Ministry of Water Resources, Basin Development Study Department Aysha Basin Reconnaissance Phase Study
THE FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES
AYSHA BASIN RECONNAISSANCE PHASE MASTER FLAN
Voiume IV: Water resources
A- Hydrology
B- Hydrogeology
C-Dams & Hydropower
D-IrrigationPreface
The dry basins reconnaissance phase study has been conducted by the experts pulled out from the basin development study department Data collection and rapid field visit was made for three diy basins simultaneously viz. Ogaden, Aysha and Denakil, between June and August 1999, then the report production was almost completed in May 2000.
Tlic report is divided in io VI volumes made up from works conducted during the study 
phase. Each volume has sections depending on the details of the sector.
Volume 1
Volume II
Volume III
Volume IV
Volume V
Volume VT
Executive Summary Natural Resources Agriculture
Water Resources Sucio-Ecunomy Environment
List of experts produced these report are;
Eyiiachew Yitayew Abebe Gulma Soiomon Mengistu Amare H'Selassie Fekaluned Sintayehu Tilahun Mckonncn Worku lsavas W.Mariam Girum Admasu Beiay Tegegn Wubshet Alemayehu Abnel G.Medhin Goshu Kebede Melaku Abebe Getachew Bevene Yeyesus Work Bekele
Geoiogy and Mineralogy
Soil survey and Land evaluation
Land use/Cover
Forestry and Energy'
Wildlife and Tourism
Agronomy
Livestock. Range land, Apiculture and Fishery Hydrology
Hydrogeology
Dams and Hydropower
Irrigation and Drainage
Geoiechnicis and Infrasiiuciure Acricultural Economics
Demography
Soil and Water Conservation Environment and Environmental HealthDry basins study project /Danakil, Ogaden and Aysha/
Hydrology report, 1999
THE FEDERAL DE0CRAT1C REPUBLIC OF ETHIOPIA
MINISTRY OF WATER RESOURCES
AYSHA BASIN INTEGRATED DEVELOPMENT MASTER
PLAN PROJECT
RECONNAISSANCE PHASE
HYDROLOGY
December, 1999
Ministry of water resources of Ethiopia
i                Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/
Hydrology report, 1999
TABLE OF CONTENTES
CONTENTS
EXECUTIVE SUMMARYii
1. INTRODUCTION1
1.1 OBJECTIVEI
2. LOCATION AND PHSYIOGRAPHY1
3. OVERVIEW OF PREVIOUS STUDIED PROJECTS3
-
PAGE
3.1 EVDSA, Master plan for the development of surface water resources in the Awash basin, HALCROW,
1989.................................................................................................................................................................................................. . 3.2 EVDSA, Water resources development master plan for Ethiopia, WAPCOS, 19903
3. DATA AVAILABILITY1......................................................................................................................................................5
3.1 METEOROLOGICAL DATA....................................................................................................................................................... 5
3.2 RIVER FLOW DATA5
3.3 SEDIMENT TRANSPORTATION DATA5
4.0 CLIMATE ........................................................................................................................................................................... 6
4.1 GENERAL DESCRIPTION6
4.2 CLIMATE OF THE BASIN7
5. PRECIPITATION8
5.1 NETWORK/SPATIAL DISTRIBUTION OF METEOROLOGICAL STATIONS............................................... ........................... 9
6.0 SURFACE WATER RESOURCE................................................................................................................................... 10
7.  PROPOSED PROGRAM FOR II PHASE ACTIVITIES, LOGISTICS AND MAN POWER REQUIREMENT.! 1
7.1 PROPOSED PROGRAM FOR II PHASE ACTIVITIES11
7.2 MATERIAL AND MAN POWER REQUIREMENT .................................................................................................................. 12
8. CONCLUSION AND RECOMMENDATION13
REFERENCES„.......................................................................................................................................................................14
Ministry of water resources of Ethiopia
ii                Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/
TABLES
Hydrology report, 1999
PAGE
TABLE 1 MATERIAL AND EQUIPMENT REQUIREMENT FOR THE HYDROLOGY SECTION TABLE 2 MAN POWER REQUIREMENT
FIGURES
FIGURE 1 :TOPOGRAPHY OF THE BASIN
12
12
PAGE
2
Ministry of water resources of Ethiopia
in               Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/
Hydrology report, 1999
Figure l:Topography of the basin
Ministry of water resources of Ethiopia
2                Basin development study department•jjorDry basins study project /Panakil, Ogaden and Aysha/Hydrology report, 1999
3. OVERVIEW OF PREVIOUS STUDIED PROJECTS
3.1 EVDSA, Master plan for the development of surface water resources in the Awash basin, HALCROW, 1989.
In the report indicated the water resource of the Awash basin as a whole. The Aysha basin founds in the eastern sub-catchment of the Awash basin, with low rainfall and barren land. The basin situated into  2  rainfall regimes /based  on  the Awash  basin  rainfall regime classification/.  In  Awash  master plan  study  report threre was no  indication  about the water resource potential of Aysha sub catchement.
3.2 EVDSA, Water resources development master plan for Ethiopia, WAPCOS, 1990.
The  study  and  masterplan  preparation  was  to  comprise  of  three  phases.  The  inception  phase,  the study phase and indicative master plan preparation.
In  the first phase of the report preparation  the analysis of all implemented  projects with  respect to hydrological and  geological features sedimentation,  adequacy  of spillway  capacities irrigable areas and land suitability, hydropower asspects and envimmental effects were discussed.
In  the intrim report,  the studies have been  mainly  directed  towards the preparation  of the indicative master plan.  Most of the studies carried  out were used  for the formulation  of the plan  and  some of them served as useful guidelines for detailed planning.
The final report marks finalization  of the preliminary  master plan.  All identified  irrigation  and multipurpose aswell as exclusively  hydrpower projects have been  described.  The projects recomended  for excution  during  the next 50  years in  phase manner have been  mentioned.  The final report consists of ten volumes.
Ministry of water resources of Ethiopia
3                Basin development study department /
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Hydrology report, 1999
In the study identified 4 major basins in the country. Aysha basin belongs to eastern basin. Based on updated  isohyets,  each  river basin  has been  subdivided  into  different rainfall zones. The purpose of zoning is to understand the spatial variability’ of rainfall, identify areas of higher suitability for water resources.
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3. DATA AVAILABILITY
3.1 METEOROLOGICAL DATA
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Source of all meteorological data could  be NMSA and  FAO.  In  this report no  detailed  informati regarding  the climate of the basin  is collected.  For general information  annual value of basin  dim characteristics is included in the report /HALCROW, 1989/.
3.2       RIVER FLOW DATA
In   Aysha   basin   no   measured   streams   exists,   therefore   the   flow   data   from   this   basin   should   not expected.
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3.3       SEDIMENT TRANSPORTATION DATA
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Since the basin  have no  perennial streams which  can  be quantified  the amount of flow,  fli measurement couldnot be done.  Beside to  this the estimation  of sediment transportation  from the seasonal streams have been impossible.
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4.0       CLIMATE
4.1       GENERAL DESCRIPTION
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Hydrology report, 1999
The most important elements for both  agriculture and  hydrology  are precipitation,  temperature and evaporation. Precipitation data are an important input in water resources studies, in particular for the study  of the rainfall-runoff process through  which  is determined  how much  runoff results form a certain  amount of precipitation  on  different catchments.  The other climatic elements /temperature, humidity,  wind  speed,  radiation  and  sunshine hours are required  to  estimate plant water requirements and reservoir evaporation.
In  the tropical belt,  variation  of climate during  the year are largely  associated  with  macro-scale pressure changes and  the air flows related  to  these changes.  The pressure changes are generally driven by the annual oscillation of the Inter Tropical Convergence Zone /ITCZ/.
In February and March the entire country is virtually dry. The southern part of the country is covered by  the wet regime in  April.  In  may  the belt moves northward; and  in  June it extends'further northward,  leaving  part of the south and south'eastern regions remain wet during July and August. In September,  the belt moves southwards and  this movement is accelerated,  leaving  the north  and central parts dry.
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4.2 CLIMATE OF THE BASIN
Hydrology report, 1999
Aysha  basin  is  included  in  BWH  (hot  arid  climate).  This  basin  is  barren  to  sparse  vegetation  wi mean annual rainfall of 325 mm (Aysha) and 185 mm (Dawele) /HALCROW,,1989/.
The maximum and  minimum daily  temperature are in  the range of 31.3  and  18.2  °C,  mean  dai temperature over the basin  amounts to  be-24.8  °C.  Mean  wind  speed  over the basin  is 2.4  m/s,  me; sunshine hours 67 % and mean of total radiation rounds to 468.0 cal/cm/day.
The Altitude evaporation  relationship  region  wise expressed  by  formulas.  As the Aysha basin  is part of Awash  basin,  regionalization  of evaporation  based  on  data collected  for Awash  master Ph The basin has regional relationship for estimating evaporation.
E = 3831 - 0.979H
where H - elevation
E - evaporation
Since  there  is  no  adequate  data  for  estimating  PET  of  the  basin,  this  task  left  for  the  II  phase  of  t masterplan study.
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5.1      NETWORK/SPATIAL DISTRIBUTION OF METEOROLOGICAL STATIONS
The present network  of the basin  is not in  the stage of fulfilling  criteria declared  by  WMO.  The aim of the network  is to  provide a density  and  distribution  of stations in  a.region  such  that,  by interpolation  between  data sets of different stations,  it will be possible,  for practical purposes,  to determine with  sufficient accuracy  the statistical parameters of the basic hydrological and meteorological estimates any  where in  the region  /WMO,  1994/.  The WMO advises the following minimum densities of rainfall stations for the different physiogrphic units.
Region
Temperate Mediterranean and
tropical zones
Flat areas
Mountainous areas
Small mountainous is lands (<20000km ) Arid & polar zones
Minimum density, range/km2/gauge/
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600-900
100-250
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1500-100000
In  Awash  master plan  report indicated  that in  Aysha basin  exists two  meteorological stations one in Aysha town  and  the other is in  Dewele town.  According  to  the WMO setup  of stations density  the basin satisfies the minimum requirement.
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6.0 SURFACE WATER RESOURCE
Hydrology report, 1999
In  the basin  flows seasonal streams like Biye Gurger,  Kobe,  Seblosa,  Lasarat,  Gerbale and  Dbede The climate of the area indicates scarcity  of rainfall at low lands,  inconsequence of this is sms amount of flows.
Due to scarcity of drinking water the people in the basin nedds to fetch it from a very far distanc Sometimes the supply of water assisted by drilling of boreholes around the villages. In some placi pastorialists construct ponds or bircas to harvest rain to give drinking water for their cattle. Hence the basin drought occurs frequently, at the time of visit of the area the rainfall occured after 3 years. 
The surface water amount is less due to rarely occurrence of rainfall in the basin. The less in amou and rarely flowing of streams of the basin to depend on water resource could be difficult. Moreov on the WAPCOS report indicated that the surface water potential of the basin is negligible.
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7.        PROPOSED PROGRAM FOR II PHASE ACTIVITIES, LOGISTICS AND MAN
POWER REQUIREMENT.
7.1 PROPOSED PROGRAM FOR II PHASE ACTIVITIES
For the II phase of the study, it would be better to consider these:
Climate
-      In  upgrading  and  installment  of  meteorological  stations  the  low  land  should  be  covered  by the program;
-     Collect daily rainfall record for selected storms;
-     Produce isoheytal maps for mentioned precipitation series scale 1:250,000;
-      Based  on  data  from  selected  recorders  and  maximum  annual  daily  data,  rainfall  intensity’ duration relations will be developed;
-     Calculate the average monthly PET with available climatic series;
-      Relation  of average  annual  data  of  precipitation  and  PET with  altitude  will be  assessed.  If possible, relations can be used to estimate average values for areas without climatic stations.
