
n
169.1
129.9
km
70.4
16.0
ft
16.8
1.9
n
33.2
2.9
n
0.9
0.4
t
2,054.9
1,139.0
^4.1. Total capital Investments
including! pay-back invest ments
A. 7/ater management construction cost 3. Temporary construction facilities
C.   Building material quarries
D.  Agricultural construction and development cost
includingi
a) agricultural construction
including:
thou.3irr 290,287.2 90,723.1
238,186.0 65,593.0 209,422.1 67,294.8
6,337*5  6,337.5 2.260.5  2,260.5 71.281.5  14,730.2 55.385.5  13,156.1
-   housing and social projects
"
-   production projects
"
42,727.1 10,324.5
12,657.9 2,831.5 15,896.50 1,574.2
I
b) organizational and technical
measures
n
E.    Acquisition of transport facilities, > construction machinery, tools and 
equipment for operation service ”
985.6r
!■
i
t
»9
Table 1. cont*d
Indices
TJHrrsrr   Quantity
measure-*
ment
Total
including the 1st
stage
5, Construction Bfficiancy
5.1. Gross produce by tile year of
complete development
/
9
- cotton
t
15,975
2,220
- rice
ff
12,753
-
- maize
fl
6,735
925
- sorghum
w
4,002
555
- groundnut
n
8,679
843
- soya bean
w
3,728
370
- sesame
n
1,609
222
- haricot bean
tf
1,066
-
- vegetables
M
x r
•
727
-
5.2.   Gross produce cost
thou. Birr
40,320.9
4,322.05
5.3.     Farm       production       cost crops)
- cotton
-   rice
(for main
Birr/quintal 62.72
n                         27.35
62.12
. 
- maize
.3 € S /7
ri
21.43
21.14
- sorghum
if
33.29
32.45
- groundnut
w
46.20
45.93
- soya bean
w
47.13
43.06
5.4.     I>abour productivity
Birr/parson
13,216
12,349
5.5.     Annual agricultural and operating 
eexpe  xpens nseess f for or on-    on-ffaarrmm pr  proj ojeeccttss thou.Birr 25,307.44 2,444.81
5.6.      Annual      operating      expenses      for inter-farm projects
5.7. Wet income
5.8. Pay-back term
5.9. Profitability rate of capital investments
w 3,647.34 371.10
w 11,366.12 1,506.14
'] years
%
21
4.8
•Fig I Location Diogram of projects under design in the Baro-Akobo valley
NEKEMTE
Phc.i Cxewa pacnOAOweHMfl oomToB npoeKTHpoBanw
B
AOAuwe 5apo-AKo6o
ITANG
AKOBO
JIKAO
Boro
GAMBE
ADOBO
BA
LEGEND
yCJlOBHblE O6O3HAHEHMB10
1« Introduction
The Project Report for the construction of dem on the Al wero River and development of 10,000 ha in the 3aro-Akobo valley in Socialist Ethiopia is elaborated in accordance with Order- Confirmation No. 7201201800 of March 23. 1982.
Water .•ilanagement Projects under design are located in Illu- babor Region, Gembella Awraja, Abobo Woreda.
During the selection of locations for tho Projects to bo designed there have been used recommendations given by Soviet Specialists from the Ministries of Water Economy end Agriculture of the USSR who visited Socialist Ethiopia during February-
April 1980 and submitted their report "Characteristics of Natu
ral and Economic Conditions of the Gambella Velley and Proposals on AgrHnil! tnTnl Development of this Area" to tho Water Resources Development Authority.
The mein conclusions of this Report were as follows!
1.  According to natural conditions the Gambella valley has a nign-fMeant agricultural potential, the area of lands which 
may be used for agricultural development is estimated to be
880,000 ha.
2.   To begin the agricultural development of tho Gambella valley it is recommended to consider the feasibility of const ructing a reservoir on the Alwero River in order to control the
run-off and irrigate some 10-11 thousand ha of lands from thio reservoir.
In accordance with the abovesaid recommendations the site for the reservoir on the Alwero River has been selocted at the distanoe of 22 km upstream of Abobo settlement. The location of the site has been determined on the basis of available favourable topographic (narrow site) end engineering—geological (hnglnning of piodnont plain) conditions.
In order to raise up levels of water in the Alwero River for i.a gravity supply into the main oanal the construction of
the Regulating Reservoir is envisaged. The site of the Regulat ing Reservoir is located on the Alwero River 8 km downstream of Abobo settlement.
During the selection of location for the Irrigation Systan the following considerations were taken into account. It is re-*12
commended that the Irrigation System be located in the aroa w. a terrain favourable for the application of gravity irrigation methods. In view of these considerations the aroa located in 
the interfluve of the Alwero and Ilyikeni Rivers within eleva tions of 425.••450 m was studied as a site for the Irrigation System. The territory studied extends for 25 tan from the east
to the west and for 16 tan from the north to the south. The area
2
of the territory studied amounts to about 400 km • 
The construction of the Irrigation System Is intended for the following purposes:
— to increase the production cf food snd industrial crops
in the Gambolla valley in order to reach self-sufficiency in 
food stuffs for the local population end reoettlers from the
eastern areas of the country in the nearest future;
-   to increase the amployment of the local population of the Gaubella valley in agricultural production.
Besides, the creation of modem settlements in the Irriga tion System area will provide for a considerable improvement of living and cocial conditions for 8,000 inhabitants of the Gambella valley.
These Main Provisions of the Projeot Report (preliminary Projeot Report) have been elaborated in order to acquaint the
Water Resources Development Authority with the planned techni cal solutions for the projects under design and acquire their
opinions on these solution so as to take them into account in 
the Final Project Report,
During the elaboration of the Hain Provisions of the Pro
ject Report the proposals and recommendations made by the Techni cal Committee of the Water Resources Development Authority on the composition and volume of the Project Report expressed in the Minutes of February 20-21, 1986 were taken into account. 
When elaborating Main Provisions of the Project Report, threo alternatives of the irrigation source location on the Al
wero River were considered as well as two alternatives for the Irrigation System location (see 4.3),
Technical and economic calculations indicate that alterna tive 33 is the most economloal, This alternative provides for the construction of the Regulating Reservoir (downstream site).T
;
r ©ai £»*zl rial df a; I 5: :•
: ■ : . -c. Z
r13
.d the Irrigation System of 10,025 ha to be located under alter native B rzhlch is recomonded for further designing and const ruction.
The construction of the hydroelectric power plant at the upstream site is inexpedient because capital investments per
1 kw of the installed power of the hydroelectric power station 
are 12...19 times higher than the expenses on the construction 
of diesel power plants. However, it may be suggested with certain ty that on the Haro end Gilo Rivers there are acceptable sites
where it io possible to ccdistruot hydroelectric power stations
that vHl 1 have equal or lower expenses in comparison with diesel power plants} besides, their power generation will be sufficient
far the supply of all the electric loads and services in the Gan- bella valley including the projects under design.
That is why the problem pertaining to the eoanooio expedien cy of the hydroelectric power elation construction in the Gsmbella valley may be finally settled during the elaboration of the
Master Plan for Complex Utilisation df Water Resources of the Gambella Valley.
It is recommended that the construction, of tho upstream re servoir on the Alwero River be postponed to the next stages of
the Gsiabella valley development and the expediency of its const ruction be finally considered during the elaboration of the Master Han for Complex Utilization of Water Resources in comparison with the possibility of constructing reservoirs on other rivers (Chiru, Gilo, flaro).1
2. Project Background Dat&
The projects under design are located mainly in the unln-u- - ted area except for the Regulating Reservoir area and they do 
not affect existing settlements. The nearest settlements of lo cal inhabitants, l.e. Pirbong end Pokedi, are located 4 and 8 to from the Irrigation System Doundaries^:!^ >
In agricultural aspect the area under  consideration is not used. Local Inhabitants are engaged in primitive farming on mall plots and cultivate such crops as maize, sorghum, bananas. 
Natural conditions of projeots under design were studied to a very low extent by the beginning of the Project Report elabo ration, except for the foil owing i In Gambella Ciero is a meteoro logical station with a long-term aeries of observations from
1905 to 1985 as well as a hydrological gauge on the Alwero River near Abobo with a series of observations for 1974-1935. Besides, topographic maps at the scale of 1:250,000 are available for
the area of projects under design.
Thorp are no geological, soil and reclamation data for the area under consideration.
In view of the .insufficient amount of background data for the area under consideration which are required to substantiate the construction of the Reservoir an the Alwero River and the Irrigation System the Soviet-Ethiopian group of specialists working under the Baro-Akobo Project executed the following sur vey and research works by the time of compiling the Main Provi sions of the Project Report:
-   topographic survey of the Irrigation System area and the Regulating Reservoir bed at the 1:100,000 scale with 1 m contour
2
2
intervals in the area of 367 km , including 300 km  made by means of aerophotography and 67 kn  by ground survey;
-   topographio survey of the bed of the Reservoir on the Alwero River (upstream site) at the 1:25,000 scale with 5.0 m contour intervals in the area of 150 km  which was made by means of aerophotography;
-   topographic survey of sites for hydraulic works on the Alwero River, settlements, hydraulic structures on the main canal and ths roads under design, quarries of building materi als, typical plots for levelling of irrigated lands at the
2
21,2,000 scale with 1.0> °-5> <>-25 " orotour ^teCTmlB *" th° area of 12.1 ta  and at the 1,500 scale with 0.5 a contour in-
2
2
2
1i2,000 in the area of 1.0 km .
-  377 boreholes 5...120 m deep, their total depth being 
9,072 l.a., were drilled within the Irrigation Systen area, on 
the main conel route ns well as at the sites of hydraulic struc
tures end settlements;
-  103 pits up to 10 m in depth were sunk, their total depth being 170.2 l.tn.;
• cluster pumping tests - 1 test;
-  pumping teats and express pumping tests from geological boreholes - 13 tests;
-  filling of boreholes and pits with water - 87 tests;
-   36 regime boreholes were equipped to observe groundwater levels;
- 184 boreholes 6...100 m deep, their total depth being
2,247.5 l.m., were drilled at the hydraulic works site and the
Reservoir bed;
-  injection of boreholes and pits with water - 71
-      300    boreholes    10..,25    m    deep,    their    total    depth 2,114.7    l.m.,    were    drilled    at    the    hydraulic    works    site tho Bed of the Regulating Reservoir;
P       10 " 46SP ”” thClr
be^'6l71i‘’.“  ‘°
tervsls in the area of 1.2 km I
-  routing of irrigation canals 60.0 km long;
-  three hydrological gauges were set up on the Alwero R - ver as well as one meteorological statlon.and a series of hydro- logical and meteorological observations too carried out during two years;
-  engineering-geological and hydrogeological survey of the Irrigation System area at the scale of 1»25,000 In the area of
2
J20 km ;
-  engineering-geological and hydrogoological survey of the hydraulic works site at the scale of 1»2,000 in the area of
2
1.0 km ;
-  engineering-geological and hydrogeological survey of the Regulating Reservoir bed at the scale of 1;50,C00 in the area
of 30 km  and that of the hydraullo works site at the scale of
tests; bo Ing and inf
I-  pumping teats and express pumping tests from geological boreholes - 14 tests;
-  a series of laboratory geotechnical tests of soixs for aptA-m-fning physical end mechanical as veil as strengvh charac toristlcs of soils;
-  reconnaissance soil-reclamation survey in the area of
2
495 km ;
j, 
2
-   soil survey in the area of 317 km , including 160 km according to the requirements needed for the substantiation of
the Project Report;
-   1,024 soil pits were sunk;
-  aqueous end physical properties of soils were studied at
5 experimental sites;
-  a series of laboratory tests to evaluate physical and me chanical, aqueous and physical as well as chemical properties of
soils in the aeration zone;
-  1 flwH-ni paring survey of the Regulating Reservoir bed, Re— servoir bed and Irrigation Syrtem area which makes up 187 km • 
For the execution of agricultural and agroeconoiaic calcula tions under the Project the following statistical data were ob
tained from the Ministry of Agriculture, the Ministry of State
Perms Development and the Gambella Awraja Administration Centrei
-  annual reports for 1976-1979 and 1984-1985 on the works of the Institute of Agricultural Research at the Experimental Stetlon in the Qanbella valley;
-   statistical data an sown areas, total production and yield of agricultural crops for the whole in the country and for HIu- babor Region during 1977-1984 as well as for state farms during 1979-1983;
-   data on population and conditions of agricultural produc tion in the Gambella valley during 1984-1985,
We would like to express our sinoere gratitude to all Ethiopian Organizations which have provided us with the data required for the elaboration of this Project Report.
2I
i
r3.1 Physiographic Situation and Rell&f
The Oeabell.  Valley  1.  eltueted in the eouth-ve.tern part of Ethiopia  and occupies the area  of 22.4  thou.  ta»  .  Its a  eva ions are 41 On in the west and 6OOm in the east.
The valley extends for 190 ten from eaat to west and for 75 to 150 to fron north to south. There are four rivers crossing the Oanbella valley from east to west, namely Bare, Alwero, Olio and Akobo.
In the eastern part between the elevations 450-600m the valley is covered with thick forest on the area of 6.0 thou.
tai , the rest of the territory is covered with savannah characterized by sparse wood vegetation.
2
In geomorphological respect the Project area is situated along the boundary between the two regions - the Ethiopian
Highlands (south-western slopes) and South-Sudanese lowland (its north-eastern part). Within the area under consideration
the following geomorphological landforms of the iat-order are singled out: The Fit Makonnen highland plateau, the Masongo mountain ranges and high and low Illubabor plains.
The Fit Nakoxmen highland plateau smoothly descends from east to west fron approximately 2,000m to 1,400m and is characterized by tableland erosive-denudational landforms.
The valleys of Bare, Bonga, Chiru and Alwero rivers and those of their tributaries which are situated within the boundaries of the Fit Nakonnen plateau are typical gorge-and oanyon like mountain river valleys, the slopes of which are characterized by intensive lateral erosion and channels - by bottom erosion.
The Masongo ranges are the system of alternating narro ridges and valleys of meridional direction, which bound the Ethiopian Highlands fron the west. The elevations of ridges and valleys descend westwards from 1,400m to 800m and from 800mto 600m, respectively. The rivers still oontinue their erosive activities, but slopes of their valleys gradually
become more gentle in the western direction, and at the near the channel ..otion. of river. wrrow local .3trl of nood.
plains appear.'• 
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• •The high deluvial-proluvial Illubabor plain which slowly descends in the western direction is characterized by weakly
hilly surface with predominance of denudational-accumulative landforms. Within its boundaries the following geomorphological landforms of the 2nd order are singled out! ihe Alwero, Gambella Gilo and Gog plains.
The deluvial-proluvial Alwero Plain on the recambrian crystalline basement (gneisses and orystallis slates) Is
practically bounded within the area under consideration by
the Masongo aountain ranges and is separated from the rest
part of the high Illubabor plain, being an in termountain
plain. Its surface is hilly and ascends eastwards aa well as westwards! its absolute elevations vary from 500m to 550m on
an average. The predominant landforms are denudational accumulative smoothed, though in the valleys of the Alwero
and Gilo rivers as well as in those of their tributaries the
bottom and lateral erosion is still under way.
The deluvial-proluvial Gsabella, Gilo and Gog plains on
the precambrain crystalline, Precambrian and Oligo cane, and Pliocene basements, respectively, occupy the northern, southern
and central parts of the high Illubabor plain) they are
characterized by weakly hilly landforma. In the river valleys
lateral erosion and on sone rivers, bottom erosion is still
observed, which gradually di mln tehee when reaching the boundaries of the lotrl- Illubabor plain. The predominant processes taking
place within their territories are of denudational-accumulative character*
The low proluvial Illubabor plain on the Upper Pliocene basement (stands tones and Alwero clays) occupies the western part of the Project area and is * constituent of the South Sudanese lowland. It is characterized by tehi al.™? reliefr
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• • .which slowly descends westwards with elevations from MOm to 420m end is complicated by numerous dead river channels and flow depressions* The predominant processes taking place
wd+hin its boundaries are accumulative ones, and o y n channels of the Bare, Alwero, Olio and Ako bo rivers lateral erosion is still observed*
3.2 Climate
3.2.1 General Characteristic
The climate of the Project area is determined by its physiographic situation, temperature regime, volume of rainfall and its annuel distribution, air humidity and
wind regime.
As the territory is protected from the east, north-east
and south-east by high mountains and due to its loz^ elevations favourable conditions are created here for accumulation of heat and precipitation.
Tropical monsoons which carry great amount of rainfa~l~l divide the year into 2 characteristic seasonal th* rainy (May - October) and dry (November - April) ones*
The basins of Bare and Akobo rivers are characterized by general increase of humidification from west to east
-    mean annual rainfall increases from 900.. .1,000— at the Sudanese border with predominant absolute elevations about 400m to 2,240mm on the highlands with the elevation of 2,130m.
.Mth higher elevation of the area decrease of variability of rainfall takes place. For the Gambella valley the variation coefficient of annual rainfells varies within the limits of 0.10...0.22, and that for the highlands
-    from 0.09 to 0.13 (Tabla 3.2.1)•..•jTdij
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' !■. oi ’ •1   Itea I Noc.
Station
Elevation
above sea
level
Number
of
observation
years
Rainfall, mm
Mean
Annual
Norm
Coefficient of variation
Cv
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16-
I 17
Ako bo
Aiea Teferl
Asosa
Bedelle Bure-school Gambella Gecha
Gore
Deabidolo I tang
Metu
Nasser
Pd.bor Post Pokwo
Hurumu
Chora
Yayo
403
1,530
1,540
2,050
1,750
480
2,130
2,002
1,800
409
1,940
400
410
420
1,800
1,930
1,810
40
10
21
10
10
75
9
42
14
9
7
30
39
25
7
•10
8
947
1,553
1,270
1,710
1,909
1,290
2,326
2,010
1,228
1,016
1,838
802
882
1,090
1,697
1,861
1,630
947
1,553
1,270
1,710
1,890
1,289
2,240
2,010
1,230
1,080
1,810
800
890
1,060
1,670
1,860
1,630
0.22
0.18
0.12
-
0.09
0.20
-
0.10
0.12
-
-
0.20
0,22
0.19
-
0.135        _uAlong with the decrease of annual rainfalls with the decrease of area elevation# the area Is characterized by sharp Increase of intensity of shower activities. Along
with the general decrease of reinfall days during the rainy season# the duration and daily totals of rainfall per rain increase sharply. Thus# if according to the observation data the maximum daily totals of rainfall for the highlands amount to 46-81 rata (Gore station), these figures for the Gambells valley constitute from 46 to 181 ma (Gambella station).
In general# the Project area la characterized by rather low variability of rainfall as well as of the other meteorolo gical elements# especially temperature and air humidity.f
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•       - c .. ■; •wJ*z*oo^t y.rr .ioaQ.: ,3,2.2. Rainfall Regime
Mean multi annual rainfall at the Gambella meteorological station amounts to 1,289 =n with the highest annual total of
1 96^nno in 1970 and the lowest one of 777mm in 1913 (for the
r
whole of observation period).
The statistical parameters of the supply curve of annual totals of rainfall were taken as follows! C  ■ 0.20j C  « C »
v
gv
The annual totals of rainfall of calculated supplies and their annual distribution are presented in Table 3.2.2.
The analysis of ™ii tl annual fluctuations of rainfall which was done usi ng the method of different integral curves hag shown that for the last 15 year period (from 1971) the Gambella Valley is characterized by lower humidification (average modular rain fall coefficient K ■ 0.90)..J-'-* I'toKc’X- O.d *   >.• <ro‘t m ’
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r;Monthly and annual totals of rainTallt Gambella Station
Monthly totals, mis
P,S*
I
ii
III
IV
V
VI
VII
VIII
IX
x
XI
XII
Annual j
Total
10
25
50
75
35
95
97
8
7
6
6
6
4
4
13
12
10
9
a
7
7
43
38
33
28
27
22
21
92
02
72
62
57
49
47
202
160
157
135
124
106
102
219
196
172
149
137
119
113
294
262
230
190
182
156
149
J22
287
252
218
199
172
165
230
206
181
157
144
124
119
132 118 104
90
82
71
68
64
57
50
43
40
34
32
16
15
13
11
10
a
a
1,635
1,460
1,280
1,107
1,016
872
335
Gj(
f*
«*—
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• •»
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O-'
3
”7 to
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&
> <y 
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1 0 H
1
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•. 7 .
The Gambella Valley la characterized by shower type of rain fall. The duration of showers varies from tens of minute a to 20 hours, the average being about 5 hours. Long rains are rarely observed and usually they consist of separate phases divided by intervals of different duration. Duration of continuous rainfall doesn't exceed 12 hours. The largest dally layer of rainfall
during the last 14 years of observations was registered on June
21, 1975 and amounted to 181 nun*
Data which characterize rainfall regime in the Gambella area are given in Tables 3.2.3. - 3*2.5.
Table 3.2.3.
ItexiniuBi duration of rainless periods in days
Gambella Meteorological Station
Years
Dry
Season
RAINY SEASON
Average
Maximum
V
VI
VII
VIII
IX
X
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985 Average Maximum
-
48
79
47
98
34
76
99
65
40
65.1
99
4
10
5
6
4
11
16
4
2
6
6.8
16
5
6
4
8
5
7
5
3
3
7
5.4
8
3
3
6
6
11
7
5
2
2
3
4.8
11
3
8
9
11
5
3
7
2
3
3
5.4
11
3
4
5
8
5
3
6
5
4
2
4.3
8
6
6
6
6
9
13
9
4
16
7
8.2
16
4
6.2
5.8
7.5
6.5
7.3
8
3
5
4.7
5.8
11.6
6
10
9
11
11
13
16
4
16
7
10.3
16■cd
o
■
.
1
•
♦ r. c*
•      >: *•?
?  -^r
•fei. X
Lt ’• .Number of rainfall days
Gambella Meteorological Station
| Years
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Annual
Total
I960
1961
1963
1975
1976
1977
1970
1979
1980
1981
I 1982
1983
1984
1985
I Average
1
-
-
2
-
0
0
2
0
2
2
0
0
4
1.2
3
7
-
9
-
1
0
1
0
0
2
0
2
0
2.1
7
8
-
0
-
4
3
1
8
5
2
1
5
8
4.3
9
9
-
-
8
4
10
5
5
4
2
2
7
8
6.1
10
7
-
13
16
11
11
11
11
7
5
10
21
14
11.3
15
-
11
16
13
12
10
12
10
8
14
16
18
13
12.9
21
-
14
10
15
19
7
10
14
11
12
22
19
12
14.3
16
15
14
18
22
11
18
7
8
12
11
21
19
17
15.0
14
13
11
10
16
17
13
6
10
13
7
19
20
20 '
13.5
14
14
—
—
16
12
8
12
4
5
6
18
4
9
10.2
3
*
11
3
8
5
5
9
8
3
3
9
6
2
5.7
4
2
4
4
6
2
1
3
0
0
0
3
3
2.4
117
—        I
102
87
77
81
70
66
118
124
110
99•<
r.-V
.f .
-
r
* J.Table 3.2.5
Average and maxituuo number of rainfall days by Intervale at the Gambella Station during 1900-1963,
1974 - 1905
^Sjtoinfall
^XWl.
Months
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-00-
10-900
90-100
100
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Annual
Total
of days
1/2
2/9
3/7
3/6
716
1/17
i/17
713
714
i/11
5/11
5/7
4.9/17
59
0/0
0/1
1/4
1/2
2/4
4/6
2/4
3/5
2/5
2/5
2/2
1/2
1.7/6
29
0/0
0/0
0/0
0/2
2/2
1/5
2/4
2/4
1/5
1/3
1/2
1/1
0.9/4
11
0/0
o/o
0/0
0/®
1/1
0/1
1/2
1/3
1/2
1/2
1/1
0/2
0.5/3
6
0/0
0/0
0/0
0/0
0/2
0/1
0/2
1/4
0/5
0/2
0/1
0/1
0.1/4
1
0/0
0/0
0/0
0/0
0/2
0/2
0/2
1/2
0/2
0/1
0/0
0/0
0.1/2
1
0/0
0/0
0/0
0/0
0/0
0/1
0/2
0/1
0/1
0/1
0/0
0/0
0/2
0
0/0
o/o
0/0
o/o
0/0
0/0
0/2
0/1
0/1
0/1
0/0
0/0
0/1
0
0/0               0/0
0/0               0/0
o/o               0/0
o/o               0/0
0/0               0/0
0/0               0/0
0/1             0/1
0/1 0/0 0/0 o/o
0/1               0/0
0/1               0/0
0/0               0/0
0/1               0/1
00
0/0
0/0
0/0
0/0
0/0
0/1
0/1
0/2
0/1
0/1
0/0
0/0
0/2
01.Table 3.2.6
Relative air humidity, Gambella
Meteorological Station, %
'^Months Yearh-x.
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Annual
mean
1976
1977
1978
1979
1980
1981
198?
1983
I 1984
1985
1
i  Average
«•
53.5
46.9
56.0
40.5
44.7
50.6
47.5
48.5
46.7
48.6
46.6
46.3
44.5
38.1
46.3
57.6
44.5
39.7
44,3
45.3
41.6
54.6
46.7
41.5
47.3
55.0
45.5
47.6
47.6
47.5
48.4
55.6
50.6
45.8
43.6
51.5
51.1
52.6
65.2
51.6
77.2
59.2
72.0
65.5
73.6
73.3
66.8
67.6
66.6
78.3
70.0
83.7
71.9
66.5
68.9
72.7
66.8
81.3
74.2
70.5
77.6
73.4
86.4
76.2
72.2
78.2
76.0
72.6
83.0
80.3
70.9
82.8
77.8
86.6 31.5
77.0
76.4
71.8
74.7 79.1 85.0 76.5 80.4
78.9
87.8
75.0
75.2
66.6
72.2 75.0 77.6 80.5
76.1
76.2
76.2
79.5 75.3 71.7
64.0
68.2
71.2
74.9
71.3 68.2
71.6
77.1 75.6
69.1
59.3
66.6
64.9
65.8
-
64.0
63.9
67.4
59.7
61.5
57.7
43.9
44.0
50.4
46.4
-
58.0
57.5
52.7
63.8
63.7
60.0
59.2
60.9
65.8
-
63.1
65.9
63.2I
JTable 3.2.7
Air humidity deficit,
Meteorological Station, mb
^Months
YearsX.
I
XI
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Annual
mean
1976:
1977
1976
1979
I960
1961
1962
1983
1984
1y85
Average
fc  L ■ 17.3 19.6
17.1
24.1
22.5
20.6
19.7
20.5 22.9 20.5
_
L.      *
21*6 21.5
1
21*7 29.7
25,4
17.4
24.9
23.8
25.1
23.2
! -
25.9 18.2 23.2
28.1
24.9
20.9
27.6 24.0
24.3 24.1
-
22.8
18.7 22.3
24.6
26.3
21.5
24.5
21.5
14.2 21*8
9.4
17.2
10,7
13.5
10,5
10.4
14.9
14.9
18.5
8.3
12.3
6.3
10.1
12,2
11.2
10.2
12.9
7.1
9.7
10.9
8.1
9.9
4.6
7.9
9.6
7*8
8.6
9.7
6.1
6.9
10.1
5.8
7.7
4.5
6.1
8.0
8.2
9.6
8.7
7.2
5.2
0,1
6*6
7.2
4.1
8.6
0.6
12.6
10.1
8.4
8.3
6.9
8.4
8.5
8.4
7.5
8.9
10.1
13.6
11.9
10.7
9,2
10.6
11.0
12.1
10.6
8.5
8.5
11.1
15.5
12.5
13.2
13.0
12.1
13.7
13.7
12.1
14.6
14.0
15.6
21.9
21.3 18.9 21.3
17.9 16.5 17,0 17.9
13.6
15a7 I
16.8
15.8
13*9
15.0
15.2
13.9
14.6
r
*7
r3.2.3. Air Humidity
Air humidity regime is characterized by its normal increase iinn t thhee r rai ainny s y seeas asonon an  andd d deeccrreeas asee i inn t thhee d drry s y seeas asonon. M.    onthly mean relative air humidity during May-October amounts to 69-79% on an
it decreases to 45-48%.
ave averrage  age, an , andd d duurriinng t g thhee d drry s y seeas asonon it decreases to 45-48%.
Annual mean data on a relative air humidity for the observation period from 1977 to 1985 vary from 59.2% (1980) to 65.9% (1985)
During the rainy season daily maximum values of air humidity in the morning quite often reach 100%. The minimum relative air humidity during the observation period was registered on 14.02.1985 End constituted 11.8%a
Monthly mean values of relative air humidity during the observation period at the Ganbella meteorological station are given in Table 3.2.6.; air humidity deficit ia shown in Table
3.2.7,
3.2.4 Water-surface Evaporation
Annual nm off water-surface evaporation ia characterized
by decrease of evaporation intensity during the rainy season
and its increase during the dry season. Maximum evaporation takes place in January-April, when the monthly layer of evapora tion during the period of reliable observations conaituted
154-224 mm j mini mm occurs in June-August, when monthly layers of evaporation varied froa 94 to 134 mm (Table 3,2.8.)
Table 3.2.8 Water-Surface evaporation, Gambell a
Meteorological Station, mm (evaporator data)
The "»< n< miim relative air
Years
I
II
III
IV
V
VI
HI
VIII
DC
X
XI
XII
Annual
Total
1983
1984
1985
192
190
174
188
!24 :
!11 '
02
54
151 00
127
116
97
112 95
94
104 134 ' 114 '
21
51
27
100
166
135
112
128
127
18
138
135
1070
1700-' ; . „• 
( • .
■ -- •_ " Hfl .."
: • .4.
- - ...
• **      J-'-           > r U
< £         >r
~
. V,     - '
r
—
r-*S ’-• 
?• ■ i -I
X.- ’ ’
i r"         »••
-r<- T j
r -*
/
*
eraReduction coefficient which is recommended when using the observation data obtained from small evaporators which are
located on non-standard wind protected sites, was taken K » 0.9*
To determine average nultiannual evaporation from water surface, the formulae of A.P. Braslavsky, N.I. Ivanov and Kayer were used. As initial data were taken the materials of meteorological observations at the Gambella meteorological station. The analysis
of data obtained has shown that the most close to the natural data were the values determined by the formulae of N.I. Ivanov and Mayer. For calculation were adopted the values, determined by the Mayer formula and corrected by the natural data of 1984—1985 (Table 3.2.9)
Table 3.2.9
Water-surface evaporation, Gambella
Meteorological Station, m.
I
II
III
IV
V
VI
VII
VIII
IX
X
U
XII
Years
Annual
total
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
Average
182
153
176
158
228
206
185
179
172 171 181
185
176
183
189
260
196
141
204
157
169
186
212
237
167
212
255
222
185
243
202
190 212
160
203
169
196
222
231
182
207
181
139
189
101 157 101 136
94
99
133 131 136 117 121
68
90 111 101 121 113
62 114 104
87
97
66
75
92
73
80
87
61
101
86
85
81
64
59
74
80
90
81
70
94
121
103
84
60
77
79 112
90
78
73 109
be 114
93
76
82
91 127 111
99
78
90 149 120
102
72
75
99
194 113 165
