Project Office Copy Do Not Remove
RVLB Project Document
No. 7
Bl l. ATE RIVER BASIN STUDY
irrigation development
WRDA/FAOBILATL RIVER BASIN STUDY
IRRIGATION DEVELOPMENT
VJRDA/FAO
MAY 1986BILATE RIVER BASIN STUDY
IRRIGATION DEVELOPMENT
CONTENTS
PAGE
1.  INTRODUCTION-----------------------------------------------------  1
2.  METEOROLOGY-------------------------------------------------------  2
2.1  Rainfall---------------------------------------------------  4
2.2  Temperature------------------------------------------------  4
3.  HYDROLOGY--------------------------------------------------------  4
3.1  Sub-basin 1: Alaba Koi it o-------------------------------- 5
3.2  Sub-basin 2: Bilate Tena (Dimtu)--------------------------  6
3.3  Sub-basin 3: Lower Bilate---------------------------------  7
4.   EXISTING DEVELOPMENT---------------------------------------------- 8
4.1   Lower Bilate-----------------------------------------------  8
4.2   Water Demina------------------------------------------------ 8
5.  POTENTIAL DEVELOPMENT-------------------------------------------- 10
5.1  Middle Bilate---------------------------------------------- 10
5.2   Lower Bilate----------------------------------------------- 10
5.3  Water Denand----------------------------------------------- 10
6.   RIVER STORAGE----------------------------------------------------  14
6.1  Development Options----------------------------------------  15
6.2   Boyo Dam---------------------------------------------------  18
6.3   Ropi Dam---------------------------------------------------  18
6.4   Dendo Dam--------------------------------------------------  19
7.  IRRIGATION DEVELOPMENT - MIDDLE BILATE-
-  19
7.1  Alaba Kolito Plains----------------------------------------  19
7.2  Headworks--------------------------------------------------  20
7.3   Distribution System----------------------------------------  21-ii-
PAGE
8.   IRRIGATION DEVELOPMENT - LOWER BI LATE REHABILITATION'-----------  22
8.1   Bilate State Farm - Unit 1---------------------------------  22
8.2   NTMC Tobacco Plantation------------------------------------  23
8.3   Bilate State Farm - Units 2 & 3----------------------------  24
8.4  Abaya State Farm-------------------------------------------  25
9.   IRRIGATION DEVELOPMENT - LOWER BILATE EXPANSION-------------------- 25
9.1   Bilate State Farm/ToDacco Plantation------------------------  25
9.2  Abaya State Farm-------------------------------------------  27
10.  DEVELOPMENT COSTS------------------------------------------------  27
APPENDICES
I.   CAPITAL COSTS II.   ANNUAL COSTS-iii-
LIST OF TABLES
2.1   Climates Station in Bilate Area--------------------------------  3
3.1   Bilate River at Alaba Kolito: Extreme flow Data----------------  6
3.2   Bilate River at Bilate Tena (Dimtu): Extreme Flow Data---------  7
4.1   Bilate River at Bilate Tena (Dimtu): Irrigation Demand
Compared with Minimum Monthly Runoff-------------------------  9
5.1   Bilate River at Alaba Kolito: Irrigation Demand
Compared with Minimum Monthly Runoff-------------------------  12
5.2   Bilate River at Alaba Kolito: Irrigation Demand
Compared with 80% Probability Average Flow-------------------  12
5.3   Bilate River: Lower Bilate Irrigation Demand
Compared with Inflow Between Alaba Kolito and Bilate
Tena (Dimtu)-------------------------------------------------  13
10.1  Biased Construction Costs - Option A--------------------------- 35
10.2  Phased Construction Costs - Option B--------------------------- 36
10.3  Phased Annual Costs - Option A---------------------------------  37
10.4  Phased Annual Costs - Option B---------------------------------  38
LIST OF FIGURES
10.1 Development Progranuie - Option A------------------------------  31
10.2  Development Programme - Option  B------------------------------  32
10.3  Phased Agriculture Development  - Option A---------------------  33
10.4  Phased Agriculture Development  - Option B---------------------  34BILATE RIVER BASIN S1UDY
IRRIGATION DEVELOPMENT
1. INTRODUCTION
The Bilate River Basin is one of the major catchment areas of the Ethiopian Rift Valley Lakes Zone. It lies between latitude 6°35' and 8°05’ North and longitudes 37°45* and 38°20’ East, partly in the province of Shewa and partly in the province of Sidamo. It covers an area of 5,650 km2 and the altitude ranges between 3,280m in the north and l,180m.a.s.l. in the south.
The Basin is broadly divided into three sun-basins - Upper, Middle and Lower Bilate.
Upper Bilate comprises the headwaters of the river basin dominated by the two miin tributaries, the Guder and Weira Rivers which flow through the Boyo Swamp and emerge as the Bilate River at an altitude of l,880m.a.s.l. Apart from the Boyo Swamp the terrain is largely mountainous with steep gradients.
Middle Bilate comprises the section of the Bilate River Basin between the outlet of rhe Boyo Swamp at an altitude of 1,880m.a.s.l. and Dimtu 70 km downstream at an altitude of approximately 1,480m.a.s.l.
A considerable proportion of this sub-basin area supports rainfed agriculture, in particular the area of the Alaba Kolito Plains north and south of the town of Alaba Kolito to the east of the silate River. This area is intensively settled with a well established pattern of agriculture. However due to the undulating topography and the marginal soil suitability, there are major constraints to large scale development of irrigated agriculture in this area.-2-
Lower Bilate sub-basin stretches between Dimtu at an altitude of l,480m.a.s.l. and the shores of Lake Abaya at an altitude of l,180m.a.s.l. approximately 120km downstream from Boyo Swamp outlet. The area is largely alluvial and a deltaic plain, sparsely inhabited and largely undeveloped, apart from the commercial estates established 15 to 20 years ago, now operated as State Farms. The topography and soil conditions offer a potential for the extension of irrigated agriculture in particular in the southern area surrounding the existing Abaya State Farm. In addition the flood plain of the Derba River, a rajor tributary of Bilate could offer a development potential although at present it is covered by thick undergrowth and thorn bush and is somewhat inaccessible.
2.  METEOROLOGY
The existing meteorological data for the Bilate River Basin is very variable and records extend for no more than 10 years. There are a number of clirate stations located both within the Bilate River Basin or in inmediately adjacent catchment areas. The majority of these are either Class 4 - standard raingauge only or Class 3 - maximum and minimum thermometer, and standard raingauge, (see Table 2.1)
In the past five years, Class 1 climate stations have been established at Alaba Kolito and Bilate State Farm but suffer from lack of maintenance. The Alaba Kolito station was vandalized in 1984 and is now only rated Class 4.-3-
TABLE 2.1:             CLIMATE STATIONS IN BILATE AREA
Equipment
Thermometer
Station
Region
Class
Rain gauge
Recording raingauge
Max. &
Min.
Wet &
Dry
Evap.
pan
Sunshine
Recorder
Anemo meter
ata j ira—
lltei7
jlbar>egi/
Dsaina
1/
Laba Kolito^7
. 1/
)e-
bone
1/
lamena—
, .1/
LK1—
-late Tena
(Dimtu)
rba Dimbicho^
•layita Soddo
late State
Farm
Shewa
fi
it
it
it
if
n
Sidamo
4
4
u
3
4(1)
3
4
4
4
4
4
1
1
x
X
X
X
X
X
X
X
X
X
X
X
X
■
(X)
x
(X)
X
(X)
(X)
(X)
(X)
it
it
«•
tt
it
X
X
X
X
X
X
X
X
X
X 1
X
X
1/
2/
Outside the Bilate River Basin
The Class 1 climate station at Alaba Kolito was established in 1980 but was vandalized in 1984 and most of the equipment was stolen. By July 1985 this equipment had not yet been replaced, thus reducing the status of this station to Class 4.-u-
2.1     Rainfall
The mean annual rainfall within the basin varies from over 
1,500mm at Shone to less tlian 600nrn in the vicinity of Lake Abaya. The available rainfall records are relatively short with some stations only 
having 7 years of records. The rainfall pattern southwards along the 