surface water
Estimate the annual runoff in the catchment based on the available precipitation data: Regionalize the flow series based on the rainfall-runoff relation;
- Survey irrigable sites based on available water resources.
Ministry of water resources of Ethiopia
11              Basin development study departmentI I I I 1
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7.2 MATERIAL AND MAN POWER REQUIREMENT
Table 1 Material and equipment requirement for the hydrology section
No.
Item description
unit
Qty
Remark
1
2
3
4
5
6
7
8
9
10
11
12
13
office   with   the   necessary 
facilities
Leveling instrument
Altimeter
Compass
Planimeter
GPS /Preferable pocket size/ Computer         processor         greater speed and capacity
Printer /laserjet/ unintereptable power system
UPS
Personal items
Stationary materials
Topo Map
Vehicle
Set
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Can  be  shared  with  other  sections  in  wate resource group.
For   all   skilled   man   power   which   are participating in the next phase of the sud;
Scale 1:250,000
1   station   wagon   for   super   vision   1   pick for field work
Table 2 Man power requirement
No
Man power
Qty.
Remark
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Senior hydrologist
Hydrologist
Hydrographer
Driver
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3 class driving license and good working experience.
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8. CONCLUSION AND RECOMMENDATION
Hydrology report, 1999
At this level of the study it was tried to indicate the available information regarding water resource of the basin. As it was known adequate information is the access to detail investigation of any basin master plan study. In this respect the Aysha basin has no adequate information^ which can be helpful to execute the master plan study of the basin.
-      Upgrading  the  existing  meteorlogical  stations,  inorder  to  get  better  informations  for  the  next phase of the study.
-     The integrated master plan study of the basin in the future should indicate all the water resource potential of the basin.
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REFERENCES
__________ Hydrology report, 1999 
.
1.  EVDSA, 1990. water resource development Master plan for Ethiopia /water and p consultancy services, India Ltd./, Vol. III.
2.   FAO, 1977. Crop water requirements, food and Agricultural organization and drainage pape 24.
3.   FAO,1997. Irrigation potential in Africa a basin approach.
4.   HALCROW, 1989. Master plan for the development of the surface water resources in the A basin for EVDSA, Addis Ababa.
5.   Lemma Gonfa, may 1996. Climate classifications of Ethiopia, Addis Ababa, Ethiopia.
6.   IGADD, 1990. Forum on environmental protection and development of sub regional strate combat desertification, Vol. II.
7.   WARREDOC, March 1996. International works shop, water resources management in dr prone area, Addis Ababa.
8. WMO, 1994. Guide to Hydrological practices, NO. 168, Geneva.
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Table of cntents
1.
2.
Physical description................................................................
Geology and geological history..............................................
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2.1.
2.2.
2.3.
2.4.
Quaternary deposit...............................................................  3
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Magdala group........................................................................ 4
Amba Aradom formation (upper sandstone)........................... 4
Afar group............................................................................... 4
3.
4.
5.
Hydrogeology of Shinile Zone (Aysha sub-basin)....................4
Water quality................................................................................6
Conclusion...................................................................................71.     Physical description
Shinile is a zone located at the north extreme of Somali regional state. Aysha a small Woreda town, Byo Gurgur, Adigala, Andibiyu and Dewele are small towns found in this zone.
The area lies mostly in the rift valley and is disturbed by uplifted sedimentary and latest volcanic  hills. The plain is  covered sometimes  by  bushes  and at other times  by  grass  and termite hills  as  it was  observed on the way  to Dewele area.
2.     Geology and geological history
Aysha basin is covered mostly by Magdala group and quaternary deposites. The  geological  history  of  Aysha  basin  begins  with  the  uplift  of  the  Ethiopian swell that was followed by eruption of the trap series and much later by rifting. Quaternary marine deposits are known along the Red sea Coast, the Danakil depression  (in  the  rift  valley).  The  property,  location,  and  rock  types  of  each series and formation is described as follows.
2.1,    Quaternary deposit.
It covers the plain area found South of Aysha and East of Jijiga area. The main formation of the coral reefs includes fossiliferous limestone with minor clastics of conglomerates, sands, silts and clays (Tesfaye Chernet, 1993). This formation is the latest of all that were deposited in the basin.
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Conglomerates, sands, silts, clays, reef limestone
Afar group Basalt, subordinate acid lava, and ignimbrites
Magdala   group,   Rhyolites,   trachites,   trachytic   tuffs   ignimbrites; agglomerates, basalts
Amba Aradom formation, clay, silt, sandstone conglomerate x
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As   observed   in   the   stratigraphy   shinile   area   has   more   young   deposits   when compared to Jijiga area.
2.2.      Magdala group
The   Magdala   group   consists   of   Rhyolites,   trachytes,   trachytic   tuffs,   ignimbrites agglomerates, and basalts.
2.3.     Amba Aradom formation (upper sandstone)
It is  comprised of lower cretaceous  deposits  including clay, silt, sand stone & conglomerate (Geological map of Ethiopia, V.kazmin 1972). The sandstones are variegated quartzose sandstones  of fluvial and/or littoral origin (60-150m). Amba Aradom formation is  a cliff forming, highly  laterized formation (Tesfaye Chernet, 1993).
2.4.     Afar group
This group includes basalt, subordinate acid lava, and ignimbrites. It is found
mostly in the shinile zone. The ignimbrites are well jointed in most cases and massive in some cases. It belongs’ to the upper tertiary period. (Geological
map of Ethiopia, V. Kazmin, 1972).
3.     Hydrogeology of Shinile Zone (Aysha sub-basin)
When  referring  to  the  Northern  part  of  Somali  regional  state,  there  are  three main formations in the Shinle zone covering most of the area.
The Afar group covers  large part of the dry  basin area in Shinile zone. It is dissected mostly  by  East-west trending faults  and occasionally  north-south trending faults (Geological map of Ethiopia, V. Kazmin, 1972).
This   series   includes   basalts,   ferrobasalts,   Hawaiites   with   some   silicic   centres near the top, and interbeded unconsolidated sediments (in a total of up toabout 1000m). Because this  basalt is  fresh and highly  jointed, it naturally  has a high degree of permeability. It also has  a high productivity  where recharge and topographic  positions  are favourable. A borehole 60-km south west of Aysha yields 5 l/sec with a draw down of only 0.7m (Tesfaye Chernet, 1993)
The Amba Aradom formation is  the second largest formation that is  highly lateritized, in some places  in the north like in the area around Hagere Selam where it acts  as  an aquiclude below the Tertiary  volcanics  and causes  a spring line in between.
In other places  where it is not lateritized it has  high permeability  and produces a large number of springs  at its  contact with the underlying shales. In the southern and eastern parts  of the country, the upper sandstone (Amba- aradom formation) doesn’t show lateritization and is  an aquifer of high productivity  (mostly  producing springs). Its  high permeability  is  a result of moderate to coarse grain size, loose cementation & limited shale intercalation.
The quaternary  deposit found south of shinile doesn’t cover the area continuously. It consists  of limestone with a high primary  as  well as  secondary porosity and permeability.
The  clastics  of  conglomerates  and  sands  can  also  be  important  aquifers  if found with a considerable thickness and cover large area.
According to the Hydrogeological map of Ethiopia, 1993; there are three major aquifer subdivisions. Extensive aquifers  with intergranular permeability, extensive aquifers  with fracture and/or Karistic  permeability, main geothermal areas  with common occurrence of thermal ground water in fractured volcanic rocks  and subordinate unconsolidated sediments. The first type of aquifer has high productivity. It covers  the southern and eastern part of Aysha town. Most of this  formation gives  a ground water with total dissolved solids  ranging from 500 PPM to 1500 PPM.
From the wells drilled from 1972 to 1986 only 50% of them are successful and is  supplied by  these wells. The average depth of these wells  is  90m and the average yield is 5.96 l/s. The deepest well drilled in the Zone is 133m found at.
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In  addition  leaching  of  rocks  by  percolating  ground  water  is  the  source  of  high dissolved solids.
This reaction increases where there is young activity volcanic or where the
crust is thinner.
5. Conclusion
Well drilling in the region started from 1957 and went on up to the late eighties as  the inventory  depicts. This  shows  that the well inventory  is  done before 1990. Therefore, it should be done on all wells found in the region.
This  applies  to the pumping test of wells  in the region too. There were only limited test pumping results  shown on the well logs. It is  known that test pumping results can help to find the safe yield of a well.
Hydrogeological map of Ethiopia shows  the general condition of the ground water of the area. Fissured basalt and quaternary  Alluvial deposits  are the main rocks covering large part of the area with some subordinate deposits.
As  it is  clear from the conclusion, the ground water resource is  not assessed in an organised manner covering the entire region. Therefore, the next phase of investigation should be done to estimate it.
□     It  is  important  to  do  aerial  photographic  interpretation  to  identify  lineaments and fractures. This can be combined with original hydrogeological maps.
□     The   well   inventory   for   each   town  including  hand  dug  wells  and  springs should be done.
0   To   know   the   litho-stratigraphic   condition   and   identify   the   water   bearing formations   it   is   useful   to   do   geophysical   survey.   Even   though   it   is   not sufficient    to    do    the    survey,    electrical    sounding    seismic   and    electrical profiling are chosen for hydrogeological purpose.
□       Prepare    contract    document    for    additional    test    well    drilling    and    test pumping
.’ ?Perform pumping test and drill deep wells where there are no representative boreholes to be test pumped.
The water resource of the area should be estimated and water chemistry analysis should be made. Thus, it is very useful to collect the representative water sample of wells and then send to the laboratory. Hydrogeological map preparation of the basin.
Finally the report compilation should be made.
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TENSIVE AQUIFERS WITH INTERGRANULAR PERMEABILITY | High productivity
Moderote productivity
HYDROGEOLOGICAL               SYMBOLS
_____
Faults
TENSIVE AQUIFERS WITH FRACTURE AND/OR KARSTIC PERMEABILITY High productivity
- - - - - -  > Groundwater movement,inferred direction
Disappearance point of intermittent stream
TENSIVE AQUIFERS WITH
High productivity
Lov productivity
FRACTURE   PERMEABILITY
CALIZED AQUIFERS WITH FRACTURE AND INTERGRANULAR PERMEABILITY Lov productivity
IN GEOTHERMAL AREAS,COMMON OCCURENCE OF THERMAL GROUNDWATER FRACTURED VOLCANIC ROCKS AND SUBORDINATE UNCOISOLIDATED
Moderate or high productivity
BASE INFORMATION
— — International boundary - - - - - - - - Basin boundary
- - - - - - - -  Road
- - - - - - - -  River
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FEDERAL DEMOCRATIC REPUBLIC OF ET
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Logistics and Man power
Table 3 The manpower, equipment and logistics of the project in the next phase
Man power
Item
Personnel
Amount
Man month
1
Remote sensing expert
1
2
Water quality expert
1
3
Hydrogeologist
3
4
Geophysicist
2
5
Driver
2
Equipment
Type of equipment
Amount
1
Stereoscope
1
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2
Compass
3
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3
Altimeter
3
4
GPS (Navigation)
3
5
Water Bottle
3
6
Hammer
3
•
7
Latest Computer with accessories
2
8
Field water sample analysis 
kit
1
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9
Resistivity instrument
1
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10
Seismic instrument
11
Land cruiser
2
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Soft wares
-
Type of equipment
■ • ‘-A