116 101
115
114
117
128
123
133
203
192
173
194 106 124 121
150
1,374
1,507
1,475
1,781
1,856
1,750
1,480
1,679
1,683
1,530
1,6139Annual distribution of w* ter- surf ace evaporation Ln an imu’ year is taken by the nultlannual vsrug.' distribution, «r-d In t*«
low water yeai**by 1984 real year*
Table 3.2.10 Annual distribution of water-surface evaporation,
Osabell* Meteorological Station, M
Average water year
1
1
1
iT
II III IV V VI
I
VII
mi
a
X
■■
XI   1 HI
i             Annual
total
11,2T 11.6 |     13.1      11.7 |   7.5       «.o      5.0    5.2
5.8
6.3
7.5    9.5 f     too
10.2 j     9.3 |     12.0
10.8 |   8.1
6.2
5.1
Low wator   year
Table 11 presents the relation between the rainfall and evaporation for the same period, which characterizes htDaidlfl-
cntlcn of the Gaabella Valley.
7.2          8.1 ,   8.8        6.8     7.6 |      100
Table 3.2.11
Humidification coefficients of the area
in design probability years, Oaabella
meteorological station
”------------------ \T»
1            X'
I
II
—-----
III
—
17
V
VI      VII
VIII
IX
X       XI
»»
73
■■
HI 4Annual
Average
50 i
0.03
0.05
75     0.04
0.05
0.15
0.37
1.19
1.85
3.02
2,41
2.35    1.11    0.42     0.38 0.80
0.13
0.32
0.99
95 ( 0.02
1.48
2.71
2.72
0.04
0.10
0.25
1.4010.71
0.22
0.05! 0.6?
0.71
1.03
1.66
_____ j
1.29
0.83
0.431
l
0.27
0.06; 0.47
3.2*5. Temperature Regime Annuri ■.« dr t—pw.tur. .coordin, to th. ■mtl-«nauu
°“b‘U* 
station 1. -7.8 Ccrc* 
c -‘ ■ * rt$
Ji JZ'rt
•■
f ’/•
•
1           * ^X            :ty ;2~ f* '^*yrc^ f T $
*iL r<
•     ’          c .
00                ^r.iihFdi
f<x^.
Jfi5
•-Table 5.2.12 Monthly mean air temperature at the Oubella
aeteoroiogical station over the period 1940-1965, degrees
I
II
III
IV
V        VI
VII
VIII
II
X
25U
f Annual
28*1
29. A
30.6
30.2
28.4 | 26.8
26.0
26.0
26.6
27.2
27.4 j  27.6 j       27.8
The dry Beason is characterlsad by high air te^>aratur»a, especially in March-April, when the monthly mean temperatures exceed 50° or approximate this valve. Daily ux1 mums constitute 38-39° with the aaxisuffl temperature over the observation period from 1940 to 1905 being <t4,9° (16.OJ.1985). The absolute value of the aaxlmrw air temperature at the Dam site meteorological station reached 47.0° on 19.03.1985.
During the rainy season monthly man temperatures constitute 26.0- 28.0° on an average, and maximum temperatures usually do not exceed 55°.
Monthly mean mini mm air temperatures vary during the year from 18.5° to 21.9° on an average, reaching their mlnlmm values at the beginning of the dry season. The absolute a ini arm of temperatur- over the observation period from 1976 to 1985 constituted 10.3° (27.12.198?)
h
Monthly and annual as an air temperature values are characterized by a very low variability. The variability cooffloimrt of annual mean temperatures is 0.02, and that of monthly mean temperatures - 0.02-0.04.
The dally run of air temperature la characterized by —— between 12 and 15 hours local time, and win 1mm - between 3 and 6 hours in the morning. The amplitude of air temperature daily variat ions for the rainy season comprises 10-15° on an average, and that r °  the dry season - 1&-20°) during some days of the dry season the
r
difference between maximum (39°-43°C) and ninlmrn (15°-17°C) dally
?
*  temperatures can reach 24°-26°C.
ir
The multiannual mean total of temperatures at the Gambella 3rte°rological station is about 10, 150°C, including 5,220° for
tbe dry season and 4,930° for the rainy one.■;.t < rv 
a .            6
>■? n«< * itttfac* 
k
T
.
TCu /'- 1»«3o ftfL Tr-
:£>  ' .'
UK*
r
• 
:9 "- '.-. t ■-,•$? y r ire r • .m
• -J.
-Monthly neim air teaperatures at th* Gera bells aotoorologlcal station over the period froa 1940 to 1965 are presented tn ’Th*
Technical Report on Hydrological Investigations during th* Period
froa 1962 to 1985".
3.2.6. Wind
The wind regime of the Genbells valley 1* characterized by
low average values of wind veloolty. Annual aown wind veloolty according to the Geabella Meteorological station data over the
period froa 1976 to 1985 constitutes 0.66 a/sec. Daring the year
the decrease of monthly mean wind velocities is observed beginning
from the dry season and proceeding to the rainy season - froa 0.9
to 1.0 a/seo. in February - April to 0.4-0.5 a/secw in June-August.
During the year southern and south-eaetern winds are prwdoainant.
The cxtreae values of wind veloolty in (Isabella can not be evaluated., because wind velocity aeaaurenents hare are conducted with the hel* of the m»ing-up anonoaeter by the Method« allowing to determine only average velocity between observation terns, i.e.
for 6 and 12 hours. Maxinun wind velocities in the Oanbella valley
are observed ever short periods of tine aalnly during the transition periods froa the rainy to the dry season and vice versa, when wind gusts exceed 2Ow/seo.
Ten-dry periods naan wind velocities over the period fro« 1976 to 1985, as well as Monthly aean velocities and wind direction over
the period froa 1947 to 1955 at the Qaaballa Meteorological station are presented in "The Technical Report on Hydrological Investigations during the period froa 1982 to 1985".
Beginning froa May, 1984 the observations on wind direction
•nd velocity are conducted at the Daa site Meteorological station. Monthly aean wind velocities for this period constituted froa
0-9 to 2.2 a/sec. with predominance of southern and eastern winds.t •£? i
, r xf
1?; ryp
ar't •
wF ;.Uv« .nJ Le-oisclcribvttMaxinua wind velocities for the observation period ar* given
l 0 Tibi® 13, aaxlsun wind 'relocities of design probabilities - in
Table 14.
Table 3.2.13 Maxlam wind velocities, Daasitv
meteorological station, a/eec.
Tear
I
II
III
IV
V
VI
VII
VIII
IX
X
n
III
1934
1985
1986
-
11.3
9.5
-
9.6
9.9
-
18.9
4.0
-
10.0
17.6
3.8
10.6
8.5
16.5
8.4
17.7
9.6
8.7
10.4
9.6
9.4
8.7
9.9
8.0
9.2
Table 3.2.14 Maximum wind velocities of design pm bablll ties,
Dane!to meteorological station, a/sec.
P
1%
3%
5%
10%
25%
50%
V
29.7
26.7
25.8
23.7
20.8
10.4
3.3 gvdrolort
3.3.1. The Alvaro River Animal Runoff Rato end ita Variability.
The gauge at the Abobo aettleaant la a reference gauge on the Alwero River with 2,790 k»  catrhaent area having ten-year flow record (1976-1985)  which la insufficient for the Alvaro River annual runoff
2
2
B
rata calculation and for the variability param tors calculation accord
ing to the record.
The Bare River at the Ganbella town waa taken am a river-analogue with 23,400 kn  catchnent area and having 74-year runoff record. The
b *«ea for selection of this river as an analogue were the slailarlty or  climatic conditions, synchronise of runnoff fluctuations in tine
homogeneity of rumff formation conditions.
The Baro River annual runoff rate at the Oaabella town site *o " 12,730 aln.ts\ variability coefficient C  ■ 0.16 and asyma try
y
^‘Tflelent C - 0.0.
s■ hJioor
1
•  - ;
• • • • • • •
• • • *
T' ~T".7 , ~ ■ i      1       nr
_
....... HFi
•
•
-i - ;-
-
JF
•
■
fr
• • • •
. .__________1 r ; . . I
r i' ’ «OXOTO£J’<*.T
:j
i.
.j i r;
*•
♦
,i !*,*•••* r
iThe analysis of dot locations on the probability curve vftich correspond to years of joint observation* Hu shown
that in general this period is characterized by decreased runoff« i.e. the relation of mean annual runoff for this
P-riod to the runoff rate is 0.90. The Bart River runoff
rtlunes during these years were either at the rate level,
or low than the rate a
The Alvaro River runoff rata at the Abobo srttl^ent
site was determined with the help of a eomection graph of Monthly runoff volumes of the Alwero River at the Abobo settlement and those of the Bare River at the Gembella town during Joint observations. The average values of runoff volumes of two neighbouring months wore used as the Alwero River monthly rurtff volumes because of the difference in catchment areas - the corresponding water regime phases of these two rivers ere somewhat shifted in relation to each
other, allowing to increase coslderably the tightness of connection and asking it possible to determine the Alwero River runoff rate at the Abobo settlement by graphic method.
Using the Baro River runoff rate at the gambol la town* i.e. 12,730 sin. m^ which constitutes 1,061 mln. when recalculated for mean monthly runoff, ths Alwero river run
off rate was determined at the Abobo settlement site amount ing to 32.2 mln. m^ per month or 626 mln. m^ par year.
To determine annual rata of the Alwero River at the Dsmsite (1,102 km  catchment area), a oonnectlnn graph of monthly runoffs of the Alwero River at the Damalta and at
the Abobo settlement was plotted for the period of Joint observations from September, 1983 to 1983 inclusive. Th- connection graph is rectilinear, tightness of connection
is high. By the Alwero River nmoff rate at the Abobo settlement (32.2 mln. per month) and using the connect
ion graph, the Alwero River runoff rate at the Donsite vaa determined, constituting 14,0 mln. m^ per month or 168 mln.m^ P«r year.
2wrr yrf
’** S«>lT-q fcl/V I-
' ;ff .0P*0 a ’
z dtfJia «*itw a*i »\ W'rf? ?■.■
.•
.
:A srff ±c
Trocar ri& tri'
•»   wto-y   a   %o   tjjad   "dJ   rb   1     '   '•■•   '   ~?r
■ '■ ./!’ o*x«a£A ."J# 1e «» .-"f' -
U:'.        42 2
t4r
• 1.’-
•3
r
2.-J ?1■s
? ■ %
•
aurr* B
. -
'±. oc
I .
nt -Taking into account 11*1 ted voluae of observstloa dat* at design aites, as wall bb the absence of high flow yaara
of rKr^ recurrence during the observation period. In order
to determine annual runoff variability coefflatsnts of the Alvero River, a dependence of variability coefficients on catchment areas was plotted for 10 rivers of the south-western Ethiopia with 13-24 year records of enrol al runoff* The determination of variability coefficients was node using ? sethods - Bethod of aoaents and graph-analytical oethod, the results of calculation differ insignificantly. In *oat of
the cases the preference was given bo the value* obtained by graph-analytical Method. By the dependence of variability coefficients on catchaant areas It was obtained* for the
Al were River at the Abobo settlement alto C  » 0.24, at the
y
Deaalta C  - 0,28. Asymmetry coefficients of annual runoff
y
at design si tee are taken by C  ■ C  correlation.
ay
The Regulating Reservoir site under design la located 13 k*. downstreaa of the. Abobo aettleaent at the (Jtaa aettla- aent with 2,900 ka  catchiaent area. The Increase of catchment
2
are* at thia section eoeprlse* leas than 4j$ of th* Alwaro River catchment area at the Abobo settlement, the section being without tributaries over its whole length. Taking
into account the accuracy of hydroaetrlcal aeasureaanta which coaprlses several per cent even under favourable conditions, and also the availability of button and lateral filtration in the channel within the taction free the Abobo settlement to the Utaa settlement amounting during low water period to 5% of the runoff voluae, it we* assumed that the annual runoff, variability and runoff bi™*! distribution
at the Regulating Reservoir site do not differ fro* those
of the Alvero River at the Abobo settlement.
The values of the Alvaro River annual runoff of design probabilities at the al tea of the structures under deal gw
«* presented in Table 3.3.1.y 
' ? WiJoV fc.Xttr’’
llHi
#         < W
»>» ■'
’ waooe. r
LI -w *•         • iTXft
* .'X?/*T *” t* * *+■
■t? ?
’f?* fib’-i.-n *c iMc
»* <sdr •JLolllr oo t      -if3*9 feat
-
tJ
'
VLr -•
1*0 *-
•
V■4b♦•
istrxfl
n :
a3
JLh *r crj'XfA
v
•XTO3 0 -•
V
0 wrf T9J& "• '■ Eli
.’Aa
llCV 1*8 ?
afoul l ■.£. to
.
** V. $.T»£ C'Mi'XqBCC H5-
0v03A
•J* VC
Jfl B 'XO
•
'■f nh - • ; fi^nsr'y *»-<* 
rt-fifyo
£ c. f-
» 
-CjLT- £L -*-;
•'         •*’      ’ -J.lr.iT. >.i# ~J< T?.~ 1
7Thp Alwero River annual runoff of design probabilities at the al tea of the structures
under design
Characteristic
of annual runoff
Probability, %
0.11
1 5
10
M
50 |75 ,85
1
l 2L
Damsite
Volum«,aln.a^
331
”86
249
?30
19S
166
134
119
109
94.
Mean Annual
discharge, a /sec
10. sB
9.07
3.99
7.29
5.7S
J. ?6
4.25
3.77
3.45
2.98
Regulating Reservoir Site
Voluew, aln.js
1*139
1,002
383
020
7?6
520
526
470
**38
386
Mean annual
di b charge, ■'’/sec
36.1
31.0
?8.0
26.0
?3.0
T9.6
16.7
14.9
13-9
12.3
Regulating Reservoir Site
(excluding runoff froa the llvero River catchment area upstream the Daulta)
Volume
?94
?.52Ljuziis
.• ■ > "i
j
13 2.2. Th® Alwero River Annual Runoff Distribution.
The rater regime of the rivers of th® region, including
that of the Alwero River, is characterized by two hydrological seasons - the flood and low water ones, which correspond to the rainy and dry climatic seasons of the year.
The flood period on th* Alwero River begins in May and ends
»  November, lasting for 7 calendar months. During this period
n
■ore than ?0% of the annual 'lV passed. Within this period the increase of runoff volimea froa May to August and their smooth decrease to November are usually observed.
The low water period is characterized by natural decrease
of runoff froa December to February - Jtoreh and its slight increase in April due to precipitation occur Ing aalnly in the mountainous part of the basin. The low water period runoff la determined, as
a rule, by the runoff volume of the proceeding flood season - in
high flow year the low water period runoff la usually incres'i
and in low flow year it is decreased.
The annual runoff distribution of the Alwero River at the Regulating Reservoir site la determined by the observation data
at the Abo bo settlement during 1976 - 1985 on the basis of
selecting annual runoff distribution for certain years as design
data.
On the basis of analysis of the Alwero River annual runoff distribution at the A bo bo settlement, 198.3 - 1984 water aanage- aent year was selected aa design year with the annual runoff volnac approximating the 2054 probability of annual runoff (740
1976 - 1977 water aanagement year was selected as design ®*an flow year, which approximates the 50% probability of annual runoff ( 601 aln.a?) and is characterized by monthly distribution
of runoff approximating the average distribution for all the
years of observation|
1982-193J water management year with the annual runoff of 4J6 *as selected as design low water year, which approximates the 90% probability of annual runoff.■iximuH XannoA -r
■ J - \ • - *
.•
•is
.
. , ... 
'.T'iS
4.-   •’. ■  «
?. uroc • ' o.‘. •' • f . .; O';    7 ■- ->!< no ' C ■'
..
■ »<.
.bl
’ •*
-ipr"'-
••
4
. 
r?
1  *ba:j
.
V-
t : ?c
- .. .
t
3’ >oJ\o •-3-
I?
. ..•>
•M
-4*
V
*•
nc 
Xi
* I*
rr .«
a’c~ 3-i ': - *>>   r;rr
4
. «4
»
'.••-■ J •-' J ’
•- -zt jci .a* ’: Ul
-•
»•
e ’          •• r
••9
}»•
-J
►f
1 -  4 j.
r;
r
r-/ i •
c» j .
s
'-.
♦. I
■j
• M'-
*
- -C :r:
J t 33 £■
*S'Z;
£jja zct i;:.
0*
4
■> r.
/X
.1
(/
■-’VC" •
*
r
*Comparison of the Alwero River runoff distributions by months of 1984 and 1985 at the Darnelte and at the Abo bo settlement site has shown their very close correspondence (Table 16). These are good reasons to recommend the design annual runoff distribution, which was obtained by the observat ion data on the Alwero River at the Abobo settlement for the Damsite as well.
Table 3.2.2.
The Alwero River annual runoff distribution
at the Dam^tte end at the Abobo settlement
for the years of Joint observations
Monthly runoff,% of annual runoff
□lie
I III
III
IV
V I VI | VIII | VIII | IX              I X ] XI | XII
19 3 4
Damsite
2.0
0.8
0.9
1.7
5.4
11.1
14.5
17.6
23.4
9.9
8.5
4.2 i
Abobo
2.4
0.8
0.8
0.9
5.7
12.2
15.3
18.3
22.6
10.3
6.8
3.7
19 8 5
Damsite
1.5
0.6
0.5
1.9
7.1
11.8
14.7
17.8
19.4
11.5    9.1
4.1 I
Abobo
1.6
O.7
Ot6
1.7
6.3
9.9
14.7
19.1
18.9
13.9    8.8
3.8
Table 3-3.3
Annual distribution of the Alwero River runoff
I Annual flow
Characteristic!
Monthly runoff,% of annual runoff
V
VI
VII
VIII
IX
X
XI
XII
I
II
III
IV
High flow
3.5
6*5
15.6
29.1
17.2
14.6
7.4
3.2
1.4
0.5
0.5
0.5
Average flow
6.3
11.4
13.8
21.4
18.6
13.6
8.0
2.8
1.5
0.8
0.9
0.9
Low Flow
5.2
13.3
12.2
24.7
15.8
15.9
6.1
2.7
1.2
0.9
1.2
0.87
iJ +£
r         •:-? I t4I n rc
.<• 
5of- .        * v r *■
WB
■ -s q«
.  33 bixa -<'2j rC “4fe
• Ji" u c * . ~
*:o 
• •.40
3.3.3 The Alwere River Maximum Runoff
Taking into account the insufficient hydrological study back ground of the Alwero River, the calculation of maximum runoff at the sites of structures under design was “de In accordant
with the existing recommendations on calculation of maximum water discharges when hydrological observations are not available or when they are insufficient•
In design practice in such cases the empirical formulae are widely used which in general take into consideration the main factors of runoff formation on the catchment area slopes and in river channels. The moat widely used kind of empirical formulae are widely used which in general take into consideration the main factors of runoff formation on the catchment area slopes and in river channels. The most widely used kind of empirical formulae are so called reduction formulae which evidently reflect the reduction of maximum runoff moduli with increase of the catchment area or that of the travel time, and volume formulae which express maximum discharge as the function of flood volume, its duration and geometrical shape. All the empirical reduction formulae are regional and have interpolations! character,
Vi th this in view, prior to using any of the formulae for unstudied catchment areas, it was checked whether they correctly reflect the factors which define the mechanism of maximum runoff formation in the given region. The best method is to check these formulae by the observation data for the rivers of this region.
With this purpose 12 rivers were selected with e»t-nh»>n+ areas ranging from 524 km  to 23,400 km  in the Baro, Blue Nile
2
2
and Gibi-Omo rivers basins located within south-western part of the Ethiopian Highlands and which have, observation records allowing to determine their statistical parameters.
For checking, those formulae and methods of calculation of maximum diacharges were selected, which had been developed either
the observation data collected in Ethiopia or In neighbouring countries:■J ‘
J     :7C \T..'
••
’*■ .
»• L
’■ : .*
WA
t'j
>.1 • Il
Wi *r<
aoi^oaifi ‘.v
“ r %.• „ r -
,
• - • • »*4»* •       - ■*-*.
’/I41
H. Shi.-, ror^l., developed lor the centrel port ol Ethiopia.
Q 1%
where ,  0^ ■
-     0.0116                k°'7?f,
maximum discharge of 1% probability,
m^/eec;
daily maximum rainfall of 1% probability,
at P1?t
p1%
P 1%
catchment
parameter
100 nun
120 mm
150 mm
area, km2;
depending on P^J
f - 0.17 - 0.1S;
f - 0.20;
f - 0.20 - 0.30
Calculation procedure based on trigger’s curves of maximum discharge reductions of 1%, 2%, 4%, 10% and 20% probability plotted for rivers of the Blue Nile basin (within Ethiopia).
3.     Calculation procedure based on "envelope curve" obtained for Kenya.
4.     Calculation procedure based on family of "envelope curves" plotted byJFrancou and J. Rodlet for 1,200 outstanding runoff maximum of probability approximat ing 1% (with data relating to tropical Africa).
The checking has shown that none of the 4 tested procedures nan be recommended with confidence ms the basic one for calculat ion of maximum die charges of design probability for unstudied catchment areas. Their common drawback is that they don’t take into account or do it insufficiently, such, important factors of runoff formation as the character of shower activities and
travel conditions of flood water on the way to a final site.
The calculations revealed that metnod of J. Francou and J. Rodiet and M. Shim's formula are the best for the given conditions and can be recommended for approximate calculations.t
•u
- * ?c.”
•
l             ricrJf5 /c
.V-
•
'• 
-• 
**’
- r .. •
*
%*
•
*- . •
7*rru
s; : ■
..
. *'
-
f. •' -*           ■**/:                 » l». * “-
.
c,
♦
•. • * • - ••! • - 1 - ' -
' *' ’ J
AC *The Sokolovsky’s volume formula was selected as design formula as it has good theoretical foundation  takes into
9
account basic factors of runoff formation and, at the same time, it is rether simple and its parameters can be determined by those relatively limited data on runoff and rainfall, which are available for the given region:
-0-^(yp )^A
o
where, PT - layer of rainfall for the period of time
T, mm;
P Q        ■     layer     of     rainfall     performing     the     Initial moistening of soil, mm;
X ■ coefficient of rainfall runoff;
f ■ coefficient of flood shape;
- influence coefficient of lakes, swamps and forests;
■^2  = coefficient taking into account channel regulation;
Q'f ■ flood preceding di acheyga
The duration of flood raising t  is determined by formula
n
where, relation of flood recession to flood raising.
For small rivers with basins covered with forests or with permeable soils/= 3.0-4.0; f » 0.92 - 0.75, this
Is true also for average rivers with ordinary flood plainn; for average and large rivers with considerable flood plains
4.0-7.0; f « 0.75 - 0.48.r
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'rr] f- ”
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.•
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%
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W-
\
rRiver channel regulation is taken into account on average end large rivers having considerable flood plains by formula
; 2 ’ Y1 ■
where.
. depth or flood plain ruling during floods I
■ flood plain area;
- vuluae of rainfall flood determined by
formula
13
W  - 10  (Pf-P^-A.
,
To calculate begin travel time which equals to flood
hydrograph raising time, the following dependences vjere used*
T. 1.2 T
p
1 -1  * lck ,
T - 1.OQOL __________
M
where, T = basin travel duration, mln;
Tck - slope travel duration, min;
L - channel length, km;
M - roughness coefficient of river channels;
J - average weighted slope, ;
q^ - maximum runoff modulus of 1% probability.
As value is included In the formula, the calculation
was made by method of sequential approximations. The value of obtained by method of J. Francou end J. Ro diet and by
M. Shim’s formula was used as the 1st approximation.
Determination of value was based on the analysis of observation data for rivers of the region, Including those for the Alwero River at the Abo bo settlement site. The fluctuation curve of pre-flood discharge with the increase of catchment area was plotted to be used later for calculations,r
*
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J?.L. ”
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• • -
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. :'
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.<?IXEP^Ot
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•
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<LAL« -i«5*XF 4 •» • •J  '* •
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•
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c’ ’flJ
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..
t
-
r--v
V
*
/r
T
-t
-pniwfall layer of 1% probability (P^^) ±or period of
design duration T with an average catchment area was defined
on the basis of processing of rainfall data for short periods
of tine. If 1^1 day,
P T1Jfi ’ P-j d*7 1*                 (T) Kp»
vhere, py-|%       " dally layer of rainfall of 1% probability,
corresponding to average weighted height of catchment area,an;
(T)     • relation of aaxLnua rainfall layer of 1%
probability    for    time    period    I    to    dally    rainfall    layer    of    the same probability;
Kp - coefficient of rainfall reduction by area defined
by formula
** where, a - catchment area, km ;
------- n
1.0.001A ,
2
n • parameter being equal to 0.80.
The value of ^(T) was defined by the curve of rainfall totals increase plotted by data of regional meteorological
stations.
The layer of initial losses (P )
Q
for    all    catchment    erees
is taken constant and equal« to 5 mm.
Flood    shape    coefficient    ranges    from    0.50    for    the    Baro    River at Oambella to 0.S5 for the Guder River at Guder.
The calculations by Sokolovsky’s formuln in accordrmna with the above-mentioned method were made at several values of runoff coefficient. The best results were achieved at 0.45 runoff
coefficient. In this case me an-root-square error for eleven sites was ±10.6%.(
• Li,'9l
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The comparison of calculation results by the given method with the actual values of maximum discharges obtained on the basis of statistical processing of natural deta shows that
within the range of tested catchment areas - from 52h tao to
23,400 km  - this method is rather good in taking into account baAic factors of runoff formation within the south-western part of Ethiopia and oan be recommended for calculation of maxima water discharges when observation data are not available or insufficient.
Calculation of maximum water discharges of the Alwero River at design sites was also made by the method of unit hydrograph.
The comparison of calculation re suits of the Alweix> River maximum discharges and runoff volumes of 1% probability for design sites which were made by Sokolovsky's formula and by unit hydrograph method la given in Table 3.3.4.
Calculated characteristics of the Alwero River
maximum runoff at design sites
Sites
Calculation
jy D. Sokolovslq
Calculation by
unit hydrograph
method
Adopted
values
3 1*.
m/sec
la:.’
Dsnsite
373
51.3
336
61.8
354
56.6
Regulating
reservoii'
538
164.4
549
162.5
544
153
Regulating reservoir [without runoff from the catchment area up-stream the Damsite
436
>
86.0
438
97.6
437
91.8Oaf'-i ^■’ " ”
.■ •
-rcl-a---
034 ’ -Variation coefficients of th. AlM.ro River
runo" **
design     sites     wore     obtained     by     dependence     ol     variation     coefflclen Of maxiiHun annual water discharges on catchment areas.
Asymmetry coefficients are adopted on tha basis of analysis of correlation of south-western Ethiopia and also taking into consideration recommendations for rainfall discharges of -ountaln rivers with monsoon climate equalling to 4C .
y
Calculation results of maximum water’discharges and flood runoff volumes of design probabilities are given in Table 3.3.5.
Table 3.3.5 Maximum discharges end flood volumes
of the Alwero River
Probability, P%
25
10
5
—     °.5 |
Damslte, C  = 0,50; C  - 4C
y
sV
Discharge, nr /sec
156
209
248
354
404
534
Volume,mln.m
24.9
33.4
39.6
56.6
64.5
85.5
Regulating Reservoir site, C  -0.41; C  - 4C
r
fl            V
J
Di scharge9 m /sec
272
348
402
544
609
772
Volume, mln,
76.5
98.9
113
153
171
217
Regulating Reservoir site, C  ♦ 0.46, C  - 4C
y
gV
(without runoff from the catchment area upstream the Damsite)
“ 1,
Discharge,® /sec
201
266
515
437
494
642
Jtolume,mln.m^
42.2
56.0
66.1
91.8
104
135• t i**'
0 27 n i.'U
:a sort
■• .
•
rtc
'i
•XC W r 7.’.
.. , ...
r<f :0 ??.-70bB SIS “'
*'              a
• _ ■•.
• ; . •• 'MiOl 8ifC
.
r
‘■
■ :1r riC775i-
. - ,. . « 1'iD'
1 — - f . ’ —
•• >•!- ■
rll '■
I17
Note: Flood volumes are given without basic runoff. Basic runoff volumes amount to:
-   Damsite -                   5.2 mln. a?
-   Regulating Reservoir site -
41.5 mln. m
-   Regulating Reservoir site (without runoff from the^ catchment area upstream the Damaite) - 15.6 mln. a
3.3.4 Design Hydrographs of the Alwero River Rainfall Floods
Plotting of flood hydrographs of design probabilities for the Alwero River at the sites of the structures under design
was based on the available observation data.
To characterize single-peak model hydrographs which are characteristic for the Alwero River, the following coefficients were used:
Coefficient of hydrograph shape fullness
B            0,01l6h
where,              - maximum mean daily discharge, m^/sec;
D      -       average discharge during flood period,n3/sec; T      «       flood duration in daysj
h - layer of flood runoff, mm
w
Dimensional coefficient 0.0116 
h is in urn, T-in days and Q - in m^/seci
*  10^ provided that
3t>,4oo
coefficient of hydrograph shape is defined by 
a
where, tQ - duration of flood raising in days.
As
a    peak    equation    describing    the
flood    wave,    the
follo
wing type of equation was adopted:-     ordinates of design hydrograph
expressed in fractions of maximum discharge of the given excess pro
bability Qpj
-     abscissae of design hydrograph, expressed in fractions of conventional duration
of flood raising t j
n
a - parameter depending on hydrograph shape coefficient
Kf.
The conventional durations of different probability floods raisings were calculated by formula
t  -
n
0,28 K  bp .
f
The hydro graph shape coefficient is defined depending on asymmetry coefficient of hydrograph K . which is calculated
by formula
where, - runoff layer prior to flood peak, mm;
h ■ runoff layer over the whole flood period,mm.
Absolute values of design hydrograph ordinates are
defined by multiplying relative values "y" by value of design discharge and values of abscissae - by reducing the
correspond< ng values Bx" by value of conventional duration of flood raising tQ.
The possibility of applying typical equation for calculation of design hydrograph coordinates of the Alwero River la affirmed hy actual observation data.
Coordinates of reinfell flood design hydrographs of the Alwero River at the sites of structures under design are given in Tables 3.2.6 - 3.2.0.VI /
rr- 1M5    to    e
•.JTCiJ OST*
an'J to      • ; •. .0 .ib
-■'■■      -
■Table
Coordinates of design probability flood
hydro graph a of the Alwero River st the Daasite
Tlae,
hours
P-O.1%
P-0.5%
P-1%
*-5%
P-10%     P-25% I
2.8
5.6
8.6
11.2
14.0
i6.e
19.6
22.4
25.2
28.0
30.8
33.6
36.4
39.2
42.0
44.8
47.6
50.4
53.2
56.0
61.6
67.2
72.6
78.4
84.0
98.0
112
140
168
10.0
15.2
67.2
146
256
366
440
497
524
534
529
508
487
450
419
387
351
314
288
256 •
209
167
130
104
83.4
47.2
28.9
15.2
11.6
10.0
13.9
45.5
112
195
278
333
376
396
404
400
384
368
341
317
294
266
238
219
195
160
128
101
80.9
65.2
38.0
24.2
13*9
11.2
10.0
13.9
42.3
103
175
244
296
330
347
354
350
337
323
302
278
258
234
213
196
175
144
117
92.6
71.9
48.2
35.8
23.4
13-4
11.0
0.0
2.4
H.4
r 1.9
122
172 205 231 243 248 246 236 226 210 196
181
165
148
136
122
100
81.4
64.7
52.8
43.3