Bilate River Valley appears to indicate a mean annual rainfall of approximately 1,000mm occurring as far south at Bilate Tena (Dimtu) with a gradual decrease from Bilate Tena to approximately 600nm at the delta leading to Lake Abaya.
2.2     Temperature
The temperature pattern is directly affected by the rainfall pattern and duration, which in turn relates to the cloud cover and humidity.
The maximum monthly temperature in the Middle Bilate (Alaba Kolito) varies between 30°C (March) and 2U°C (July/August) and in the Lower Bilate (Bilate SF) between 34 C (March) and 28°C (July).
O
The minimum monthly temperature in the Middle Bilate (Alaba Kolito) varies between 13°C (April to August) and 10°C (November/December) and in the Lower Bilate (Bilate SF) between 1U°C (March to September) and 12°C (December).
3.  HYDROLOGY
For analytical purposes the Bilate Basin has been divided into three sub-basins, determined by the location of the two gauging stations established on the Bilate River, at Alaba Kolito and Bilate Tena (Dimtu)
Sub-basin 1: This comprises the catchment area of the upper reaches of the Bilate River to the gauging station at Alaba Kolito.-5-
Sub-basin 2:  The catchment area between the gauging station at Alaba Kolitoand the gauging station at Bilate Tena (Dimtu).
Sub-basin 3: The catchment area between Bilate Tena (Dimtu) and Lake Abaya.
2
3
3.1     Sub-basin 1: Al ana oolite
Hydrological observations on the Bilate River conrnenced in 1971 with the construction of an automatic level recorder at Alaba Kolito. This basin has a catchment area of 1,980km  with a mean annual run off at Alaba Kolito of approximately 346 x 10^m  . The mean annual runoff from the Alaba Kolito sub-basin is thus approximately 175mn and the mean annual flow modulus coefficient is 5.5 1/s/km2.
Since the record is relatively short, long term assessments are difficult to make. However the available data indicates that there is a wide range in the monthly flows with variations of over 300 percent during the low flow periods (November to June) reducing to variations of 100 percent in the high flow period from July to October.
The maximum and minimum flow data indicate a similar wide variation of flows. The minimum flows in the river fall below 2m3/s for some period of time during 6 months of the year (December to May) although the average monthly flow in the Bilate River at Alaba Kolito is above 2m /s for 8 months of the year (April to November).
However for irrigation use the risk related to a given level of water supply should also be considered. As can be seen from Table 3.1 the 80% probability level [i.e. the probability that 80% of the time the level 
of flow would be equalled or exceeded (4 years out of 5)] the availability of water in the Bilate River as measured at Alaba Kolito is extremely limited for irrigation dependent on run-of-river flows.
3-6-
TABLE 3.1; BILATE RIVER AT ALABA KOLITO: EXTREME I’LOVJ DATA
JAN.
FEB.
MAR.
APR.
MAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
. flow m3 * *
/s2.09
5.15
8.75
13.45
16.02
14.3
22.98
41.04
47.11
37.38
20.58
3.9
. flow m3 /s
0.31
0.44
0.42
1.52
1.98
3.02
7.44
17.94
29.54
10.0
3.64
0.6
'age flow
i3/s
0.73
1.12
1.97
4.71
6.33
6.40
14.24
28.94
37.11
27.30
8.02
1.8
probability
0.50
0.27
0.77
1.50
2.35
2.89
8.26
20.45
27.04
14.58
3.36
0.5
'age flow m3
 /s
3.2 
Sub-bas
in 2 - 
Bilate 
Tena (Di
mtu)
Initially, hydrological data at Bilate Tena (Dimtu) was based on a gauge post installed in 1971. In 1976 this station was upgraded to
include an automatic level recorder. Over the 7 year period for which data 6
are available, the mean annual runoff is estimated to be 610 x 10 m  .
The area of the catchment above Bilate Tena is 4,022km . The annual inflow to this sub-basin is therefore approximately 264 x 10 m  from a catchment area of 2,042km  with a mean annual runoff from the Bilate Tena sub-basin of approximately 129mn and a mean annual flow modulus coefficient of 4.1 1/s/km2.
3
2
63
2
The maximum and minimum flow data indicate similar wide variation of flows. The extreme flow data and the 80% probability risk level is given 
in Table 3.2. Again it is the low flows that affect the run-of-river development. The data indicate that for 6 months of the year (December to May) the minimum flow is less than 3m /s and drops below lm /s from December to March although the average monthly flow in the Bilate River at Bilate Tena falls below 3m /s for only two months of the year, December and January.
3
3
3-7-
TABLE 3.2: BILATE RIVER AT BILATE TENA (DIMIU): EXTREME FLOW DATA
JAN.  FEB.   MAR.  APR.   MAY    JUNE  JULY  AUG.   SEP.    OCT.   NOV.   DEC.
flow
s
3.92
11.*40
3*4.77
*40.65
37.89
50.93
75.73
81.72
106.68
85.1
30.59
6.51
flow
S
0.70
0.91
0.83
2.77
2.76
5.73
6.20
16.56
19.39
9.86
3.71
0.9*4
age m3/s
1.75
3.6*4
9.18
12.*47
15.68
18.33
20.*45
*43.27
56.6*4
36.05
12.96
2.50
ability*
ige j m3/s
0.93   0.86  2.5*4  3.78   8.18  5.*45 15.6*4 27.82  39.12  20.61  6.72  0.78
* Note: With only 6 years of data available, these figures are very conservative.
3.3     Sub-basin 3 - Lower Bilate
There are no further gauging stations along the Bilate River. 
With the reduction of mean annual rainfall in the lower region of the Bilate Basin to approximately 700mm, it would be anticipated that there would be 
a considerable reduction in the runoff. The mean annual flow modulus for this area has been estimated at 2 1/s/km2 for a catchment of 1,628km2.-8-
4.  EXISTING DEVELOPMENT
4.1     Lower Bilate
The existing irrigated agriculture in the Bilate River Basin is confined to the Lower Bilate sub-basin. The developed area comprises some 2,100 ha (gross) 10km south of Bilate Tena (Dimtu) incorporating Bilate State Fann Units 1,2 & 3 and the Tobacco Plantation, and some 1,400 ha (gross) a further 30 km south comprising Abaya State Farm.
The existing estates depend on the run-of-river flows for their water requirements. No reservoir storage facilities are provided on the river or within the individual estates. There are separate offtakes on the Bilate River for the individual estates with the following control structure:
Bilate S.F. Unit 1 Tobacco Plantation Bilate S.F. Unit 2/3 Abaya S.F.
gabion fixed weir gated regulator gabion fixed weir no regulation
4.2     Water Demand
The present water use for the existing development of 3,000 ha (net) assuming a 40 percent irrigation efficiency for conveyance from the 
river offtake to the field, is estimated to be 27.5 Mm-/a for the 8 month period March to October.
As can be seen from Table 4.1 the minimum monthly runoff at Bilate Tena (Dimtu) exceeds the irrigation demand throughout the period and thus with efficient water management no river storage is required to satisfy present demands. Similarly, from Table 4.2 it can be seen that the 80% probability average flow at Bilate Tena exceeds the irrigation demand based on 24 hour irrigation. Dependent on the individual estates, night storage might be required within the fam conveyance system.TABLE 4.1:   BI LATE RIVER AT BI LATE TENA (DIMTU)
IRRIGATION DEMAND COMPARED WITH MINIMUM MONTHLY RUNOFF
JAN.
FEB.
MAR.
APR.
LAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
Mean monthly runoff,
Mm3
Standard Deviation Min. monthly runoff,
Mm3
Irrigation Demand, Bilate SF + Abaya ST
(3,000 ha) Mm3
Excess/
Deficit
4.7
3.0 1.7 %
8.8
7.9
24.6
20.6
33.4
25.0
42.0
28.2
49.1
42.3
54.8
24.4
115.9
49.5
151.7 57.0
96.51
462
34.7
22.8
6.7
4.3
0.9
4.0
8.4
13.8
6.8
30.4
66.4
94.7
50.3
11.9
2.4
1.7
0.9
2.0 
»
2.0
2.7
5.7
3.1
10.7
6.7
0.1
3.6
26.8
5.9
60.5
2.1
92.6
1.4
48.9
11.9
2.4
TABLE 4.2: BILATE RIVER AT BI LATE THIA (DIMTU)
IRRIGATION DEMAND COMPARED WITH 80% PROBABILITY AVERAGE FLOW
JAN.
FEB.
MAR.
APR.
LAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
80% probability 
3
average flow m /s
Irrigation Demand, Bilale SF+Abaya SF 
(3,000 ha) m3/s 
Excess/
- c < -: +■
0.93
0.86
2.54
3.78
8.18
5.45
15.64
27.82
39.12
20.61
6.72
0.78
0.93
0.86
0.77
1.77
1.04
2.74
1.19
6.99
2.58
2.87
1.38
13.26
2.26 24.56
0.81
38.31
0.54
20.07
6.72
0.78-10-
The existing conveyance systems within both the State Farms 