Amount
1
Satellite image processing
1
2
Resistivity interpretation
1
3
Seismic interpretation
1
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Water quality analysis
1
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Ground water flow modeling
1
Field equipment
Type of equipment
Amount
1
Tent with accessories
3
2
Generators
2
3
Air fan
3
4
Bed
35
Mattress
3
6
Sheets
3
7
Pillow
3
8
Blanket
3
9
Gas lamps
3
10
Paratrooper shoe
2
11
Gowns
2
12
Umbrella
3
Other
Amount
1
Topographic Maps
Covering the
area
2
Arial photographs
Covering the
area
3
Satellite imagery
Covering the
areaTentative work schedule of Dry Basin in Somali Regional State
Figure 3:             Tentative work schedule for Somali Regional State
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'•References
1.  Geological map of Ethiopia, V. Kazmin, 1972.
2.  Hydrogeological map of Ethiopia, Tesfaye Chemet, 1998
3.  Hydrogeology and Water Resources of Ethiopia, Tesfaye chemet, 1993
4.  Managing and Developing the Southeastern Rangelands, Richard Woodroof.
5. South Eastern Rangelands, Livestock Development Project, AGROTEC, 1974.Ministry of Water Resources, Basin Development Study Department
Aysha Basin Reconnaissance Phase Study
THE FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES
AYSHA BASIN RECONNAISSANCE PHASE MASTER PLAN
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A- Hydrolog'
B- Hydrogeology_________ i C-Dams & Hydropower]
D-Irrigation
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AYSHA BASIN INTEGRATED DEVELOPMENT MASTER PLAN PROJECT
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■■1.         Introduction
1.1        General description of the project area------------------------------------------------ 3
1.2         Objectives  of  the  storage  reservoir  and  hydropower  reconnaissance  —  3 studies
2.          Previous Studies---------------------------------------------------------------------------------------- 3
3.          Water Resources---------------------------------------------------------------------------------------- 4
3.1       Surface water----------------------------------------------------------------------------------  4
3 .2      Sub-surface flow--------------------------------------------------------------------------------  4
3.3        General Consideration in hydropower development and data needed— 5
4.          Detailed work program for the second stage investigation — -------------------------------------- 5
5.          References-------------------------------------------------------------------------------------------------  6Aysha Basin
I. 
Introduction
1.1 
General
The Aysha Basin is located in the Northern parts of Somalia national regional state. 
The Ethiopian side of the basin has a catchment area of about 4,312 km  The eastern 
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bounding of the basin is Djibouti Republic and the test Surrounded by Awash Basin.
Like Ogaden basin, Aysha basin contribution to the countries water resources is negligible. 
The basin has arid climatic conditions and doesn’t have any perennial streams but there are seven dry streams. The mean annual rainfall of the basins is below 400 mm and the
evaporation estimated to be above 2000mm per year.
The topography of the Aysha basin is flat with the elevation ranging from 1714 m.a.s.l on 
the high lands where Biyo Kobe and Biyo Gurgus dry streams commencing place and 450 
m.a.s.l. in the low lands near Kakle dry lake.
1.2       Objectives of Storage Reservoirs and Hydropower Reconnaissance Studies
1.        Collection of previous Studies and data such as existing study reports on water resources of the basin, topographic maps with the available scale, transmission line
and power Station etc.. 
’ *      ■
2. 
Review and examination of for all possible reservoir and hydropower sites.
3. 
Making use of existing hydrological study and geological study
4. 
After the preliminary analysis, inventory of existing and potential storage reservoirs
on main rivers and tributaries will be considered to get a first hand knowledge of
the sites using topo maps field trips to accessible dam sites.
5. 
Based on the above activities, accessibility, distance to the national grid for
hydropower projects, and identification of possible dam sites in the basin.
6. 
Preparation of detailed work program for the second stage investigation.
2.        Previous Studies
Preliminary water resources development Master Plan report for Ethiopia. (EVDSA 1990). The study carried out by WAPCOS (Water and Power consultancy Services). In this desk study Ogaden basin was grouped with the Aysha and Danakil basin based on arid climatic conditions.The three basins, i.e. Ogaden, Denakil and Aysha basin were mentioned together in the study as “the Eastern Basins.
The study was conducted based on topographic maps 1:250:000 scale of the
basins. This study which was not supported by a field trip to the actual basins
failed to indicate contribution of individual basins to the water resource potential
of the nation. This situation and the consideration of the three separate basins as a
single entity shows- that the study could not conform to the standard required for master planning.
3         Water resources
3.1      Surface water
During the field visit no suitable dam site has been identified. The topographic
maps available for the purpose of this study were of the scale 1:250,000 survey, 
which is for too small a scale to be of much practical use for dam site selection for
the determination of the small-scale reservoirs and dam site potential areas the
1:250,000 topographic maps with the contour line interval of 100m, cannot be
used instead a 1:50,000 mapping is the minimum requirement for this purpose.
To develop the available water resources, which is excess run-off from rainfall in 
the rainy season, river courses have to be blocked in suitable places, forming 
reservoirs from which water can be drawn for drinking and small scale irrigation in 
the dry season.
Therefore, the study could not come up with small scale reservoir and potential dam sites.
For the purpose of irrigation, and hydropower development in the basin, no dams
would have to be considered. There are some strong evidences that there may not
be suitable dam sites. However, these conclusions from Such short field visits may 
not be decisive, the main limitation to reach final conclusions at this stage being 
again the availability of suitable topographic maps and hydrological data. When this becomes available, the (non-existence of suitable dam sites would be verified.
3.2. Sub-surface
During the reconnaissance field trip it was observed that the dry stream called Biyo Kobe is wade type. According to the observation during the visit, the local people
use the sub-surface flow by using hand dug wells on the stream channel.
Where rainfall is seasonal and erratic building sub-surface flow dams can be a good alternative for water resource development the more common reason for damming
4sub-surface flow is to store water below ground level in the reservoir upstream of
the dam. As indicated in the above paragraph, topographic map and hydrological
data available to the study was not the required scale to enable to identification 
potential sites for sub-surface water development. It is however, thought that sub
surface dam development is the most economical and technical way to provide
water for rural water supply and small scale irrigation development in arid and 
semi-arid region.
3.3       General consideration in hydropower development and data needed.
There are two ways of developing hydropower potential. The first
is to divert the river flow and develop run-off-river type hydropower, and 
the second is through the construction of a dam for storing water. Run
off-river type hydropower development cannot be developed on the rivers
found in Ogaden basin. Because, the rivers are flowing in the wet months
of the year only for a few days. The remaining option thus is developing 
hydropower through storage.
To develop hydropower through a storage scheme the following points
should be taken into account.
I Availability of suitable dam sites:- Dam sites can be identified either form
small scale topographic maps (1:50,000) or/and by field visit. The existing topographic map of the Ogaden basin, however, is of large scale 1.250,000 
and identifying dam sites reliably is impossible based on this map. The
expert visited the Aysha basin in July 1999. Possible dam sites have not
seen in the Basin.
2. Assessment of stream flows:- Due to the absence of Hydrological gagging 
stations in the basin, there is no a data of estimated annual sediment yield 
for catchment and monthly stream flows of the rivers.
Conclusion
Due to the fact that rainfall concentrated to a few days of the year only and it is
amount also very small, catchment area of the streams are very small, so perennial
streams exist, there-to those stream diversion as a basis for year-round irrigation development is not possible
Due  to  shortage  of  water,  sedimentation  problem  and  unavailability  of  suitable  dam sites development of hydropower in the basin seems unlikely.
Detailed work program for the Second Stage investigation1.        Sites already identified and studied should be checked on aerial photographs and with helicopter surveys. Various characteristics of the sites will be analysed using appropriate maps, including hydrology, reservoir characteristics, potential generation capabilities in relation to other projects (irrigation).
2.         Assessment of demand and load forecast for export potential
3.         Collection of information on sub-surface flow dam in the basin for water supply purpose.
4.                     Sites will be ranked, taking into account preliminary cost per KWA, benefits for other projects, distance from load centre etc.
5.         For the attractive sites, assessment geological and geotechnical properties affecting design of dam, power house and sub-surface dam will be made.
6.        For previously studied sites, assessment and updating’of existing data will be made.
7.         For the selected sites mentioned above, more detailed studies will be including preliminary designs and costing of dams rules house, sub-surface dams and accessibility.
8.         carryout seismicity, tectonic, geophysical survey for foundations at proposed dam sites.
9.         Investigation for construction materials.
•, •....
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References
WAPCOS preliminary water resources Development Master Plan Report for Ethiopia (EVDSA, 1990). In this desk study the three basins Aysha, Danakil and Ogaden named as the Eastern basin.Ministry of Water Resources. Basin Development Study Department Aysha Basin Reconnaissance Phase Study
THE  FEDERAL  DEMOCRATIC  REPUBLIC  OF  ETHIOPIA MINISTRY OF WATER RESOURCES
AYSHA BASINRECONNAISN
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V oiunie IV: Water resources
A- Hydrology
B- Hydrogeology
C~Dams & Hydropower
P-Irrigation,~r
Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
Table Of Contents
Abbreviations
1.  Introduction.
2.   Back Ground. 
3.    Objectives
4.    Study Approach & Methodology
5.   Institutional & Policy Aspects....
6.   Need For Development
7.      Description Of The Study Area 7.1. Location & Accessibility ....
Page
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7.2 Topography & Land Feature
7.3    Climate.................... ...................... .............
7.4    Water
Resource........ 
7.5
7.6
7.7
AGRICULTURE, LAND USE & LAND COVER..
Soils..................... ........ ...............................
Socio- Economic Aspects .............. ...........
8. Existing Irrigation Development Practices
9. Potentials For Irrigation Development
Possible Areas Of Small Scale Irrigation Development Sites...
10.   Previous Studies Reviewed
11.  Data Gaps Of The Study  
12.   Conclusion & Recommendation 
13.   Annexes
I.   Field Trip Report.
II.   Terms Of Reference For The 1st Phase Study 
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14.  References.
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15.   Map
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Ministry of Water Resorces River Bsin Development Studies DepartmentAysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
ABBREVIATIONS
1.   APS
2.   CECE
3.  CO-SAERAR
4.   EHDA
5.   ESRDF
6.   EVDSA
7.   ha
8.   Ips
9.   Km
10. L/s
11. LWF
12. m
13. m.a.s.l
14. mm
15. m3/5
16. MOWR
17. MO A
18. NG0
19. NRDEP
20. PET
21. REST
22. SERP
23. SCF
24.  SAERT
25. WAPCOS
26. WWCE
27.   WWDSE
Agricultural Projects Study.
Concert Engineering & Consulting Enterpris
Commission For Sustainable Agriculture &
Environmental   Rehabilitation   for   the   Amhara   Region East Hararge Development Agency.
Ethiopian Social Rehabilitation & Development Fund. Ethiopian   Valleys   Development   Study   Authority Hectar.
Industrial Projects Study
Kilo meter
Litres per second
Lutheran World Federation
meter
meters  above  sea  level
milli   meter
meter cube per second 
Ministry of Water Resources
Ministry of Agriculture
Non governmental organization 
Natural Resources Development & Environmental Protection 
Potential Evapo-transpiration 
Relief Society of Tigray 
South East Rangelands Project
Save the Children Fund