26.9 18.6 12.4
10.7
10.0           10.0 I 12.2           12.2 29.7           26.9 65.7           53.8
108          84.5
147          112
175          133
195          146
205           153
209           156 I 207          154
199 l     149 191          143 179          136 167          127 155          118
141 i     109 129          100 119          93.2 108          84.5 89.6         71.3 73.7         59.6
59.8         49.4
47.8         40.7
39.8         34.8
25.7         2J.6 18.2         17.4 12.3         12.2
10.6         10.6\
i
I
J. ■ -*■
Table 5.3-7
Coordinate. of deelgn prob-blilty flood hydros^
of  th. flvero River et th. Regulating Reeervolr .!«•
Tine*
hours
P-0.1?*
P-0.5%
P-1%
P-5%
P-10%
P-25%
5.4
10.8
16.2
21.6
27.0
32.4
37.8
43.2
48.6
54.0
59.4
64.8
70.2
75.6
81.0
86.4
91.2
97.2
103
108
119
130
140
151
162
189
216
270
324
40.0
44.4
91.2
208
362
508
633
713
757
772
757
728
691
648
596
545
494
443
406
362
289
230
176
150
128
79.5
59.0
44.4
41.7
40.0
44.2
85.5
176
296
416
501
563
598
609
603
580
552
512
478
438
398
364
330
296
245
199
159
131
108
75.3
57.6
44.4
41.1
40.0
43-5
77.3
161
262
368
448
504
534
544
539
519
494
458
423
393
352
322
292
262
216
176
141
121
100
69.2
54.1
43.5
41.0
40.0
42.9
76.2
130
206
282
337
377
395
402
390
384
366
344
319
297
272
250
220
206
174
145
120
102 .
87.1
63.9
53.3
43.2
40.9
40.0
41.7
69.0
123
188
249
296
326
342
348
345
333
320
302
200
262
240
222
206
188
160
136
114
95.4
83.1
63.1
52.0
43.1
40.7
40.0
41.2
67.8
110
161
205
237
246
267
272
270
260
251
240
230
214
198
166
175
161
140
121
105
91.0
81.8
63.0
51.9
43.0
40.2— r
{
r> r»
•
•
•
t
f1
1
r« A
•
S' •
C. r<
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80c'
FOc   i
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eoa
rod
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ver
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-
'TT r t’ A fl -
fTable 3-3-8
Coordinates of design prob.hlllty flood hydrographs of the Alwero River at the Regulating Reservoir site
(without runoff lion oatchaent area upstrean the Daaalte,
Tine
(hours)
P-0.1%
P-0.5%
P-1%
P-5%
p-10%
4
8
12
16
70
24
28
32
36
40
u
48
52
56
60
64
68
72
76
80
88
96
104
112
120
140
160
200
240
20.0
23.7
63.5
163
294
410
524
592
630
642
630
605
574
536
4P3
449
406
362
331
294
231
182
144
113
94.6
53*6
36.2
23.7
20.8
20.0
22.9
50.8
124
224
319
399
451
484
494
484
466
442
409
380
342
309
276
243
224
176
138
100
06.4
71.2
43.7
31*4
22.9
20.7
20.0
22.7
50.6
120
203
291
358
404
429
437
433
416
395
366
357
312
278
254
228
203
166
132
103
86.2
70.0
43.2
31.1
22.6
20.6
20.0
22.4
42.6
90.8
153
215
259
291
309
315
312
300
285
265
247
226
206
168
170
153
126
103
83.0
67-2
55.4
38.3
29.1
22.4
20.6
20.0
22.2
42.1
84.1
136
187
222
249
261
266
264
254
244
227
212
197
180
163
150
136
114
93.8
76.6
64.3
54.4
37-5
28.8
22-3
20.5
20.0
21.8
36.3
67.1
105
143
168
188
197
201
199
192
185
172
161
150
138
125
116
105
88.8
74,3
61.6
52.6
45.3
32.8
26.5
21.8
20.4■•
•*
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3.3,5 Minimum Runoff
The minimum water dlocherges at .the Alwero River are
observed during the low water period of dry season, usually
in February - March, reaching absolute minimums aftar rainy
seasons of preceding low flow years.
The  absolute  minimum  on  the  Alwero  River  at  A  bo  bo  during the   observation   period   was   observed   on   March   20,   1985   when   the value of water discharge reached 0,47
The ml rd mum water discharge at the Damnite was registered on March 18-20, 1985 end amounted to 0,04 m^/sec.
The minimum mean monthly water discharges are also observed in February - March, reaching absolute minimum in March, 1985 ~
0.96 q '/sec at the Abo bo site and 0,26 m^/sec at the Damsite.
The mlnlnruni water discharges of th? Alwero River during the observation period at the Abo bo site and at the Damsite
are presented in Table 3.3.9.
Table 5.3.9
Minimum water discharges of the Alwero River, a^/sec.
fears n~
II
III     lIV    lV
VI
VII   [nil
IX
X
XI     kii
1 Annual *
hinlDUM
Abo bo  Settlement
1976
1977 1979
1 979
1980 1981 1992
■ 983 ’984
<985 1984 iBQS
( -
2.90 2.99 5.67 2.24 2.56 3.07 1.60
1.18
1.82
0.34
0.52
-
(.78
1.93
3.16
1.57
1.64
1.57
0.90
1.01
0.64
0.18
0.14
—
1.50 1.24 1.93 1.24
—
2.16 0.95 1.12 0.47 0,18
0.04
2.56
1.64
1.24
1.37
1.64
1.18
1.57
1.67
0.54
1.08
0.14
0.34
4.20
1.12
3.81
4.20
7.18
7.30
4.71
1.07
2.18
1.68
0.90
0.36
12.6
9.88
13.5
12.3
15-5
12.3
13.5
1.07
11.1
10.8
2.61
1.35
15.2
14.7
22.8
18.2 19.5
21.3
13.8
7-96
15.7
17.2
2^07
1.71
27.4
20.4
30.0
15.7
20.4
29.4
12.6
25.6
20.9
20.5
4.95
3.02
25.4
24.7
24.3
16.9
31.0
22.0
17.0
17-8
23.9
24.1
4.35
4.17
>0.1
18.5
25.1
19.5
14.7
16.4
14.6
23.5
9.68
11.9
2.07
3.49
3.88
10.2
13.0
7.80
10.2
5.02
7.42
12.8
8.25
8.62
2.20
2,61
♦«81 6.94 7.5‘ 4.54 4.6' 3.8' 3.6; 16,( 3.7; 4.44 0.9?
1.r
—
1.12
1.24 •
1.37
1.24
•
1.57
0.90
0.54
0.47       . 0.14
0.04• • I
• •
' • (. Ms
3W  mcTT vr f
no a'ur/.'itz
.f? :>■• &<•?".
r noi?*r •
J.
.      "*r
-
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'
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fc0M *a
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7> xr<V- J
The analysis of regional rivers runoff with long records has shown ths* 19A4 for the Alwero River wrf r low flow year and can be defined as a year of 90# orobabtlity,
■
3.3.6, Sediment Runoff
The rivers of south-western Ethiopia are insufficiently studied for sediment runoff, and data on the Alwero River sediment runoff up to 1984 are not available. During 1984 -
1985 Soviet end Ethiopian specialists executed systematic sampling of water for turbidity, granulometric composition, sampling of bottom sediments and measuring of suspended load discharges, which allowed to determine suspended load nmoff volumes for these yeers. 1984 and 1985 are low flow years
and, consequently, the sediment runoff values obtained are lower than their average values for multiannual period.
Characteristics of the Alwero River suspended load runoff at the sites of structures under design are presented in Tables 3.2.10, 3.2.11.
Table 3.3.10 Suspended load runoff volumes of the Alwero River
for 1984-1985* t
fears
id IV VI VH
Damsite
mi
IX
X
n
XII
Annual
total
1984   16.0     '».o      5.0     16.0     130   371     639
1985
?o.o     3.3       3.2     27.3     305    540   10^0
855
1528
’.432
J.176
336
596
207
380
52
80
5*063
6,699
1984 533
]995 519
Regulating Reservoir site
118  126  |  155  |l972|5573  |6934  (9486  [l  17161132  ^350l  917   44012
107       82     388 2592 4501 [7852 £734 £729 K79 p97i 1024
46304 .■
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; b g 
'1 -?r
{, ''r
-i!)
».
’"r ?      ’0      ?♦?
k c.'U.iS       ' OJu/
<* */<
• •
. k»    31   fjoictt       f
r
i-J?
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o/r-
*- 4
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•     ’     * a
in* ?• r‘       L ?.           H’’-
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. ? ?                  M0 '        1 . ’
/cTl- Ho/''
•
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t J * »          • •
«rTable 3.3.11
Mean aultiannual suspended load runoff of the Alwero River at the Regulating Reservoir site
for 1976-1985
X. Months Vsluee\
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Annual
OjioVsec
R,kg/aeo
», t
3.65
0.18
482
1.84 0*07 169
1.73
0.07
187
2.81 0.12
311
13.2
1.25
3,348
20.7
2.21
5,728
32.0
3.70
9.910
45.9
5.50
14,731
36.5
4.28
11,094
29.6
3.36
8,999
14.8
1.47
3,810
6.79
0.40
1,071
17.5
1.88
59,840Atr-tA
t
•• i
si
■?
r
o
J
r33
Due to absence of systematized observation data on sediment
runoff of the rivers of the region which could have been
used as analogue, it Is practically impossible to determine
with sufficient accuracy the multiannual characteristics of
sediment runoff at the sites of the structures under design.
Direct measurements of entrenched sediments on the Alwero River and neighbouring rivers were not carried out. Taking
into eccount a certain approximation of suspended load calculat ions, small values of water turbidity and bottom sediments size, the fraction of entrenched sediments can be determined as percentage of suspended load runoff. For the Damaite this percentage is taken 40%, for the Regulating Reservoir site - 10%, which correspond to the recommendations of Soviet and foreign authors for the similar natural conditions.
The Alwero River water runoff during flood periods Ln mean multiannual respect comprises 65% of the th-ht! runoff. During low water periods the sediment runoff is negligible
and can be neglected.
The highest mean monthly water turbidity during the observation period at the Damsite constituted 94g/m^, mean daily - 197t/m^, Instantaneous - 214g/m^(September, 1984).
The magnitude order of suspended load runoff values during flood periods can be shown by unit water samples taken during measuring of suspended load runoff on 21.09.1985, when water turbidity on two verticils amounted to 230 g/a\ On the basis
°f the analysis of the Alwero River sediment runoff at the Reservoir under design, mean suspended load runoff can be taken 200 g/m^ (including entrenched sediments the total sediments the total sediment runoff comprises 280 g/m” ). Then, mean “tultiannual water runoff amounting to 166 mln. will be
39,50St.
5<•
X
♦
.
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r
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, ; *e
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•
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♦ •I
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1
I
I3
The highest mean aonthly water turbidity during the observation period at the Regulating Reservoir site reached
-f20 g/m . The magnitude order of the Alwero River suspended load runoff can be shown by the average turbidity which was obtained during measuring of the suspended load runoff at the Regulating Reservoir site on 21.08.1985 and amounted to 27U g/m , and water turbidity on one of the verticals constitut
3
3
ing 714 g/m  On the basis of the analysis of the Alwero River sediment runoff at the Abo bo site and Regulating Reservoir site the suspended laod mean runoff during the flood period can be
3
taken JOO g/m , and including entrenched sediments - 530 g/m . Mean multiannual water runoff comprises 620 mln. m  (excluding runoff from the Alwero River catchment area upstream the Demalte
- 454 mln. m ). Then, mean annual sediment runoff during the flood period will comprise 173,910 t(127,347t).
3
3
3*
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.3,4. Engineering-Geological and Hydrogeological
Conditions
3,4,1. Reservoir on the Alwero River
The Reservoir is located within a highland valley of the Haoon-
end a high delnvlo-proluviul plain on Precambrian basement (south eastern part).
Within the limits of the Dam Site the Alwero valley is asymmet rically V-shaped with steep slopes; the right slope is 25-30°, the
left slope is steeper and amounts to 35-40°, sometimes there arc
sheer cliffs.
Folded structures of the crystalline base of the Reservoir area formed under the conditions of a mobile zone of the Late-Precambrian geosyncline, and regional metamorphism end granitization are rela ted with it. At the last stage of geosyncline development active
tectonic processes took place which complicated the terrain.
The Dam Site is located in the core of on anticline whose axis
is perpendicular to the river valley and parallel to the Dam 3ite. Precambrian rocks of regional met amor phiam take part in the
geological structure of the Reservoir area. According to structural
and lithological peculiarities as well as to the degree of metamor
phism the Reservoir area is made up by two complexes of Precambrian rocks. Granitoid augen gneisses and cherty gneisses with interlayers
of mylonites and breccias make up the northwestern part.
Gneisses and crystalline schists of mixed origin, para- and
oi'thogneiageg^ para— and orthoschists make up the southeastern part.
Proluvial sedimentary rocks of Pliocene age represented by
clays and sandstones commonly occur on Precambrian basenaut in the a °utheastem part of the Reservoir area. Their thickness is diffe
rent, frequently irregular along the strike reaching sometimes 20 a °r more.
Quaternary deluvial, deluvio-proluvial deposits are mainly de-1-'*'^--'tfi t ^3' Xofifc--OX' sxu-
______________
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r» ■•jiecent depoaits ura represented by colluvium that la spread t  the feet of large slopes in the form of accumulated blocks and
debris as well fl  by alluvial sands with various size of gmln n
0
e
tectonic fissures of type B deserve the utmost attention, hinc e etonic dislocations hn-oa been found along the axis of dam, at its
PhyI1<3atiOn’ by raeatls of boreboles and according to the data of geo- QlcfQ survey and mapping ( sheet 7, Fissuring Map).
Tectonic dislocations Nos. 1 and 2 are classified as 1Yth order ai’f, a' ^ey have zones of mylonites and teotonic breccias which
uotg of tectonic grinding of rocks•
which occur as narrow thin bands within some areas adjacent to
■ 0Qpjcs and make up some stretches of ths river bed.
Active tectonic events that took place in the Late-Prectuabrian tine complicated the area through a series of fault-like disloca
tions with breaks in continuity sublatitudinal in trend, thus hav-
,j ng determined the character and direction of rifting, the presence
of orushing and mylonization zones.
Three types of fissuring have been distinguished within the area on the basis of genetic classification.
1.   Tectonic fissures:
A- fissures connected with formation of folds; they belong to cross and diagonal fissures as against the trend of folds, make up
a thick system of minor flseures and commonly occur in the area.
B- fistrurea connected with zonea of tectonic faults ( fault fissures).
2.   side-rupture fissures. Disintegration is characterized by detachment. Such fissures occur on the left bank of the Dam Site
area in the reaxr parts of large benches.
3.   Fissures of weathering. They belong to primary and inherited fissures which form along fissures of various genesis and are de veloped in the surface part of the rocky sass. Primary fissures are
0
a  a rule open, 1-3 mm in width and penetrate up to the depth of 4»*.7 m. Sometimes the width between separate fissures amounts to a few centimetres. Inherited fissures of weathering penetrate up to the  depth of 10-20 m and are mainly healed. Primary kaolin and, ClOl’  seldom, cherty mata-r-ipl serve as aggregate.
^ithl^
eCtO11:Lc faul± No  1
-  along which the Alwero liver b
the  Dam Site area has been investigated by means
id passes
of boreholes*’?•             JHh-
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rcQ^ar^c ‘W:.,’G fpuf fort b^rct yr '
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’
-£>• MfefaSMMFf pl c jr-WJJOO 3OO-A and 300-B up to the depth of 100 3. Faultt bedding |Ofl*cnts; dipping azimuth - S» 190°, dipping angle - 30°. The total
° j-v. of fault amountB to 6 a and consists of a zone of j^/lonitiea
fl) a zone of weakly cemented breccias (1»5»*»2 atronglyoemented breccias (2...2.5 m). In natural bed :lng the
J  i nites have a hard to hard-plant la con ale toney, plasticity num- ^er is 18..*26, moduli! of deformation is 24...33 'IPs.
Tectonic fault Ho.2 is represented by a zone of mylonites which 1° natural bedding are below the gro mdwizier table and. eako
a zona
up a
 senlhard rock.
Tectonic dislocations Nos. 3, 4, 5, 6, 10, 11, 12 belong to
minor faults, large and medium fissures and repressit zones of higher fissuring of rocks, their width being 3.5 m. As a rule their modulus of fissuring exceeds 30 and continues up to the depth of 30...40 m. though the fissuring diminishes with the depth, still it remains sufficiently high. From the depth of 15...20 a fissures
are healed. Kaolin and, more seldom, cherty material serve os aggre gate.
According to the fissure void coefficient the surface fissuring is attributed to medium and weak, more rarely to strong. The mnin direction of fissuring is west-noMhwestem with dipping angles about 70-90°. The azimuth of gneisaousnass trend is
At the Dam Site the rocks are intensely weathered from the surface. The boundary of Intensely weathered rocks penetrates to tho depth of 10... 15 ai on the right slope and J...5 m on. the left slope. The thickness of a rottenstone sone on the right slope
founts to 3...5 m inareasing to 10...15 a in zones of tectonic dis-
°ca(,ions. Qn the left hqnk rottenstones oocur only above the ele- VQti°n of 510 m,
Ihe weathering zone la 20 m thick and increases up to 30...40
a 011 Slopes.
Within the Reservoir bed area the water complex is confined
a
fi  ^irst from the surfaoe and embraces the entire thickness ofs-
0 th 8aured Zones of crystalline Precambrian rocks, it is considered
ft
zone. Low—fiaaured, pr>nnti pally impermeable crystalline Qccur®kng at the depth of 35...50 a make up the confining bed.hlch ln natural boddlns or. below the sroundw^ter table end nah® up a semihard rock.
tectonic dislocations lios. 3. 4* 5t
minor faults, large and medium fissures and represent zonw of
11  • belong o
higher fissuring of rocks, their width being 3.5 m« Am   rule their
a
modulus of fissuring exceeds 30 and continues up to the depth of
30..*40 in, Though the fissuring diminishes with tne depth, still it
rpnninfl sufficiently high. From the depth of 15...2O m fissures
are healed. Kaolin and, more seldom, oherty material serve as aggre
gate.
According to the fissure void coefficient the our face fissuring
is attributed to medium end weak, more rarely to strong. The main
direction of fissuring is west-nodrthwoatera with iUpp^ng angles
about 70-90° . The azimuth of gneisaousnaos trend is .
At the Dam Site the rocks are intensely weathered from the
surface. The boundary of intensely weathered rocks penetrates to
tne depth of 10.,.15 m on the right slope and. 3«.,5 m on the left
slupe, The thickness of a rottenstone sone on the right slope
amounts to 3...5 ra inor easing to 10...15 m in nones of tectonic
locations, Cta the left bank rottenstones occur only above the ele
vation of 510 m.
The    weathering    zone    is    20    m    thick    and    increases    up    to    30...40 n  on slopes.
to ‘mhlJa th° R0Servoijf bod a™ the water complex is oonfinod
saurad zones of crystalline Proeambrinn maWb 4 * < - A — J Jt — gI
•.
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‘•r :ju.{ tne water-bearing complex.
° The Alwero valley la a natural drain of tho water-bearing
igx. On watersheds groundwater tables aro at elevations excoed-
C0B1P the PM* 1x1 the RQflorvoir.
105  fhe intake area of the water-bearing complex is located 
vTithin the boundaries of Masongo ranges and the increment is effect ed exclusively due to precipitation. Water discharges into deeply 
cut river valleys and a ravine and river system of the high plain 
area as well as into the water-bearing complex of Gog basalts. Waters of the complex are sweet, predominantly hydrocarbona-
ceous, sodio-calcif erous with mineralization of 0.2 g/1 and pH of
6.2...o*S« Groundwaters display slight carbonic-acid corrosion agninat concrete of standard density.
Permeability properties of rocks were investigated by means of injections, single fillings with water, cluster and single pump-
ln^ests. A seepage section along the axis of dam was plotted on 
the basis of permeability tests. The upper zone that is the most weathered and fissured and looated on the right slope and whose thickness      is 3... 5 m is characterized as very highly permeable. However at the depth of 10 m permeability properties sharply decrees down to the average value of the permeability coefficient, i.e. 
to 0.1 m/day. Seepage losses at the dam foundation will amount to 700 thou, np/yeor. Losses at dam sides will be 500 thou, cP/year. Total constant losses from the Reservoir will equal 1.2 mln. nP/ year making up 0.75% of its capacity.
Physical and mechanical properties of rocks making up the Site area are characterised by high strength and deformation 
’aluea. Density of gneisses is 2.5...2.6 tf/cP. Ultimate strength unweathered and weakly weathered gneisses usually exceeds 100 
and that of cherty gneisses is much higher.
x  Strongly weathered and intensely fissured rooks (rottenstones,
29) possessing low et-nongth and high permeability properties be removed.
Pt>Q  Recent physico-geologioal events are characterised by the
hillside wastes on steep slopes; they are composed of
ai
Qo
 °°arse debris and their thickness is 1*«*3  « 
a
are
tetla^Chea with side rupture fissures. It is especially charac-
a   C foi> the left slope which needs some measures to improve lt
al0 ^ stability.r
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•Jtfatnr YAM xi£e»*The route of outlet passes in strongly weathered and highly , iaaiired granitoid gneis.ea (rottenstones) crossing steeply dlpp-
j-jg tectonic fissures with crashing zones at a sharp angle* The ^< imaaa of rot cans tones changing to a block rock amounts to
n
2    ,3 m and exceeds 9 m in the zones of tectonic rtminhing.
The route of outlet canal paasea in less weathered and leaa fissured granitoid gneisses representing a block rock which turns
into relatively monolithic rocks from the depth of 1...3 a. 
The stretch of tunnel route in the area of the inlet portal is
coa posed of monolithic rocks and has no loose cover deposits* At
the stretch of the outlet portal loose cover and strongly weathered rocks (rottenstones) have their total thicknes-'S of 3...4 m. The
route of tunnel passes in medium-fissured chorty gneisses* Their fissuring modulus is 3...5* strength ooefficiant exceeds 15» ulti
mate resistance to one-axis oompreasion ia 150...200 -LPa. 
£
The tunnel will be driven in rocky mass containing water and composed of large blocks, it will also cross tectonic dislocation 
No.6 with a zone of higher fissuring up to 2 m wide. The predomi nant fissuring along the tunnel route has stoep dipping angles and trends along its axis. The crossing fissuring with S^»l° and 
W-270° dipping azimuths and dipping angles of 50. ..oO® is unfavour able and may result in wedge—like inrushes of the tunnel crown. 
Pormeability properties of rocky mass at the tunnel route stretch are characterized by low ralnan of the permeability coeffi cient. It averages 0.05 tn/day and reaches 0.1 m/day in zones of tectonic dislocations where an insignificant suffosion of loose afisregate of fissures is possible. In the process of driving tho forking vdll drain granndewater and as the water ooluntn over the tunnel floor does not exceed 5...10 m the inflow will be insigni ficant.
Coarse debris soils with loam aggregate and heavy grass loan ^*6 recommended for filling dam body. The depositee of soil have
. 9en P^spected, i.e. deposit No.3 on the left bank-reserves amount 0 2 5O thou. 3, and deposit No.4 on the right bunk-reserves amount
a
° 350 ^ou.  3
m  e Total dQtailed prospected reserves amount to 600
The thickness of useful strata equals 3m-, groundwater is
ao
VQ f lQaent* Preparatory works inolude uprooting of forest m °f soil and vegetation layer 0.3-0.5thick.r. *
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»jhere are no sands in the pro J oct nreo which could be used for preparation of concrete and execution of filters. Minor deposit
iio.3 
reserves about 5...7 thou, up was prospected in the
mouth Of the May Shet 6.5 km from the Dsn Site and ”111 need a motor road to be constructed on the right bank of the river or
a bridge crossing on the Alwero River for the Dan Site- Abo bo tcotor road passing along the left bank of the river.
Aggregate for concrete nay be obtained in situ by means of breaking stone for crushed stone and sand or it nay be transported from prospected sand quarry Mo.1 located in the area of the Irri gation system 37 km from the Dam Site,
At present prospecting of building sands is going on in the radius of 7... 10 km from the Dam Site.
Gravel and pebble soils with loam aggregate to be used for filters and pavings were prospected at the distance of 4 km from the Dam Sito near the Dam Sito-Abobo motor road (depoeit Ho.3). Preliminarily prospected reserves equal 50 thou. cP. Useful strata ore 1.5...2 m thick, the thickness of overburden is 0.5 m. 2he de posit area is afforested. Groundwaters arc not present.
Building atone may be obtained, in situ by quarrying granitoid, gneiaaes and cherty gneisses occurring from the surface (depo
sit Ho.1).■-r.
1 at r-'aa Qr.
■ 2. vo ' ■' b!S6 -3’ * c !c :it
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• ~~2              ating Reservoir on the Alwero River
j?he area of the Regulating Reservoir is located in the Alwero
slopes to the weet from absolute elevations of 500 m to 450 m Jn  geological Harms the area is composed of effusive, volcano-
out into effusive rooks.
ihe effusive rocks belonging to Lower Pliocene (Ng) occur averywh.fc e and at low depths, they are represented by (log basalts
,
whose thickness exceeds 170 m. These are flows of olivine basalts cons^isting of several overlying beddings of successive eruptions aepa^rated, as a rule, by scoria zones and dipping to the west. 
They are represented by grey a^nd dark-gray massive and porous (vesicular) basalts. The rocks are highly and medium fissured with healed. Joints, the aggregate being calcite or clay material. The
roof of effusive rocks is represented by a weathered scoria zone composed of highly porous (vesicular) basalts whose upper and moat weathered part has been attributed to the weathering crust. Basalts
have no outcrops within the area of the Regulating Reservoir.
The interlayers d series of tuffitea ( Up ) baa been attribu
ted to volcanogenio-sedlmentary rocks and was formed as a result of accumulating various volcanic materials, i.e. ash, sand, bombs and normal sedimentary rocks represented by layered clays and more seldom64
Mid-     Quaternary     dopoaita     (     o     i
basalts,  volcanogenic-aedimentaiy  gtrat on fathering  Qruat of posits.  They  are confined  to  buried  Val*  &nd ^'^•"Quaternaxy  de- hydrographic network  of the ancient AlwJT °f “^uateraaiy 
by bed and floodplain facies of alluvia! f
loams and clays whose thickness amounts to 
Upper-Quaternary deposits (Q i 3 6 '
latlng Reservoir area overlapping ^evw^«>a in the Regu-
1    dep°Sita* 
form up the recent slightly undulating reli” ^ by proluvial and, more seldom, deluvia/q ferruginous gravel soil with clay 
30(1 rePrea®nted i,e ‘ sanda»
2
*** rePreaented aya ’ heQvy loam8 and
characterized             by             a
formation             honog^^'^0/6’’0814’
to 2-3 m within the Regulating Reservoir hlckneaa which amounts
Recent deposits (Q_ )
i
nQ
n  -
“*** ' WIV' aro fspresented fay allinrtoi
deluvial sediments which are spread in th wero River and make up bottoms of
Alluvio 1 deposits rest on an eroded 
° l00d
lVlal and alluvio- ° f tha U’
channals.
-t       Of       basalts       reaching       the
gravel,  silty  to  gravel sands,  loamy  sands and  loams*  Sand  and 
gravel deposits are poorly sorted and clayey a3 a rale*
Alluvia-deluv
ial
depos
its
are
lithologically 
repr
esented 
by 
loamy    sands    , 
loams    and 
clays,
some
times
silty 
and    w
ith    an 
insig
nificant    amount
of    gravel
and 
grUss• 
They 
fill
ravine
bottoms
and 
are     not     widely
spread, 
their
thickne
ss     is
Insi
gnificant
and 
makes
up 1 -2 nu
voiced end tectonic>
here  connected  with  x®pl rent Gog basalts. That 1b
is characteristic tor ail
** of lava flows the Gog 
of fissuring connected «1 Main angles of fissuring are 2° 3 degree of fissuring the basalts be
e of th.   lolt their recent 8t0S°8
halloo  the  ooltuneox  a  -hill forooi during
. tr.,u«* ’ te<jtooio aotlvlty oniw
As the basalt cover consists o regjlariy tha form of bedding the fissuring '
*• floor and the roof of every fissuring ia always lower and
OQ dium
flows occurr
middle of oa
m the middlo of oaoh flow
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»■The area is located witnin the limits of effusive lava flows
oO niposed medium to highly fissured and porous basalts which 
3er V0 as water-bearing rooks in the area of the high Gog volley, 
jydrogeologicnl conditions of the area are characterized by a
peculiar feature, i.e< during the entire annual cycle groundwater
tables are directed from the river into the slopes, thus the
a quifer is by tho river. However, towards watersheds the levele
re ~ularly raise up and reach, the FJIL at the Dara Site at the dis
tance of 5 tan from the river (left slope J and about 15 km (right
slope); the groundwater flow from watershed is directed towards
the vailay of the Alwero River. It is especially characteristic
for the left slope where the depression drawdown between, the river
and watershed is the most significant which is due to a non fining 
layer that occurs from the surface and excludes the infiltration 
recharge in this area. Low p erne ability properties of basalts make
it difficult for the groundsreu-ter flow to recharge the resulting 
shortage in supply because the aquifer discharges in this area
through more permeable interlayer scoria zones into the Alwero sand
stones located in the west of the area.
Permeability properties of basalts vary within a wide range, 
from 1.0 m/day to pwan11 r-a.1 ly impermeable. For tile water-bearing 
complex of the Regulating Reservoir area the permeability coeffici
ent averages 0.2 m/day.
■The    described    waiter    —    hen    ring    complex    has    no    distinct    confining bed.      in      filtration      calculations      a      weakly      permeable      series      of      basalts "ith    permeability    coefficients    of    001    »    0.05    m/dsy    occurring    at    the    [■ depth about 40 m was assumed as a confining bed.
The intake area of the
trw—hearing complex is located on the
eastern margin of the liigh Gog plain where groundwater scops from the  ^hter^beaning complex in fissured zones of crystalline Procamb- ri an rocks as vzell na the Infiltration of rainfall takes place,