and Tobacco Plantation are in a very poor state of repair with few if any control structures operating satisfactorily. As a consequence, no efficient water management is at present being practised resulting in apparent lack of water availability in the early months of the irrigation cycle and overvat ering during the months of high rainfall.
5.  POTENTIAL DEVELOPMENT
Resulting from the soil survey undertaken in the Middle Bilate and Lower Bilate sub-basins, a limited area of potential expansion for irrigated agriculture has been identified.
5.1 Middle Bilate
An extensive area of this sub-basin at present sustains rainfed agriculture. However, the combination of undulating topography and soils 
that are susceptable to structural degradation, limits the land suitability for irrigated agriculture in this region. The conrnandable area of the Alaba Kolito pl a-in.q to the east of the Bilate River extends for some 20,000 ha but only limited areas of land with suitable topography exist and these are scattered over a wide area in small blocks, each block probably not exceeding 50 to 100 ha. As a consequence, until a detailed topographic survey has been undertaken it has been estimated that the potential area for gravity irrigation is limited to 2,000 ha.
5.2     Lower Bilate
The reconnaissance soil survey indicates that there is an expansion potential in the vicinity of both the existing developed areas.-11-
The reconnaissance soil survey indicates that the soils in 
the vicinity of the Bilate SF/Tobacco Plantation have low infiltration rates which may restrict the area for gravity irrigation. Until more detailed soil tests are undertaken, the total area of development in this location is restricted to an area of 3,100 ha (gross), which would result in a limited expansion of some 1,000 ha (gross).
The area in the delta region of the Bilate River around the Abaya State Farm between the Geda Hills and Lake Abay a offers wider scope for development. The soils appear to be well structured with good infiltration rates and moisture storage capacity. However appropriate drainage methods will have to be applied and strict water management enforced to preclude the rise in the groundwater table and to prevent salinity problems occurring. Taking these precautions, it is estimated a total area of some 5,600 ha (gross) 
could be developed for irrigated agriculture in this region which would result in an expansion of some 4,200 ha (gross).
5.3     Water Demand
The water demand for the expanded development has been based on a single cropping pattern (cotton) as at present practised in the Lower Bilate areas. It assumes planting conmences on 1 March and continues through 31 May with a six month irrigation period.IRRIGATION DEMAND COMPARED WITH MINIMUM MONTHLY RUNOFF
JAN.
FEB.
MAR.
APR.
MAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
Mean monthly Run off,
I Im3
Standard Deviation Min. monthly Runoff,
Mm3
Irrigation Demand, Alaba Kolito plains, 
(2,000 ha)       Mm3
Excess/
Deficit
1.9
1.8
2.9
3.0
5.1
3.9
12.2
12.2
16.4
13.1
16.6
14.1
36.9
17.6
75.0
25.4
96.2
25.9
57.8
20.6
20.8
15.9
4.8
4.4
1.2
3.3
2.7
19.3
49.6
70.3
37.2
4.9
0.4
1.2
1.0
2.4
4.4
1.8
3.0
-
0.9
2.3
17.0
1.0
48.6
0.5
69.8
1.0
36.2
4.9
0.4
1.0
1.7
TABLE 5.2: BILATE RIVER AT ALABA KOLITO
IRRIGATION DEMAND COMPARED WITH 80% PROBABILITY AVERAGE FLOW
JAN.
teb.
MAR.
APR.
LAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
80% probability average flow m /s
Irrigation Demand, Alaba Kolito Plains, 
(2,000 ha)  m3 /s
Excess/
Deficit
3
0.50
0.27
0.77
1.50
2.35
2.89
8.26
20.45
27.04
14.58
3.36
0.54
0.50
0.27
0.48
0.29
0.37
1.13
0.94
1.39
1.70
1.19
0.89
7.37
0.38
20.07
0.19 26.85
0.38
14.20
3.36
0.54TABLE 5.3: BI LATE RIVER: LOWLR BILATE IRRIGATION DEMAND
COMPARED WITH INFLOW BETWEEN ALABA KOL1TO AID BILATE TH A (DIMTU)
JAN.
FEB.
MAR.
APR.
MAY
JUNE
JULY
AUG.
SEP.
OCT.
NOV.
DEC.
Min. monthly Runoff, at Bilate Tena, Mm3
Min. monthly Runoff, at Alaba Kolito,Mm3
1.7
.9
4.0
8.4
13.8
6.8
30.4
66.4
94.7
50.3
11.9
2.4
-
-
1.2
-
3.3
2.5
19.3
49.6
70.3
37.2
4.9
0.4
Min. monthly Inflow, Alaba Koiito to 
Bilate Tena , Mm3
Irrigation Demand, Lower Bilate: 7,900 ha
,Mm3
1.7
0.9
2.8
8.4
10.5
4.3
11.1
16.8
24.4
7.0
2.0
-
-
5.3    7.0    8.2   17.6
9.6
15.5
5.6
13.1
3.7
Excess/
Deficit
1.7
0.9
1.4
2.3
1.5
1.3
19.8
9.4
7.0
2.0
2.7
13.33
The annual irrigation requirement for the development of 
2,000 Jia in the Alaba Kolito plains is estimated to be 13.8Mm . Based on the Bilate River minimum monthly runoff at Alaba Kolito, Table 5.1 shows that reservoir storage will be required to supply the irrigation requirements in 
the months of March through June.
The annual irrigation requirements for the overall development of 8,700 ha (gross) in the Lower Bilate Basin (7,900 ha net) is 72.5Mm . 
Based on the Bilate River minimum monthly inflow between Alaba Kolito and Bilate Tena (Dimtu), Table 5.3 shows that reservoir storage will be required to supply the irrigation requirements in the months of '-larch through June.
3
6.  RIVER STORAGE
It is considered that there is adequate water in the Bilate River to supply existing irrigated agriculture development in the Lower Bilate without providing any further regulation assuming that rehabilitation of the existing irrigation system is undertaken and improved cultural practices 
are introduced together with strict water management.
For additional irrigation development, storage will have to be provided within the Bilate River Basin. On the basis of storage being provided for the first four months of the growing season, a storage of 10Mm3 will be required for the Lower Bilate development. Dependent on the 
location of the river storage reservoir, an additional allowance will have to be added for river losses between the point of release and the offtakes. It is estimated that there will be a river loss of approximately 10 1/s/km or 26,000 m /mth/km of river length.
3-15-
6.1 Development Options
Four alternative dam sites have been identified as follows:- Boyo Dam ! 
Ropi Dam ] Dendo Dam’ Derta Dam
on Bilate River
on Derba River
If development is to include supplemental irrigation to areas of the Alaba Koi it o plains, Boyo Dam will provide storage for irrigation in both the Middle Bilate and Lower Bilate Regions. If development of the Alaba Kolito plains is not deemed viable, then the storage requirements for the Lower Bilate Region would be provided by either Ropi Dam or Dendo Dam which would enable control of the Bilate River to be located nearer the areas of demand.
A dam on Derba River would only benefit the Abay a State Farm expansion and therefore for the present investigation this option has been excluded.
The storage requirements for the alternative development options would be as follows:
A. Middle & Lower Bilate
For the supply of the Alaba Kolito plains, Bilate SF/Tobacco Plantation and Abaya SF, a storage would be provided by _Boyo Dam:-16-
Boyo Dam
Distance to offtake
km
Alaba Kolito                                         20 Bilate SF/Tobacco
Plantation                                        65
Abaya SF
Allowance for dead storage
25 ’
River Loss (4 mchs)
Mm3 2.1 6.8 2.6
11.5
Irrigation Den an cl (4 ruths)
Mm3
8.3
13.3
24.6
46.2
Total Mn3
10.4
20.1
27.2
57.7
22.3 80.0
B. Lower Bilate only
For the supply of the Bilate SF/Tobacco Plantar ion and Abaya SF, a storage could by provided by either Ropi Dam or Dendo Dam.
Distance
River Loss
Irrigation Demand 
Ropi Dam
to offtake
(4 mths)
Fjii3
(4 mths)
Total Mm3
km
rim3
Bilate SF/Tobacco 
plantation 
45
4.7
13.3
Abaya SF
25
2.6
7.3
24.6 27.2
37.9 
Allowance for dead storage
18.0
47.2
12.8
60.0-17-
Dendo Dam
Bilate SF/Tobacco
Distance to offtake
km
River       loss (4 mths)
Mm3
Irrigation Demand (4 mths)
Mm3
Total
Mm3
Plantation 30 Abaya SF 25 Allowance for dead storage
3.2
2.6
13.3
24.6
16.5
,27.2
43.7 6.3
50.0
3
The Bilate River Basin has been the subject of a number of studies since 1974. The Bilate River Basin Development Study: Preliminary Report prepared by NWRC/EO in 1974 presented outline designs for two of the dam sites presently under cons ideration - Boyo Dam and Ropi Dam.