Sustainable    Agriculture    &    Environmental Rehabilitation for Tigray
Water and  power Consultancy  Service Water Works Construction  Enterprise Water Works Design & Study nterprise
Junuary2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
1. Introduction
This study  report is prepared  as the result of the reconnaissance study  conducted  by  the Ministry  of Water Resources,  River Basin  Study  Department under its recently  launched project, the Dry Basin Study Project. The project carried out this study program from June
1999  to  Dec.  1999.  This  reconnaissance  level  study  is  one  of  the  first  consecutive  studies  to be  conducted,  in  view  of  preparing  the  final  master  plan  for  the  basin.  And  as  part  of  the many  integrated  development  studies  incorporated  in  the  study,  this  particular  study  report deals with the irrigation & drainage part.
The study  in  general attempts to  give the required  answers in  response to  the issues given  in the Terms of Reference.  Accordingly,  it briefly  describes the back  ground  and  objectives of the study  in  the first section  followed  by  the description  of the methods applied  in  carrying out the study.  Institutions involved  in  the development of irrigated  agriculture and  the policies set by  the government concerning  irrigation,  are also  pointed  out.  Following  this,  all previous studies found  available are briefly  reviewed.  The detail description  of the study area is given  including  the location,  topography,  climate,  water resources,  land,  and  the socio-economic conditions.  Most important of alL  the potentials of the area for irrigation development as a pre- liminary  identification  together with  the existing  irrigation  practices currently  undertaken  in  the area are shown  & described  in  detail.  The last pages of the report show the data gaps found  and  suggested  means of filling  these gaps,  followed  by  the general conclusion & recommendations given at last.
The field visit report and Tor is also annexed.
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.. - v. January 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report_________________  2
2.  Back Ground
In  arid  and  semi-arid  areas of the world,  where the annual rainfall is not sufficiently available,  agriculture can  not be dependent on  the direct precipitation- Such  areas suffering  from shortage of rain  fall have therefore been  practicing  the art of irrigation  to make agriculture dependable and  productive business.  The world  has witnessed  the existence of irrigation  practice to  have a long  time history  recorded  since the beginning of civilization.  It is however,  a recent experience in  Ethiopia which  started  around  1960 in  a modem way  at larger scale level,  although  a few small scale traditional irrigation has been  practiced  some years before.  Currently,  not more than  190,000  ha of land  is irrigated  in  the country  which  accounts only  about 4% of the total estimated  potential irrigable area of 3.5to 4 million ha.
The  Aysha  basin  is  the  smallest  of  all  other  basins  of  the  country  with  estimated  area  of about 2,220 km2
The total basin  area is characterized  by  low rainfall,  high  evaporation/ evapo transpiration,  low or poor soil fertility  and  no  or little surface water resource which makes irrigation difficult.
In an area where agriculture is the only economic activity and means of survival, like
the region in focus, and where rainfall, the most required input without which 
agriculture can not succeed, is very scarce or totally unavailable throughout the year, 
irrigation will be the only alternative for development.
On  the other hand,  water as the most important resource for applying  irrigation,  must be available at any  accessible or obtainable location  with  regard  to  the land  to  be irrigated.  With  this regard,  the Aysha basin  is however,  not endowed  with  all the resources in  question  in  order to  apply  irrigation  for the agricultural activities carried  out in  the area.  Inhabitants of the basin  area are entirely  engaged  in  a pastoral life,  rearing of cattle.  Therefore,  the land  in  this area is mainly  to  be used  for the growing  of pasture, although most of it is considered unutilizable barren land.
• • ’ - •’ ■■
__________________________________ ___________
Ministry of Water Resorces River Bsin Development Studies Department Junuary2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
In  search  of relevant informations and  data related  to  any  development of irrigation  in  the basin  this study  has carried  out more or less sufficient investigations and  collected  as much data as possible.
Among  the many  developments constraints or reasons for being  unable to  utilize the resources Ethiopia possesses,  lack  of development master plan  is the one to  mentioned. The Ministry  of Water Resources as a responsibled  government body  with  this regard  is mandated  for the study  and  preparation  of integrated  development master plan  for each river basins of the country.  Most of these basin  studies have been  accomplished  in  the past few years and  recently  such  a study  for the dry  basins is launched.  The so  named  ‘ dry basins ‘ is consisting  of the three separate basins namely; Ogaden  ,  Aysha and  Danakil which are all located in the eastern areas of the country.
3. Objectives
As part of the dry  basins integrated  development master plan  project,  this study  has its major objective of conducting  a reconnaissance survey  in  the field  of irrigation  & drainage in the Aysha basin.
Of  the  intended  three  phase  studies  to  be  conducted  consecutively,  this  study  is  the  first phase study and is aimed at accomplishing the following tasks
-  To collect all existing information & data on previous studies and 
existing schemes regarding irrigation development in the basin.
-  To conduct a physical observation at all accessible areas of the basin and assess
the potential land & water resources with respect to irrigation development.
-To identify all potential sites suitable for irrigation in the basin
including  all  alternative  methods  of  water  abstraction  for  each  proposed  schemes, based on the field assessment and map observation.
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Ministry of Water Resorces River Bsin Development Studies Department
Junuary 2000
--------------- -Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report_________________  4
4.        Study approach & Methodology
In  accomplishing  the study  at this level,  two  major approaches,  the field investigation  and  office level assessment methods were used.  Prior to  the field  visit, an  office level assessment was carried  out in  search  of all available documents (Previous studies, maps, etc.) that are relevant to the subject of our study.
In  this office level study,  activities such  as,  collection  of data & information  from available studies of previous years,  reviewing  of these study  documents, investigation  of potential sites from available topo-maps of scale 1:250,000,  etc. were thoroughly  undertaken.  Under this circumstances,  several governmental or non-governmental offices at Addis Ababa that are expected  to  operate in  the area in study  or super vision  of relevant projects,  were contacted  to  obtain  the required  data and  informations.  However,  not much  information  was obtained  except one brief note from one of the river basin  studies conducted  previously  by  WAPCOS of India, in 1990.
After the office level assessment has been  accomplished,  the field  assessment program was then  launched  to  take*  a physical observation  of the basin  and  collect first hand  information  & data from relevant offices and  local people in  the area.  In anticipation  to  this field  visit,  questionnaires were prepared  inorder to  generate all required  informations from the available sources.  Using  these questionnaires and through  other informal discussions,  informations were gathered  from various responsibled  regional office authorities and  professionals.  However,  the field  visit
for direct physical observation of the basin was accessible.
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made only to areas that were
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Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
6.  Institutional & Policy Aspects
5
A relevant legislation  so  far,  as regards water resource utilization  in  Ethiopia is issued  in proclamation  NO.  92\94.  The proclamation  contains statements concerning  regional and  central government responsibilities on  water resources; which  applies to  all water resources,  surface or underground  with  the exception  of mineral waters and  geothermal deposits.  It also  demarcates the responsibilities of the central and  regional governments in administering water resources.
The central government (the Ministry  of Water Resources) is delegated  as the appropriate body  for the administration  and  management of all transboundary  rivers and  water that flows across or lies between  more than  one regional government The regional Water Mines and  Energy  Bureaus,  on  the other hand,  are responsible for administering  the water resources existing  within  their respective regions including tributaries to  trans-regional rivers.  It is also  indicated  that utilization  of trans-boundaiy rivers shall be governed  by  international treaties.  Utilization  of tributaries of trans- regional or trans-boundaiy  rivers shall be dealt with  specific directives to  be issued  by the council of ministers.
According  to  the proclamation,  a permit issued  by  the appropriate authority  (Ministry  of Water Resources or Regional government bureaus shall be required  to  use water resources for irrigation  and  others.  A permit holder has to  pay  water fees and  charges for different consumptive uses and  has the obligation  of using  the water onlv  for the authorized  purpose without causing  harm to  the environment Likewise,  the authority has the.  responsibilities of ensuring  the water resources to  be utilized  in  the most beneficial manner,  supervising  permit holders strictly  to  utilize the water in  conformity with  the condition  of permit,  collection  of water charges and  fees and  settling  of disputes arising between permit holders.
Regarding  the  land  issue  the  policy  states  that  both  urban  and  rural  land  are  owned  by the government and will be made available to investors on lease-holding basis.
Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Bacth Master Plan Project Reconnaissance Irrigation & Drainage Report
6
Based  on  the size of land  to  be irrigated,  irrigation  schemes in  Ethiopia are classified into  3  groups,  namely,  large,  medium & small scale.  Large scale schemes include those with  irrigated  area exceeding  300ha,  medium scale schemas include areas between  200 and 3 ha, and small scale schemes are those below 200 ha.
Several national institutions (governmental & non-governmental) are undertaking  the responsibilities of promoting  the irrigation  development activities in  the country.  The following  are concerned  institutions involved  in  the field  of irrigation  & drainage in  the basin (among other responsibilities.)
Central government
I) Ministry of Water Resources
It is responsible in different water resource studies and integrated development master pla preparation for the country’s basins including irrigation development.
ii)  Water Works Design & Supervision Enterprise (WWDSE)
Being under the MOWR, it is responsible for the design & supervision of irrigation schemes in the country.
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iii)   Water W’orks Construction Enterprise (WWCE)
Being under the Ministry of Water Resources, it is responsible for the construction of large & medium scale irrigation schemes.
• •• • •’ •" . ’. . ' • iv)  Ministry of agriculture
Through its agricultural extension department, has limited involvement in small scale irrigation development promotion.
V-
V) Prime Minister’s office, desk of the Somali Region. It is invoked in the
follow up offer the study, design and supervision of small irrigation 
projects, in support of the region’s development activities.
Ministry of Water Kesoroes River Bsin Development Studies Deparmeni-----------------iunuMy2000---------Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report_________________  7
Regional governments:-
Through   the   following   appropriat   bureaus   regional   governments   have   the   respective powers and duties in relation to irrigation development
i) Water, Mines & Energy Bureaus of the regional state of the Somali
This  has  the  responsibilities  of  study,  design  and  construction  of  small  scale irrigation schemes.
ii) Agricultural Bureau of the regional state of the Somali
This has the responsibilities of supervising the operation and
maintenance  of  the  small  scale  irrigation  projects  constructed  by  other  bodies, through their extension workers.
Other NGOs and private investors