in the southeastern- eastern 
northeastern parts of the ■
Pluin.
discharge area is located on the eastern margin of the * Sh GoS plain where water seeps into the water-bearing complex of
* eik° san da tones. General direction of grounwater ia westGrn ha  °-00l  slope.
5
cv
el  AtUlLLal fluctuation range of grounwater levels in ^he aan
2      ° Of observations was about 1 ra for the left slope and excee e
toe eight ^9pet
tos oompie-j bn„ OTeet, prcaomluffi'.tly hydrooorW“ate ™«ne£' J
£t
•          4da
lciJero^  more seldom, hydrocorbonate-ohio,^
t
fsrous    waters    with    mineralization    from    o    2    t
lfl  from 300 to 350 mg/1; Qi fron 5 to , J"
;.Ig from 30 to wo mg/1. Iotal hardness is oquiv./l; pH makes up 5.6-7.8; corrosive oo roa 5 to io og-
a
n    !’
* 5 HOOJ content
’ '°
Groundwater        mineralization        regularly        lnoreJs^°^2        *°        2’"23            Q2/1* 
towards watersheds# 
• 
r
rora tlxe river bed
Two engineering-geological elements x
amon^S-ocks         of         the         Regulating         Reservoir         area         idiatln«ulshed
fine-grained basalts and lawyer 2 7-
tosolve fine-grained basalts are rop«s2tH°^ar) grey fissured strong rocks with high values if ’
/     *9* layar 23“Qaasivo
7
mation      properties.      Density      is      2.84      tf/nr3         n--.      3vrangth         00(1         ^foav 
one-axis compression e auals 140-150 sn> \
Jolting (fissures of priaj curing connected with 
Porous varieties capability depends on
tectonic dislocations.
* tQ resistance to the COl“^
a  ^enetic i/po of fls-
of     basalts     ore     less     strong,     their     deformation porosity coefficient; the higher are porosity
-a        fissure,        the           iOBsr        are       strength        properties.        ntb
being 25-30^, they have following average values: density -
2.1-2.3      tf/m\      ultimate      resistance      to      one-exLs      compression      in      air dry state - 40-50 L£Pa and 35-37 MPa in water-saturated state.
Hon-rooky soils serve as foundation for doomed 
*
the     Regulating     Reservoir.     1...     heavy     loams     (loyer     5),     h.avy     sra
b
loose (layer 5 ), clays (lazyer 6). 
ola da alth ®ra’
„ 4 de-
In      natural      badding      these      soils      possess      high      strengr      _aatu- formation properties which sufficiently decrease >
rated atate but in general their values remain rather hign.*'
*
ITfiblo 3.4.1.
Maia values of physical and mechanical properties /oiindzitXon soULs
: in       natural       bedding 
* In water-saturated state
-*■ $
i
X
o  :
I 4»
X
:
x
:
§
x
•HO
t
x I’
x5
1
X
X
X
X
g
g
s  §     x « o
X3
x
t
Cx
£
o
o
o
•H£
(0
O
h
o
3<
t
x
x
x
x
x
13.0
15.0
18.2
22.8
-0*40
-0.30 
-0.35
-0.20
0.66
0.70
0.73
0.75
0.39
29
36.0    0.062
23
18.5
0.40
30
37.0     0.07
24
19.0
0.40
28
32.4    0.075
18
22.8
0.42
29
33.0     0.06
22
23.0
Clays and loams possess swelling properties. For clays the value of unloaded swelling amounts to 315 — swell ing pressure is
0.1 35 MPa; for loar-ms - 9.3%, swelling pressure is 0.046 HPu. Clays belong to medium-swelling soils, but at the pressure pf 0.05 MPa relative swelling amounts already to 1.55. Looms belong to law—swell—
3oils. At the load up to 0.025 MPa relativo swelling amounts to 15.
Portions o£ dam. -da
outlet structures a^re compose
U          —7^^d a— Of. view. In natural and wat
strangth ond deformation prop oally impermeable. Foundati
loams does not need special prepare
•he dam are insignificant. seepoco Xaaaes saturate
Cal culated be means of a
.             rouioo 3”ill,TOy “d hydros*510sic ’. .
loW-perneabl -
manor de up by         ks. Seecpala^g
loaSes under the  Reservoir
ah
aan
0Q  of river recharge with. gr
d08
tf J^conf  iXotiremLs (under the ^^^zon-
1h
’^un^ater basin); aquifer is homogeneo* full roaervoir level is 454.5 m.
jja order to calculate seepage losses the Reservoir site was
j vided into ao^parate sections similar in engineering-geological nditions. The sum of losses in separate sections represented 
total losses due to saturation of rocks making up Reservoir slopes. Calculations of losses from the Reservoir sito were done for
differernt * ” pe *-ri-ods  ---- of --  time _ 
)• The amount of losses was as following: q
 on the JOth day - 10.9 thou.nr/dayj
- at the end of the first year of operation - 3.1 thou.m^/day;
•                      W— —     - --------- ----------
v
the end of the fifth yoar of operation - 1.4 thou, m^/doy
*
---
-            w-
Gonstant losa93 under the dam foundation amount to 0*47 thou# 
m^/day.
Thus* 
seepage
losses
due
to 
saturation 
of
rocks
in 
Res
ervoir
slopes
reach 
signific
ant
valuos
only 
during 
the
initial
period
of
time and than ro,gularly decrease with time.
Total losses during the first year of operation amounted to 
2,4 mln, m and to 5,9 mln, nr during 5 years, with tho Reservoir
3 
3
volume    being    73.0    mln.m^    and    the    annual    runoff    volume    of    the    Alwero River amounting to 620 mln. m •
Coarse debris soils with clay aggregate are recommended for filling dam body, thoir deposits have been prospected near the left and right abutmentsof dam. Thickness of usefull strata is from 2.3 to 2.7 ra. Groundwaters are not pros-ent. Total detailed prospected reserves amount to 050 thou, m\
Sandy soils in natural bedding which may be used for concrete preparationsand exooution of filters are weakly developed in the
area of works. All sandy deposits in the area investigated are cha racterized by clayinosa a nd heterogeneity as well as by their deep bedding a^nd water— encroachment.
Sand for concrete preparation may be obtained from gravel sand deposit Ho.2 located in the flood plain of the Alwero Rivar at the
q 00 Site with preliminary washing-out of soil particles less than 
•15 ram in diameter whose content is 15-17% by weight. The reamln- G  sand end gravel mixture is to ba sieved into fractions. 
iO 'tal reserves of gravel and coarse sands are estimated to bo j ^hou.m^. Approximate volume of stripping works is 40 thou. cP. 
xU - sand strata contain water.T. i'
ai aarea
Sand deposit No.1 is located the lTrlgatlm 3yBten
17  to from the Regulating Reservoir alto near txmcixmrk 
------ Useful strata oocur at the depth frco 2 to 4 3. Prca the 092.
depth of 2.0 m sands contain water. Reserves of a odium and coarse-grained sands are estimated at 40 thou, o' , the thick
3
ness of overburden being up to 2 a and its volume amounting 
to 15 thou, nr.
Gravel and pebble nolle nth mnd-clay aggregate have been prospected in the Irrigation System area 14 tan from the Dea Site near benah-aark083 (gravel deposit So. 2 , 2 ). Useful strata of gravel soils occur from the depth of 0.5-1.0 a. Ground water is not present. The deposit is covered ulth coppice.
The deposit of building stone is located 27 fan from the Dam Site of the Regulating Reservoir in the piedmont part near tho Dam Site of the Reservoir on the Alwero River, and a gra vel motor road has been constructed to it.
ab2-a.3. Irrigation ft
2he irrigation area under investigation io located in the northeastern part of the South-Sudanooe plain with-fp the boun daries of its lowland part. It io characterized by 3 table-llko surface that is partially flooded during the rainy neaoon, Ihe surface is gently sloping westwards and is complloatod by numo- rous minor contraction depressions, dead channels and runoff rills. Absolute elevations of its surface are within 450-420 a.
Zhe most ancient rocks which have been found in the eastern part of the investigated territory at the depth of 120 a are
Gog basalts belonging to the Lower Pliocene ( pij ). Gog basalts are overlain by Mid-Upper^-Pliocsne Alwero sandstorms and clays (              ). These are kaolinized feldspar-quartz sandstones inter layered with alouritrs and montmorillonite cloys of various thickness, frequently non-persistent in trend, soaotlmes forming up lenses. There are interlayers of gravelltes, aleurolltos
and sands with various grain sizes. The thickness of prospected strata amounts to 100 ra in the east of the area end exceeds
140 m in the west.
Quaternary deposits are represented by all four divisions, i»e. Lower, Middle, Upper and Recent,
Lower-Quaternary deposits (Qy) have been discovered by boreholes in the entire area to be irrigated. They overlap the eroded surface of Pl indene sedimentary formations and ore rep resented by proluvial and lacustrine-alluvial deposits persis
tent both in area and section and made up predominantly by Toartz pebble and gravel with subordinated sands, loams and
c lays. Depending upon the hypsometrlo surface of Pre-Quaternary ^lief their thickness varies from 2 to 13 □ and averages 6-9 a.
Mid-Quaternary deposits (Qjj) are com only developed in
6  area under investigation and conformably overlap Lower-
'Ornary deposits. They ere represented by proluvial and
Uv ^ -lBcustrinG formations. They are composed of intorlaye-
o
?he fac*esly replaced sands, loamy sands, loans and clays.
“^-Gknesa of deposits varies from 2 to 9 2 and averages
rQ Uppe^uaternary deposits (Q  ) i* the northern and cont-
m
pa rta of the area overlap Mid-Quaternary formations andars represc*i^Q^ bj proluvial Btrata of olays end heavy loams ch faaiesly rapines .hem. -neae deposit3 serve as cn impermeable base— fjent for curfcce water, The texture of olays and heavy Ioann incl —
n
des an insifTilficent amount (up to 10%) of fine—grained oandy me— t a rd al (especially in the first 1 •5-2,0 n froa ths ff.xrf&oo) end gparsa poorly rounded gravel grains, sauetimes mull pebbles.
Clays end heavy loans appear to be coarse, lumpy, though let, for- rngjnnus, moniaorillanits, predamlnantly light brown in colour* jfaeir thickness varies from 2 to 7 a mostly amounting to 5—6 Fre quently they overlie LIid-Quaternary olays and heavy loams (but with a higher content of gravel groins and pebbles, up to 25-30%) and then their total confining strata reach the depth of 9—10 □
or mors.
In the southern part of the area investigated Upper-Quaterna ry deposits ere represented by lighter soils, l*a. silty sands,
loony sends, light loons, with their total thickness being from
0.5 to 3*0 a, as well as by heavy loans with a high content of
iron and manganese hydroxides which are fade sly replaced by gra
vel deposits, wi tfc "day 
'whose gruels' consist of Iran
and manganese hydroxides. In sane places these gravel deposits are cemented up to the state of conglomerates and. form up ferrugdneus cruste (pans). The thickness of these deposits makes up 1-3 a.
Recent deposits (Qjy) ar® represented in the area invoetigatod by alluvial, proluvial, alluvio-deluvial and lacustrine foxnationn.
Alluvial sediments ere confined to floodplain end bed parts of the Alwero River and are represented by looms, losmy sands, sends with gravel and pebble which have their thickness from 2 to 5 a.
Proluvial formations are spread in the beds of eoaDcnnl ri- Voi’£J ^nd streams end are T-aprenented in the lower part of tho s °c-ion by various-groined sands with gravel and pebble, in the
u Pper part of the section by loamy sands, loams and olays with
5rQV°l and pebble. The degree of material granularity and cloyi-
03  Gradually increases in the area from east to west. The scaso—
01  their thickness.
^Ihvd.o—de]wvfni deposits are confined to young dead channelsLacustrine deposits are developed in liraltod areas of lake dopresBions which ore fill-up with water during the rainy season
and get dry 
the dry season# They are ropronontod by well
layered fine-elutriated lacustrine clays resembling vnrved cloys
and silted with heavy loams, Clays moke up the lower part of the section and silted loans form up lte upper part# The thickness of lacustrine deposits does not exceed 2—3 □ •
From the hydrogeologioel point of view two wator-bearing cot pl oxo o are distinguished In the area under invootlgntian.
The first water-bearing complex is confined to Mid-Upper-Pllocane and Quaternary loose deposits. It is developed in the entire arsa
of the low Illubabor plain and canflnod to frequently intorlayered and facie sly replaced loamy sand-clay-sand-gravol deposits end loose kaolinlzed sandstones, alenrollten and gravelltos. In sone
local areas it is subdivided by local confining beds into two independent agulfors with oloso but different hydraulic surfaces.
A Pliocene clay rock bend of Alwero sandstones and clays is the regional confining bed of the wn tor-bo Firing complex under coral— deration.
Puc to the foot that a greet pert of the low Illubabor plain area is overlapped by inpenueable clays end heavy loans fma the surface the recharge of water-bearing complex by mshjj of rainfall ie  Practically exaluded. It is recharged mainly duo to the inflow
e *ceeda 907S of the entire territory investigated. Seasonalz -■tua tions of groundwater table In thin area ere practically
present end amount to 0.1-0.2 m.
Groundwater table depth® up to 15 m are confined to the
floodplain o£ the Alwero River and to the bed of the Hylknni
Ki ver* Their distribution area in the territory investigated ano-
unts to 10%. Hera seasonal fluctuations of watartable have a
range of 1.5-2 m with Its maximum during the rainy season.
The mineralization of groundwater of the first water-bearing
complex is 0.2-0.8 g/l and its chemical composition varies from
hydrocarbonatic-chloridic in the areas of recharge by rivers to
hydro carb ana tic—sulphatio in the central end north-western parts
of the territory invoetigsted. According to its cation composi
tion water belongs to a magnesium—sodium type.
Groundwater    of    the    first    water-bearing    complex    may    be    recom mended    for    water    supply.    Water    ia    to    be    taken    from    coarse-grained sands    occurring    at    the    depth    of    50-60    m,    their    thickness    being
1.5-J.O    □*    Operational    reserves    of    groundwater    will    meet    the    needs in aold water supply of settlements under design.
The mineralisation of water in the wells drilled within settlement areas of State Paras Kos. 2 and 3 Is O.I-O.^g/f'jfn"  “ the settlement area of State Para No.1. In the settlement area of State Para No.1 iron content in water is 89 mg/1, with Pe
7
making up go mg/l and p +3
e
9 mg/lj in the settlement area of
State
total
and 1
hate,
pH is
lisp (3
. icr water supply in the newly-built settlements of resettlers are located to the south of the investigated area in the
Action of the Gilo River.
second water—bnnying complex is confined to a fissured c                        Pliocene rocks represented by Gog basalts. Water of this
ls  confined. Absolute values of ito heed increase west-
9a twarda as Gog basalts plunge under loose Pliocene depo— -^lwQr  sandstones and days.
o
S  ^ter-b earing complex is rscharged due to the inflow of °  the boundary of the [Ugh and low Illubabor plains from
Farm Ko.2 iron is not present; in that of State Farm No.3
+
+
iron content is 7 mg/1, with Pe ^ and Fe ^ making up 6 mg/1 tng/l, respectively. Water is attributed to the hy (trocar bo- hydrocarbonate-chloride, sodium-calclum-eagnesium type,
7*0-7.5.
At present, water of the first water-bearing complex is
n3
safljuaa .  si ’
•
'c r 'tf
. . ■ . ,.
.1- ... , rr
.- —
♦74
tb0  water-bearing complex that in
pltdn. 
2he groundwater ficzv l  dlr
0         9cted Q .
nxt ™to *» hlch mubobor
It discharges beyond the boundaries 7f ’*Ot“norti»TOs Swards whoro
" 9 arpa m<i°  canoideTa-
r
tlon.
Groundwater ntaerellzatlon of the Moond complex counts to 0.2 g/1 acocrtliw
.
™-e^boarlng
... r:.“
any are represented by elays. 
lorao,
sends as well as gravel and pebble deposits with sand-e^y^-
gate.
Clays and clays with gravel (layers 6, 6 ) of proluvial
a
end, more seldom, lacustrine as well as alluvlo-deluvial origin have solid consistence in natural Bedding. Their density is within 1.79-2.10 t/m\ porosity coefficient equals 0.695-0.886, permeability coefficient is 0.001-0.0015 a/day. Clays possess swelling properties. Their relative free swelling obtained by means of instruments for soil swelling determination averages 3116, with. its maximum values being 44^. Swelling pressure am to 0.1-0.2 MPa and more seldom to O.3-O.4 ’-!?&• Ac°°
these factors clays belong to medium end more sei on ly swelling soils#
Heavy loams, heavy (layers 5. 5*.  b of pr^i^
5
. fr**ivel»             loss0 _  d nore seldom. 
d  state,
&
deluvial, lacustrine or ^’ 3 porosity °0°nl0
Their density is 1.79-1.9 
efficient mokes up •
o/dfly.
0.647-0.791     and     permeability    c°
Their relative swelling obtain __  ^oiling P
nQS3l3      of       instrvn 
s
eoil     swelling     determination     ave        gelling     soU®*     .     and, 
0.04-0.05 UPa. They belong to 
Light lotos (layer 4)
m °re seldom,  proluvial origin.  ,  porosis
■tats. Their density is
e <r-ial8 0.637-0.950 and permoab 
elluvlo-4^ they o- Ic116lant
^d,
°' 2-0.35 ra/day. 
Loamy 3ands (layer 3) x
^lurlol. BlWrl®-4*<
I
li
»
«
I
*
/
*73 * fflcient equals 0.700-0.903 and permeability coefficient makes 0,2-0.68 m/day.
P  Sands (layers 7-11) occurring within the investigated area classified according to their granulometric composition as
silty to semigravel sands. According to their mineralogical oao- ltion these are mainly quart* and quartz-feldspar sands, with
their specific weight being from 2.66 up to 2.74 t/a . Their den sity in loose state is from 1.16 t/m  to 1.50 t/m  and 1.30—1.75
3
3
3
3
t/m  in compact state. The permeability coefficient of silty and fine sands is 0.5-1.1 m/day and that of coarse and semigrevel sands is2—20 m/day depending upon the a on tent of day particles.
Gravel and pebble deposits with sand-clay aggregare (layers 12, 13). Gravel and pebblo are represented by well rounded quarts end make up 6O-80T? of the total soil mass. Sand-clay fraction emount a to 20-40%. The permeability coefficient of gravel end pebble deposits is within 0.5-1.0 m/day.
Ferruginous gravel deposits with clay aggregate (layer 12 ).
a
Gravel is represented by ferruginous nodules in the fora of con cretions from 5 to 20 mm. In some places they occur as conglome rates cemented with ferruginous solutions and fora up ferruginous Pana non-persistent in their area, their th4 r'lmnns varying from
4?o m. 5ently sloping westwards from elevations of 450 q to
s are distinguished within the proluvial accunrala-7.
pynnJn A-II ±b a diving plain with runoff rills and alluvial
cones.    2his    area    is    naturally    poorly    drained    and    rather    poorly drained.
Tho poorly drained area is confined to the southern port of
the area investigated. It is made up from the surface to the depth
o f 5 rn by relatively light lithological varieties of rocka, l.e.
loony sands, light loans, heavy loams, ferruginous gravelitee,
gravel and pebble deposits with sand-olay aggregate. During tho
rainy season the area has excessive moisture from the surface.
The design irrigation regime ought to be obeerved.
The rather poorly drained area is made up from the surface
to the depth of 5 m by clays and heavy loams. Oils area is seaso
nally flooded and excessively moistened with surface water. The
execution of the gravity collecting and escape networks as well
as the observance of rhe design irrigation regime are needed to
maintain favourable reclamation conditions of lands.
—ie alluvio-proluvial accumulative plain is also divided in
two domains.
Domain B—I Id the fl, nodpl, Mn part of the Alwero and Hylkani
Rivers.    Thia    la    a    naturally    poorly    d-mined    area    with    clay-loeo- sand cover beds. The area is flooded during the rainy season.
are distinguiBhed, with their groundwater table depthsAg  stated above, groundwater belongs to the hydrocarbonate-
The soils of aeration zone are deeper than 1,5 a in the en
tire investigated area, non-sallne end have mainly sodlo-sulphatic,
Bodic-hydrocarbonatic chemistry. In the range up to 1.5 3 in the
southern pert of the area the soils are non-Boline and in the
northern end central parts the soile are deep aolonchak-like week
ly saline with chloridic-aodio chemistry.
3.4.4. Main Canal Route
The route of the Main Canal passes through the investigated
area from east to west from elevations of 452 in in the east to
438   m   in   the   west.   It   is   25,275   tn   long   end   crosses   nome   areas   with different engineering-gcologicel conditions.
In the head part from D.U.O to D.M.19 the can'J. trill run in Upper-quaternary clays (layer 6) of proluvial origin which possess telling properties. Their physical and mechanical properties are given in Table 3.4-2. Tho thickness of olays in this ares varies from 3,5 to 9 tn. The cleys are underlain by the weathering crust of Mid-Pliocene basalts (layer 26).
further on, up to D.M.128 tha canal route crosses a field of
Q G2regato. Though sone deviations ore possible. Thus,at D.M.117 where the clay fraQtlon
in the ^['r&ryxtQ th  poxneability 
0
P  bbl<> °°U
amounto to 5.41 m/dajr. 3elow pebble-bods tjtL/*  ° velly loans (layer 5°) which, in their
llld-Upper-Pliocene sandy days (lfiyM, 
Ptoq D.H.125 to D.M.252+75 alcnr th L ,
e
alto ore represented by silty sands (inYoa
»  >
7
(layer 3), light loans (layer 4)
deposits is ncinly within 2-4 h thn-f ° " thickness of thoao
not  Pr*°'®t
^erlaln by
* ho ^P”
’ loea7 hands
13            Iron        0.2        to        0.95        n/da7            to            n^'        lo^T^'"^J”"1"10”*
up to 1.1 n/doy in silty 3rada. 
Owlr shaking is TOIy rapMr instanton™,,
tokon into account in dosi^ taoauM
subsidence properties. Uhese deposits are inderlaln by heavy loans, heavy loans with gravol, hoavy gravel loerns (layers 5, 5 » 5°). Below loans thore oocurs a pebble-bed with oand-cley
maids and
a
aggregate. 2his Quaternary band of rocks is 6-11  thick. Qua ternary deposits are underlain by ItLd-Upper-Pllocone sandy clays.i t' y
if
/ /
TuVLo 3.4.2
/Jean values of physical and moohanloal properties of anil a
<?i3countered alon/? tho Hain Canal route
___
■Layer          / Natural          IConsistence, a u/n her       / moisture.       / index
I Density of toy,soil,
t/nr
Density  in v/ater-aatureted state under the conditions of impossible free swelling
Value of free I Bv/elling, %
Angle of
internal
friction,
degrees
Spoolfic cohesion, MPa
Deformation modulus
Swelling oressure
®a
6
5
4
3
23.1                 <0
10.2                 <0
7.4                 <0
5.4                <0
1.51 18 3.056 26.8
1.68 22 0.022 14.0
1.59                 19                   0.01
7.4
26.4
-
-
1.52                 19                   0.007               6.3
0.3
-
-
-
Grounw&tor   occurs   along   the   canal   routo   In   Pliooano   dopoolts   at   the   doptlio   of   15   in in its head part and up to 27 ra in its tall part*
3ollo aro nan-online along tho ontiro oonol route.
1-r .
IT'f
»
ICo -gZ '■
c i s of tropical belt are the most anolent among the soil
r the Earth. They formed up as a result of very intensive
/■nVGZ* O
thering and soil-forming processes. Alkaline hydrolyses of prl- *** ainerals takes place during these processes with a rapid
^e30v-l of bases (Ca, i-Ig, K). Then lattices of mineral disinteg rate and ion forms of Si, Pe, Al are released. Iron migrates in various forms and n.lso stabilises on positively charged clays;
also it may be accumulated in soil profile or carried away on
alopes forming up conoretions and a pseudo sandy struoture of soils In dry tropical sones (. with ths dry season lasting about
4-5 months) weathering and soil-forming processes develop much weaker than in humid tropios resulting in ths formation of more
shallow soils of
Ferruginous
oiduous tropical
during the rainy
different composition.
tropical soils develop in these sones under de forests. Iron, silica and aluminium are released season. Silica is not carried away so intensively
but binds al mini nm forming up clays with kaolinite and illite composition.
Shallow red-brown and brown soils form under the conditions a longer dry season lasting for 6-7 months. Side by side with
tkia on automorphic and hydromorphic siallltie process takes place in dry tropics that results in forming up clays of the
lllte-aiontaioviiionlte type and building black tropical soils, X,# * vertisol-;.
foll  Cn the whole, the soils of tropics may bo divided into the siain zoness ferrallitic soils, ferruginous soils, red-
»nd black tropical soils.
e 3011 forming prooess la the interetTeam area of the deyei° ^3rikani Hirers and in the Gaabella area on the whole tei3 Petat Under *ke conditions of a tropical climate with high
r» 
la  ures during the entire year (mean annum air temperatu- •
4 n,°hthB)69C) ’ °* clearly distinct dry (duration is more than
' )ein« 8-0(3 rainy seasons, with the total annual preclpitatl- Mny a 9O°" »3OO mm (85.6 of rainfall are reoorded during the
1
g oii
aB  a
° ^ a*i insignificant entry of organic matter into and an intensive biologioal cycle of matter.o
i&
Ie d-brown and brown savanna soil* as well as hydromorphic
.  f depressions formed up in the surveyed area which ver tisoi9^^ piedmont plain and represents a specific region
from western foothills of the Ethiopian High! ,mdn
iudaneo. Plata.
, w literature there were little data on soils of 5ortb-2ast especially on those of Ethiopia. The 1:5,000,000 scale
****  f Africa compiled by D’Hoore (1964) and the Soil lap of
o
50
the
’   rin   bv   FAO   uhisco   (1975)   at   a   scale   of   1:5,000,000   give   a
broad summary .
The most adequate and completo model of the Earth soil co ver is given in the new Soil Hap at a scale of 1:10,000,000 edited by V.A.Kovda in 1975. It made use of previous soil nape of Afri ca. It is compiled on a new principle basis and substantiated by a large amount of initial actual cartographic asterial.
By the end of works under the Alwero Project in 1965-1906 no new additional data appeared tn the literature which could introduce changes in the classification of soils of the African tropical belt. The papers written by B.G.Eosanov, I.HIosanove d9e2) about Xenyar. soils and by B.G.Roeanov, P.T.Tchelianik (1983) about the soils of the Gambella valley did neither intro duce changes into this problem. That is mhy the Soil .’lap of the
’' rid edited by V.A.Kovda was taken as a basis when disclosing
c
basic regularities - of eoil cover structure, distinguishing sain y?ee and subtypes, making classification and compiling a work-
acc 8ysteraatlc
.'.‘of soils for the entire surveyed area. In
^cordance with the legend of the Soil Hap of the World the «o£Ls f*0?3611 formations and facies. Formation is ths highest
«*
taxonomic level
• of grouping distinguished by the intensity of
_ ___ —-
aoll building, thus determining general, princl-
Pal processes. *. --^-h--a s---oi --l-s- ar-  e grouped in fcoror** *-    mroat0?i-oon-U-7 t s wo bithlool   low^ t*1o® fathering and . 
energy of soil "building 
is th*
geTocaehleesm ariceal d bisetlitnsgu.  ished
-a thin foroatio^9
vaxioU>
of soils differing in
the rhythm of seasonal temp c onn«cted with latitudinal a» 
^fcogeography of the country* a
second      taxonomic      level      in      9O~
? ro?  *
’ and
er   lefl         .      and      b3‘S°
featureP ^forninS
of eotl® a°d
'■«
»
1euta exists and pane, tropical brown sibarld and ethwr scliw
tor.'. i?»
northaestom   part   of   Uis   airrwycd   oroi   beloxjo   to   the facies   of   the   clinnte   with   a   lane   dry   ooaocu   with   blaox   trepi- eel sslie or vertisols.
In canparIsen with the legend of the Sell iftp of the lerld edited by V.A.Xorda the floil noaanclatur© vaa alltfitlj chared
in accordance trJth the lotest paper of 3<G.--ossaaT ex Ga-bclla
soils.
2hio, 'ho final Dsaenclatire of -noln soil type© that has
beoa accepted by 13 io as follows* fOTSiallltic rad-broon MStbd- na  ooli»  tropical brown oitrophio (slallitio brertn aavannn)
t
3p '-°» chro-JLc -nd collie iwMfrta, tropical reaics-staxap culls* alluvial floodplain soils, elanos^ls* llthocolr.
better lrdlccs urod ear'lor (3. G. Toe anew. 1933) hzve been
• •• i
tlb-4t/
%
C  ’e ic lie
ceil© - A| llthoeol - L.
‘  cf soils. T/?oa» cabtypes, genera. L'fct-
t
«isn area.
■S
• T’rtiaoi
n
•         ■***-         brown eutrophlo (elal ltic brvn covansa) soils4.  Planosols
5.   Tropical meadow-swamp 30ile
6.  Alluvial floodpl^ soils
7,iithoeois
In red-brown and brown soils subtypea
A )   proper    red-brown    soils    and    brown    floUa     wlth let- profile; b) red-brown and brown weakly A * 
oo«p-
/•rrallitlc     p;ins     with     the     fine-earth     ataX     *7elo^i        —1U     cn
0 ) brown soils transitional to red-bro^ distinguished in vertisols: chromic ver-  i ’ 5Ubtyptg «•
a
areas and pellic vertisols confined tn rfJ °* ^led
l
«1—«. 
®;
lttd .
fems.
Subtypes are divided in genera;
non-oalcareoue    -    no    efferveeoenee    in    the    2-seter    soil    profile; calcareous - effervescence or preaonoe of oaloiux carbonates
in the form of mealy powdering, white soft spots; colonciiak-like - presence of easily soluble salts according to
the resul.s of water extracts;
solanstsic - absorbed sodium content exceeds 35 of the eua of absorbed cations;
eolodlc -
c«apact -
tn
presence of a continuous albic structureless eolodlc horizon or its eonarate spots underlying the nanus horizon;
presence of a compact horizon in the 0—100 ca layer- soils are divided in species: according to their humus
In V«*—a -t . - he     7horizon,   according   to   taeir   humus   hox^cn   dep   a, ^tent
hi varieties - according to their
(soli map legend). 
The distribution ares of main the  surveyed area is giver in Tabl® * '
4 ^enuloaetrio ooxpo-ition
type- sub1**®1
rlption      of      soil      typ-^      fl^dix
subtypes
______ :_____ r
-T                   2        ~~         —j—— little red-brown savanna
3h              1,487.5         4.7
Bh
617,5        2.0
Bh°               870,0        2.784
We 3.5.1. 
con
t>d
-^THHo’tion of soil types : Soil
Saud subtypes
: index
:Area 
s ha  i 3>
:i area
of   total
’ _ — - - '
"tropical brown eutrophic 2. (giJiiiltic brown savanna)