In both cases they considered a high dam which would have both irrigation and hydropower potential. Boyo Dam was designed for a storage capacity of 18^ Mm  and Ropi Dam for a storage of 176 Mm  . With the advent of major hydropower development in other regions of the country and the establishment of a national grid, the hydropower element has become obsolete and has been omitted from the present study with the storage requirements
being confined to irrigation demands.
3
3
In 1985, WRDA undertook a detailed survey of the Boyo Swamp and potential dam site appaa on the Bilate River just downstream of its outlet from
Boyo Swamp. A decision was made by NWRC to construct a 13m high dam with a storage capacity of 600 Mm  utilizing the Boyo Swamp as the storage reservoir, flooaing an area of some* 120 km2 .
As previously stated, the irrigation demands in the Middle & bower Bilate would require only a proportion of these quantities and consideration Therefore has been given to smaller dams to provide^ alternative storage capacities, as follows:-18-
Boyo Dam
Ropi Dam
Dendo Dam
80 Mm3
60 Mm3
50 Mm3
3
Boyo Dam
The location of Boyo dam is just downstream of the confluence of | the Weira and Guder Rivers which forms the outlet of the Boyo Swamp. A low
cam of 4m height above river bed level would provide the requisite storage
of_8£ Mm . An overflow masonry dam with bottom outlets for the irrigation supply at low flows would satisfy the storage requirements and preclude the necessity of a separate spillway. The area of Boyo Swamp that would be flooded would be restricted to 50 km2 . The cost of the dam and associated works
' is estimated to be Birr 1.25 million to which has to be added the compensation costs resulting from permanent flooding of 50 km  of the Boyo Swamp. These are estimated to be Birr 3 mi"i Tion for the resettlement of some 2,500 households and provision of alternative grazing for some 50,000 cattle.
2
I
3
By comparison, a 13m high earth fill dam with a separate side spillway which would provide a storage of 600 Mm  would cost Birr 2.3/million. However, by flooding an area of 120 km2 , some 5,500 households would have to be resettled and alternative grazing required for more than 100,000 cattle.
In this case the compensation costs are likely to exceed Birr 6.5^ million.
6.3 Ropi Dam
The location of Ropi Dam is on the Bilate River some 40 km downstream of Boyo Dam. It is sited in a high sided valley suitable for an 
e ^thfill or rockfill cam with a side spillway. Due to the relatively steep gradient of the river, a 45 metre high dam will be required to provide the
^Quisite storage of 60 Mm  but the flooded area of the reservoir will be only 
3
4,5
km  of river valley which is sparsely inhabited. The construction cost
2
ds estimated to be Birr 16.1 million but no compensation costs would be attributable to this development.-19-
6.4 Dendo Dam
Dendo  dam  would  be  located of  the  confluence  with  the  Che  rake  River, Dam site and 55 km downstream of Boyo Dam
on the Bilate River just downstream some 15 km downstream of the Ropi site.
3
2
A 20m high earth-fill dam with a side spillway would provide the required storage of 50Hn . The reservoir would flood an area of some
5km  of the Bilate/Cherake valleys which is largely marsh land providing cattle grazing and would incur resettlement of some 250 households. The construction cost is estimated to be Birr 13.8 million with an additional compensation cost of Birr 0.3 million for resettlement of displaced households.
7. IRRIGATION DEVELOPMENT - MIDDLE BILATE
7.1 Alaba Kolito Plains
The Alaba Kolito plains are located to the east of the Bilate River between latitude 7°20' and 7°05'. The area is bounded to the north 
and east of the town of Alaba Kolito by the ridge forming the Bilate River watershed. The land rises to the east from an elevation of approximately 
1,700m at the river to an elevation of 1,900m. The plains are dissected by numerous drainage channels leading to the Bilate River making the topography relatively undulating.
Extensive rainfed agriculture has been developed in this region uhich has an average rainfall of 936nm at Alaba Kolito (l,700m.a.s.l.) rising to 1,130m at Aje (l,900m.a.s.l.). Like all areas of rainfed agriculture,
this area is prone to variable rainfall both in intensity and in seasonal variation. The years 1983 and 1984 both experienced low annual rainfall and consequently low crop yields. As a result of this the possibility of
utilizing water of the Bilate River for supplementary irrigation was promoted.-20-
In November 198U, the WRDA put forward a proposal to divert water from the Dilate River by constructing a diversion weir 10km north of
Alaba Kolito with an offtake canal conveying irrigation water to the Alana Kolito plains along, the 1,800m contour.
The gross area that this canal would command between the 1,800 and 1,700 metre contours would be approximately 20,000 hectares extending over the southwestern sectors of the Alaba and Soraro Woredas. The area
of existing cropped land under conrnand is estimated to be approximately 13,000 hectares (65 percent) but owing to the gradient of the undulating land and the texture and weak structure of the soils, it is anticipated that the
total irrigable land under conmand would be restricted to a total area of
seme 2,000 hectares (10 percent) in variable sized plots not exceeding 50 
to 100 hectares scattered widely over the extent of the area.
7.2 Headworks
Assuming a storage dam is constructed at the outlet of the
Boyo Swamp, the flow in the Dilate River will be controlled during the low flow periods of the year. To supply the Alaba Kolito plains, the irrigation supply will’have to be diverted from the Dilate River downstream of the
B°yo Dam. For water to be abstracted from the river, two alternatives have
Been considered:
Bedene Diversion Weir
A diversion weir to be located at Bedene lUkm downstream of the ooyo        site with a side offtake to supply a canal following the 1,800m
contour
• me rirst 10km of the feeder canal leading to the irrigable area
’
^°Uld h
e to traverse very rough terrain requiring a number of major cross
Bined StructureP- *t is wst likely that this section would have to be
’ Wj-th either syphons or concrete flumes provided to traverse the major channels.-21-
B) Alaba Kolito Pumping Station
A pump station to be located at Wokdela 21km downstream of the Boyo Dam site abstracting direct from the river and raising the water a
height of 40m through a 2km pipeline to discharge into the feeder canal on 
the 1,800m contour at the head of the irrigable area.
The comparative costs between the two alternatives supplying the main canal at the head of the irrigable area are as follows:
A) Bedene Diversion
Earthfill Embankment Offtake Structure Feeder canal (lOkm-lined) Cross drainage structures
Alaba Kolito P.S.
Pump station
Pump /motors (4 Nr. 0.5m /s) Pipeline (2km; 2Nr. 600jnn dia.) Electricity power line (5 km)
3
ETB x 103 2,000
50 1,800
150 4,000
ETB x 103
200
200 2,000
100 2,500
The apparpnT favorahie capital cost of the Alaba Kolito pumped Cari only be assessed after taking into consideration the annual
3tion and maintenance costs together with the depreciation costs in the derail economic analysis.
7.3       Distribution System
As previously stated the area suitable for irrigated 
is _
only likely to be some 10 percent of the command area ^ ising widely
J scattered plots probably not exceeding 50 to lOOha.
p-22-
To serve the whole area a 30 km main canal would be required.
Due to the sodic nature of the soils and their weak structure, the main canal
would have to be lined. Until a detailed topographic survey has been 
undertaken of the conmand area, no detailed distribution layout can be
developed. For estimation purposes it has been assumed that there will an 
offtake at 1 km intervals along the main canal each serving a secondary canal