Although  no  private sector activity  has been  observed  in  the basin  currently,  any interested  private investor can  participate in  the investment or development of irrigated agriculture in  the area.  One NGO Lutheran  World  Federation  (LWF) is currently operating  in  the basin  in  the study,  design  & construction  of small scale irrigation schemes.
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Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000
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6. Need for Development
In  spite of the significant or dominant role it plays in  the economic sector to  the country, agricultural production  remains to  be at a subsistence level.  As in  all other parts of the country,  crop  or livestock  production  in  this basin  is characterized  by  a highly  rudimentary method  or technique.  The application  of modem agricultural inputs like fertilizer, pesticide,  improved  seed,  e.t.c.,  and  the use of modem farm machinery  & implements are not widely  practiced.  Similarly,  the rainfall in  most part of the basin  especially  in  the lower basin  area,  is inadequate in  amount and  erratic or irregular in  distribution,  and  hence is largely unreliable. On the other hand, agriculture in the basin is mainly rainfed.
For this and  other reasons,  the agricultural productivity  of the area remains to  be very  low. Such  crop  failures coupled  with  the high  population  growth  rate (in  other words,  high  food consumption) will further aggravate the food  deficiency  in  the area or the country  as a whole.  Therefore,  to  avert such  occurrences of food  shortage and  ensure sufficiency  in food  production,  the promotion  of the existing  agricultural practices into  an  irrigated  one, would be inevitable and highly recommendable.
In  addition  to  securing  the food  supply  of the country,  irrigated  agriculture will also  play an  important role in  the supply  of products for local agro  industries and  the production  of exportable items which  will be earning  the country’s foreign  currency  need.  Irrigation development can  also  play  an  important role in  the generation  of employment opportunities and balanced regional development in neglected regional areas.
Ministry of Water Resorces River Bsin Development Studies Department ~ Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report____________ 9
7.   Description of the Study Area
7.1. Location & Accessibility
Aysha basin  is located  in  the eastern  part of the country  and  entirely  included  in  the Somali regional state,  Shinile zone.  The basin  as delineated  on  a topo-map  of scale 1:250,000 is bounded between the geographic coordinates of 10° 10’N to 11° 05’N lat. and 42° 15’E to 42°58’E Long. The distinct boundaries of the basin are Somalia in the cast,  the Awash  basin  in  the west & south  and  Djibouti in  the north.  The basin boundary starts at around 125km north of Dire Dawa on the Dire Dawa-Aysha-Dewele route, and extends north upto the Ethio-Djibouti border.
Regarding accessibility, the basin is in a relatively better position compared to the size of the basin. An all- weather road of about 90 km and the Ethio-Djibuti rail-way line cross right through  the middle of the basin.  Further more,  there are also  some dry weather roads and rough tracks crossing over the basin area in different directions.
7.2   Topography & land feature
The Aysha basin consists largely of a plain topography in the middle section and small scattered  hills in  the north  and  south-east areas.  The northern  part of the basin,  which includes the area starting  from some 20km north  of Aysha upto  the Ethio-Djibouti boundary,  mostly  consist of rocky  & hilly  land  feature with  undulating  topography ranging  between  800  & 1100  masl elevation.  About more than  50km length  between Biyo Kebobe ( a small village 135 km from Dire Dawa) and Adele ( a small Rail way station 15-20 km from Aysha) lies a wide plain topographic land stretched widely left & right.  The elevation  here ranges between  600  & 900  masl.  The southern  part consists of small scattered  hills and  a wide plain  land  of elevations ranging  between  1000  and 1200 m.a.s.1.
The land feature in general is characterized by a nearly flat land on one part and some undulating land feature composing of various dry stream courses dissecting through, on the other parts.
Ministry of Water Resorces River Bsin Development Studies Department           Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Repoi 7.3  Climate
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The Aysha basin  is generally  described  to  have a hot arid  to  semi-desert climatic nature. Although  any  recent or past records of meteorologic data are not available,  a rough estimation is given for someof its elements.
Rainfall being monomodal (occuring once in the year) is generally very low with annual
rainfall amount estimated to about less than 400 mm in most parts of the basin. 
Temperature is very high most of the year. Evaporation similarly is estimated to be high, 
more than 2500 mm per annum.
7.4   Water Resource
Reference could not be made to the hydrologic report of this recent study for it is not yet
produced. Therefore, a short information from the previous study by WAPCOS and a map reading from a 1:250,000 scale topo-map is taken to tell about the water resource potential
of the basin.
According to informations from WAPCOS Study, the surface or ground water yield of the
basin from the point of view of its contribution to the country’s water resource potential is
almost negligible. There is no any perennial river existing in the basin except a few traces
of dry streams that come into life during the wet season. About 7 of such dry streams
known by name are shown on the map. This include; Kobe, Biye Gurgur, Gerbale, 
Lasarat, Seblola, Delad and Debeder, among which the first two are the major ones. All
these dry streams mostly flow along sandy river beds and terminate into the plain sandy 
fields.
The only  water sources available for use in  the community  are these sandy  stream beds.  A shallow depth  digging  on  these stream beds would  produce water that fills the size of the dug  hole.  Perhaps this would  be an  indication  that flow exist in  these stream courses mostly  underground  in  the dry  season.  Therefore,  apart from the wet season  surface flow occurring  in  these streams,  the underground  flow should  also  be considered  in  the full exploitation of the resources available.
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Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 7.5  Agriculture, Land Use & Land Cover
Almost the whole area of the northern part which covers nearly half of the total basin is characterized by a barren sandy & rocky land of rugged topography, some scattered hills with  almost no  vegetation  cover.  The central part characterizes mainly  of a sandy  plain topographic land  with  very  little or no  vegetation  cover.  The southern  part,  however,  is composed of some scattered hills and plain land of some scrubs, bushes and grass cover.
The land in general as already in use (in the southern part) could only be used for grazing and  probably  for crop  production  (if water is made available) while the northern  part is unutilizable.
Agriculture,  although  experiencing  several limiting factors, is however the main economic activity  of the study  area.  Of this activity,  livestock  development is the major one followed  by  small cultivation  of crops.  Only  crops of drought resistant such  as sorghum are grown in a few scattered small size plots.
7.6  Soils
According to the previous study carried out by WAPCOS, 1990, the soils of the study area are described into three groups of suitability level,- marginally suitable, moderately suitable and permanently not suitable.
Parts of the north, north-west, west east & south top areas are classified as N  which is
2
permanently not suitable with several physical limitation for irrigation development. A small part of the central basin and southern areas are classified as S , moderately suitable
2
with some limitation which slightly reduces productivity, medium to fine textured, slope 0-8%, effective soil cover of 100-150 cm, none to slightly salinity & alkalinity and moderate to well drained. The north-east area is on the other hand classified as S3 marginally suitable with moderate to severe limitation which reduce productivity, fine or coarse textured, slope 0-8%, effective soil cover of 50-100 cm, none to moderate salinity & alkalinity and impeded drainage.
Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 7.7 Soc/o- Economic Aspects
j 2
The Aysha basin is totally included in the Somali regional state of the Shinele zone. The area is entirely occupied by the Somali ethnic group. The population cover\distribution\ is generally very low with estimated population density of not more than 20 persons per km2 area.
The economic condition  of the area can  be over-viewed  as generally  poor,  with  low economic resource,  low income,  high  shortage of food,  etc.  The major economic activity is agriculture to which the whole population is engaged. Inhabitants of the area are living a nomadic pastoral life and  are engaged  mainly  in  livestock  herding.  Cultivation  of crops is also rarely practiced.
Infrastructural development and  public services such  as education,  health,  communication, water supply  are generally  poor although  possessing  a better road  & railway  facility compared to other basin. Urban development is almost non-existent except a small sign in the small towns or rather villages of Aysha and Dewele.
Only  a few organizations like Lutheran  World  Federation  are involved  in  very  few development activities such  as in  community  water supply  and  small scale irrigation development.
8.  Existing Irrigation development practices
Except one or two  small scale irrigation,  there is no  significant attempt made to  promote irrigation  development activities in  the basin,  despite the fact that successful development in agriculture could not come true without irrigation.
The Lutheran  World  Federation,  a non-governmental organization,  has designed  two  small scale irrigation  schemes at Biyo  Kebobe and  Semeka which  are currently  under construction.
Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
The project at Biyo Kebobe consists of a sub-surface dam across Kobe stream and diverted for irrigating an area of abt 50 ha land downstream.
The Semeka scheme on the other hand is designed to irrigate about 40ha land by diversion. 
Apart from these two small scale schemes, a few traditional irrigation practices are reported to exist in few localities.
9. Potentials for Irrigation Development
13
Investigation  of potential areas for the development of irrigated  agriculture,  has been  the major objective of this study  as indicated  earlier.  Accordingly,  all possible investigations from the available topo-maps of scale 1:250,000,  primarily  for the availability  of the required  resources,  are thoroughly  undertaken.  Land  & water which  are the primary  and most required  resources for irrigation  development are,  however,  not appropriately available.  Topographically  plain  and  suitable land  for irrigation  may  be available where as none of these areas are endowed  with  the water resource.  But the availability  of land  alone without water cannot be considered a potential irrigation area.
Therefore,  the basin  as a whole is identified  to  be a low-potential area for irrigation development.  However,  the need  for the use of irrigation  in  crop  production  or even  in pasture development in  the area is very  well noticed.  To  make the area self-sufficient in food  production  and  earn  extra income,  the agricultural sector of the economy  which  is for the moment the only  feasible alternative,  should  be promoted.  And  it is only  with irrigation  that sustainable development can  be achieved  in  agriculture in  such  arid  regions. Large or medium scale development in  irrigation  is unthinkable.  However,  small scale irrigation  schemes can  be introduced  in  some selected  areas,  with  the use of the available rain water as source of irrigation water.
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Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
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Different rain  water harvesting  techniques can  be applied  inorder to  avoid  the existing water shortage problems.  It increases the amount of water that can  be available from the only  available source,  the rainfall,  and  satisfies the crop  water requirement of the selected cropping land. With this regard, the following techniques may be suggested.
- Run off farming:- This is a system of farming in arid areas, where that portion of
the rain water converted into surface runoff is harvested from the sloping 
uncropped field in the upland of larger area, and made to flow and stored into the
soils of the relatively smaller area of the cropping land below. The runoff water
is to be collected and directed to the cropping land using bunds and channels
provided in the system or through natural wadis.
-  Micro earth dams:- Small earth dams can be built at appropriate
storage sites to trap and store the small rainy season flow in the wadis and make