soil®
1 Tropical brown eutrophic soils (transitional to red-
brown soils)
2.   lion-calcareous tropical brown eutrophic soils
3.  Calcareous tropical brown eutrophic soils
Be
B
Be
13,378.8 43.9
209.2         0.7 5,643.7        21.0
Be
4.   Weakly saline solonohak- like tropical brown eutro
phic soils
Be^
5.   Solonetzic tropical brown eutrophic soils
6.  Weakly developed troploal
Bem
brown eutrophic soils on ferrajlltio
Be
pans
3.
Verti oi
Sa
*• Chronic vertisols
1.1.    Non-calcareous chromic vertisols
vp
Vpb
VP
1.2.
1.3.
line
daloareous chromic verti^gls
Vp'
Solonetzic weakly sa- i aolonchak-like chro-
4.
5.
6.
7.
talc ■vertlaols
2.  Pelllc vertisols
2.1.        lion-calcareous     pellic vertisols
2.2.      Calcareous
tlsola
2.3.    Solonetzic weakly sa line solonohak-liks peliJ- vertIsols
-Ianosol3
topical meadow-swamp soil3 Pluvial       floodplain       soils lithoeols
Vp^
vp
Vp
VpCa
Vp^
P
Me
A
L
673.1 2.823.2 2,341.0
1,138.6 14,772.2 12,034.7
2,133.2
470.2
9,431.3
2,737.5
470.0
505.0
1,762.5
115.6
500.9
570.0
■ ..27^0.
2.1
8.9
7.4
3.B
46.3
38.2
6.3
1.5
29.9
8.6
1.4
1.6
5.6
0.4
1.6
1.8
0.8
Total:
31,600.0 100.0-
.
k
--
< r • -
a.
•
•
.
1
.r _
«
•*
*
•
•
♦
•
•
tCharacterlstics
Soil 2ms
J^TTniltlo Eed-Brown Savanna Soils - Hi
£0 <lfl are distributed
the  elevated Illubabor ola-
j’iieae eofltern and southwestern parts of the surveyed area
* ^undulating watersheds with absolute elevations of 450
.gher
total area within the survey boundaries is
he characteristic features of fersialllti- red-brown soils include the following:
-  red-brown colour of the entire profile with numerous bright brick-red scots, with greyish dark brown A horizon;
-  strong ferruginaticn of the entire soil profile mani festing itself in accumulations of iron-nanganese nodules, their size being 2-7 mm;
-  good water-stable structure due to a high oontent of the free aggregated iron;
-  absence of compact impermeable horlsons;
-  wide distribution of ferrallitic pans occurring near to the surface (30-100 cm);
-  high humus content, weakly acidic reaction of sail solu tion in the lower part of profile and close to neutral in its upper part j
~ relatively low cation absorption capacity.
soils are subdivided in two types, i.e. fersia- nite ° red~broWn savanna soils od red-brown ferruginous kaoll-
l^'
it   c
riOnt[nori-l-Ionite loams and eJays; weekly developed ferslal- ^red-brown savanna soils on ferrallitic pans.
dar '<    brown  with  reddish  hue,  granular  nutty  cloddy, heavy loam, weakly compacted, frosh, abundance of
•• Oarklsh reA-onm, clod* Oley, compacted, fresh, sparse fine nodules 1-2 nm in on Is noticeable in colour*
ro!te.red-brown, cloddy nutty granular, heavy cloy, compacted, humid, fine-nodule number increases, fine roots. Transition is noticeable in colour and
density*
. rad-brown with brick-red hue, nutty oloddy, hea- C, 44-95 o» V5' day, dense, humid, abundanoe of fine nodules,
ocliric red streaks, few fine roots. Transition is noticsaoie in colour and presence of nodules.
□5-200 cm: brick-red orown, nutty coarsely cloddy, medium
'2 '
clay, very dense, out easily disintegrating into
structural separates, humid, gloss on structural separates,   abundanoe   of   large   5-8   nodules,   ochrie red streaks. Carbonates are absent in the entire
profile.
According to rhe granulometric composition these soils are
heavy, their medium granulometric composition of soil contour is ■        5 • . The 0 - 30 cm layer contains 56.8 - 70.7% of phy sical clay. The predominant fraction la a lay.
The structure-aggregate analysis has shown a good structu ral state of noils in dry sieving. 0.25 -10 an aggregutea case
up 82$ in tne 0 -11 layer and 93$ in the 15 - 25 cu layer.
*hen sieved under water the structural state cf soil is also
8°od, water-stable aggregates make up 68$ and 70», respective ly (SRA?ps_2^
Accordtng to their humus con
long to humic and highly humic varietie . 
‘ horteon varies within 4.46 - 8.45* ™d ■har7*1' B, horizon dem to 1.3 - 1.9*. 
cation absorption oapaolty is re
the red-brown soils be-
3ontent Ln the
dccx^ageD in
nak«. a»
16 3 tag-
”•8   ‘   17.1   cg-equl..   in   th.   4,   horlson   an*   10.7   -   16-3   *-
•’«v. in the B, horinon per 100 g of «» "
u
calelws
** “ 77.7*) and nagneeiun (13.4 - 3*1 • £ -»Unt is 1,  . 3.6% and that of
4
(61. 'h'-’b8Crtlns            CO'"I>I*X            18            ^turatsi        n        ^,'ibaort,4            sodl-
2
Ojm Of absorbed bases. 7he soil. aI* 
0 00-• 
O1
ih th. o - 200 ® .oil
■> 1 - 5.3%
0.010 -
“ °;h. 
'
tl]
2 7^ “4 ths content of HCO . Ba Ion. *»•’ »ot
}
“bold of toxlolty. ihe soils ar* non-ealln«.-
■
'i'
*
.>
• £: ■:■ , ' . • * - ■ ■ '»
•
'
4 t ’ ‘■'•-> -'*L "A• ihe soils arc highly provided with aobile potassiu®
, t . 18.0 ?er 100 8 of
poorly provided with uobile
-
3
(15 ' hArus (0.47- 1.25 per 100 g of eoil) and contain ouch
3.26 - 3.37*).
The equeous and physical properties of these soils are oboiacterized by the data obtained at SHAPPS - 2 (Tables 3.5.2. 3.5.3)* 
The soil density is sufficiently high, i.e. 1.53 g/csT in
tao o - 25 cm layer, 1.60 g/cnr  in the 0 - 100 ca layer, and
-rcctically docs not change at the field capaolty moisture. It signifies that red-brown soils practically do not swell.
Their total porosity is low, i.e, 40.8% in the 0 -25 an layer and 39.5% in the 0 -100 era layer. In accordance with the evaluation made by h.A.Katohinsky the soil coopaotneee is high and its porosity is unsatisfactory. The aeration porosity is suffuaiient, i.e. 19.0% in the 0 -25 cm layer and 14,6% in the
0 -100 cm layer.
Their iiaxir.u.u air-dry moisture (liADLi), wilting moisture (WM), field capacity (PC) are respectively 4*7; 1j 21.7% hy volume in the o -25 oa layer and 11.1; 14.4; 24.9% by* volvene in tlie  o -100 cm ley »r.
‘Jointure reserves corresponding to WU, PC and available t?1 Dianla “ ah) are respectively 154, 543, ^390 n^/ha in
the
e 0  -25 cm layer and 1,424, 2,442 and 1,010 nr/ha in the
trol'thZ
0  -100________ 1 ciu layer, Water permeability is high and amounts to 1.44—
— _• surface at the end of the first hour, its
'•ady-atate
value is 1.0 - 2.3 m/day (Table 3.5.4). The steady-
m/Q , CUl'ie of permeability from the depili equals 1.01-1.73 and prove  that ferrallitic pane have a high permeability,
B
hour fXG ^
ink  La
-   8 tiae of tne 1,000 m’/hs irrigation rate is 0.3
&it.i0nO>\the fi«rt irrigation and 1.0 hour for She second irri- Petrae 441 accordance with S.I.Dclgov*s classification the water it is ' lty io 03 tinaied to be high. During furrow irrigations
^eer *5 1/100 linear m/'e for the firot irrigation and 2.5 1/100 De3 C ^O1*  ®cond one.
I
s
^4 ■)
rates ore 406.0 and 355 a'/ha for 0 -50 100  cm. respectively (Table 3.5.5).‘!-/
Pl^aloal prop* rt loo at .oil*
V7.
? Porosity,% \viutox x»»«rv«»,a?/hB V
"ToIaT
FL!
10
I
L.tlull
IN    , 10            20 - IM ’
*1V             0-5              2.67         1.61       1.51        2.7       3.9        5.1          29.7 5-1C            2.67          1.60      1.61        3.6       3.9         5.1           25.4
B 1          10-20             2.60         1.64       1.59       8.7      6.9       12.4           30.9 20-30             2.60         1.63       1.61      15.6        6.8       12.2          30.1
BC         30-40             2.51         1.54       1.66      21.5      12.8       23.0           29.3 50-60             2.61         1.61       1.64      19.8       8.0       14.4          23.1
C 1 70-80 2.63 1.70 1.58 2 4.0 12.2 22.0 30.4 «a 90-100 2.55 1.78 1.64 26.0 20.3 36.3 36.3
110-120           2.55         1.87       1.69      23.2     21.3       35.7           35.7
130-140           2.55         1.88       1.71      25.6      21.2       34.6           34.6
° 3             150-160           2.66         1.70       1.76      26.3      19.2       34.6           34.6
173-180           2.59         1.61       1.56      25.8     19.5       34.6           34.6
190-200           2.59         1.60       1.57      28.0      18.9       34.0          34.7
39.7 43.4 13.7 25 143 123
40.0      39.7      13.3        25       132            107
36.9       38.8       7.9      124       309          135
37.3     38.1       8.0     122       301          179
33.6 33.9 4.6 230 293 63
38.3 40.9 12.8 144 231 137
35.3 39.9 9.5 220 304 34
30.2       36.3       0.0      363        363                 0
25.7      55.7      0.0      357       357                 0
26. 3      34.6        o.c      346       346                 0
36.1       34.6        0.0     346       346                0
37.8       39.7       5.1      346       346                 0
38.2       38.6        3.9      347        347                  0iBtela 3a3i .
a
Lay or / Spoaitlo
dopth,  weight, 1
cm / g/cnP /
/ Soil 1 /r/ar:
penalty J Moioture.'.i hy voluno
Porooity tf            I Vinter rooonci^rna
t
™J
PC | ™
MAM
WH
rc
Total
ra
FC
tiS'\ ™ \ * \10 -TO
Ao
0-5
2.60
1.50
1.52       4.8
4.8
6.0
23.9     42.3     41.5
17.6
30
120
90
A1
5-10
2.54
1.48
1.43      8.2
3.5
4.6
19.0    41.7     43.7
24.7
23
95
72
B
10-20
2.61
1.56
1.58    11.5
5.1
6.7
20.8    46.2      ^.5
I8.7
67
208
141
20-30
2.58
1.56
1.56     11.5
5.1
6.7
24.0     39.5     39.5
15.5
67
240
173
°1
30-40
2.56
1.57
1.57    11.5
13.3
17.3
24.9     38.6     38.6
13.7
173
249
76
80-100
2.78
1.68
1.68    12.4
14 .3
18.6
26.7     39.6    34.6
12.9
372
534
162
150-200
2.65
1.68
1.68    12.4
14.3
18.6
26.7      41.0     41.0
14.3
930
1.335
405/*
7
i| Water racorvoB w«PAbix ~
Ii08.
/ dept
/ an
hl Height
I g/azn?
I ”  >■  |eadm        VM          FC
Total
EU FC
Aom-
tlnn
WU            PO \to  - m*
0-5
2.67      1.61         1.51       9.3        3.1       4.0       21.9     4 *.6    42.2     20.3       20         110           90
5-10
2.67
1.60
1.61
9.2
2.9
3.8
19.8
40.3
38.0
18.2
19
99
80
10-20
2.60
1.64
1.59
11.0
2.6
3.4
18.6
38.0
41.1
22.5
34
186
152
20-30
2.60
1.63
1.61
8.4
2.6
3.4
18.5
36.6
39.2
20.7
34
105
151
30-40
2.51
1.54
1.66
3.7
2.5
3.3
17.8
37.8
38.2
20.4
33
178
145
50-60
2.61
1.61
1.54
1.4
2.6
3.4
20.3
4^eS
38.5
18.2
34
203
169
70-80
2.63
1.70
1.58
1.2
S.7
3.5
19.1
35.9
32.4
13.3
35
191
156
90-100
2.55
1.78
1.64
2.8
5.5
7.1
18.5
35.4
32.3
13.8
71
tar
114
110-120
2.55
1.C7
1.69
8.0
5.8
13.5
21.3
30.7
33.5
12.2
135
213
73
130-140
2.55
1.88
1.71
14.2
11.1
20.0
24.5
26.9
32.3
7.8
200
245
45
150-160
2.66
1.70
1.78
15.4
10.0
18.0
25.9
34.8
36.9
11.0
100
259
79
170-180
2.59
1.61
1.56
16.4
12.4
22.3
25.8
32.6
33.7
7.9
223
258
35
190-200
2.59
1.60
1.57
16.9
13.0
23.4
26.0
33.7
30.8
4.8
234
260
26
I
IAlois tux*e.£ by volume
Tt\\?XO                       onn^’(\
lorooity./S .i ’«c.tur rooorvoe.ft1'/;uk
Total TO     A era-1       WU i W I W - <I
PM '             t<ftn '
'
Ao
0-5
2,60
1.61
1.57
2.9
3.0
3.9
26.2     38.1
39.6
13.4
20
131
111
A1
5-10
2.65
1.56
1.56
3.9
3.0
3.9
23.7    41.1
41.1
17.4
20
119
99
S1
10-20
2.68
1.61
1.61
8.9
2.5
3.2
24.2     39.9
39.9
15.7
32
242
210
B2
20-30
2.68
1.58
1.64
10.8
5.9
10.6
25.0     41.0
38.8
13.8
106
250
144
30-40
2.68
1.70
1.66
15.6
6.5
11.7
25.0      36.6
38.0
13.0
117
250
133
°1
50-60
2.68
1.57
1.64
16.4
8.2
14.8
25.8     42.5
38.6
12.8
143
258
110
70-80
2.76
1.55
1.62
13.1
11.3
20.3
26.4     43.8
41.3
14.9
203
264
61
90-100
2.70
1.60
1.64
12.6
12.9
23.2
26.7     42.6
39.2
12.5
232
267
35
°2
110—120
2.70
1.59
1.69
14.4
13.5
24.3
31.0     41.1
37.4
6.4
243
310
67
130-140
2.70
1.58
1.73
16.1
14.8
26.6
30.0      41.4
35.9
5.9
266
300
34
°3
150-160
2.75
1.C3
1.78
17.6
15.8
28.4
30.5      4 .7
35.3
4.8
284
305
21
170-180
2.73
1.74
1.88
19.6
16.1
29.0
29.0      39.9
31.1
2.1
290
290
0
190-200
2.73
1.79
1.06
21.3
16.8
3 ’.0
30.0      34.4
31.4
1.4
30o
300
0•'ATrnVXg
0-5           2.57           1.61     1.18       8.7 5-10         2.66           1.81     1.24     14.9
AB            10-20        2.73           1.99     1.28     18.3 20-30         2.78            1.75     1.42       32.0
.'-'oiotui'o, 5 by vo? uno
NADU        we rc
10.5       10.9 43.5
Porosity
3
ru Qory c n  /Yux
Total ill—
K  1
Aera-
tian
xna       yc       ^yc   - ru
29.6       54.1     5.6       95          243              143
15.4       27.7     43.4     31.9       53.4     6»o    139           242              103
S1
B2
30-40 2.04 1.70 1.50 41.6
5O-6o 2.37 1.7j 1.41 38.9
7^-80 2.86 1.75 1.50 37.3
90-100 2.80 1.74 1.61 42.6
20.5
21.3
24.2
36.9 45.5 20.4 53.9 3.4 369 455 83
33.3 43.1 37.0 48.9 5.8 383 431 43
43.5 40.5 40.1 47.1 3.6 435 435 0
24.2       43.5 43.5
24.2       43.5 43.5
24.2       43.5 43.5
40.7        50.8     7.3      435           435                  0
39.2        47.9      4.4      435           435                  0
39.6        44.5      1.0      435           435                  0
EC       110-120       2.95           1.76     1.58     36.9 130-140       2.95           1.70     1.54     35.3
150-160       2.91            1.79     1.55     36.0
C         170-1CO      2.96           1.76     1.59     41.6
190-200       2.96           1.62     1.54     35.8
24.2
24.2
24.2
2A.2
24.2
43.5     43.5     40.3        46.4      2.9      435           435                  0
43.5     43.5     42.4        47.8      4.3      435           435                  0
43.5     43.5      38.5        46.7      3.2        435         435                  0
43.5     43.5     40.5        46.5     3.0     435           435                  0
43.5     43.5     45.2        47.9      4.4      435           435                  0
3RA1T3  —  alto  for researching  aqueous and pliyoioal
Fn - field molature
properties
of aollo
UADM — maximum air-dry moisture
WM        - wilting r.oicturo
FO          - fiold capaoity•>
«•- v. C>
•
>w o
V-
•««•
f
-f       •?
iU9aa value* of nhjr.lcal oroaertXee ot eolXe by 1ayora
icy  or depth, c.a
Specifio    1    8oil    donalty, wn 1 yrh t -  / ly/i-ga 3,
_
c/<yP 1 ’•If
Moisture         by volume
Poroaity,%             Iviator reeorvea, m^Aia
FC
ra     I5IAHI
1»
FC
Total 31
PC
A oral   WM i                   PC - VP4 tlnnl           I
TC I
Medium   loan   deep   calcareous   eurfacely   coupaot
tropical brown eutrophic eoil
ehaliow
0-25
0-50
0-75
0-100
0-120
0-150
0-200
100-200
2.62
1.62
1.53
7.9
5.7
9.5     29.6
30.0
39.8
10.2       237
740
503
2.57
1.59
1.61
14.1
8.2
14.3     29.5
38.2
37.9
0.5       715
1,470
757
2.59
1.60
1.59
16.3
0.7
. 15.3     29.2
37.8
38.0
9.5   1.151
2,195
1,047
2.58
1.64
1.60 
10.4
10.8
19.2      33.4
36.4
38.4
7.6    1,916
3,046
1,130
2.57
1.68
1.61 20.2
12.5
21.9     31.2
34.9
37.7
Ce4   2,632
3.763
1.130
2.50
1.72
1.63 
17.4
14.2
24.5      31.8
33.5
36.8
5*1    3,677
4.007
1,130
2.50
1.70
1.63
19.6
14.7
27.0     32.5
34.5
37.0
4.5   5,394
6,524
1,130
2.50
1.76
1.67
26.6
20.1
34.0     34.8
32.6
35.5
0.9    3,470
3,478
0
1.
I •■— — •*
PI
•                <*           4ft
•"F
>
•»
♦
4
*
&
• —
•                <•                 •         ■»              ■w               a
—
*• •
<
<-•
•*•
• t
♦
*->
••
•
*
<*
•
.
.• -
—              -1
•
•F
•
/
t
*i
f
♦
/■
<
•
•••
• r
ii
•
#’ •
•4•
• ‘ 1
|-
•
•
•••
•
’•■ r
•
»
*
•••
r ?                •<
•4•
*t
*r
—>             • /
t
•
~F
c
<
•
0/
♦
*—r
•<;
••
•
ip
4
f>
4
•
•v                  —/
•kx
•
•
•
•*—*
4
•
4
4
• f
*-■/
•/
• /
-1
•
*
•
•
•
•
■
•
•
«
ITablo 
'3. atmyg
5724.PJ9   /   Lay   ar   I Op&cifla I I wodj^“CU^*'^7“V
Soilylenalty,
Uoiature,^ by volume
Poroolty,56               Wat or
5
Toooyvto,n /ha
»>* 1 aP'1‘"l
/ 1
y-             f          k
Jir  T yc                 JPHlEAEM, WM
1           I          1
c/cn^ y
FC
Total      FC I Aora-|   VIM 1  " M 170 - TU
ZJ                      L tlanJ
11
2
$ yh :ront hloan lc soinl on odl fuor’Dralweaklyr    developed   tropical   bro'vn
title unn
0-25
2.59
1.53
1.53
9.5     4.7      6.1
21.7
40.8
40.7    19.0
154
543
390
0-50
2.5G
1.55
1.55
10.5     8.2     10.7
23.2
39.8
39.8     16.6
533
1,161
628
0-75
2.61
1.58
1.58
11.0   10.0     13.0
24.2
39.5
39.5      15.3
966
1,784
813
0—10>
2.66
1.60
1.60
11.4   11.1     14.4
24.9
39.5
39.5     14.6
1,424
2,442
1,018
0-120
2.60
1.62
1.62
11.5   11.6    15.1
25.2
39*3
39.5     14.3
1,796
2,976
1,180
0-150
2.71
1.63
1.63
11.3   12.1     15.7
25.2
39.6
39.6      14.3
2,377
3,760
1,383
0-200
2.75
1.64
1.64
11.6   12.7     16.5
25.8
39*9
39.9     14.1
3, >’7
5,095
1,708
100-200
2.05
1.6c
1.63
12.4   14.3     18.6
26.7
4^.3
40.3      13.6
1,883
2,653
700PTC
• • OO 9
'1
' /
/
fay or dap til,
an
l liktor rouorv<in, 7Via.
•va
ru
Tot .1
____
10
Aoi'Ub-i
ttfUl I
A ' l '
- 'TO V
J
Sandy  solodlaod deep oonpeot deep tropical
broiffl eutrophic soli
0-25
2.63
1.62
1.50
8.6
2.8
3.6
19.5
39.0     40.3
20.8
90
430
398
0-50
2.50
1.59
1.60
6.4
2.7
3.5
18.9
38.6     39.4
20.5
174
943
775
0-75
0-1 CO
2.59
1.59
1.59
4.7
2.6
3.4
19.2
3S.7     33.3
19.1
260
1,444
1,184
2.59
1.64
1.59
4.1
3.1
4.0
19.1
37.9     36.8
17.7
401
1,912
1,511
0-120
0-150
0-200
2.30
1.67
1.60
4.3
3.3
5.3
19.4
36.9     36.2
16.0
639
2,324
1,605
2.50
1.71
1.63
5.0
4.5
J.O
20.3
35.3     35.6
15.3
1,197
3,050
1,854
2.59
1.69
1.63
3.4
5.9
11.3
21.7
34.9     35.2
13.5
2.264
4.344
2.O01
10J-200
2.59             1.75          1.66     12.8        9.6       18.3       24.3       31.8     33.5        9.2       1,863     2,432        570
If! ;
2
*-r/ ^7^/
Spool £i   C/ Soil ^donsi ty  I koi u cure  ,5 Dy"Tdl*JHd
/      r-/n/n^                     /
___            __________
9t
Tnimr
ru in'
X ■
/ 00 i
g/cs^             1 r*        I FC          IFM  / JUDtf
1”
Tott-l                    Aort^—                                         VC - MU V
11!                         tlQXk .
r« i
_
** I
L
\
4
Tdrizt loiun shallow tropical brown eutrophic ocil
0-25
2.66
1.59
1.6o     7.1
3.4
5.0
24.5
40.0      39.9
15.4
126
617
491
0-50
2.67
1.62
1.62     10.9
5.1
8.5
24.8
39.3     39.1
14.3
429
1,246
817
0-75
2.62
1.60
1.63     12.3
6.5
11.4
25.3
40.6    39.3
14.0
854
1,397
1,043
0-100
2.63
1.60
1.62     12.4
8.0
14.1
25.7
41.2     39.5
13.8
1,405
2.562
1,157
0-1 ?0
2.63
1.59
1.6?     12.7
C.8
15.7
26.5
41.2      39.2
12.7
1,386
3,160
1,274
0-150
2.C3
1.59
1.65     13.4
10.0
17.9
27.2
41.2      38.6
11.4
2,683
4.067
1.384
—200
2.70
1.62
1.70     14.9
11.6
20.7
27.9
40.5      37.1
9.2
4,150
5,555
1,405
100-200
2.72
1.65
1.78     17.5
15.2
27.3
29.9
29.9     34.7
4.3
2,745
2,993
248
<•
4J7
"T
■f
r
t
/f URAWE       /          Z^'-iT i    <*® n th
,
/ Spccliiol           r*    7    7      . •»                    •      X-TL- 5a ? by
-xsZnn2
Pnvo«lty| ’JC                                   Wt\t)OT rooowan, ni5         /tux '
j on                  j g/aa-'                   ’<?         FC         /re        HADSf          WM
11
Total'    vc ]                     viu          yc ?c      - WM Wf                    I   t.inn !
5
Heavy loan-
Jeep pelll
shallow cBlceroouB  Dhallov; compaot
c vartieol
0-25
2.71
1.B7
1.28
10.4    17.6     31.7
46.2
31.1     52.8
6.6
794
1,156
361
0-50
2.77
1.79
1.37
28.8    20.3     37.1
44.8
35.3    50.5
5.7
1.856
2,241
385
0-75
2.81
1.77
1.40
31.9    22.3     39.2
44.4
36.9    50.2
5.8
2.944
3,328
385
0-100
2.32
1.76
1 >44
34.1    23.2      46,3
44.2
37.5    49.1
4.9
4,031
4,416
385
a-120
2.35
1.76
1.46
34.9    23.2      40.8
44.0
38.0    48.5
4.5
4.901
5,286
385
0-150
2.37
1.75
1.48
35.0    22.9      41.4
43.9
38.7    48.3
4.4
6,206
6.591
385
0-200
2.33
1.75
1.50
35.7    22.3     41.9
43.8
39.3    47.9
4.1
3.381
8.766
385
100-200
2.95
1.73
1.56
37.4    21.4     43.5
43.5
41.1     46 >0
3.3
4.350
4,350
0
M
L-< <flojla nhon flooded In inf11trooptera ai^fl
vhtvld
SRAH
Koo*
S Irrigation  at  tho  o  ana  tout  10  on  water  head  in  infiltro- aetorn. n/dav
Tine
of-sinking    of    the
from tho aurfaco
frats tho depth
cad of the 1-st hcrir
l-nt irrign- jisa
□toa
dy-
•tate
2-na Ik'X’Xga- tlQfl---- -----
1-Ct irrl^n-e ------tion
1,000  n-’/ha  irrigation
rate into wot aoll
2-nd 1 t f fir
Jzrign- '
♦at lrriga-
lion
Permeability ootlmatian
and of the 1-Bt hour
□tea* dy-
•tat<
end
oof
the
1-ot
___
etoa
dy-
state
2-nd        irriga-la202rdln«        to
and
of
the
1y«t
ttilonon
I
3
otea-
stato
•I*Dolgov
i 1‘urrcffl It- rigatian at the oona- tent 5 cm water head, L/100 r?7a
H1at ir riga
tion
1       6.48         1.15       1.73     0.62    0.46         0.08    0.034          0.05
2       2.88         2.30       1.44    1.01     4.68         1.73    2.88            1.22
3      5.33        2.44     2.02    0.85     1.32         0.95    0.69            0.63
4 1.58 0.35 1 .01 0.23 2.13 0.66 0.69 0.43
5 6.91 0.06 0.43 0.02 0.26 0.02 0.06 0.01
0.30
0.30
0.13
0.53
0.30
1.0
1.0
1.0
2.3
4.6
high
high
high
high
the host
1.4
3.3
5.0
0.8
2-nd
irri
Gati
an
1.2
2.5
3.1
0.5
0.35       0.28Tabla, 3.5.5
generalised ftauAfl Mid physical jjidlQOa of bo«,
----------------- T
SJUPM
rnn._______ L
i rtvnr flnnth.an
SRAPPS-1
Doaorlptlon of soils Medina loan deop caloareous aurfaooly oompaot shallow tropical brown eutrophio soil
Oharaotorlatica, a^/ha
0-25           b-5o
0-75
0-100
Porosity at PC Field capacity (FC)
995
740
1,895
1,470
2,910
2.195
3,040
3,046
Lower Unit of optisum soil molatoning   during   the lrrlgatian period (o,7 FC)
lntor-
510
1,029
Irrigation rate
1.536
2,132
222
441
659
914
SRAPW-2
Light loan nadiun deep weakly developed tropical brown eutro phic soil on forrallltio pan
Sandy solodisod deop ooapaot deep tropiaal brawn eutro
phic soil
Porosity at FC
Field capacity (FC)
1,018
543
Lower linit oX np 11 mim soil
1,990
1,161
2,962
1.784
3,950
2,442
□oistening    during    the    Inter- irrigation period (0,65 PC)
353
Irrigation rate
755
1,160
1 5A7
190
406
624
855
3RAP2S-J
Porosity at PC
1,006
Field capacity (FC)
1,970
2.872
488
3.600
948
Lower linit of optlauQ soil nolo toning during the inter- irrigation period (o,5 FC)
1,444
1.912
244
Irrigation into
474
722
956JJv
244
474
722
956-/
- 4    v
--^4*
*!
- > KJ
•• « -*
* •
•
* F
• ♦
!
• J , * t
•
••
’“V
•
o
• •
.• ‘
•’
f
•
■ .*
.•
* *•
.: •
•
Ji
7    *•
•i •
I
•
*!>’ # *
«
• -» •
.•••*
• ,•     . t •       X.J     '
•
I<             ’ 1
•
f-4- C
:&
• > >*■>
h
i
: Av
-•.LKAJ7S
Hoe,
Dooorlption of ooilo
3
I ~  Charuo tax'll tloa, cr/ha
Tn.bln 3.5.5.
[--------- ----- Xnynr? 
:    0-25 I 0-50 I 0-75
pm
0-100
SRAZ?J-4 JtdriJt loan shallow tropioal bxv.®
eutrophic soil
royalty at KJ 
993
yield cupaaity (KJ)
617
Lower Unit of optimal ooil
.loifltanlac during the intar-
lrrlGutian period (>,bp HJ) 401
Irrlcatian rate
ft A
HAWU-5 Hoary loon flhallow oalcarojua shallcr.7 coapact doap pollla
vortical
Porosity at PC
Plaid capacity (KJ)
1,320
1,196
Luwosuevrra l- A-i-sie-t-O of --15 ox op  op * timatima soil
coistcnlnG during tho intar-
irrigation period (0,85 W) 983
Irrigation rate
173
1,955
1,246
810
436
2,525
2,241
1.905
336
2.943
1,397
1,233
664
3.765
3,320
2,829
499
3,950 2.562 1.665
097
4,910 4.416 3.754
662i
i•101
<2ropicnl Brawn Eutrophio (Siallitic Brown Savanna)
Soils - Be.—
These soils occupy flat watersheds of the low plain. Their
total area within the survey boundaries is 13,873.8 ha or
43.9$» 
___ These soils formed up on proluvial red-brown and brown
ferruginous heavy loams end clays, light loams end loamy sends, ferrollitic pans of relict origin and gravel-pebblo ferruginous deposits. Groundwater occurs nt the depth of 15—30 m or more andoes not take part in the soil- forming process.
The formation of tropical brown eutrophlo soils is connect ed under these conditions with two main processes, i.e.the au tomorphic siallitio process on ono part, and the surface hydro— morphism due to the annual seasonal flooding of soils with rain and flood water an the other port. z
Tho first process results in a low cantant of humus, carbo nation, weak salinization and solonetzicity, a wide development
of compactness i the second process brings about a o arm cm inten sive ferritization of soil profile that sometimes reaches ita maximum in the lower part forming up a complete ortsand horizon of lron-manganese nodules.
It should be noted that all automorphic soils of the low niubabor plain bear the marks of surface metemorphiam. The degree of hydromorphism increases in the soil series from san dy and light, and theredue more drained (streaks, nodules), to heavy varieties which sometimes have cloying features in the lower part of profile.
The highest degree of hydromorphism is observed in low relief elements (padinga, vast depressions, dells) in which the soils of the aemlhydromorphic and hydromorphic series formed up, i.e. plenosols end pellic vertisols.
SOU varieties with a compact horixon and Q ooaroe naO[ri_, ve lunpy otruetura are considerably different fron the bulk of cello. A8 a rale they ere oolonohok-Uke. weekly online oolonetxio. Such cccpact brown eutrophlo soils form up under «tT®»l, poor drainage conditions of the area end
vXool^ dte,”iC TOrtiBOlB “a aoQpor aopraoolonn to pelller102
Ihe characteristic features of trtpical brown eutrophic
Boils are as follows:
-   light brow colouring;
-   distinct differentiation of profile into genetic
horizons;
-   intensive ferruglnation of the entire profile with fora-
Vig up iron-tr.anganese nodules;
-   sandiness of the top soil layer;
-   low humus content in the A^ horizon (1.21-2.8%) and
it sharp decline down the profile.
finer.-nd-Ing to their granulometric composition tropical
brown     eutrophic     soils     are     subdivided     into     heavyt       light     and
sandy.
Trouical brown eutrophic soils are subdivided into main subtypes, i.e. brown (transitionol to rod—brown) soils; proper
It07m soils with a distinct complete profile; brown weakly de
veloped scilo an forrrllitic pans.
Tropical brown eutrophic (transittonal to red— brown) soils occupy on insignificant area (0.7%) in the southwest om
pert of the surveyed territory on gentle slopes of the elevated plain with elovatians of 445—450 m.
□oil-forming rocks are red-brown ferruginous kaolinite— rjontmorillftnite looms and days. The thickness of humus horizon
varies within 12-19 am.
Weakly developed tropical brown eutrophic soils on ferra- llitio pans also occupy an insignificant area (3.8%) and occur
Ln tho medium and lower parts of slopes The thickness of their humus horizon is
Both subtypes belong to low humic, 1.68-2.1% in the horizon.
"2he cation absorption capacity is, , ... 
of the elevated plain.
7v14 cm.
the humus content is
5.2-7.7 in the k^ hart— xjaj71
son ana 3.1-4.6 nus-equlv. pen 100 g of soil in the'a” hirtz'oT rteontdns eOTpl« la saturate! orjnly -.rtth ealoilm (31.6-68^
S) and nogneslvm (24.3-66.5%). The eodluB content la 3.8 -
7.6S, tho noil, exo nau-oolonetzlo. The reaction of soil eola tion la veekly aeiaie, pH ta S.2-5.6. The eolle ere nen-eallne.
o ou.- of salts in water extracts makes up 0.014—0.045%.103
She aqueous and physical properties of brura (transitional red-'orov/n) soils and weakly developed brown soils on ferrol-
lltic pans aro close to abovedesoribed fersiallitic red-brown av
vanna soils. 
According     to     their     generic     features     tropical     brown     eutro- ptdc      soils      are      subdivided      into      non-calcaroous,      calcareous,      so- lonchak-like and solonotzio.
Among the tropical brown eutrophic soils the groatest area
is occupied by the non-calcnreous ones. Heavy-textured varieties
aro compact in most cases and light-textured varieties are non
comp net.
'Thn average thickness of humus horizon is 10-13 cm
(8...25 cm).
Description of a characteristic morphological propile.
Soil pit Ho. 810 located 2,100 m southeast of the Abobo-Gllo
road and 1,250 m northeast of the Nyikani Hl ver.
A^ 0-12 cm! grey with brownish hue, cloddy, granular flilty,
heavy loam, strongly sandy, dense, abundance of fine roots, large amount of coarse quartz grains. Transition is sharp in colour and density.
B 1 12-33 oni grey-brown, coarse cloddy lumpy, light clay, can
dy, vary denoo, oom pact from 15 cm, fissured, frosh, separato fine roots, rusty ochric mottles
and streaks on edges of struotural separates, coar— so quartz graina. Transition is notiooable in
oolour.
D 2 33-72 cm: dirty brovm, heterogeneous with rusty
mottles, coarsely cloddy lumpy, day, sandy, frosh, very denae, compact, fissured, rusty ochric and separate black mottles on edges of structural se parates, coarse quartz grains. Transition is no- ticoable In col
C1 72-130 cm: Albic dirty brom, heterogeneous with ochric mottles, coarse lumpy, day,  mdy, fresh, very
8
danse, compact, rusty ochric mottles an edges of structural separates. Transition is gradual
A
2  130-200 «,ou. lifiht
hatarOEaneouo oohrto‘
notileo, atruotuieleos. clay, vary dense. oaopact.Mr
fseparate iron-mangsnese nodules 3-5 na in dia- netsr. fresh, coarse quartz grains.
Eolonetsia saline varieties are represented nainly by hfftVy-texturei soila with a lighter A horizon (day 
1£,5-36.95) and the clay content in lower horizons from 42.0 tc 53.7%. Then© aoile are medium humic (2.1-2.34# in the A ho
rizon). 
The cation absorption capacity of the A and 3 norizona i 1C.5-21.9 and 11.2-24.5 ng-equlv. per 100 g of soil, respecti
vely. The abcorblng complex is saturated mainly with calcium (40.0-66.0%) and magnesium (22.0-55.0#)* The absorbed codiuzi content is 2.5-3.25 in non-sclonatzic varieties. 3.8-4.6# in wanMy solonetsic varieties, 6.^9.2% in medium solonetzic va
«P
___
ries io ej and 12.7-16.2% in strongly solonetzic
(Table 3*5.6).
In non—saline varieties the sum of colts in. the 0—200 al soil profile, end the content
V&TiOtlQO.
io 0.010-0.064#
of bicarbonate iamj
chlorine and sodium does not exceed the threshold of toxicity. Tn weekly saline varieties, mostly in the 8<,—150 cm layer,
the 3wi of celts is 0.108-0.204%. The chemistry of salinization is eulphatic-uodic, sodic-sulphatic, chloridlc-aodic (Table 3.S7).
The aqueous and physical properties of the an soils may oo characterized by the data obtained at SRAZPS-1.
According to its granulometric composition the anil of 3RAPTS-1 Id heavy. Its density la high, l.e. 1.62 end 1.64
a/ra . in the c-25 and 0-100 cm layers, respectively; Its total po-ceity la low, l.e. 33,0 and 36*4# in the 0-25 end 0»100 co Ir^TB, soopeotlvay. Aooordlag to lUl.ZatehlMky- the porosity lu v^tlataotovy for the plorta- horizon. The aeration pore?
XVtiX 10,2 ma 7,6S