with an average length of 5km. The gradient of the land traversed by the secondary canal will be an average 0.02 (2 percent) which will require drop structure at approximately 100m intervals. The average area served from each secondary canal would be 70ha.
The main canal and secondary canal system with associated access roads are estimated to cost Birr 9.5 million with land development
costs for 2,000 hectares an additional Birr 6 million.
Allowing for contingencies and engineering costs the comparative development costs for 2,000 hectares, are:
A)    with Bedene Diversion
+ Feeder canal B)    with Alaba Kolito P.S.
+ pipeline
Birr 12,300/ha
Birr 10,900/ha
g
IRRIGATION DEVELOPMENT - LOWER BILATE REHABILITATION 8.1       fcj-late State Farm - Unit 1
Bii
•^ate si ^l °
The Bilate State Farm Unit 1 has an abstraction point on the er approximately 6 km downstream of Bilate Tena (Dimtu). A gabion 
e   ntr°1S the Water level in the river, the side offtake comprising a
fuil
v   ctanguiar sliding gate which appears to be left permanently in the y position.-23-
There is no flow measuring device at the intake to the 1km
long nviin canal, and excess water is diverted back to the river at the first
control structure at the head of the farm distribution system.
The whole irrigation system - main canal, secondary canal
and field distribution channels, is very poorly maintained. The original
control structures are either badly damaged or the gates are missing. There
are no flow measuring devices at any of the offtakes thus precluding any 
effective water management.
The present irrigation practices are characterized by the
•inefficient and non uniform water application resulting from:
-     uneven field surfaces;
-     lack of water control structures;
-     overgrown canal banks and poorly maintenanced channel ways.
The estimated cost for rehabilitation of the existing main offtake, main canal and irrigation distribution system and land improvement for a net area of 495 hectares, is Birr 708,000 or Birr 1,430 per hectare.
8.2 NTMC Tobacco Plantation
RiVer c °nt
Tobacco Plantation has a gated regulator on the Bilate downstreajn of Bilate Tena (Dimtu) which has a potential for
g river level and providing limited river storage. This
armstattxor wae ~ coni,nissioned in 1975 but ten years later, of the six drop gates
U’Ad radini
ox gate. s, only two of the drop gates are operational.
gates i
ie adinp m
design of the side offtake comprises two rectangular slide a cwo“c^npartment desilting basin. However, the desilting 
..
■into th              never been completed and the irrigation supply flows direct e nain feeder canal.I
-24-
The original design was for a sprinkler irrigation system but it is doubtful whether this ever operated due to the silt concentration in the river water. A surface irrigation distribution is now practised but
as with the Bilate State Farm, the whole of the irrigation system is very poorly maintained.
Ihe estimated cost for rehabilitation of the existing river regulator, offtake structures, main canal and irrigation system and land improvement for a net area of 370 hectares is Birr 1.05 million which includes Birr 0.53 million for the headworks. This equates to Birr 2,840 per hectare including the cost of the headworks or Birr 1,405 per hectare for rhe rehabilitation of the plantation excluding the cost of the headworks.
8 -3 Bilate State Farm - Units 2 & 3
point on
A gabion
The Bilate State Farm Units 2 & 3 have a single abstraction tne Bilate River 2km downstream of the Tobacco Plantation regulator, weir controls the water level in the river, but there is no intake
s ^cture at the str ucture i- -
entry to the 4km long main canal. The first control
s
is approximately 1km along the main canal where an escape is 4
to di“ rt---- - - excess water back to the river. Below the first control
^tun. there i-
i  measuring flume (Parshall flume) and at each offtake from
canal there
being iTaint •
------ » are flow measuring devices provided, but none of them
un
apY_.
Sec  n
° <iary 
axnea and no control or measurement of water is being on the farms.
Unit 1, the whole irrigation system - nain canal,
■ i':''2x-Jding(~ana^S
distribution channels, is very poorly maintained
a                           Active water management. The present irrigation practices char
ized by inefficient and non uniform water application
ntiin 
estajnatec* c°st for rehabilitation of the existing river
a          her       Canal       and       irrigation       distribution       system       and       land       improvement
ar e a of gnn R •
„.
ha is Birr 1.32 million or Birr 1,465 per hectare.-25-
8.U     Abaya State Farm
The Abaya State Farm has an abstraction point on the Bilate River 22km downstream of the Tobacco Plantation regulator. There is no control structure across the river, only a side offtake on the left bank on 
the outside of a right hand bend of the river. The intake to the main canal comprises two rectangular sliding gates which are only intermittently adjusted and very quickly become clogged with river debris.
The main canal is 10km long following the right bank of the river, the latter section in embankment. There is no flow measuring device
on the canal and the first control structure at the head of the distribution 
to the State Fhrm incorporates an escape for excess water. The main canal
fias become very overgrown with the canal regime severly affected by contracting and expanding cross sections.
Within the State Farm, none of the secondary canals are well "Stained and although there is evidence of a planned distribution system
tbe control structures are either damaged or the gates are missing. As with Ihe dilate State Farm, no control or measurement of water is being undertaken reSd^ting j_n inefficient and non-uniform water application.
The estimated cost for rehabilitation of the existing river ° fxtaxe> main canal and irrigation distribution system and land improvement for a net area of 1,250 ha is Birr 1.96 million or Birr 1,570 per hectare.
'^1 CATION DEVELOPMENT - LOWER BILATE EXPANSION Bilate State Faim/Tobacco Plant^klQn
------------------------------•
r
es that the Bilate SF/
The reconnaissance soil survey 
• oba<*o Plantation area has only limited soil tests are undertaken, the expans
J hiS location has been assessed to be restr ' ares (gross) - 900 hectares (net).
potential- Untl1 1110126 Kure
for irrigated agric area of 1,000-26-
To supply the expansion area, it is assumed that the existing river intakes will be utilised together with the existing feeder canals. However, as a prerequisite any further development of irrigated agriculture
in this area is dependent on the rehabilitation of the existing development.
This will include reconditioning the existing gated regulator serving the Tobacco Plantation with a complete overhaul and repair of the eight control gates. This structure would then provide both the requisite
river level at the intake and a night storage capacity.
The existing gabion weirs serving Bilate SF Unit 1 and Bilate SF Unit 2/3 would require renovation and control gates installed at the river offtakes. The existing feeder canal system will require cleaning out and 
repaired and the installation of control structures and/or reestablishment of the control gates.-27-
g o2 Abaya State Earm
The reconnaissance soil survey indicates that there could be a four fold expansion in the area of irrigated agriculture in the vicinity of the present Abaya SF expanding the existing development to 5,600 ha (gross) - an increase of U,200 ha (gross) or 3,800 ha (net).
To supply the expansion area it is anticipated that the existing intake and main canal will be incorporated in the scheme but the headworks aru conveyor system will have to be redeveloped, upgraded and expanded.
At present there is no control structure on the Bilate River the intake to the main canal supplying Abaya SF. A diversion weir will be
re Q ired and a gabion structure similar to the existing diversion weirs
u
lOr Bilate SF Unit 1 and Units 2/3 is proposed.
