Borkena Irrigation Project Summary

BORSCTA IKRIGAT1U1 PJOJIXI
BRIEF FrVL'.'T fllTLUZ
C. J* It DAVEJT
WOTR RESOURCES DEVELOP 21-T EMDEZF FR3JDCT ETH '97/OOF
rACi/WEJtt FFWECT EIH/flJ/OCF
;JFZL 19 f£
ALOIS ABAi'-.Borton irrigation rwr
BRIEF PROJECT DJILIIE
coffrorrs
FACE
I. GDERAL-----------------------------------------
2* WPTD? WSOURCS........................... ... ................ ..............
3. CROP WATER REQUIPIhUn’S—-------------------- ---------------------------------------- DESIQJDETAILS-
t
“.1
Project Ama-—
U.2        Hain Canal
H.3
■ijl
u.5
Seccnoary Canals Drainage
riood Protect icn---------
<6            Reads and access tracks
S. SUMMARY Of KEY FdDfTS------------- —
2
3
3
u
5
S
5
£
*BORKDJA IRRIGATION PRIXHIT
1, GENERAL
The pxqjosed Barkena irrigation project is located in the lower Borkena Valley or Oiaf fa Plain approximately 330 km north of Addis Ababa cn the rair. road to Dessie  as shown in Figure 1- As a
t
result of the recent drought period a decision was made (in 196*4) to proceed inneiiiately with the constrjcticn of three dams on the Borkena River, These dams are now in various phases of constructitr. with the lowest dam due to be ccnpleted later this year. The design of the main canal and part of the distribution system has rev comenced to utilize the water being re.de
avai WAe for irrigation development,
3. KATES KESOUROS
The Borkena river has a total catchment area of approximately tan* at the site cf the JmsT dam on the river, Bzrkena I* The mean
amjal runoff (rec this catchment has been estimated at over 100.0 x 10&ttr’, and with the Constructicn of sufficient reservoir storage capacity, approximately 65 x lt^r? could be made available for irrigation purposes in the fcrkena valley. At present three dams are under ccfistructiwi with a total estimated storage capacity of 2C-1 x 10 ib3 * 5, as sfxxci in Table 1,-2-
Tablel:         Borkera Deras, Storage Capacity ana Height
Dara
Height
m
Storage Capacity
103 * * 6r?
Barkers I
Borkena II
fcrkena 111
IB
31
25
1.0
12.0
6.3
Total
20.1
Allawir^ for transmission losses between the reservoirs, and seepage and evaporatim losses, it is estimated that oonpletian of these three dais vculd provide approximately 15.0 x W’n’ of water for irrigation purposes.
Additional dar. sites have been identified above the lower sites, and it is possible that sufficient dans could be constructed to harness the
ccn^lete uater resources of the Bcricena River above the Chaffa Plain.
3. CROP K-Jg. REQ-'iRD^rrS
From the meteorological stations at Harbu and Kaobolcha it is estimated that the mean annual rainfall ever a 30 yaar period exceeds
l.BCQm per ar#n&. Ln order to deterraine the effective rein fall available for cropping requirements the 75% probability rairJall has been estimated at ato.it 900 nr., and the effective rainfall at 630 m.I11
-3
The crop water requireiEnts for the project area have been determined assuming that two crops are grown each year ti.e, 200* cropping intensity), and, for calculation jxxrposes, it has been ass^ied that supplementary irrigation would be required for a miize crop pown during the mair. rain sensor,  and full irrigation would be required for a wheat crop
t
during the dry season. The selection of other crops or a mixture of
is unlikely to result in a significant Increase in the estimate of the
r*r» a.
water iequirenent $ .
The overall project efficiency lias been estimated at **0^  arid 
+
with the above assumptions the project crop water requireirent has been calculated as 1,1SO me,, with a peak requiie’nenT of 300 nr: during February.
x. EESIGtr DZIAILS
M .1 Pteject Area
The total area             of irrigable land in the Bcrkena Valley exceeds 13,000 ha, but the land to be irrigated would be United by the available water resources. The corp Let ion cf the first three dams would provide a total storage capacity of jp.i x lcV and it is estimated that
these would yield Sufficient utter for approximately 1,100 ha cf full and supplementary lrrigctko. Construction of the additioMl uperrean dr?/ would 
possibly inet^iEje this arra to abc-jt
ha.Approximately 1,000 ha of ideally suitable land for irrigation development is available above the Dima River. It is expected that the
initial develqpnent based cn the three dams presently under ccdstnjcticn wadd not extend beyond this natural boundaiy.
The irrigable area along the right bank of the Borkena River his been selected for initial development since the gradients ait lower, and the area is closest to the lowest Boixena dam; thus reducing the length of ite nuin canal* The total area to be irrigated is limited by the availability of
water and it is intended that the irrigaticn devtlcpnenl wxdd all be concentrated along the right barv cf the corkena River.
4.2 Ifain Carjl
With the exception of the section of the raaiii canal hmediatejy telow xhe dam it is intended that the sain canal would be unlined, and located it a ncn-^rcdible gradient of l;2 000, A lumber of drop structures would be
t
ntees&dry to maintain this profile, and the largest would be a 5 tetre drop within the initial lined section of ti*e noin canil.
The first sta^e of the drvelcpment to utilTze water frer. 
borkem I wxild. require HiSOO rctres of Bain canal to a control reservoir to Eervt approxjjTBtely 100 hi of irrigation develcpn^nt  To fully utilize the
a
available water when all three forkena d^a arc completed, the soin canal WDj.d U- extended an additional 2,£Q0 n, to a total estimted length of
1  t^OO metres
rs-
Tte nain canal is designed to pass a maxirtz? peak flow cf
1.6 tf/s or 1.2 litres/sec/ha based on continuous water delivery in rhe main 
canal. Naturally this peak flow wuld t* reduced at various stages along the
tmiri canal.
H.3 Secondary Canals
■r ■■>
For the first l,O0C ha of deweloiJCEnt there are 6 secondary camlt with a total length exceeding l£i,Z0O metres. These secondary canals
vary in size depending cn tlie areas they serve, Tls irrigation system
1
proposed for barkena is based or, continuous flov; in tne nuin canal (2 * tiOUI-5 per day during the peak desard period) and continuous flow in the secondary carals (10 hours per day). Thus water would always be available in the Secondary canals tc be diverted into Use tertiary canals vhere rctalicciil irrigation af the areas would be practised.
•>.* DramAge
The brief soil survey carried cut by the TAO Soil Expert has indicated that there already exists a relatively high water table in the proposed irrigable area. Thus it will be necessary to incorporate sore deep open drains even during the initial development, and it rosy be necessary to install Sub-surface drairs to provide eOe^rare control of the water table, 
<f> Flcod Protecticr,
The ccryleticn cf the three dans she ill reijqpe the flooding
presently experienced in tire k:'rtr.± plains area, bat sox flooc protectionwill also be included in the design. In addition a fund is included in the design to protect the main canal and to divert the surface flood waters into the Dirro River.
u.fi toad; gd Access Tracks
Since the project area is on the right tank of the Borkena river a permanent river crossing will need to be provided^ possibly at the location of the existing causeway. Wo prevision has been made for crossing the spillways of the daps.
Access trucks will be inogrparated in the design of the
irrigable area
i + g-lt ftR!r OF KT:
1. fean Annual fajnoff from Sarkerc Fiver
2- Potential water available fcr ixrigdtico Iron Sorkena River
3, Reservoir storage capacity of Barrena Cars Estinuxed irrigation water available fra?. gqrkena
iMervolrs
Total potential irrigable aroa in tafctm Valley E*‘ Mean Annual Rainfall
' - Assumed project irrigat icn eft icitney 6. Lstirwted crop water requirement (nsizc > ihwi) 9* Irrigable aron iron. 3 Barkens. reservoirs
ioo*o x io6e»
t&.O x W*t’ 20.3 x iofw
1S*D x lO6^ 30,000 ha*
1,017 rm
l fc25O nr. 1.100 ha"1-
10.     Estimated maxima potential irrigable area
11.     Hain canal naximm capacity
12.     Length of rein canal for stage 1: 100 ha
13.     Length of main canal for state 2: 1,000 ha IM.    Length of secondary canal for stage 1: IDG ha 15.    Length of secondary canal far stage 2: 1,003 ha
M 000 ha
t
3.5 tf/s **,600 tn
7 W0 »
t
1,550 q 10,200 a6**en
finur Uii«
s
r'
/
0
LESE-SE
Tftank
1* »*Qth*r flggd
*** Cfl'Eto** &*10* 5tteoi<rifMR* fr-rd* ItU
Svemc
tk> Stream fwe<*
_ ■~ '
r
s J
\
■
J
F A 0/ W fl.DA PROJECT £TH/8??00e
*ATER ftESDVRCES DEVELOPMENT lUTHOWfTY
•wn
BOfiWEHA IRRIGATION PROJEC LOCATION MAP
T
t*u
■XC rafr! lerir
i a* ■ m
omma >rj
-wicre h |   ■
b
I         hr 1
r-rc«ra »t I
-
j i-in •*