use of it for irrigating the down stream selected land.
The   Appropriate   sites   for   applying   the   above   water   harvesting   methods   as   small   scale irrigation practice, would each be identified in detail in the second phase study.
The following  3  sites are indentified  as potentially  irrigable areas.  From these sites about 4300  ha.  of land  is estimated  to  be topographically  suitable for irrigation  if adequate water is to  be supplied  from the corresponding  streams.  However,  since the flow amount of each stream is not known  or availability  of water is never expected  reliable,  the irrigable area estimation  should  not be taken  as a potential figure.  It is only  the topographically  suitable area that can  be commanded  from th  identified  diversion  sites.  In  any  way  these streams may only be capabl e of serving (supplying) small scale irrigation schemes.Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report___________ 15
Possible areas of small scale irrigation development Sites
1. Irrigation from Kobe stream
The Kobe “shet” (stream) is a seasonal stream which appears as a surface flow only in the wet season  of the year but exists as a subsurface flow under its sandy  stream bed.  It originates from the small hills of the southern  basin  border at elevation  1300  mask  and flows north-ward across a wide plain land , crossing the Dire Dawa- Aysha road near the village of Biyo Kobe and ending up into a sandy plain area around elevation 800 m.a.s.1.
A diversion at elevation 1050 m.a.s.1. would have a potential of irrigating about 1300 ha. of plain  land  down  stream on  both  sides of the banks.  As an  alternative,  a dam site (mostly of a sub-surface dam) may be proposed down stream at elevation 950 m.a.s.1 near Biyo  Kobe to  store both  surface & sub-surface flow and  make available a dependable water source for irrigating the down stream field covering an area of about 3200 ha. But currently construction of a diversion scheme is undergoing for the purpose of irrigating 50 ha- of land.
2.  Irrigation from Biye Gurgur
Biye Gurgur shet is a small stream originating  from a similar (very  near) area where Kobe originates and  flows north  ward  parallel to  Kobe crossing  a large plain  area which finally ends into the Ethio-Somali border.
The stream may be diverted at elevation 950 masl near Biye Gurgur village to irrigate an area of about 2700 ha downstram on the right bank of the stream.
Ministry of Water Resorccs River Bsin Development Studies Department Junuary 2000 
‘ A ’Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 3. Irrigation from the other streams
16
The other dry  streams shown  on  the topo-map,  namely; Gerbale,  Lasarat,  Seblola, Delad and Dcbcder arc all small in size and flow across the unsuitable soil areas and thus no irrgation is expected from them. Only Gerbale may however be able to irrigate an area of about 300 ha. if small to medium storage dam is to be built
10.      Previous studies Reviewed
Except one study  document prepared  by  WAPCOS ( Water and  Power Consultancy Services) of India,  1990,  no  other document was found  available for review.  In  this study , only a very brief information in not more than one page, is shown about the general situation of the basin.
The source document entitled as “A Preliminary Water Resource Development Master Plan for Ethiopia ” Vol -II Main Report by WAPCOS & EVDSA, 1990, produced a study report, combining the three basins (Ogaden, Aysha & Danakil ) in one report as “Eastern Basins”. This report briefly describes the Aysha basin as an arid area with an almost negligible water resource or irrigation potential.
The study generally lacks sufficient data & information and detail descriptions about the basin, thus not reHable.
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Ministry of Water Resorces River Bsin Development Studies Department         Junuaiy 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
11.  Data Gaps of the Study
17
As indicated  earlier,  one of the major objectives of this study  is the collection  of data from the study  area.  It is evident that these data are not sufficiently  obtained  as required,  and  hence data gaps were made in  the overall study  result.  This is because the field  visit was not carried  out as intended  & planned  and  first hand  information could  not be gathered  right from some parts of the basin  area.  Secondly,  the data obtained  or expected  to  be obtained  from the regional offices and  existing  study documents were not satisfactory ones.
Therefore,  it  is  inevitable  that  gaps  could  be  made  in  the  data  collection  of  this  study. These include:
- Lack of topographic maps of the basin area( Scale 1. 50,000) These maps
were very essential for detail investigation and extraction of more dependable
data on the basins physical features. More over, better identification of sites
for recommended micro earth dams or other rain water harvesting, could be
made at least with such large scale maps. Although these 1: 50,000 scale maps
are not still appropriate for identification of small scale development sites, 
they give at least a better view of the area.
As a means of filling this data gap, a request has to be made to the National
Mapping  Agency  of  the  making  of  the  required  scale  maps  of  the  basin,  since they are not available at the moment.
- Lack of a full field observation data Since the field observation (a field visit
in the basin) has not been fully carried out due to its inaccessibility and security problems, the required field date were not collected sufficiently.
This gap shall be filled in the next phase study when accessibility is improved and security confirmed. An aerial field visit (with a helicopter flight) can be made if accessibility will remain a constraint.
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Ministry of Water Resorces River Bsin De^lopment StafesDqrsrtment----------- ~Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
18
- Incompletion of data gathering & compilation from related study 
sectors.
Data that are relevant to the irrigation & drainage study, but which are to be obtained from other study sectors, such as data on soil suitability (from soil study), water availability & quality (from hydrology), crop suitability(from agriculture) etc. are not yet collected.
These will be collected and reviewed in relation to irrigation & drainage aspects, in the next phase study.
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Ministry of Water Resorces River Bsin Development Studies Department
Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report____________  19
Conclusion & Recommendation
The study results shown above reveal that the whole basin area is in great shortage of water resources.  This water shortage problem coupled  with  the severe climatic condition of the area, has made irrigated agriculture somewhat difficult. However, the availability of such vast & topographically suitable land could be utilized for cultivation 
of  crops  and  pasture  if  every  effort  is  made  to  make  use  of  the  available  water  for irrigating it in any possible technique.
According  to  the estimated  climatic information of the basin, rainfall amount is very small, not exceeding 400mm at average, and even worse than this in the far northern parts which  is less than  200  mm.  This amount occurring  in  .an  enatic distribution pattern,  is never to  fulfill the evapotranspiration  demand  of any  crop  intended  to  be grown in the area. The potential evapotranspiration of the area, estimated to be more than 2500 mm perannum, is much more than the annual rainfall amount.
The only means of converting this small amount of rainfall into a useful resource, into something  that could  be sufficient for growing  crops,  is by  applying  a rain  water harvesting technique. In doing so, the amount of water collected from an area will be made to  flow concentrated^ over a smaller area of crop  land  and  stored  in  the soil profile to be used by the crop until the next flood comes.
In general, the study has come up with a conclusion that the total basin area is identified to be a low-potential irrigation area in large or medium scale level, due to mainly of water constraint. Except two or three dry streams, no significant stream flow has been identified.  Probably  some wadis and  dry  sandy'  streams,  where underground (subsurface) flow occur, could exist in many parts of the basin.. A short period surface flow in the wadis may be observed only in the wet season while the subsurface flow may stay until the dry season period.
Therefore, the existence of such areas could be accounted for the suitability of spate irrigation or run off fanning system, and reservoir irrigation using micro-earth dams and sub-surface dams.
Ministry of Water Resorces River Bsin Development Studies Department                January 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
As  a  conclusion,  the  basin’s  potential  for  irrigation  development  is  limited  to  only  small scale level, where the source of water would be made available from either;
i)  Diversion of spate flow in the wadis or other rain water harvesting 
techniques.
ii)  Construction of small storage earth dams on existing dry stream
courses for intercepting and storing the wet season surface flow.
iii)  Construction of small sub-surface dams for intercepting and storing 
the sub- surface water flow in the sandy stream beds.
iv)  Construction of wells for extracting the ground water resource.
It is therefore recommended  that the above water development techniques be applied inorder to  make the required  water available for the intended  small scale irrigation schemes.  Investigation  of suitable areas from larger scale maps,  such  as 1:50,000  should however be undertaken in the next phase study.
Since the overall population of the area is largely bound to a nomadic pastoral life and the land is mainly suited for or classified as pasture land, development in this field will be given the priority. Therefore pasture land irrigation using the above mentioned water harvesting techniques can be practiced for improving the range land condition of the area. 
It had earlier been described that adequate field visits have not been carried out due to problems of security & accessibility. Therefore, serious attention must be paid to a reconsideration of a field visit program using vehicles or helicopter in all important and possible visiting sites of the basin for better observation and data collection.
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Ministry of Water Resorces River Bsin Development Studies Department
Junuary 2000—-W
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Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report------------------------------------------- 21
Field Trip Report
1.   Introduction
1.1   General
To  properly  develop  and  utilize a country’s resources,  development master plan  is very essential.  In  this regard,  the Ministry  of Water Resources,  given  the responsibility  of studying  and  preparing  master plans for the country’s river basins,  has been  doing  its best on  the preparation  of integrated  deveopment master plan  for many  of the river basins. Similar program has been  launched  recently  for the Aysha basin.  Since the master plan preparation  is intended  to  be accomplished  in  three phase studies,  the first phase or the reconnaissance level study is one of these phase studies which this field trip is committed
to.
This report deals with  the irrigation  & drainage aspect of the basin  considered  as one study sector among  the many  others in  the program.  The report will briefly  show the overall activities conducted,  local areas visited,  institutions and  individuals contacted,  etc while staying at field.
The field trip was carried out from 18 June. 1999 to 28 July. 1999 which totally took about
20   days.   This   field   program   generally   covered   only   those   visiting   sites   that   are   accessible by  vehicle.  Since  one  of  the  objectives  of  the  field  visit  is  to  collect  required  data  from  the main  data  sources  ie  the  regions,  all  the  regional  &  zonal  offices  which  are  included  in  the basin  are  visited.  Likewise,  existing  rivers  of  the  basin  and  their  adjacent  land  are  visited 
wherever accessible. 
.
The trip was conducted in group consisting of four members of different professions.Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report___________________ _____ 22
1.2  Group members
The group members participated in the field trip consist of the following staff of the project.
1.  Wubishet Alemayehu
2.  Belay Tegegne
3.  Abinet G/Medhin
4.  Eyilachew Yitayew
1.3     Purpose of the trip
Irrigation & drainage Engineer Dann of Hydro power Engineer Geo-technical Engineer and infrastructure Emgineer
Geologist
As a partial fulfilment of the terms of reference prepared  for the irrigation  & drainage sector of this reconnaissance study,  the purpose of this trip  was in  general to  conduct a preliminary visit to all accessible parts of the basin. The particular purposes includes