, m rhe river to be maintained 
To enaole a 2U hour
cycle, night storage
’Whilst supplying the farm area on a i
tem A new 10km main
reservoirs      will      be      provided      within      the      main      CaDa^applying      two      night      storage
canal is proposed with an intake capacity of 5 m
system comprising
reservoirs      each      with      a      capacity      of      0.25      Hn3-      e         ^-^l      structures      and 
secondary and tertiary canals totalling 100km wit off takes serving 25 hectare field plots would be Q <ana Preparation will comprise a major element
Land clearance and sion costs.
, -rhe Abaya St 9 oo„ for «                                                 3.
costs for river storage, is estimat (net), or Birr 8,950 per hectare.
^i'LOPl-tENT COSTS
cv excluding
« 3-B““
Capital costs and annual operation an st ijnated for the following development options.
> maintenance costs have-28-
Option,. A
Middle Bilate +
Lower Bilate
Rehabilitation
Rehab Hit at ion
Option B
Lower Bilate only
- Alaba Kolito Plains
Bilate         SF/Tobacco         Plantation Abay a SF Rehabilitation
Bilate SF Expansion
Abaya SF Expansion
Bilate SF/Tobacco Plantation Abaya SF Rehabilitation Bilate SF Expansion
Abaya SF Expansion
For option A, to develop the Middle Bilate and U>wer Bilate, a storage aam on the Bilate River is required at the outlet of Boyo Swamp.
*° ser'« the Alaba Kolito Plains, abstraction frcm Bilate River will be
?^de
d by a
at Wokdela with a pipeline feeding the maincanal at
’ he neaa of the irrigable area. For the expansion of the Bilate SF and
SF, the existing intake works will be upgraded and the distribution MDt*s extreende habid.liFtaort ion  each area, ’ Nation of the existing developmen
15 a Prerequisite for any
For Option U require on the Bilate
expansion.
Bilate only, a storage dam
B, to develop the Lower
River, but not necessarily Boyo Dam.
—. For the intake works will be
^pansion of the Bilate SF and Abaya
■^■aded ana rhe distribution works ext ^ilitation of the existing development
For each option, an 
* sh°wing the rate of development o Potential expansion areas together annual costs. The development Plan
'"Station and new developnent works tn
SF the existing
As for Option A,
a prerequisite for any expansion.
development plan has been drawn rehabilitation of existing areas
re
habil
ixa c
' ^'‘‘ burSement of
rraattee oof disbursement " all
on cOmple
^ ve years-
summarx^• aesd faols low55
The costs of the development optto-29-
^abHitation of l^wer Bilate^
Eilate SF/Tobacco Plantation Abaya SF
Operational Costs
Capital Cost
ETB X 103
2,600 2,400 5,000
Annual Cost
ETB X 103 45
31
300
RilAtp + Lower Btlate-------------- Option A Capital
Cost ETB X 103
fcoyo Dam + Res  Compensation f4 -^a Kolito Plain Development
P
* Pipeline
ligation Distribution Operational costs
' £Mer Bilate Development:
dilate SF/Tobacco Plantation Abaya SF
^?0^tiOnal COStS
& itate SF
Abaya SF operational costs
4,250
3 ,160 19,640
Annual
Cost
ETB X 103 12
24 
265 460
2,600 2,400
7,750 34,000 73,800
45
31
82 360 300_
1,879-30- kvelopcEnt of Lower Bilate only - Option B
Capital
Cost
Annual
Cost
ETB X 103
ETB X 103
Boyc Dam ♦ Res Compensation 
(1)
4,250
12
Lendo Dam + Res Compensation 
r
(2)
14,100
138
rehabilitation:
Bilate SF/Tobacco Plantation
2,600
45
Abaya SF
2,400
31
Operation Costs
300
Expansion:
Bilate SF
7,750
82
Abaya SF
34,000
360
rat ion Costs
300
with Boyo (1)
51,000
1,130
^^entjcLth Dendo (2)
60,850
1,256
1 & II.
io,i
The capital costs and annual costs are detailed in Appendicies
The development programmes for Option A and Option B are gi & 10.2. and the phased agriculture development is shown in 
>
-gures i0 >3    & 10.4.
The phased construction costs
„d 
costs for option A -d
^*1 B 3^
given in Tables 10.1 - 10.4.J ’/ t
JV7 / r < * i-vrn
' >' I I . 
'
Secondary Canal
Land Development Lower Bilate Development
Bilate SF Rehabilitation Abaya SF Rehabilitation Bilate SF Expansion Abaya SF ExpansionUL. VL^OI TlLl'Tl I 'KCX llWIMl..
f ""                               Year
/ Activity ****--------------
o
1
u
5
Design
Boyo Dam Construction (1) Dendo Dam Construction (2) Lower Bilate Development
Bilate SF Rehabilitation Abaya SF Rehabilitation
Bilate SF Expansion
Abaya SF Expansion
Lztz/vjed zujhzi th.iuri:                                                              < r~rm- /\> u\ iiaj option
/
Year
2
3
4
5
6
Total
/ Location
Kolito Plains Development Louer Bilate Development
Bilate Rehab  (1769 ha)
n
865
Abaya Rehab  (1254 ha)
n
Bilate SF Expansion
Abaya SF Expansion
500
1769
1254
450
1250
1769
1254
900
1200
2000
1769
1254
900
2500
2000
1769
1254
900
3800
—->
--- >
--- >
--- >
---- >
2000 1769 1254
900
3800
I
GJ
GJ
I
865
3973
6373
8423
9723
--- >
9723
Figure 10.3PHASED AGRICULTURE DEVELOPMENT (NET AREA HA) - OPTION B
Year
Location
1
2
3
4
5
6
Total
Lower Bilate Development
Bilate Rehab  (1769 ha)
n
865
1769
1769
1769
1769
--- >
1769
Abay a Rehab "  (1254 ha)
11
1254
1254
1254
1254
--- >
1254
Bilate S.F. Expansion
4 50
900
900
900
--- >
900
Abaya S.F. Expansion
1200
2500
3800
--- >
3800
865
3473
5123
6423
7723
--- >
7723Table 10.1: PHASED CONSTRUCTION COSTS (ETR X 103 ) - OPTION A
Year
Item
1
2
3
4
5
Total
Bc.yo Dam + Res’r Condensation Kolito Plains Development
Pump Station + Pipeline
Mr. in Canal
Secondary Distribution
Land Development
Lower Bilate Development
Bilate Rehabilitation
Abaya Rehabilitation
Bilate S.F. Expansion
Abaya S.F. Expansion
1750
2500
4250
1660
1840
1550
2000
2200
2600
2000
2000
2500
2000
2500
22800
2600
2400
5000
1630
3120
3000
7750
3100
9750
10150
6800
4200
34000
Total Construction Cost
12580
26070
19650
11300
4200
73800Year
/ Item
1
2
3
4
5
Total
1 Boyo Dam + Res'r compensation
(1)
1750
2500
4250
Dendo Dam + Res’s Compensation
(2)
4800
5300
400
14100
Lower Bjlate Development
Bilate Rehabilitation
Abaya Rehabilitation
Bilate S.F. Expansion
Abaya S.F. Expansion
2600
1630
3100
2400
3120
9750
3000 10150
6800
4200
5000
7750 34000
Development with Boyo                               (1)
9080
17770
13150
51000
1 Development with Dendo                             (2)
12130
20570 |
17150
6800
4200
60850!^\t. .u.yrj.- (J.-IK J< JO- J - OITJ.utl zx
/
YeciT’
/Item
FP
—
3
5
Boyo Dam
Kolito Plains Development: 1
.
Pump station + Pipeline
Main Canal
Secondary Distribution
On Farm
n1
Irrig  op  costs - Power
- Staff
Lower Bilate Development
Bilate Rehabilitation
Abaya Rehabilitation
lrrig  op^ costs - Staff
Bilate S.F. Expansion
I           Abaya S.F. Expansion
lrr’ig  opl costs - staff
L
6
7
8
rz
12
12
12
12
-- >
24
26
23
30
24
52
58
75
24
52
93
120
24
52
93
120
-- >
-- >
-- >
--->
40
100
100
200
160
300
160
300
160
300
--->
--->
22
45
31
45
31
45
31
45
31
--->
--- >
n
100
200
300
300
300
300
--->
41
24
82
152
82
256
82
360
--- >
-- >
n
100
200
300
300
-- >
1 Total Annual Costs
100
362
956
1491
1775
879    -
-- >/
Ye<ar
/ Item
r
2
/
3U
5
6
7
8
/ Bcyc Dam
(i)
—
12
12
12
12
----- >
/ Der>do Dam
(2)
100
138
138
138
----- ■>
1 Lower Bilate Developinent
Bilate Rehabilitation
Abaya Rehabilitation
Irrig  op , costs - -Staff
Bilate S.F. Expansion
Abaya S.F. Expansion
Irrig  op , costs - Staff
22
45
31
45
31
45
31
45
31
----- •>
n1
100
200
300
300
300
300
----- >
41
24
82
152
82
256
82
360
----- >
----- >
n1
100
200
300
300
--- >
Development with Boyo                              (1)
100
222
553
822
1026
1130
----- >
Development with Dendo                            (2)
100
222
641
948
1152
1256
----- >'J
lx / xz(^/C
S' I rJ
f?-£H A 2> IL. ITATiO/'J£i LZ)-n.:                                                                                                             s i /Ay
Tt'EVGZ.Of^&^T - OPTION A
Km?a
$
G\j b E /~
@--
'Ws 2>n w
—I /ItAVN kOHTJ
"*—’ Pl/\.          >tve^‘ ic~r
-^^^,t2/2
@~
be«>3A ----------- &
' —g]j fl^sf-• * <
•
«< •< ■*
♦
t*f
« ••* #•• •
' if W*.< •
**■
*'-*—•* D
.' *
( n  >
OI
*Z
€»<kVtiPA
fxur* £AL <?
CSm/?/K rrt
0 If^rL-Oi^J
O IT7-)2>x2/¥vj/3vVAPPENDIX I
BILATE RIVER BASIN STUDY
IRRIGATION DEVELOPMENT
CAPITAL COSTS
1.1           INTRODUCTION