Its Him air-dry rotators, vrtltlnc nolo tare. Ileia ca- pno ty ,5-Tte up 5.7) 9.5) 29.6S by voluae in the 0-25 m l.vyr- vneptatlvsly, Klil those in the 0-700 => layer equal to
19.2 and 30.4S by volume. 
•
1 °*E’
««-...»; s.-tG.hl:”'Description of soils
Sanpllug
depth,on
Abaorbod cations mg-equiv.per 100 g o- aoil
Ca I Mr ! -fa 1 >K .* Sw! «Klea
"j o£ absorbed oation
I. ‘tel
Na 1 K
Humber of rage  aved
pita
Tronloal brom outrophio aoilai
1 a) -.voakly solonetzio
0-25
3.4
3.1
0.3
0.2
7.0
43.6
44.3
6
41.2
4.3
2.8
25-50
5.2
4.0
0.3
0.2
9.7
53.6
3.1
2.1
50-75
7.4
3.6
0.6
75-100
0.3
11.9
62.2
14.7
30.3
5.0
9.4
4.4
0.6
0.3
2.5
11.5
6.1
0.8
18.3
63.9
61.2
29.9
4.1
2.1
150-200
100-150
13.3
5.9
1.0
0.4
0.3
20.5
64.9
32.4
28.3
4.3
2.1
4.9
1.4
2 bjnediun oolonetzio
0-25
4.6
2.6
0.8
25-50
5.5
4.6
1.0
0.7
0.6
8.7
52.9
29.9
9.2
8.0
3
50-75
6.3
6.0
11.7
47.0
39.3
8.5
5.1
75-100
7.2
1.3
c.4
14.0
45.0
42.8
9.3
2.9
100-150
6.9
1.5
0.2
0.3
15.8
45.6
43.7
9.5
1.2
150-200
13.1
17.5
12.1
7.9
2.7
1.4
22.7
0.4
32.7
57.7
53.5
34.3
37.0
6.2
8.2
1.3
1.3
3 o) otrongly oolonotzlc
0-25
1G.3
4.8
25-50
2.3
0.6
13.9
3.4
3.5
0.6
18.0
57.2
21.4
65.0
26.7
15.9
12.8
16.3
3.3
50-75
15.0
2.0
3.0 •
0.5
22.1
71.5
9.0
17.2
2.8
3
75-100
21.4
2.4
3.7
0.6
28.1
76.2
8.5
13.2
2.1
2.3
100-150
25.7
2.3
150-200
23.9
3.8
3.3
3.1
0.5
0.8
31.8
31.6
80.8
75.6
7.2
9.8
10.4
1.6
Chromic vcrtiools*
4 a) woakly oolonotzlc
12.0
2.6
0-25
6.0
3.7
0.5
25-50
0.5
0.7
4.4
0.7
0.4
11.5
14.2
59.2
32.1
4.3
4.3
5
50-75
75-100
8.4
4.8
0.8
0.3
9.5
5.0
0.9
14.3
61.3
58.7
31.0
33.6
4.9
6.6
2.8
2.1
100-150
10.0
5.3
1.0
0.4
15.3
60.1
0.4
16.7
31.6
59.9
5.7
31.7
6.0
2.6
150-200
11.7
7.2
1.0
0.3
20.2
57.9
35,6
5.C
2.4
1.5
I
>
II
I
I
I
I---- T
———
Iteni
nos. 1
Sampling depth, cm
C-25
25-50
50-75
75-100
103-150
150-200
0-25
25-50
50-75
75-100
100-150
150-200
0-25
25-50
50-75
75-100
100-150
150-200
Abaorhfld-aaiXQna. -
iSg^equlVapox- 100 e of soli
I
K StDE
5.2 5.0 c ■ 6 0.3 11.1
______________________________ w
.............. ... ......... ......... AMunber
>j of abaorb.jd cation mm I of avo- ;
TaWLO 3.5.6.
DoPcrip^-^ of Golls
I
™ I
Vj
Y
4^.8
5.4
2.8
X
O
5 b) aaulua aolcnatzio
3.8         6.5          1.2        0.4        16.5
7.5         5.5          1.0       0.3         14.3       52.4      38.5         7.0       2.1
10.2          6.9          1.2        3*3       18*6       54.8      37.1         6.5         1.6
52.1       38.5         7.1         2.3
12.0 7.2 1.2 0.3 20.7
13.3 6.5 1.4 0.3 21.5
61.9
58.0      34.3
nc **»
5.8 1.4
6.5 1.4
6 c) fitronrly solonetzlc
Pnlllc vertisols1 7 a) modi™ solonetric
5.4          3.3          1.3        0.3         10.3       52.4      22.0       12.6         3.0             3
8.3          4.2          1.5       o*3        14.3       58.0      29.4        10.5         2.1
10. 4         4.5          1.8        0.4         17.2       60.6      26.2        11.0         2.3
11.4          5.1          2.0        0.3         18.6       60.6      27.2        10.6         1.6
13.2          6.0          2.4        0.2         21.8       60.6      27.5       11.0         0.9
12.4          6.5          2.2       0*2        21.3       58.2      30.5       10.3         1.0
9.3          9.1          1.2        0.4         20.0       46.5      45.5          6.0         2.0             6 13.0        11.1          1.9       0*4         26.4       49.2      42.0          7.2         1.5
Tropioal noadow-w^P o6H« e  &) weakly oolonst-lc
0-25
25-50
50-75
75-100
100-160
150-200
0-25
25-50
50-75
13.6 13.2 2.2 0*5 29.5
19.3 10.2 2.6 0.3 32.4
1E.2 13.0 2.7 0.4 34.3
18.8 10.3 2.6 o*5 32.2
6.9          5.6          0.4        0.2        13.1
9.8 5,5 0.7 0*1 16.1
9.2          5.5          0.6        0.1         15.4       59.7        35.7        3.9        0*7
46.1        44.7        7.4        1*8
59.6       31.5         8.0         0.9
53.1      37.9         7.9         1.1
58.4       32*0        8.1         1.5
52.7 42.7 3.1 1.5 1
10.9          6.5        0.7       o*2         18.3       59.6      35.5          3.8        1.1
60.9       34.2
4.3         0.6
11.4          6.9        0.7        0.1         19.1
14.0          8.5          0.7        0.1         23.3      60.1       36.5          3.0         0.4
59.6       36.1         3.6         0.7
Alluvial floodplain colli 9 fl ) waakly aolonotzlo
5.7 3.0 o.3 0*1 9.1
6.3 3.0 0.4 0.1 9.8
7.5          3.8          1.0        0.1         12.4      60.5      3 v.6        8*1        0*8
62.6 33.0 3.2 1.2 1
64.2        30.6       4.1         1.1
75-100
100-150
150-200
8.6
4.7
7.5
5.4
1.7
1.5
0.1
0.1
14.9
14.7
57*8       31.5
51.0       36.7
10.1
11*6
0.6
1 -*
1.0
0.1
<)
10.8
7.3
20.0
54*o       36.5
0.8
9.0
0.5»ghaminol composition of water extract pf soils <1 aS)
'TnWi 2.5,7
Anions
Catlona
Anion
J             faauolinfj
Cntinn |F
sum h
7 pit
depth,         nquaoun 0J3              P“
cc3 I nco-j
(51  SO.
*
Ca
T!a
VJ1 of %
Numerator - %
Denominator - og-equiv. per 100 n of noil
fflf-aquiv.per 10  **  of soli
n
A----------u
Medium               Atria deep fl.
re ffoe^cl
0-25
2*221
0.020
0,260
0,260
0.018
0.009
25-50
0.003 CTO
0.480
0.480
0.034
0.024
50-75
0.690
O.tgo
0.052
0.036
75-100
1.120
1.120
0.074
0.051
100-150
6.3
3*150
3.150
0.203
0.097
150-200
7.7
1.650
1.650
0.124
0,078
Had
lun dolonfitslc
deep aolpnch
ak-liko we
ekly online
 oellip vertlool
6.4
" - °*° °
cro
g
0.001
0,006
SRAFJ9-5 0-2
£*2?i
0,083
0.001      0,007 0,001
beCaii o * 3o • O,83o
0.496
0.496
0.037
0.030
2-11
6+7
- g'WP
cro
0.0 >3
CTO
w
0,001
Co 62
0(042      ■ ,280 C026
0,001      0.006 0,001
0.4P4
0.404
0.029
0.023
20-30
7.3
- ftoy o, 3s5
QJ)03
o*o55
0.00a
CTO
0,009
CTO
0,002
CTO
0.001
O.O42
0.031 0.010 0,001
CTO 0.430 0*020
40-50
a.3
- 0,026
CTO
0.004
CTO
0.001      Q.Q13      0.001 cw     CTO CTO
0.664
0.727
0.664
0.727
0.049
0.054
0.040
0.049
f
tH
3* ».
i
«
1
i
r
-»      I
••
*
i
•‘
i
*- r
ITable 3.5.7. oont'd
r
lAquoous 00 PH                J
Anions
HCO3 ! 01
Cations
of soil
Ha             K
numerator
Denominator - ng-
Knlon
- aura
--Bg-equJ 100 g c
Cation
sum
.v. per >f noil
Sum o aalta,
*
flSum of toxio aalta,
*
SRAPPS-5 60-70
80-90
80-90
120-130
150-160
190-200
6.6
8,8 traooe
0.767         0.767             0.057        0.048 1.314         1.314             0.102        0.092 1.294         1.294             0.100        0.089 1.14b         1.143             0.088        0.082 0.640         0.640            O.O49
0.043■
i'
J
I1 ijtCBL'" —£?£**■*rrtiitl Tat* H^il0 SGCOTld OELCS.
tho 0-25, 0—5G and 0-100 cm layers, respectively*
file 1 jwer Unit oi ths optimina soil moistening during -iie inter-irrigation. period tjqiu-la 0*7 TO and makes up 1,029 snd. 2,132 m- /ha in tbe _-50 and 0-100 am layers, respectively.
light end sandy vericties ol‘ tropical bzov/n outropbic soils ere distinijuiElie<1 by tiie absence ol cocipcct iJoriaon and finsur— inr; an well as by c. h_Lcb aea'llnans of upper horizon*.
3
Jlioir j^rajiuloeietrio coupon! tian la characterized by a >H gh
(up to 
content ci sand fraction In the entire profile,
capoclaiiy ia the upper part (Table 3.5.8)j by a low content of nlity fmctlan (10.7.&); by the accumulation of clay with depth
CO-10 cm - G.7 and 60-70 am - 21.3?;).
rhe soils ere mainly low humic <1.21-1.9755). Che 0-100 cm layer oontainc only 0.11-0.17^ of free iron, but in the 100-200 era lay«i- its content ahnrply inSTancee <0.82-2.9^SJ*ITable 3.5«B
Mt
Horizon
Granulatncti'lo composition
Sampling depth Fraction content3 (particle alr.e in mm)
CT
1-0.25
1
0.25* 0.05
0.05- < *01
0.01-
ft ft —, *
■ 0.005- | Iorio
v.COI | iiitui 0.001
Sus Of “particle b
in«jp +h°Jl ’ 0.01
Xii/ght tropical brogn aitrciohio aoil
585                *1
132a
”1
°2
SilA^-5          Ao
A1
AB
*1
B2n
BO
B0
0
0-10
42.3
39.1
8.5
2.2
16-26
50.0
32.3
5.6
3.2
35-45
33.9
33.0
5.0
3.3
60-70
00-90
120-130
39.1
30.2
4.2
2.8
lu.G
24.8
5.2
3.2
46.4
23.1
4,0
3.3
Heavy naUie vec
0-2
11.7
42.3
15.6
1.7
2-12
11.4
25.4
14.9
3.6
20-30
17.6
12.4
5.1
3.2
1.2                S.7
1.9                 7.0
2.2               20.6 2.4              21.3 1.1              19.1
1.2              22.0
2.5               26.2
10.4               24.3
5.8               55.9
40-50
60-70
80-90
15.3
6.5
6.7
2.2
8,5
60.8
14.5
6,5
6.6
3.0
12.6
14.2
5.6
7.2
120-130
13.5
11.9
10.1
4.3
150-160
o
uli«-
2.4
11.4
6.2
190-200
18.7
3.0
16.7
7.3
7.9 60.5
9.8               50.4
12.0               47.4
9.3               49.5
6.2               43.1
10.1
12,1
26.1
26.5
23.4 26.5 40.4 3G.3
64.9 71.5
72.4
67.4
64.5
65.0 56.6ill
godlum is due to the lcr-> absorbing capacity which is
gjGilP^S
rather cherccterlstic for light-textured dessert soils. 
___a
1 
drtflneT*t 3oilS«
lIs basis we attribute these soils to nen-solonetzlc.
The     coil     profile     p.s      well     as     underlying     soils     (depth     up 7    m)    are    non-    sol    ire.    The    son    of    salts    is    0.011-0.17?*    in 
D-200 cm layer and 0.015—0.027/5 in tho 2-17 n layer.
The aqueous and physical properties of sand and light non-
for send soils snd SRAPPS-4 for light snoc.
SRAPPS-3. Sand deep non-c^lcaroous tropical brown eutro
phic soil. 
Its density is high, i.e. 1.62
. 
and 0-100 cm layers, respectively. The total porosity io law, i.e. 39 and 37.9% in the 0-25 and 0-100 cn layers, renpoctively. J According to IT.A.Katchlniky’s evaluation the porosity is imsa-
tisfactory for the plowing layer but chamctoriatic for can- pacted Illuvial horizons. The aeration poi'oedty is sufficient, i.e. 20.3 and. 17.73 in the 0-25 and 0-100 era layers, respecti vely.
Its maximum air-dry moisture, wilting uioiature, field ca pacity make up respectively 2.8; 3.6; 19.5% by voluno in theI112
the
3
nerten Irrigation mteo aro 244. 474 and 956 « Aa tor
_           0-50 and 0-100 an layerfl, respectively.
^PPS-4.  Light loan  shallow tropical bromi eutrophic soil. 
end
and
^Tensity 43 high. l.e. 1.59 and 1.6 
0-100 cm layora. the total porosity lo 
«.2< and the aeration porortty mounts to 15.4 and 13.W. 
r.oistire and field
Its marinun rit-dzy noloture. rililng nolahire and Meld
In tha 0-25
« i n.a*
3
capacity    nake    up    3.4,    5.0;    24.54    by    volmo    in    th.    0-100    m    layer, Water reserves corresponding to UM, 20 end PC - WM are ,
617, 419 n /ha in the 0-25 <n layer end 1,405 , 2.562 and 1,157
nP/ha on the 0-100 am layer.
Ito      water-permeability      is      high,      i.e.      1.58-1.01      m/day      froa the    sixrfoco    by    the    end    of    the    first    hour,    and    the    steady-state permeability is 0,35-0.23 m/day. The steady-state permeability
from the depth is 0.66—0.43 m/day.
I
3
The sinking time of the 1,000 m /ha irrigation 0.53 hour during the first irrigation an-? 2.3 hours
RACon* one which provoB its high perr.ee’-111 iy.
■Then irrigated in furr<yv3, the permeability is 0.5 1/1 CO linear metros per second during the first
irrigations, respectively.
i*ate io during the
0.8
and
and nacand
irrigation r^tee ore 2l6, A?6 and 897 in "'/ha the 0-25, 0-50 and <>-100 an layers, respectively. 
VertiaolB
They occur in the northern and •.Tostarn parts of the
a continuous massif and in its central part as eepaxete
in -licrodepresrlona. They occupy flat dmLnleso '.mt nr sheds of the low plain numerous patcllold depreseions es v=oll as
for
xrea       an apotn
tT
n0O Ied  n PartB of the
The-r total area ia 14.772.2 lia or 46.3,;.
/
-               **«*<> and Tyiknr.l Rivers. 
They are ^dividod in two subtypes, i.Q
.  ^
c  tulc
pollxc vortlaoloe
The vertisol formation (vertiseneais) lr cheated with > various oio-and hydrothermal conditions an well xs rfth
v^l
^ lsraaat, ,-,wlop: eXX p^0*
ground o£ a lev tamusnoaa ot coll, and any b  p-L——
condory according to the sencols.
ttu. iSt!.; "
tlol ooononal ovraolotaUne kA «n aMt caao. doo. hot
o
1 117 " •°’-"™’-phlo vartlgonooia 1. MMtted ri th • I •
I
Ito         bo      a      consequence      of     the      Influence      of      eoil-foralng fle6° chemical composition of surface and underground vat ora.
The cecondary vertigenoeie io due to the interaction of
9O il-foroing rocks with the trenflit transportation of soil 00-
lutions or cloy containing higher amounts of megnoaium and si lica. Hydrogen is replaced by magnesium and silica in the latti
c0  of minerals bringing about their transforation into nont- morillonlte.
Vertigenesis dovelops in calcareous-calcic and non-calco- reous media. The soils of these groups may have only e neutral
or Al Im] inn reaction of the soil solution. If magnesian or so
dium montmorillonite is available the alkalinity may be due
to the Ions of sodium and magnesium.
Finally. under tropical conditions the interaction of
vertisols with water in the paste state frequently determines
the eph am eric emergence of soda.
The colour of vertisol3 depends an two main elementary processest a) fersiallitization duo to the increase in the iron
oxide content as woll as due to paloogleyio features such as nodules end films of iron-manganese oxides  end b) hydroaor* 
t
phism ( especially paleohydromorphiam) which determines darker colour hues which might have been acquired in the result of transforming hnlo acids and fulvoacida into humins.
fomatton ot vertlaola iB OMm9otea nance ot intaorillonlto In then. „hlch la p
-
pi at5cnl_ ?
mineral nopweonted meinly by aoGoaBlra ooaila The annual eeaaenal overaolotonAns of nontaeriiionlte
^iZ
polling ana contrition proceaaoa. t<>Iolag np m
000 ^04 
1171116 brtn8° “ peTio^°
of
-y pnlmetie atiuctuno. Such oolla ano ohaxuotertaed byO trong fissuring (depth up to 1.5 m), presence of a deep ooa- ptiot horizon and a mulch layer (up to 5 cm deep) that is
lighter-textured as a rule.
Chromic Vertisols - Vp
They occupy 11,957.2 ha or 37.83 and are distributed in the northern, northwestern and central parts of the surveyed 
area on flat watersheds of the low plain with abundant patello— id depressions.
Their main soil-forming rocks are proluvial and alluvio- d eluvial deposits.
According to their specific and generic features they ore subdivided into:
a)   non-calcareous chromic vertisols - 2,133.2 ha or 6.73; b)   calcareous chromic vertisols - 470.2 ha or 1.5%;
o) solonetzic weakly saline solonchak-llke chromi c vertisols - 9,431.3 ha or 29.9%.
According to their granulometric composition these soils ere heavy and only 370.0 ha or 1.2% belong to light ones. 
A characteristic morphological profile of chromic verti sol is given below. Soil pit no. 130 is located 1,550 m south of bench*□ark 5O7«
K1
0-9 era:
B1
9-34 cm:
grey with rusty ochric veinlete, fine lumpy cloddy, light clay, sandy, dense, dry, porous, fissured, plant roots, fine rusty ochric mottles. Transi
tion is notioeable in colour.
dark, brown, coarse lumpy, medium clay, strongly sandy, very dense, oompect, fissured, structu
ral separates are powdered, with fine quartz sand, porous, dry, borings of small burrowing animals, fine rusty ochric mottles, coarse gra-lnn of various minerals. Transition is gradual.
B2
34-47 cm: greyish light brown, coarse lumpy, light loam.
Bandy, very dense, compaofc dry, coarse grains of minerals up to 3 mm, rusty ochric streaks, very
BparBe tine rootB. Transition is noticeable in colour and structure,
G 1 47-96 cmi dirty light brown with pale yellow hue, structu
reless, light clay, cemented, very dense, ruBtyReties these
values meke up 29.5-48.0 and 28.5-56.0%. 
Tne The share  of sodium in heavy soils is 3.3-5.8% in the , nnd A 7-12.8% in the B horizon; in light soils the
‘X-Such “ 7^of
absorbed sodium Is Indicative of the weal:. medium and s.rong solonetzlclty of these soils.
The content of free iron layer, 0.53—2.2% in the 10—25
50-60 cm layer.
is 0.31-1.06% in the 0-10 cm cm layer and 0.95-1*39% in the
The analyses of water extracts has indicated a weak sa -
nity of the lower part of this soil. The sum of anions and cations varies within 0.100-0.135%. The chemistry of salini zation is sulphatic-sodic, aodic- sulpha tic, chloridic-sodic.
Pellic Vertisole - Vp
Pellic vertisole occupy 2,737.5 ha or 8.6% andaie c.onfihed to lower relief elements.
vn fh-tn the surveyed area these soils occur along the Alwero and liylkani Rivers end in the western part they are
encountered in a ehallow ravine and a large pading. Main soil— f owning rocks of pellic vertisols are alluvlo—deluvial, la custrine-alluvial and proluvial deposits with clay and heavy clay textures.
Groundwater tables in the near-bed floodplain are 3—7, 5-10 metres end 15—30 metres at higher elevations.
According to specific and generic features there hnva been distinguished!
a)  non-oalcareous pellic vertisols - 470.0 ha or <_4«cL*6 - 1.2*| b)   calcareous peUio vertisols - 505.0 ha or 1.6% (K2 " 1),
1.762.5 ha’tr 5^K l^^l°olonohak-llkfi Pellic vertisols -
Ol send fractions l  46.eS>, a low content of t^TUT^
r^TeXer7tXXo3f78) 18
0
«on end a high content of the elay flection urn 7 
Its distinct accumulation In the B horizon (60.8S>,
is Given below.^T.TT^OTMTTi* PGl110 VBrtlBo1
-b of the field camp at’the’ 8Wth-
Heavy deep shallow compact shallow callous
pellic ver-•I
• • •
• ” • / - .
• ♦
1 i I.
17'
1
1 :
•
..   -
i      **  *
• *»
—
• ■
• ♦ •
** > *■
• ♦
• •
• •
ztifiol on ollve
2-11 cmt
bluish-mottled carbonated kaolinite-montmorillo-
nutty     powdery,     heavy     loam,     weakly     sandy,     loose, dry, crumbles into fissures. Transition is sharp
in density.
dark grey, lumpy coarse cloddy nutty, heavy loam weakly sendy, very dense, dry, porous, borings of termites and other burrowing animals, very sparse and fine rusty ochric mottles, sparse grains of minerals. Transition is noticeable in colour and density.
AB 11-37 cm» dark grey with brownish hue, coarse lumpy, some
times     columnar     lumpy,     porous,     fresh,     light     clay, very dense, compact, humus streaks on structural
separates, gloss, sparse rusty ochric veinlets and
nodules. Transition is noticeable in colour.
37-74 era j brownish grey, coarse lumpy, clay, fresh, very den
se, compact, porous, gloss on structural separates, 
sparse rusty ochric veinlets, nodules, efferves
cent from 65 cm an separate washed-out carbonate
spots when treated with 10% HC1. Transition is
gradual.
b2 7 4-97 cmt slightly lighter than the previous one due to
abundant carbonates,  albic brown  grey,  coarse lum py,  clay,  fresh,  very  dense,  compact,  rusty  ochric
spots and veinlets Increase, nodules, carbonates
i^the form of abundant mealy powdering and sparseinto flaky foliated structure, dull lustre on
structural separates, Abundant rusty ochric
mottles and yellowish veinlets; iron-manganese
nodules, large sparse carbonate spots, olive
bluish spots appear from 200 cm.
The thickness of humus horizon averages 13-15 cm (10...21cm), 
the compact horizon occurs at the average depth of 12-15 cm
(  ” According to their humus content pellic vertisols belong 
to medium-humic (2.7-3.9% in the A horizon).
The structural-aggregate composition is unsatisfactory,
i.e. the total amount of 0.25-10 ram fractions is 19.7-32.9% in 
dry M                  at the same time the water-stability of aggregates
is high meking up 64.7-74.1%.
The content of free iron in the upper part of profile is
high, i.e. 2.3-2.4%. being only 1.1-1.4% in the lower part. 
The cation absorption capacity is 1444—25.9 and 17.7-37.0 
mg—equiv. per 100 g of soil in the A and B horizons, respecti
vely. The absorbing complex of the A horizon is saturated with 
calcium (37.5-54.1%) and magnesium (37.0-54.2%)» the sodium
content la 4.2-5.4%. In the B horizon their values equal 46.3-
54.B;     37.6-44.6     and     5.6-7.9%     of     the     sum     of     cations,     respectively. The soils are medium 3olonetzic.
The analyses of water extracts of weakly saline solonetzio verietleB display sulphatic-sodio and chloridlc-sodic saliniza
tion. The sura of salts in horizons below 80 cm makes un 0.108- 0.117%.
The aqueous and physical properties of these soils are c racterized by the data obtained at SRAPPS-5.
. Th°
3
layer end 1.76 g/on  In the o_1oo layer
3
1.87 g/on>  in th. 0-25 on
" °
25  ”
la     extrenely     loe     and     uneatlofaetory     1     .     22!     <     *5     Poroalty layer end 37.5% In the 0-100 on Zer2L’m
6.« dn the 0-25 . layer and 4.^2 2 ^elr naxd^ air-dry nodeture. editing ty are respectively 17.6’ M 7» /c n « layer Xd 23.7- 2 3 2 2 , 
la
““ Per°Ont tho
layer, 
’ *°’3
ieiU capaci— *-> the 0-700 on
Moisture reserves corresponding do 'fltt, pc and TO - WM exoJ*
itfr*
«
•
• •
r
-•
•
•
•
, •
•
• •■
•
*>
•
•
•-IIS
3
794; 1.156 end 361 m /ha in the 0-25 co layer,
3
^ 031* 4,416 and 385 m /ha in the 0-100 cm layer.
804  Vermeebillty of heavy compact pellic vertisols depends
alnly on their moisture. Being high at the initial moment
m/day by the end of the first hour), it sharply decreases with the swelling of fissures and stabilizes at a permanent low level (0.06 m/day at the end of the sixth hour). When water sinks into a moist soil the permeability changes not that sharply an equals 0.43 m/day by the end of the first hour and 0.2 m/day by the end of the third hour. The steady-state permeability of com pact horizon is extremely low (0.01 m/day) and practically appro- a ch as the rate of evaporation fron the wp.ter surface •
The sinking time of the 1.000 m /ha irrigation rate is 0.3 hour during the first irrigation and 4.6 hours during the second 
3
3
one.
When irrigated in furrows, the permeability is 0.35 1/100 linear metres per second during the first irrigation and 0,28 
1/100 linear metres per second during the second irrigation. 
The lower limit of the optimum soil moistening is 0.85 FC during the inter-irrigation period.
Their design irrigation rates ere 173 m /ha for the 0-25 
cm layer, 336 nr/ha for the 0-50 cm layer and 662 m /ha for
the 0—100 cm layer.
Planosols - P
These boUs ocoupy 115.6 ha or 0.4 % of the area and are represented by heavy medium deep medium humic medium compact raolodic pianobo1bw
dlsttac/L^11^’ Planoso18 8X6 c^iaed to smoothed flat
tinct depressions and ravines of the low plain. They foiroed up on proluvial clay and heavy loam deposits.
3
Their characteristic feature, la the presence 2  horizon consisting mainly of amorphous silica,
of   an and a
albic heavy 
I
weakly permeable B horizon with a higher content of
sodium and overmoistening evidenced the lower
absorbed 
—" P rt of profile, 
a
Planosols may fora up under the conditio Posure of non-saline soils to weak solutions of
in this case the profile gets solonetzV ' - ter flows wa3h . .. 
~“
ions of periodic ex-
- —’ bodiura Balta.
ialc IUId J hen
-    downward wa-
an carry out the products of alkaline12J
The silicic acid is present due to a certain diolnteGre-
tion 04-
f the alwnooilicate part of soil attacked by alkaline so-
lutic®®*
The solo<51zation brings about a sharp differentiation of pT-ofilG which is clearly displayed by the granulometric ocopcsi- tion* The upper aolodized horizon is impoverished with clay par ticles and the illuvial horizon is enriched with them (7.0-11.6% in the B horizon).
A characteristic profile of solodic planosol is described below. Soil pit ITo. 37 was sunk at bench-mark 812.
f
s 2-14 cms
*3
14-21 cm:
Ao 0-2 cm: grey, silty powdery, strongly sandy, medium loan, loose, dry, lino plant roots, Transition is sharp
• in density end colour.
albl.c grey with separate white spots of glassy powdering, unstable coarse cloddy nutty, flaky leninated in its upper pert, medium loam, strongly sandy, abundant glassy powdering in its lower port, compacted, dry, fine roots. Transition iB sharp, light grey, albic, unstable cloddy powdery silty, tedium loam, weakly compacted, dry abundant amor phous silica partially cemented with iron oxidea, coarse quartz groins, dark brown, spots of iron 
S1
24-32
om: daoxi  rk br desow, Tn, c ransoaitrion i   se lums shapy crp iloddy, l       n colour ight  and de     clay, ve nsitry,  y dense, aosipact, amorphous silica powdering on structural separates, abundance of coarse quartz
32-gq Qund, sparse fine roots. Transition is gradual.
033 x
°1
' CO; d'<’tv+
^- ty bluish, grey, coarse lumpy, very dense, com
1
 Tight bi  own with small white and rusty ochric spots, coarse lumpy, light clay, very dense, compact, no roots, rusty ochric spots Increcue downward. Transition in noticeable in colour.
r
°5
pact, fresh., mon-distinot small rusty spots of
ir °n, Treneitlfin is noticeable in colour, 
^•bluiah grey with, abundant bluish violet spots, coarse lumpy with manifestation of horizontal la- ^ination, medium clay, less dense than the previous °no, moistened., sparse rusty ochric mottles, hfrun-••121
dant doit violet WMaeee abundant white eeft epot8 Md cence    when    treated 
J
d
“
«    -    pld      eff0rveo-
w-t+i, 
 with 10% HC1
The humus horizon thickness is 11 (Q
horiZon occurs at the average depth of 42 
According to their humus content these soil’*’ humic (2.1-2.44%). She absolution capacity of then^ “'®diun
\ 0Qapact
eao^ine to 7.9-11.7 WlT
.^  ?
r
profile   and   only   to   3.6   mg-equiv.   per   100   g   of   6oil    , risen. Ihe absorbing complex is saturated □airly \
XTx ™                  »<
“-
,  the
iacreaaes up to 66.7%. Zhe shores cf codlua and potassiun ncke up
6.9 end 2.8%, respectively.
The   v/ater   extract   analysis   ic   indicative   of   she   absence   of salinization. The sura of salts is 0.014% in the horizon,
0.0C85S  in  the  A2   horizon,  0.013%  in  the  B  horizon  and  0.014%  in tho c horizon.
■Tropical Meadow—Swamps Soils - Me
Buy axe ^
r
----- TMCTtStZ^
^^edi’an deep ______ 
^ep gl0^10
weekly 3olonetzic meadow----------- ------------------------------- Acrordinfi to
1.6% of the area. 
Theao 3oils belong -
relief conditions they ere oo ' reaaions where an excessive moi round; they formed, up under ■•» -
Kccording to their graxw-0
are heavy (  >2 ■=-*-). 
orpbic »crie * _ dosed dep-
to deep 
the yes*
l0  doser.’0 MdromorphiBa‘
of TeC
gft 30
ils
caeipc0i'io10
1
with
h
Their humus horizon dep -
* ® humus content up to 6£- But
r «aa BB downward the profile end e. i  ei
3     reaay about 1%. 
enrages
humus con»°--
depth * '
35
oon "
the depth of 30-50 cm tuex - _ p e3Bes W ^tive of the development of mono-
-, 1 coaplojnOotlg-^-
appeal c
or iz<sn i*“
the 0oi1’ <7en>iy
burni0  c0O?eC
- e'.zlc weekly saline solonchek
*   * 
re
8£• ■ Soccupy^ 570•° or ae* aro confined to tho 
noer-bod part of the Alwero rdver floodplain and to n °7d0op la^o-like depressions. They are distributed along the
v0 °'
Q
o
 pivor r.o o. narrow bolt, The Groundwater table la 3-8  . Shese soils formed up on Incustrlne-allwittl deposito. 52idr texture is heavy ("• g ^4), hut thoir Insaus hori-
io 11(5^ nediun loan, its thickness being 19 aa
(1 >...26). ho compact horizon occurs at the average depth of jg cn( 22...51 cni )•
Thn A  horizon caateins 4.91 ' of hraus, In the B  horizon 
1
1
Its ccaitant is 1.9B5, with u.745 in the Bg horizon.
The absorption capacity inoreases with depth fraa 8.3 ng-
eqxiv. in the A^ horizon up to 2t.O ng-oqulv. par 100 g of soil
in tho C horizon, ihe absorbed calcium content ie 51.C-64.Opr, 
that of nugnosium is 3O.4-3G.75, end the sodiun content io 
3*3-11.45 of the cation sum. Cha .toils have boon attributed to 
really solonetzic.
-ho water extract axuAysic indicates a wonk salinization In 
lower part oi* profile iron the depth of eo-100 era. The sura
o* aoits makes up 0.-97-0.1575 wish codi-.-sulphntio end sulpha-
tic-sodic ohenistry.
veyu<iIieaVy     Eisal3-ow    humic    lithosols    ore    distributed    In    the    sur- ^opeB^f 00"*             -Oc-upy 275.3 ha or 0,05 and occur on gentle
08  <0.-1-O.O2) of the high Hlub?.bor plain.
°°rphi   1X1X2    k7ea^4’   devolopoa.   noils   which   forced   up   under   outo-
•t®ata .^°U5^’^'i‘ons Qa form.lld t-tq pens, with thoir fine-earth
9 <sj thiei^"*1938 °air<; lean than 25 cm, The hruuo horizon is
•10), the fermlHtio pan or ferruginous con anted 01  2i                    Eruvol uxid pebble derodte occur froa the depth
1,3/7 <2l)         a** °
CC1  QU
-   ^ axeoedn 45 and the texture is heavy -
^^obqc
,; o tixelr physioel end chc-dcd properties tho
0  ®ccu-. DQ ua®d for irrigation. However, as ferrallitio th ^^saa ' v0 tho aurfaw the sgrl«!ltw«l iraplaaants nay 
Uo  t^ ^  cultivrtion of these soils. That Is why 
o
13
Q^OQole * -.q?  irri€Jiiioii <*•'<&* to te limited. Snail spots of
ClX^turcii '7J ^ii3 -wriest! an eren will net interfere with tho J  -lop^ont of tho ej?oa«»
I
»—
123
Soil—'Reclamation Zoning*
distinguishing soil-reclamation groups within the purveyed area the following main factors were taken into
peculiarities of soil cover structure, composition
^^^erties of soils and soil-forming rocks, geomorphological
^hydrogeological conditions, general reclamation evaluation
^nodern conditions in the area and degree of its possible
tt^formation due to irrigation, compoeition of main reclamation jeasiirea reguired during the periods of construction and
operation.
Total five main soil-reclamation groups have been distingui
shed.
Soil-reclamation group I is divided in three subgroups,
6
i.e. I , 1^ and 1°.
Subgroup I*. It occupies 617.5 ha of 2.0% of the area and includes only one type of soils, i.e. heavy feral alii tic red-
brcwa savanna soils formed up on rad-brown highly ferruginous loans and clays, r________    They oc __________           cur on the upper part of gentle slopes
i the elevated Illubabor plain.
i*e. 0.01-0.02
> Predominant: slopes are minor,
^undwater <
* and there 1b no danger of erosion processes.
** affect
°ocnrs at the depth of 20-30 metres of more and does
mt *orphic.
acoil~forming processes. Soil-forming conditions are
. aetUb*own r ” soils are the beat in the entire area according
Natural drainage conditions of the area are medium,
the
^Pertiee.
Their h
umus content is high, i.e. 4.46-8.45%.
Ctlo» -
capacity i8 not
making up 11.2-17.1 ag-e^niv.
4.UJI CSn A
••Uld    - J The abso ooil   r                   —VUU^XV
rbing complex is predominated by
A -L<=> /**'**“■■
Bi.ua * 
? »2)| the contents
a
 of magnesium, sodium and
to 15.4-51.7, i.a-3.5. 5.1-5.?% of the sum of
•M J5*'.on’    r - ’
;
Of
• —        , hi8hly proviFd4.Ued¥l w(ieui WX th mL4 BobUUJUile.U p yuotuoooxu   assiia xum (16.0-18.0)
^7
—They 