-  Visiting and collecting informations from all regional and zonal offices found in the basin, regarding all existing studies and project activities in the area of irrigation and drainage
-  Taking a general view of the basin through physical observation of the resources available.
-  Identifying potential sites for irrigation & drainage projects in the
basin and justify the map identification for the proper location of both diversion dam sites on the rivers (water sources) and adjacent irrigable land.
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Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
2.  Activities conducted
Being arranged as a reconnaissance visit to all accessible parts of the study area, the field trip has come up with the accomplishment of several important activities. The major activities of the trip may briefly be described as follows.
- Visiting of government offices involved in the field of irrigation & drainage works in the basin. The regional and zonal offices were visited and discussion held with concerned officials inorder to obtain required data and informations on existing irrigation schemes and newly proposed or ongoing project studies within the basin.
- Assessment of other non-governmental and private organizations which are involved in the study and construction of irrigation schemes at regional & zonal levels.
Conducting of discussions with indivdual farmers involved in irrigation activities.
- Physical assessment of all accessible irrigation potential sites that have earlier been identified from the available topographic maps of scale 1:50,000 and 
1:250,000
In the overall reconnaissance visit which have been found accessible, only a small portion of the total basin area have been visited.
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The major travel route include the following.
I) Addis Abeba - Jijiga ii)  Jijiga - Dire dawa
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Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
2.1 Visited Government Offices
Offices
Region
Zone
Town
1
Water, Mines & Energy bureau
Somali
Jijiga
2
SERF
cc
-
3
Agricultural Bureau
cc
-
4
cc
cc
cc
Shinile
Dire Dawa |
ESRDF
cc
Jijiga
Among these offices, only the Water, Mines & Energy Bureau of the Somali region is
found responsible for irrigation works but so far has done nothing in this basin.
2.2 NGOs Contacted
Among  several NGOs operating  in  the basin,  only  a few are involved  in  irrigation activities.  The following  offices were contacted  during  the field  trip  for search  of relevant data & informations.
Offices
Region
Zone
Town
1
OXFAM
Somali
-
Jijiga
2
Save the Children Fund Uk-(SCF)
cc
-
cc
3
Lutheran World Federation (LWF)
Diredawa
-
Dire Dawa
4
EHDA
Somali
Jijiga
2.3   Private organizations
No private organization involved in irrigation activity has been found in the area 3.    Visited sites
Site
Region
Zone
1
Elbaye
Wereda
Somali
Jijiga
2
Biyo Kobobe stream
cc
Jijiga
Shinile
3
Aysha
cc
——-------------.------- Aysha
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4
Dewele
cc
cc
Dewele.
Ministry of Water Resorces River Bsin Development Studies Department---------------------- 1^2000---------------- “Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
4.   Government Officials Contacted
25
M
Place
Name
Official Post
Office
1
Jijiga
Giday
Irrigation Team leader
Water Mines & Energy
2
tc
Siyoum
Agronomist
Agricultural Bureau
3
Ct
Mohammed
Project officer
ESRDF
4
tc
-
Project Coordinator
OXFAM
5
tc
-
tc
tc
SCF
6
DireDawa
Elias Mohamed
Head of Zones Office
Agriculture Bureau              ;
7
Ct
Yideg
Area Coordinator
LWF,Diredawa
tC
L
Awlachew
Abebe
Technical Section head
CC                        Ct
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5.  Problems Encountered
Although  the  field  program  has  been  completed  as  scheduled,  problems  of  different  sorts were however encountered in the course of the trip. Some of these are as shown below.
- Accessibility is generally poor for most of the basin area. Because the field visit
was carried out in the wet season of the year, rivers were filled and roads & bridges were over flooded at some places. This has made some of the accessible sites difficult to cross or sometimes caused delayance in the travel program. Other proposed sites to be visited (identified from topo-maps, especially those located in the eastern low- lands) are totally inaccessible due to either lack of roads or climatic problems. There fore it was not possible to have a visit to these areas.
— Concerned officials or other resourceful individuals to be contacted for obtaining the required informations, would sometimes be not available at their offices during our visit. We had to waste some time for waiting or otherwise compelled to contact some other persons who have a lesser knowledge of the information we require.
- Topographic maps of scale 1:50,000 which are more appropriate for identification of irrigation command areas were not adequately available for the whole basin area.
Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000-     Some minor problems such as vehicle maintenance, defective roads, etc have caused some delayance in our daily travel program.
-    Group members combination was not appropriate. For instance the hydrologist and hydrogeologist should have been assigned with us (the water resource group) because it could have been very convenient to exchange ideas and discuss matters in site identification work.Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
6.  Conclusion & Recommendations
27
Every possible attempts have been made to cover the proposed activities of the field trip which  was limited  to  only  accessible areas of the basin.  As much  information  as possible have been collected from concerned offices and field investigations carried out from all accessible sites in accordance with the terms of reference.
However, the area coverage of the field trip was not large enough to be able to show the full view of the basin. Only the areas along the Diredawa Dewele road were visited while other proposed sites could not be visited due to accessibility problem.
Therefore,  to  conduct  a  complete  investigation,  to  the  basin,  the  following  may  be recommended.
- A helicopter tour program shall be arranged to visit those inaccessible areas of the basin.
- .Topographic maps shall be made available through the Ethiopian Mapping Agency.
- Group members discussion shall be made especially among those related study disciplines.
------ — - - -------------------------------------- ------ -------------  -
Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report---------------------------------------- 28-----------
Annex- II
Terms of Reference for the Reconnaissance Phase study of the Dry Basin
Integrated Development Master plan Study Project.
IRRIGATION AND DRAINAGE
1.         All  existing  studies  within  the  basin  in  the  area  of  irrigation  and  drainage  and  relevant  sectors will be collected and reviewed.
2.          A  reconnaissance  visit  to  all  accessible  parts  of  project  sites  will  be  done  for  a  first  hand information.
3.         For the identified irrigation and drainage projects, water resources availabihty, climatic conditions, soil suitability, population density, food deficit, location accessibility etc. will be examined in consultation with the other experts.
4.          Where  major  storage  is  required  for  irrigation  development,  the  location  of  this  will  be indicated to the relevant expert for the selection of appropriate dam site.
5.         The data gap for the study will be identified, and means of filling the data will be suggested.
6.          Work program for the second stage of the study will be prepared.
7.
All  logistic,  laboratory  requirement  and  other  relevant  materials  requirement  for  the sector will be identified for the second.stage of the study and presented.
8.          With  all  the  above  information  a  reconnaissance  report  will  be  prepared  and submitted.
9.
The  work  program  for  each  activity  is  given  in  the  overall  activity  program  of  this  study  and submission of the output will be in line with this work program.
10. Preliminary identification of potential irrigation sites if possible.
•
MMsny oCWaMr R«»c« River Bs„ Development Stu*s----------------------------- j^,Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report
Annex III
THE DRY BASIN INTEGRATED DEVELOPMENT MASTER PLAN STUDY PROJECT TERMS OF REFERENCE FOR PHASE II AND III STUDIES
Irrigation and Drainage
1.         All data, information & maps relevant to the field of irrigation & drainage study shall be
collected, analyzed and existing studies reviewed as to recent information & maps availa e.
2.          All potential areas of irrigation development shall be identified (including those obtained 
from the reconnaissance study) on the basis of suitability of topography, soils, water, c.t.c
and availability of sufficient water quantity.
3.          The need for major storage dams shall be assessed and indicated to the relevant expert for
selection of proper dam sites serving the respective irrigation sites.
4.         Field visits (with helicopter & vehicles) have to be carried out on selected irrigation sites
for further close investigation.
5.        All sources of irrigation water (surface & ground water) and means of abstraction shall be
assessed and identified for all proposed irrigation schemes. AH engineering options shall be
compared to select the most appropriate head work. Inter basin or basin transfer of water
sources into potential irrigable land, where there is shortage of water, shall be considered.
6.          Collected data & information available from relevant study sectors like soils,
hydrology,   agronomy,   socio-economy,   environment,   etc.   as   analyzed   by   each   sector   shall   b( examined in relation to the proposed irrigation sites.
7.          The total project water requirements ( net, Gros and peak season demands) of each scheme must be estimated\calculated and compared with the available water quantity of each identified source, in order to determine the size of the maximum irrigable area. This may include.
- Estimation of irrigation efficiency, water lossesdue to
Ofcropwa,er
»f rouble cropping pattern and cropping
8.
9.The prefeasibility studies contain,
10.
proposals. Typical sample blocks and irrigation & drainage structures shall be made.
11.        Surveying of sample areas at scale of 1:5,000 has to be carried out consultation with the responsible experts on the proposed irrigable lands. All required maps (topograpluc an canal sections) shall be prepared at required scales with one meter contour interval and detail design of sample blocks shall be earned out
12.       For all prioritized and selected irrigation sites, preliminary costing shall be made including for all engineering works of the diversion weirs, off-takes, canals & drainage works and other infrastructures, in order to estimate the cost of the whole project This may include.
-  estimation of development cost (costing of tertiary units)
-  estimation of major irrigation & drainage canals associated with 
major structures.
-  estimation of abstraction systems ( head-works like dam for
multi- purpose or irrigation development, diversion weir and pump stations)
-  estimation of total project cost.
13.       problems of drainage, flooding, salinity or others shall be identified wherever is existing or expected to occur in the course of operation of irrigation projects, and thus proper solutions such as: appropriate drainage designs, flood protection works, land reclamation & soil management practices shall be proposed.
14.       Plan of development scenarios has to be prepared with a guide line for water allocation for normal conditions and extreme years.
15.
Each small scale irrigation sites shall be dually inspected as far as possible. 
Design and costing of the proposed schemes shall be carried out
16.Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 31___________  3$
References
1.   APS & NRDEP, 1995. Teru Depression Reconnaissance Study, Final Report
Addis Abeba
2.   CO- SAERAR, 1998. Irrigation Project Study for the Afar Reg. State, Executive Summary. BahirDar.
3.   CO-SAERAR & CECE. Kobo-Girana Valley Development Program Feasibility Study Report, Vol IV, Minerals, energy and water Resource Assessment, Final report. Addis Abeba.
4.   FAO, 1995. Irrigation in Africa in Figures \Water ReportX, Rome.
5.   IPS, 19998 Resource Potential Study for Industrial Development in the Afar National Regional State, Vol. IV, Minerals, Energy and Water Resource ssessment, Final Report. Addis Abeba.
6.   IPS & the Afar Desk of the prime Ministers Office of the Social, Administrative & Regional Affairs Sector, 1998. Technical Proposal for the Feasibility Study of an integrated Development of the Teru Area in the Afar National Regional State. Addis Abeba.
. ■ '■
■■ ■ i
7.  REST, 1998. Feasibility Study Report for the Raya Valley Agricultural Development Project, Vol H Water Resources Annex-D Irrigation Development Plan.
8.  WAPCOS & EVDSA, 1990. A Preliminary Water Resource Development Master for Ethiopia, Vol-II Main Report, The Eastern Basins. Addis Abeba.
Ministry of Water Resorces River Bsin Development Studies Department              Junuary2000