1.2 ALABA KOLITO PLAINS DEVELOPMENT
1.3           LOWER BILATE REHABILITATION
I.U          LOWER BILATE EXPANSIONg§
APPENDIX I
BILATE RIVER BASIN STUDY IRRIGATION DEVELOPMENT
CAPITAL COSTS
1.1       INTRODUCTION
Preliminary costing of the irrigation development has been undeiTaken using EWWCA unit rates as at December 198 5. In the event of international funding with tenders from international contractors, the construction costs are likely to be higher.
Construction costs have been estimated for the following development options:
Oprion A
Middle Bilate +
Lower Bilate
-      Alaba Kolito Plains
-      Bilate SF/Tobacco Plantation Rehabilitation Abaya SF Rehabilitation
Bilate SF Expansion Abaya SF Expansion
S*ionj5
Bilate only
- Bilate SF/Tobacco Plantation Rehabilitation Abaya SF Rehabilitation
Bilate SF Expansion
Abaya SF Expansion
For each option, an indicative development plan has
'
the rate of development for the rehabilitation of exxstmg areas and expansion areas together with the rate of disbursement over
truction period.
development option, rehabilitation ls a  prerequisite for any expansion.
i1.2     ALABA KOLITO PLAINS DEVELOPMENT
LTB x 103
ETB x 103
i)
Bedene Diversion
Embankment
Offtakes Structure
Feeder canal (10 km-lined)
Cross Drainage
2,000
50
1,800
150 
4,000
3
ii) Alaba Kolito P.S.
Pump Station
Pumps/Motors (4 Nr. 0.5 m /s) Pipeline  (2  km;  2  Nr.  600  mm0) Electricity Power Line (5 km)
iii) Kolito Plains Distribution Main Canal (30 km)
Road Crossing Syphon Road Bridges (15 Nr.) Cross Drainage
Access Road (30 km) Control Structures (6 Nr.) Offtake Structures (30 Nr.) Secondary Canals (150 km) Drop Structures (1,500 Nr.) Offtake Structures (100 Nr.) Access Roads (150 km)
iv)
^Ijevelopment Levelling;
Field   Canals   ‘
200
200
2,000 100
2,500
3,600 150
150
100
540
30
30
1,800 300
100
2,700 
9,500
Field Drainage, Field Roads '
(2,000 ha)
6,000LTB x 103
Alternative A
i)       Bedene Diversion
iii)          Kolito Plains Distribution iv) Land Development
Contingencies 15% Engineering 10%
Total
4,000 9,500
6,000
19,500
2,900
22,400 2,200
24,600
Alternative B
ii) Alaba Kolito P.S.
iii) Kulito Plains Distribution
iv) Land Development
Contingencies 15% Engineering 10%
Total
2.500 9.500 6, OOP
18,000
2,700
20,700
2,100 22,800I
1.3        LOWER BILATE REHABILITATION
ETB x 103                      ETB x 103
i)        Bilate State Farm - Unit 1 Gabion Weir
Inlet Control
Main Canal (1 km.) Control Structures (3 Nr.) Offtake Structures (5 Nr.) Secondary Canals) (1Q Tertiary Canals )
Offtake Structures
5
10
10
15
5
20
20
Land Development (500 ha)                                                  500                          585
ii)      Tobacco Plantation
Weir Gate Structure                                                                400                          400
Desilting Basin )
Inlet Control )
Main Canal (1 km) Control Structures (3 Nr.) Offtake Structures (5 Nr.) Secondary Canals j (? 5
Tertiary Canals ) Offtake Structures
40
10
15
5
15
20
Land Developmenr (370 ha)                                                     370                        475 iii) Bilate State F rm Unit 2/3
Gabion Weir
Inlet Control
Main Canal (4 km)
Control Structures (6 Nr.) Offtake Structures (10 Nr.) Secondary Canals ) 25 Tertiary Canals ) Offtake Structures (45 Nr.) Land Development (900 ha)
5
10
40
30
10
45
900C
/F 2,550
I
IETB x 103
ETB x 103
B/F
2,550
iv)       Abaya State Farm
Inlet Control
20
Main Canal (10 km)
200
Control Structures (6 Nr.)
30
Offtake Structures (10 Nr.)
10
Secondary Canals)
Tertiary Canals j
5 (30 km)
60
Offtake Structures (50 Nr.)
50
Land Development (1250 ha)
1,250
1,620
4,170
Contingencies 10%
415
4,585
Engineering 10%
415
Total
5,0001.4      LOWER BILATE EXPANSION vV/v X v
ETB x 103
i)    Bilate State Fann/Tobacco Plantation Main Canal Extension (5 km) Control Structures (4 Nr.) Offtake Structures (10 Nr.) Secondary Canals) (2£.
Tertiary Canals 5 Access Roads (25 km) Offtake Structures (40 Nr.) Land Clearance 1,000 ha Land Development 1,000 ha.
Contingencies 15%
Engineering 10% Total
300
20
10
300
450
40
2,000
3,000
6,120
920 7,040
710 7,750
Abaya State Farm
Diversion Gabion Structure)
Inlet Works
3
Main Canal 5 km 5 m /s)
3
5 km 2 m /s]
j
)
Night Storage Reservoirs (2 Nr.) Access Road 10km
Control Structures (6 Nr.) Offtake Structures (30 Nr.)
Secondary Canals) (10Q
Tertiary Canals )
Access Roads (100 km) Offtake Structures (150 Nr.)
Land Clearance (4,200 ha) Land Development (4,200 ha)
Contingencies 15% Engineering 10%
1,000 800
660
180
30
30
1,200 1,800
150
8,400 12,600
26,850 4,050
30,900
3,100
Total
34,000APPENDIX II
BILATE RIVER BASIN STUDY IRRIGATION DEVELOPMENT
ANNUAL COSTS
INTRODUCTION
ALABA KOLITO PLAINS DEVELOPMENT LOWER BILATE REHABILITATION
LOWER BILATE EXPANSIONAPPENDIX II
BI LATE RIVER BASIN STUDY
IRRIGATION DEVELOPMENT
ANNUAL COSTS
II. 1 INTRODUCTION
The annual maintenance costs of the engineering works have been assessed as a percentage of the construction cost for each section of the works as set out below:
Section of Works Dnbankments
Dam
Night Storage Res '
r
Pump Station
RC Structure
Pumps & Motors Pipeline
Powerline
Diversion Structures
Gabion Weir
RC Gated Weir
Main Canals
Lined
Unlined
Secondary/Tertiary Canals Unlined
Structures
Syphons
Road Bridges
C^oss Drainage Control     Structures ^°P Structures
Off take Structures d ^elopnjent
Percentage of Construction Cost
1% 1% 5%
0.5% 2% 2% 1% 1% 2%
Ccess Roads
2%
2%II.2 ALABA KOLITO PLAINS DEVELOPMENT
ETB x 103
ETB x 103
i)            Bedene Diversion
Embankment (1%)
Offtake Structure
Cross Drainage )
Feeder Canal-lined (1%)
20
2
18
40
ii)          Alaba Koiito P.S.
Pump Station            (1%)
Pumps/Motors           (5%)
Pipeline                       (0.5%)
Powerline                  (2%)
ii)                                 Kolito Plains Distribution
Main Canal - Lined
(1%)
36
Syphons
Road Bridges
Cross Drainage
4.6
Control Structures
Offtake Structures
Access Road
Secondary Canals
Drop Structures
(2%)
(2%)
(1%)
Offtake Structures
Access Roads                              (2%)
10.8
36
4
54
iv) Land Development
Land  Levelling, Field  Canals J Field Drainage!
Field Roads !
120
120Alternative A
i) Bedene Diversion
iii) Kolito Plains Distribution
ETB x 1Q3 ETE x 1(P
40
145.4
iv)         Land Development                                                                                         120 Alternative 5
305.4
ii)         Alaba Kolito P.S.
iii) Kolito Plains Distribution
iv)         Land Development
24
145.4 120
289.4jl,3 LOWER BILATE REHABILITATION
El’B x 103                     LTB x 103
i)
Bilate State Farm - Unit 1 Gabion Weir
,
Main   Canal   -   unlined   !
Secondary Canals Tertiary Canals
Inlet Control
Control Structures Offtake Structures’
Land Development
ii) Tobacco Plantation
Weir Gated Structure Main Canal - Unlined, Secondary Canals
Tertiary Canals ' 
Inlet Control
Control           Structures! Offtake Structures!
Land Development
!
!
(1%) (2%) (1%) (2%) (1%) (2%)
0.7
0.5 10.0
11.2
0.0
0.5
0.8
7.M
12.7
iii)      Bilate State Farm Unit 2/3 Gabion Weir
Main    Canal    -    UnlinedJ
(2%)
Secondary 
Tertiary Canal
Inlet          Control          ! Control Structures! Offtake Structures!
Land Development Abay a State Fann
i
!
(1%)
(2%)
1.0
iv)
Ma   iii   Canal   -   Unlined,
Secondary 
Tertiary Canals
Inlet Control
Control       Structures       ! Offtake Structures !
band Development
!
!
(2%)
(1%)
(2%)
5.2
1.1
TotalII.4               LOWER BI LATE EXPANSION
El’B x 103 ETB x 103
i) Bilate State Farm/Tobacco Plantation Main Canal - Unlined, Secondary Canals           J
(2%)
12
Tertiary Canals
!
Control Structures )
Offtakes Structures)
Access Roads
Land Development
(1%)
(2%)
(2%)
0.7
9
60
81.7
ii) Abaya State Farm
Diversion Gabion Weir
Main Canal - Unlined Night Storage Reservoirs (1%)
(2%)
Control Structures) Offtake Structures)
Access Road
(1%)
(2%)
20
6.6
0.6
3.6
Secondary Canals)
(2%)
24
Tertiary Canals )
Offtake Structures
(1%)
1.5
Access Roads
(2%)
36
Land Development
(2%)
252
Total
360.3
442.0Date Due