*’'** aoniwxeit phn mosobphilore puhs osphorus (0.47-1.25 8 Per 1008
g per iwg
^^aiine C°ntaia ^ch free iron (5.26-3.37%). The soils
8
non“ °lonetzic and have a good water-stable
r
S/cm5
-5 in th 8 hiSh* i’e* 1*55 8/°®^ in the 0-25 cm layer e  0-100 cm layer. The total porosity 1bI
I
I
i
L*
Ie
.  _ 19,0 and 14*6% in the 0-25 and 0-100ca layers, ^ficiect’ X* Their wilting moisture (Wtl) and field capacity
r«ePectiVGly" respectively 6.1; 21.? and 14.4; 24.9% by volume
(fO) 03X6 0-100 cm layerB. Moisture re serve a correspond-
toe O
FC-WM (moisture available for plants) make
lag W ^5* 39° ® 5/ha in the 0-25 C“ l8yer ’nd
2 »442
« 
“ 4 1’ perIloability is high, l.«. 1.44-2.88B/day from th.
®at the Qnd. of the firstfhour, the steedy-state permeabi- il 1.01 - 2.30 w/day» and the steady-state permeability
’/h* 1X1 the 0"',0° “ lay<>r*
th. depth i=
ae  PW*Mhlllty lb
Mrowa   is   5-3   1/10°   linear   metres   per   second   during   the   first irrigation and 2.5 1/100 linear metres per second during the
a
second irrigation^
«
DeBign irrigation rates amount to 406 and B55 * A  in the
0-50 and 0-100 cm layers, respectively.
Red-brown fersiallitlc savanna soila may be used for the cultivation of any standard, crops with/out preliminary reelam-
htlon measures. When executing levelling works it is necessary to arrange for the obligatory preservation of . hnnua horizon
scans Of its preliminary clamping. The depth of stripping aiouid not exceed 5-10 cm. It is recoamonded that agrotechnical
•®asureB aimed at the conservation and increase of soil fertility Elemented alongside with the application of organic (green
aajttuxe) and mineral fertilizers.
f<i ^eae soils are rather peculiar because the cleaning of cj* ** the Plowing of new areas bring about an intensified
Ol aoi^ surface to the tropical sun. Poe to so
hcabpe iron oxides may cement and. form up an imper~
a^CrUBt On the surface. Main protection measures in these
Qt
Eventing overdrying (such as ®iching, planting eaa?1^g crops under the trees).
'**>7^®-^ It occupies 1,050.0 ta « 3-5» 
* Pe<i fersi*llitic rad-brown savwna Boils on
S “1“,e*
^leai h Pa3lS
of * 
as light and heavy weakly developed eutj’°Phlc (transitional to red-brown) soils on
They are confined to the upper and middle ° *  of the elevated plain. Th® fine-earth part of
P8i
■i
*
•/
>
j
*»
r
-z
»
I
I !
I
r
n
«»
v'
i »•
t
L
*
<
•i
«
r
*
»■
<
ito their numuB
their humus content (1.21-1.9?% in the A
x
rtXTutsht wld °“d-tertare4 br°'m aoila belone "ainlT t0
““ Cateorptlon capacity ia 1« acd equal.
’ll'horl tone ot sand aoilas Ion light soils this value is
, „ 9 0 and 4.7 - 17.6. The absorbing complex is saturate
«LL’*ith calcium and magnesium, their contents amounting Actively to 59.0 - 52.0 and 26.0 - 44.0% in the A horizon
u  sand soils and to 42.0 - 56.0 and 55.0 - 48.0% in light
soils. The share of absorbed sodium is sufficiently high, especially in sand varieties, making up 4.1-8.6 and up to
12.5%. However, such soils are non-solonetzic
Their free iron content is not high in the upper part of profile, i.e. 0.11 - 0.17%, but it sharply increases in
lover part up to 0.82 — 2.9%. The soils are not saline
17a).
The soil density is high, i.e. 1.62 and 1.64 g/cm5
0-25 and 0-100 cm layers of sand aoila ; for light soils respective valves are 1.59 and 1.60 g/cm^j their total porosity 1b unsatisfactory, i.e. in sand soils it equals 59.0% in the
0-25 cm layer and 57.9% in the 0-100 cm layer; for light soils these values are 40,0 and 41.2%, respectively. The aeration porosity is sufficient making up 20.8% in the 0-25 cm layer and 17.7% in the 0-100 cm layer of sand soils, in light soils these values are 15.4 and 15-9%, respectively.
the
(up to
in the
the
Their wilting moisture and field. 5.6 and 19.5 for 0-25 cm,4.0 and 19.^ cm in sand soils; 5.0 and 24.5 volume
light soils.
Moisture reserves correspond-i ng 90 488 598                < 2 COrre8pondi*e to
capacity  are as follows: volume percent for 0-100
percent for 0-25 cm in
*     *53® m /ha in the 0—25 cm lajrer* 40*1 qio 4 X
and PC — WM are
u the <M00 cn Lyec Iw
W
0-25 cm layer and 1*405* 2 5GP- a 4cn _3 /?                  > 91 /ha in the
5   2>562’ 1’1* 
leyec t0^i8ht ,X ’
it
- the ^00 c
“ the “d ot tha £i*“
V100
sand.I
I* — - — — -
hunus horizon. The depth of stripping is 5 cm.
The design irrigation regine crust be strictly observed.
Otherwise, the soils may be locally oveimoistened in some
places where local confining beds consisting of strongly cemented
f<ruginous heavy loams and days occur close to the surface.
In view of a low humusness of these soils and an intensive
loss of humus after plowing, as pointed out by Senegalese scientists, it is reccsnended that organic (green manure) and
mineral fertilizers be applied.
b
Subgroup II  occupies 2,585*1 ba or 8.2% of the area and includes light and heavy nd>-calcareous and calcareous tropical brown entropbic soils. Sclonetzic soils occur as separate spots.
Their soil-forming rocks are proluvial highly ferruginous deposits partially with carbonate concretions. They occur in the southern and western parte of the flat low plain with 0.001- 0.005 slopes.V.teds occurring close to the surface significantly regime of soils in the western part of the
tb9  *dnr these conditions the upper stratus (O.S-I.Om)
° ar«ft’ °             ~ ,-nf 5 ni ng bea is rapidly saturated with water ^17^ tb,liny season, tenpor^y perched water fans up and the
jjring tb
°^
e   fflOi£tened and partially flooded. During the irri-
joil 10 OV^ Decessary to strictly control ths design irrigation 11  order to prevent soils fron ovormoBtenimg.
reG*6 ^
j   ptoup XIX i» divided in three subgroupo.
laBat on
The soils of this group occupy sore than half of the survey- area (57-9^) • They need more serious realisation measures
tor their agricultural development.
Subcrcnr HI  occupies 1,956.0 ha or 6.2% of the area and
n
includes heavy weakly and medium solonetaic non-cal careens
tropic el brown eutrophic soils in complex with light and sand
soils.
These soil 8 occur in the central end northwestern parts of
ths flat low plain with numerous closed patellold depressions,
slopes are less than 0.001.
Groundwater table is at the depth of 15-30 maters. Katural
drainage conditions of the area are rather poor. The upper local
compact impenneablo horizon occurs close to the surface (0.5-
th.    *    *nd     in     tiie      central    pa*t    the    regional    confining    bed    la    at
“• -Ptb ot ,  _ 
5
aOM plaMte
80S 1 n
“trvctui-
576 low “ediuM
with a low water-stable
tt< * 3°~10o Phe CQa®act horizon la widely distributed and. occurs
Th©
®®ila 
fron the surface averages 0.3-0.6 m/daye
^eorlwjd    °    Unf«vourable    chemiaal    and    physical    properties, aodiuai content is 3-5, 5-10% of the sun of absorbed
Physical properties of light-textured
ar6  eivX^0^1^ by th® **** obtained at dBAPPS - 4
a  hQav* vari^111 details for subgroup U*, and the property
^i.
" 1. 
ifes axe characterised by the data obtained at
van
eties have a high density, i.e. I.eZg/cm5J
II1&;
•Layer and 1.64 g/ca^ in the 0-100cu layer; at
2
5
0* °" ^Lg ere 1-58 and 1.60 g/ca , respectively. Their tte0e VS IB unsatisfactory and makes up 38 % f»r 0-25ca
P oro9i Q.'iooca. Their aeration porosity Lb low and
isA
56  4
’ ^ °L>d 7.7%» respectively. When moistened, these soil
f
rf'1’ their density decreases.
arell wiltinK moisture and field capacity are 9.5 and 29.6%
Ibelr iI1 the 0-25 layer, 19.2 and 30.4% by volume in the
ty volu®eiayer< Moisture reserves corresponding to WM, FC and ^^“are respectively 237. 740, 505 a^/ha for the 0-25 «
7C- and 1,918; 3,046; 1,130 m^/ha in the 0-100 ca layer.
1<,8r tteir permeability is high and sakes up 1.75-6.48 a/day
troa the surface at the end of the first hour, with the steady, state permeability being 0.62-1.15 n/day. That from the depth la 0.34-0.46 m/day, with the steady-state permeability being 0,05-0.08 m/day. In furrows it amounts to 1.2 - 1.4 j/100 linear
■etwes per second.
OeBign irrigation rates are 441 and 914 a^/ha far the 0-50 ind 0-100 cm layers, respectively.
The agricultural development of this subgroup needs some reclamation measures. Th«B, sol one t tic soils, especially heavy- t6xture<i ones, need gypsuming during the period of contraction
deep * 
1    Pate
 °  2.0-4.0 t/ha in the 0-30 ca with an obligatory
f
^eos^ning in order to distract their compact horizon. °vhr to lrri?:ation regime ought to be strictly observed in
?Or thia I?rovon^ soils from overdrying and overmoietening.
Be
»erai at'^p °
r ^ h^
r
* ice. st8 °* 
P  9e is exD®dietrt to apply tho Irrigation rata in
group may be used for cultivating cotton
te     used     to*114       ®bova^Baid     measures     be     implemented     they ^han              PI>OVinE ®aisse» groundnut, legumes.
^?^Katorily land-leveliing the
horizon should be
4nd n^e3erVed> The application of organic (green
l Acl ^Woup
f ®rtiliaeM is compulsory.
c
he *vy Co ^^Piea 5.413.9 ha or 17.1% a* the area and
° IlpRct medium and strongly solonetzic deep
h °avy^ ^*Qaicly saline calcareous tropical brown eutrophic light non—calcareous and calcareous
> Pl-WBOI,.*I
z—koiogi *
01
conditicua are similar
l B»°®°rP 0Ubg^oup I11* except for the following: natural t      B0 °f f the area are drainless, the upper local impermeable
.. b°
*’       1 1 on iB close to the surface at the depth of O.>1.>.
b- VA
e o<P0ct llOriiB are low and medium humlo with an extremely un- B ° cO{rse lumpy fissured water-unstable structure, The
f0 oijrable izon coBBttoniy occurs from the depth of 1O-2Dea. Their
6 °*p8
t
°  i°ty from the surface is 0.2-0.6 m/day.
5>Br°eab golls arc mainly weakly salino deep aolouchak-like with ^Ic-^Hphatio-sodic chemistry, medium aolanetaic, with the
^^bed sodium content being >10% of the sun of absorbed bases.
*
bS  r
° Their aqueous and physical properties are simile* to those
of subgroup III • 
,
The soils of subgroup IU° . need a series of reclamation
Manures anr-i ng the periods of construction and operation includ ing their pr^i i nH nary gypsuming at the rate of 5-0-10t/ha in the
0-30 cm layer with a compulsory deep loosening.
The irrgation of heavy weakly saline deep solonchak-like
Boils may bring about a gradual rise of salts to the surface, thus causing the secondary salinization of the area. In order to avoid
the Secondary salinization weakly mineralized moisture flows ought to be prevented from riaing np during the inter- and post-irrigation Periods, for thia purpose it ia necessary to maintain an insigni-
Permanent downward moisture flow and keep the soil 0Vc-iry . constant level in order to prevent the soil from
ought to b^ °ther 8ide* weakly mineralized teapoxairy perched water perttan*ntly prevented from accumulating over the dose
“Puclfijj ti
*^  ^rigB^ "'
e
1
Thus, it is necessary to arrange for a COntT°1 fxxis^ion regime by means of using one -
to p*<>vid
e r ^ nS *itb higher (not exceding 10%) irrigation rates
Pev<5hed. wat
v
er ° r pr« entive washing. The resulting temporary
ah °uld. be discharged by means of permanently operat-
'h'al'5'1 teinbor aiX
,
cp .®. 
|
ditches to he supplemented with sballo^cloae-
bor iBontal drainage as well as with grid mole
Eationa in several steps may also be applied*ceS sary t0 ifflP]®ment ®  «hre6 alned
ea
a t preventing
It i0 n0° £looding and overmoistering with rain water,
nt *oiie ^Ttbe western part of the area.
eel®117 inaffures are similar to those In subgroup III*.
<lP  Otl»er XIIc occupies 10,935.8 ha or 3*.6% of the area
----- and light medium and strongly solonetsio
.like weakly saline calcareous chronic vertisols| iB ep fl0l0B^diUni solonetaic deep eolonchak - like partially
•** ^^line pellic vertisols.
^sjiy sa chcmiCBi and physical properties are similar to those
49
 m
a 5 — 0.1 
Tbeir c XIb^ Their permeability fraa the surface is low, sU  2T ,. The absorbed sodium content le 5.0 - 10.0 ,
* •
o - 15.0% Of the cation sum.
Geoiaorphological and hydrogeological conditions ere the laie  aa for subgroup H?.
Reclamation, measures are similar to those of subgroup III .
Soil — Reclamation Group IV
It occupies 2,517.7 ha or ?.# of the area and
heavy medium solonetxic deep eolonchak-llke non-
sallne calcareous pellic vertisols as well as heavy weax y
Mtlie deep solcnchak—like weakly saline alluvial floodplain Boils and. heavy calcareous chronic vertisols*
They occur in the low plain, in the near-bed and floodplain parts of the Alwero and Nyikani Rivers as well me in vaflt laKo“ Uk ° depneesions. Slopes are 0.001-0.005*
Their soil— fcnnlng rocks are proluvial, alluno-dcluvial ^^^i^alluvial deposits with mainly heavy gr.uralw»trie
Qcley content up to 60.8%).
4a Pth 6
It
lay6t
local compact impermeable horiton occurs at the 5-1*5*11. When irrigated and during the rainy season
iS acc'U3nuiatin€ temporary water over the compact
C °n8e'qh-ncbtins about overmoistoring and swamping of soil"* M *
^ainage conditions of the area are poor. Tbe floiis ^ainlees, strongly overnoistened with diet
3 -S^                     "orison 1, -10-22 „ thick. ». >«—
btl
? Ee A horizon, due to this reason those soI
■ ■ -■
‘'e
< rtl»id<’ ’
r ble P
‘
Their chlorldle and
*“• '* "•«* •*’!>. ft*
Jg
„ on* ourablo- Suite., -.hey .r, .lK
.    -h*7                        alju,
<^* „ione«*  “
c
ffdip 9
d their ^’orbed .odl* 
u
tbfl suia of abcorbod catioMe
"l       «<>       90ilB           “•       char£,ct',ri“d           by       KlMMl,       nftr^l.
—j
A              —• A A >1 A A -t —A
a  prop® !•■>• ,rhsir dewity 1. hljb, 1...
ies. Their density is high, i.e. 1^7
.___ J -4 OQ                      >1 s ____
it n** 
? ’7 “   ld    soisture
_     . .□_,------------ -------------------, _      .
Their total porosity is unsatisfactory aakljag up 51.15
and   1.28   g/cm   at   field   capacity   in   the   O-JS
(
-J
- layer*
_ .................................
’
th their
th aeeirr ae atironat pionol pity b o»*ai eintg 6.6%. I            y being 6.6%. I       n the onn teh-«ee ter layer
their respective density is 1.76 ard 1.44 g/«5fWltt tbeir
yorcsity being 57-5% and their aeration peroalty eating up
t ,9<. These data prove that these soils are cosqpact, stresgly (welling^ fissured and possess extresely unfavourable air pm- pertieQ"
The results of dry sieving obtained during their structural* lEgrepate analyses indicate an unsatisfactory structural state
of these soils, with the total amount of the 0.25-10 ■ fraction
•veraging 19.7-56.8% in the profile and the content of an un favourable lumpy—structured fraction sore than 10 m in slw ^oing 'k .4 - 77.8%. Howaver, the aggregates have a good water- rtebllity,
Values of WJ1 and FC are sufficiently high and sake up JI .7 it th^*2* b7 volume tn the O-25c« lsyer, W.J w-2% by voluae
a nrt °~1°0cm ^ y° * Moisture roservas corresponding to Ji,PC
nr
l«y,  and IlUal rospectlvely 794|1,156?361 a5/ba in the 0-25«
r
e
***ilabi  *05n    4   4
*  » 16 and 585 n^/ha in the 0-100 cm layer. The
to"01"1^0 res<,rve does not change below 30-50 cm and
’ 0rr«8pon<i,           /ha. It means that from thia depth their Moisture *°^*ture                 ^®ld capacity Moisture becomes equal to witting ‘•to.        011(1 tho reserve of Moisture available for plants equals
^ ti®ati
on
Wr
°  limit of optimum soil Moistening during the iater-
>?5<l *5/ha.Pe3?iOd iS 0,85 70 or 9®3^/h< in the 0-2$cm layer and U Th*                  th° On»-MGtre layer.
* 5/hLa ij?riKation rate for moistening the O-25ca layer
at
n ^5/ha for O.> and
for 1.<M.
* 
t < Qn *hd Baitr<leability ia high only at the beginning of irri»- h 0Ur a °H Up ^*9lM/day from the surface at the end of the
tho rir«t irrigation, the steady-state p.reeabi-
ly  low, O.OGm/dnyj during tho second irrigation*dj«ir permeability 0- 3 a/day at the and of the first hour, at b th® steedy-state permeability being 0.02a/dsy; from the de ptb these values equal 0.26 and 0.02, 0.06 and O^Hm/dsy,
4
respectively.
During the first furrow irrigation their permeability is
0.55 1/100 linear meters per second and during the second irrigation this value equals 0.28 1/100 linear asters per second.
The soils of this group need sone reclamation measures to
be implemented. Their main aim is to prevent inundation with
rain and flood water. They include diking, banking and dis
charge of surface water from the area.
They require preliminary gypsuming at the rate of 8.0-11.0
t/ha in the O-JOca layer.
For weekly saline irrigated soils it ia aoeeaaary to arrange
for a specific dual-control water regime similar to that for
soil group IH by means of applying soae irrigations with higher (not excoeding               irrigation rates during the vegetation period. The resulting weakly mineralised temporary perched water ought to be discharged by means of permanently operating dual-purpose ditches to be supplemented with shallow close-spaced harisoatal and mole drainage.
Special agro technical measures aimed at improving physical properties of cloy compact aoila ought to be implemented such am surface and deep loosening, moling, slitting.
It ia necessary to strictly observe irrigation regime, it
ia poaaible to Irrigate with fractional rates in order to
provent nolle from ovordrying and cracking.
kreservation of humus horizon is compulsory during land levelling. The depth of stripping is >10 cm*
Application of organic (green manure) and mineral fertili zers is compulsory.
aoll-reclzmation group ▼ occupies 775.9 ha or 2.4* of the area and includes two types of soils, i.e. heavy tropical
meadow-swamp soils and heavy lithosols.
Heavy medium deep humic deep gleyic weakly solonetslc tropical neadow-swanp soils are confined to deep ravines (slopes
O.Ol) and closed depressions where excess moistening is observed round the year. They farmed up under the conditions of recent hydromorphism. Groundwater table is >10a or lees.<
!
It '
i>4
•
I
-wl
.•;? .,wr
•>'■0; 6H.J **            X*rf£ S>*\ ?» -8-#* '
• jwX
-
^4> r », •
ITheir soil-forming rocks are clay-textured deluvial depo-
»lt8 of ravine bottoms.
Their huaras horizon i« 5G-2D co thick. The A horizon
c0Otains up to 6% of hums, in the B horizon it* content is
2.4?% with less than 1% at the depth of AC-jOcm.
The absorbed sodium content io 2.>-4.1%, the chore of calcium   equals   48.G-   60.9%   and   that   of   magnesium   is  J4.2   -4?.0% of the sum of absorbed cations■
The gleyic horiion occurs from JO - JO cm• Under the
conditions of excess aolstening it becomes practically imperme
able and there forms up a horizon of temporary perched water
over it. Such conditions bring? about the development of reduo-
tion processes, a vary weak gas exchange and intensified gley-
fonaing and water-logging processes.
The7 soils are unfit for curtivnting irrigated crops.
Lithosols occur on castle (0.01-0.02) alopea of the high
plain. They formed up on ferrallitic pans and ferruginous
coaxes-carted gravel and pebble deposits. Groundwater table
exceeds JO meters.
They are fertile, contain novo than 8% of humus, possaaa good  aqueous  and  physical  properties  and  may  bo  used  for  irrig ation.    However,    they    have    shallow    fin^earth    strata,    i.e.    25cm (18.     25) .overlying the “her alii tic P*nj that is why tillage
implements   may   be   damaged.   The   use   of   lithosola   for   Irrigation should be limited*V .....
; '•
Q *•
;‘-
•
••) ’J .
i. . r • •
•
•
'
f
J0H       ••’. •
•
• ~ • r;
•
,. _
.’•
tj.6 Evaluation of Natural conditions
As a result of field engineering survey and studies of
natural conditions of projects under design the following
main conclusion can be made.
The    meteorological    station    in    Gambella    with    a    73-year series    of    rainfall    and    air-temperature    observations    was assumed   to   be   a   reference   station   for   evaluation   of   meteoro logical    elements    for    projects    under    design.    Observations    of relative    humidity    are    available    for    10    years.    This    ten-year series      of      observations      (temperature,      precipitation,      relative humidity)    is    taken    as    a    basis    for    designing    crop    irrigation regime.
Mean annual rainfall in the Gambella valley area amounts to 1,280 im (75% probability - 1,107 mm| 95% - 872 hb). The distribution of rainfall is uneven during the year. There is
a cl par distinction between rainy and dry seasons. In order
to arrange an efficient anr’ stable agricultural production
Ln the area of the Irrigation S.yatem under design it. is needed to implement deaquation measures during the rainy season and moistening measures during the dry season. Besides, the analysis of rainfall distribution during the rainy season
(see table 3.2.2) proves that almost every year there are rainless periods from 10 to 16 day which will affect the
yield of crops.
Calculations evaluating moisture supply of crops during the rainy season prove that the mean annual shortage of water balance equals 1.000 ... 1,200 m /ha and 1,500...2,000 m /ha for a 95% probability year.
3
3
Mean annual runoff of the Alwero River at the Reservoir site equals 166 mln.m  (85% probability - 119 mln.a ) and
3
5
620 mln.m  at the Regulating Reservoir site (85% probability
3
- 470 mln. m ), with the annual distribution of runoff being
3
extremely uneven. Annual runoff makes up 90% during the
rainy season and 10% during the dry season. To arrange for"fa? >HJ‘
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irrigation during  the dry  season the runoff ought to  be controlled,  i.e.  a  reservoir needs to  be constructed to accumulate water during  the rainy  season and use it for irrigation during the dry season.
Topographic conditions of the Irrigation System area
are favo’^ble for application of surface irrigation methods. Ground surface slopes are mainly from 0.0008 to 0.005 reach ing 0,01 in some places.
The site and bed of the Reservoir on the Alwero River
are mad, up |jy pre—Cambrian rocks of regional metamorphison which are represented by gneisses and crystal 1 ine schists.
The Dem Site area is complicated by a series of tectonic
fault dislocations with zones of mylonites and tectonic
breccias and characterized by a high degree of fissuring extinguishing with depth. Fissures are healed as a rule
except for the upper intensely weathered zone. Kaolin and more seldom cherty material serve as aggregate.
Hydrogeological conditions of the area are characterized by the presence of a water-bearing complex in the fissured zone of crystalline rocks. Weakly fissured, practically impermeable rocks occurring at the depth of 35... 50 a make up a confining bed.
Middle site i-i i  -th
se
favourable for the construct-
ion of ta according both to engln.erlng-geologlcl and hydro- geological condition, and it 1. „«„end^ „ the Mio site.
With th. run reservoir level being at the elevation of 513.5 m, permanent seepage losses from the Reservoir wm equal 1.2 mln, a  per annum, thus making up less than 1# of
its capacity.
5
Physical and mechanical properties of rocky formations making up the Dem Site area are characterized by high strength v. and deformation values.i
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©The site and bed of the Regulating Reservoir on the Alwero River are located within the boundaries of Gog
basalt development overlapped by Lnpermeable sedimentary strata of clays. Permeable alluvial deposits through
which seepage will penetrate from the Reservoir occupy
4...5% of its area.
Hydrogeological conditions of the area are characteriz ed by the presence of a water-bearing complex at depths upto 20 m whose water-accumulating rocks are fissured and porous basalts. At the stretch of the Regulating Reservoir bed the Alwero River recharges the aquifer during the entire annual cycle, but groundwater tables raise up towards watersheds and reach, the elevation of the full reservoir level that is
454.5 m. Permeability coefficient of basalts average 0,2
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m/day.
With water level being 454.5 m. permanent seepage losses at the foundation of dam amount to less than 1% per annum of the Reservoir capacity. Seepage losses due to the satjuration
of rocks making up Reservoir bank elopes emount to 2.3 iiP per annum during the first year of operation, i.e. to 2,7% of the Reservoir capacity. During next years the losses will
decrease and amount to 1.4 thou, m^/dary by the end of the Sth year of operation. Total losses for this period will equal 1.9 thou. m /dsy.
3
Physical and mechanical properties of soils ng up foundations of structures are characterized by high strength and deformation values both in natural and water—saturated states. Clays and heavy loams (layers 6, 6*. 5. 5 ) possess swelling properties. At insignificant loads up to 0.05 MPa their relative swelling is less than 1.5% and it will not be observed at ail at 0.1 MPa loads.
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Along the routes of irrigation canala the following
soils will occur* clays, heavy and light loams, loamy
sands, silty sands, gravel and pebble deposits with sand
clay aggregate.
Clays (layer 5) and heavy loams (layer 5) possess swelling properties. Clays belong to medium - swelling
end heavy loams to weekly swelling. Swelling pressure
for clays is 0.1...0.2 MPa and 0,04...0.05 MPa for heavy
loams. At permanent loads the value of relative swelling
of these soils considerably decreases. Permeability co efficient of clays and heavy loams is 0.001...0.1 to/day. Approximately 30% of the Irrigation System area will bo represented by clays and heavy loams from the surface.
Loamy sands (layer 3) possess subsidence properties and high soaking in water. Relative subsidence amounts to 3.0 - 5.8% at 0.025 MPa. Permeability coefficient equals 0.2-0,68 m/dsy. Approximately 5% of the Irrigation System area will be represented by loamy sands.
About 65% of the Irrigation System area will be represented by light loams, silty sands, gravel and
pebble deposits with sand-clay aggregate which possess satisfactory building properties both in natural and
water-saturated states. Permeability coefficient of
these soils is 0.2...1.1 m/day.
From geological and hydrogeological points of view
the area of the Irrigation System under design is a poorly drained plain with some 30% of the area made up by clays and heavy loams to the depth of 4,.,6 m and about 70% made up by more permeable soils, i.e. light loams, loamy sands and silty sands to the depth of o.5...3.0m. Groundwater table depth is 20...40 m. in the main part of the Irrigat
ion System. Irrigation is not expected to raise up ground water table. Reclamation will be based on the discharge
of surface water during the rainy season and excess irrigat ion water during the dry season as well as on a strict
observance of crop irrigation regime.r:-i
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According to the data of Pierre Gouin's paper "Seismic Zoning in Ethiopia" that was made by the Geophysical Obseva- tory on the request of the Ministry of Public Works and
Water Resources the seismicity of the area la classified as
a zone of minor damage corresponding to Intensity VI on the Mercalll Modified (W) intensity scale*
Boundaries of the Irrigation System under design include the following soil types: heavy fersiallitic red-brown savanna (1°) and tropical brown eutrophic (transitional to red-brown) soils (1 )j light sandy tropical brown eutrophic
c
(ll ) and light and heavy non-calcareous and calcareous
a
tropical brown eutrophic soils with separate spots of weakly
solonetzic soils (II®, 
heavy compact medium and strongly
solonetzic ca.lrc.rotuts tropical brown eutrophic soils (III**) and heavy  compact medium and strongly  solonetzic chronic vertisols in complex with light ones (IIIC).
Fersiallitic red-brown savanna soils and tropical brown eutrophic (transitional to red-brown) soils occupy 290 ha or 2.6% of the Irrigation System area. Their natural fertility, chemical and physical properties are favourable for agricultural development. Groundwater table depth is 30-40 m. These soils may be used to cultivate any standard crops without preliminary reclamation measures.
Light, loamy sand, sandy tropical brown eutrophic soils, light and heavy non-calcareous and calcareous tropical brown eutrophic soils with separate spots of weakly solonetzic soils occupy 7,358 ha or 65.4% of the Irrigation System area. Natural drainage conditions of the area are poor. Groundwater table is at the depth of 20-30 m. According to their humus content light and sandy soils are low-humic, medium and heavy soils are medium-humic. Chemical and physical properties of soils are good or satisfactory, they may be mainly used to cultivate any standard crops without preliminary reclamation measures. Should stripping and fulling exceed 5 cm it isi-recommended that lend-levelling be done with a preliminary removal of humus horizon and alts eventual replacing. Pre ventive gypsuming of soma areas nth weakly solonetzic soils is expedient at the rate of 1-2t/ha in the 0-JO era layer. Design irrigation regime ought to be strictly observed during the irrigation in order to prevent excessive moistening of soils.
Heavy compact med turn and strongly solonetzfc deep solonchak-like weakly saline calcareous tropical brown eutrophic soils as well as heavy and light non-calcareous and calcareous chromic vertisols occupy 3»6O5 ha or 32% of the Irrigation System area. Natural drainage conditions of the area are rather poor. Groundwater table is at the depth of 15-30 m. The soils are low-and mediws-htmic. Chemical and physical properties of soils are relatively unsatisfactory. During the agricultural development of
these soils the following reclamation measures are recommended.
- preliminary gypsuming of soils at the rate of 5-IOt/ha for a 0-30 cm layer with obligatory deep Ion sewing;
-   irrigation of crops with higher 00%) irrigation rates in order to provide for descending water flows and prevent secondary salinization;
-  construction of permanent duel-purpose ditches in complex with temporary drainage;