Summery

Aysha Basin Reconnaissance Study Summary

Aysha Basin Reconnaissance Phase Study Summary

1. Project Overview

The Aysha Basin Reconnaissance Phase Study was conducted by Ethiopia's Ministry of Water Resources between June and August 1999, with report completion in May 2000. The study covers the Aysha Basin located in the Somali regional state, characterized as a hot arid region with low rainfall and high evaporation.

The report is organized into six volumes:

Volume I: Executive Summary
Volume II: Natural Resources
Volume III: Agriculture
Volume IV: Water Resources (including Hydrology, Hydrogeology, Dams & Hydropower, and Irrigation)
Volume V: Socio-Economy
Volume VI: Environment

2. Key Findings

Hydrology

Mean annual rainfall: 325mm (Aysha) to 185mm (Dawele)
Mean daily temperature: 24.8°C (max 31.3°C, min 18.2°C)
Evaporation formula: E = 3831 - 0.979H (where H is elevation)
Only two meteorological stations exist (Aysha and Dawele)
No perennial streams - only seasonal flows like Biye Gurger, Kobe, Seblosa, etc.
Surface water potential deemed negligible by WAPCOS report

Hydrogeology

Main formations: Quaternary deposits, Magdala group (Rhyolites, trachytes), Afar group (basalts)
50% success rate in well drilling (average depth 90m, yield 5.96 l/s)
Water quality issues with high TDS (500-1500 PPM) and fluoride levels
Recommendations for future geophysical surveys and well testing

Dams & Hydropower

No suitable dam sites identified with current 1:250,000 scale maps
Hydropower development deemed unlikely due to water scarcity
Sub-surface flow dams suggested as alternative for water storage

Irrigation

Basin classified as low-potential for large/medium irrigation
Three potential small-scale irrigation sites identified (total ~4300ha)
Rainwater harvesting techniques recommended (runoff farming, micro-dams)
Only two small schemes under construction by Lutheran World Federation

3. Challenges and Limitations

Severe data gaps due to lack of monitoring stations and previous studies
Inadequate topographic maps (only 1:250,000 scale available)
Accessibility and security issues limited field observations
High evaporation (estimated >2500mm/year) vs low rainfall (<400mm/year)
Poor soil conditions in much of the basin

4. Recommendations for Phase II

Hydrology

Upgrade meteorological stations
Develop rainfall intensity-duration relations
Calculate PET and establish altitude relationships
Estimate annual runoff and regionalize flow series

Hydrogeology

Aerial photographic interpretation for lineaments
Well inventory and geophysical surveys
Additional test well drilling and pumping tests
Water quality analysis and hydrogeological mapping

Dams & Hydropower

Helicopter surveys for site verification
Assessment of demand and load forecasts
Sub-surface flow dam investigations
Geotechnical surveys for potential sites

Irrigation

Detailed investigation of rainwater harvesting techniques
Survey of potential micro-dam sites
Focus on pasture land irrigation for pastoral communities
Consider helicopter surveys for inaccessible areas

Logistics Requirements

Category	Requirements
Manpower	Senior hydrologist, hydrogeologists, geophysicists, water quality expert, etc.
Equipment	GPS, resistivity instruments, seismic instruments, computers, water sampling kits
Software	Satellite image processing, resistivity interpretation, groundwater modeling
Field Equipment	Tents, generators, vehicles (Land Cruisers), topographic maps

5. Conclusion

The Aysha Basin presents significant challenges for water resources development due to its arid climate, limited water availability, and data deficiencies. While large-scale development appears unfeasible, targeted small-scale interventions focusing on rainwater harvesting and groundwater exploitation may provide solutions for local water needs. The Phase II study should focus on filling critical data gaps through enhanced monitoring, detailed surveys, and testing to enable more informed development planning for this arid region.

Key constraint: The basin's extremely limited water resources (surface and groundwater) fundamentally limit development potential, requiring careful water management strategies.