Summery

Project Overview

The Borkena Irrigation Project is located in the lower Borkena Valley (Chaffa Plain), approximately 330 km north of Addis Ababa, Ethiopia. Initiated in 1984 in response to drought conditions, the project involves the construction of three dams on the Borkena River and development of irrigation infrastructure.

Water Resources

The Borkena River has a catchment area of 465 km² at the Borkena I dam site, with mean annual runoff estimated at 100.0 × 10⁶ m³. Three dams are under construction with the following specifications:

Dam	Height (m)	Storage Capacity (10⁶ m³)
Borkena I	18	1.8
Borkena II	31	12.0
Borkena III	25	6.3
Total		20.1

These dams are expected to provide approximately 15.0 × 10⁶ m³ of water for irrigation after accounting for losses.

Crop Water Requirements

The project assumes a cropping intensity of 200% (two crops per year) with:

Supplementary irrigation for maize during the rainy season
Full irrigation for wheat during the dry season

Estimated crop water requirement is 1,350 mm annually, with a peak requirement of 300 mm in February. Project irrigation efficiency is estimated at 40%.

Design Details

Project Area

The Borkena Valley contains over 10,000 ha of irrigable land, but initial development will be limited to:

1,100 ha using water from the first three dams
Potentially expanding to 4,000 ha with additional upstream dams

Infrastructure

Main Canal: 7,400 m total length (4,600 m for initial stage), maximum capacity of 3.6 m³/s
Secondary Canals: 10,200 m total length for 1,000 ha development
Drainage: Open drains and potential sub-surface drains due to high water table
Flood Protection: Bunds to protect the main canal and divert flood waters
Roads: Access tracks and a permanent river crossing

Key Project Points

Mean Annual Runoff: 100.0 × 10⁶ m³
Potential irrigation water from Borkena River: 65.0 × 10⁶ m³
Current reservoir capacity: 20.1 × 10⁶ m³
Available irrigation water from current dams: 15.0 × 10⁶ m³
Mean Annual Rainfall: 1,017 mm
Initial irrigable area: 1,100 ha
Maximum potential irrigable area: 4,000 ha

Project Status

As of the 1986 report, the three dams were in various phases of construction, with Borkena I expected to be completed later that year. Design work had begun on the main canal and part of the distribution system.