Summery

Baro-Akobo Project Summary

Baro-Akobo (Gambella) Project Summary

Project Overview

The Baro-Akobo Basin Study Project involves the construction of a dam on the Alvero River and the development of 10,000 hectares of irrigable lands in the Baro-Akobo Valley in Socialist Ethiopia. The project was initiated based on recommendations from Soviet specialists who visited Ethiopia in 1980.

Key Objectives:

Increase production of food and industrial crops in the Gambella valley
Provide self-sufficiency in food for local population and resettlers
Increase employment opportunities in agricultural production
Create modern settlements to improve living conditions for 8,000 inhabitants

Project Components

1. Reservoir on the Alvero River

Located 22 km upstream of Abobo settlement, selected for favorable topographic and engineering-geological conditions.

2. Regulating Reservoir

Located 8 km downstream of Abobo settlement to raise water levels for gravity supply into the main canal.

3. Irrigation System

Located in the interfluve of the Alvero and Nyikani Rivers within elevations of 425-450 m, covering about 400 km².

Technical and Economic Indices

Parameter	Unit	Total	1st Stage
Total area	Ha	11,379	1,171
Irrigated area (gross)	Ha	11,146	1,138
Irrigated area (net)	Ha	10,025	1,020
Number of state farms	Farm	3	1
Total water consumption (gross)	Mln.m³/year	150.60	10.70

Natural Conditions

Climate

The Gambella valley has a tropical monsoon climate with two distinct seasons:

Rainy season: May to October (85% of annual rainfall)
Dry season: November to April

Mean annual rainfall: 1,289 mm (ranging from 777 mm to 1,964 mm)

Hydrology

Key hydrological characteristics of the Alvero River:

Annual runoff rate at Abobo settlement: 626 mln.m³/year
Annual runoff rate at Dam site: 168 mln.m³/year
Maximum daily rainfall recorded: 181 mm (June 21, 1975)

Engineering-Geological Conditions

Reservoir Area

The reservoir area is composed of Precambrian rocks (gneisses and crystalline schists) with:

Highly fissured zones (up to 40m deep)
Estimated seepage losses: 1.2 mln.m³/year (0.75% of capacity)
Total prospected reserves for dam construction materials: 600,000 m³

Project Implementation

The project was developed in multiple books covering technical, agricultural, and construction aspects:

Explanatory Notes (Sections 1-21)
Natural Conditions Cartographic Materials
Water Management Construction Drawings
Agricultural Construction Drawings
Estimate Documents

Note: This document represents a preliminary project report from 1986, prepared for the Provisional Military Government of Socialist Ethiopia by the Water Resources Development Authority.