Summery

Bilate River Basin Irrigation Development Summary

Bilate River Basin Irrigation Development Study

Document No.: RVLB Project Document No. 7

Prepared by: WRDA/FAO

Date: May 1986

Executive Summary

The Bilate River Basin study evaluates irrigation development potential in Ethiopia's Rift Valley, covering 5,650 km². The basin is divided into three sub-basins (Upper, Middle, Lower) with varying agricultural potential. The study examines existing irrigation schemes, potential expansions, and proposes dam construction options to support development.

Key Findings

1. Basin Characteristics

Location: Between 6°35'-8°05'N and 37°45'-38°20'E
Area: 5,650 km² with elevation from 1,180m to 3,280m
Sub-basins:
- Upper Bilate: Mountainous headwaters with Boyo Swamp
- Middle Bilate: Alaba Kolito plains with rainfed agriculture
- Lower Bilate: Alluvial plains with existing state farms
Hydrology: Mean annual runoff varies from 175mm (Upper) to 129mm (Middle)

2. Existing Development

3,000 ha (net) currently irrigated in Lower Bilate
Major schemes: Bilate State Farm (Units 1-3), Tobacco Plantation, Abaya State Farm
Poor system maintenance leading to inefficient water use
Current water demand: 27.5 million m³/year

3. Potential Development

Location	Potential Area (ha)	Key Considerations
Middle Bilate (Alaba Kolito plains)	2,000	Undulating terrain limits irrigation potential
Lower Bilate (Bilate SF/Tobacco expansion)	1,000	Limited by soil infiltration rates
Lower Bilate (Abaya SF expansion)	4,200	Good soils but requires drainage management

4. Storage Requirements

Additional irrigation development requires river storage:

Middle & Lower Bilate development: 80 million m³ storage
Lower Bilate only: 50-60 million m³ storage

5. Dam Options

Option	Location	Storage (million m³)	Estimated Cost (Birr million)
Boyo Dam	Bilate River outlet	80	4.25 (plus 3.0 compensation)
Ropi Dam	Bilate River (40km downstream)	60	16.1
Dendo Dam	Bilate River (55km downstream)	50	13.8 (plus 0.3 compensation)

6. Development Options

Option	Description	Capital Cost (Birr million)	Annual Cost (Birr million)
Option A	Middle + Lower Bilate development (Boyo Dam)	73.8	1.879
Option B	Lower Bilate only (Boyo Dam)	51.0	1.130
Option B	Lower Bilate only (Dendo Dam)	60.85	1.256

Recommendations

Rehabilitation of existing irrigation systems is prerequisite for any expansion
Storage dams required for reliable water supply to expanded areas
Option A (Boyo Dam) provides most comprehensive development but highest cost
Option B (Dendo Dam) offers focused Lower Bilate development at moderate cost
Detailed topographic and soil surveys needed before final implementation