J? Birin Dewk>omcnt Study Depeamgn THE FEDERAL DEX IOCR.[TIC REPUBLIC OF ETHIOPIA MINISTRY OF H ATER RESOURCES AYSHA BASIN RECONNAISSANCE PHASE MASTER PLAN Volume IV: Water resources A- Hydrology B- Hvdrogeologs C-Dams& Hydropower 0 Irrigation [Water Resources!Preface The dry basins reconnaissance phase study has been conducted by the experts pulled cut from the basin development study department Data collection and rapid field visit was made for three dry basins simultaneously viz. Ogaden, Aysha and Denakil, between June and August 1999, then the report production was almost completed in May 2000. The report is divided in to VI volumes made up from works conducted during tire stud} phase. Each volume has sections depending on the details of the sector Volume 1 Volume II Executive Summan Natural Resources Volume III Volume IV Agriculture Water Resources V olume V’ V’olume VI Socio-Econom\ Environment List of experts produced these report are. Eyiiachew Ynayew Abebe Gulma Solomon Mengisru Amare H Selassie Fckaluned Sintavehu Tilahun Mckonncn Worku Isavas W.Manam Girum Admasu Belay Tegcgn Wubshet Alemayehu Abncl G.Mcdhin Goshu Kcbede Mclaku Abebe Getachew Bevene Yeyesus Work Bekele Geology and Mineralogy Soil sun ’ey and Land evaluation Land use Cover Forestry and Energy Wildlife and Tourism Agronomy Livestock. Range land. Apiculture and Fisher}' Hvdrology Hydrogeologv Dams and Hydropower Irrigation and Drainage Geoicchnicis and Infrasiiuuinc Agricultural Economics Demography Soil and Water Consenation Environment and Environmental HealthDry basins study project /Danakil, Ogaden and Aysha/ Hydrology report, 1999 THE FEDERAL DEOCRATIC 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 Basin development stud) departmentDry basins study project /Danakil, Ogaden and Aysha/ Hydrology report, 1999 TABLE OF CONTENTES CONTENTS EXECUTIVE SUMMARY PAGE ..—...... ii 1. INTRODUCTION I 1.1 OBJECTIVE I 2. LOCATION AND PHSYIOGRAPHY 3. OVERVIEW OF PREVIOUS STUDIED PROJECTS 3 1 EVDSA, Masterplan for the development of surface water resources in the Awash basin, HALCROW, 1989: 3.2 EVDSA, Water resources development master plan for Ethiopia, W aPCOS. 1990 1 3. DATA AVAILABILITY 3.1 METEOROLOGICAL DATA5 3 2 RIVER FLOW DATA... s 3.3 SEDIMENT TRANSPORTATION DATA > 4.0 CLIMATE 4 I GENERAL DESCRIPTION6 4.2 CLIMATE OF THE BASIN7 5. PRECIPITATION8 5 I NETWORK SPATIAL DISTRIBUTION OF METEOROLOGICAL STATIONS Q 6.0 SURFACE water resource 7. PROPOSED PROGRAM FOR II PHASE ACTIVITIES, LOGISTICS AND MAN POWER REQUIREMENT ! I 7 1 PROPOSED PROGRAM FOR II PHASE ACTIVITIES 7.2 MATERIAL AND MAN POWER REQUIREMENT 12 5 10 II 8. CONCLUSION AND RECOMMENDATION.............................................................................................................................. 13 REFERENCES 14 Ministry of water resources of Ethiopia n 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 I TOPOGRAPHY OF THE BASIN 1 1 PAGE Ministry of water resources of Ethiopia hi Basin development stud) departmentDry basins study project /Danakil, Ogaden and Aysha/ Hydrology report, 1999 ABBREVIATION AND ACRONYMS BSH: Hot semi-arid climate BWH: Hot arid climate E.C: Ethiopian calendar EVDSAi Ethiopian valley development study Authority FAO: GPS: Food and agriculture organisation Geographic positioning system HD: Hydrology department IGAD: Inter governmental authority for development ITCZ: m.a.s.l: Inter Tropical Convergence Zone Meter above sea level m.b.s.l: Meter below sea level MWRE: Ministry of water resource of Ethiopia NMSA: National meteorological serv ices agency Qty.: R.H: Quantity Relative humidity UPS: Uninteraptable power supply WAPCOS: Water and power consulting serv ice WARREDOC: Water resources research and documentation centre WMO World meteorological organisation Ministry of water resources of Ethiopia IV Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 1. INTRODUCTION Hydrology report. 1999 This is the reconnaissance study report for Aysha basin master plan development. The basin is the sub-catchment of the Awash basin, HALCROW, 1989. In Awash river master plan study, this basin included in the eastern lowland /dry land/. At the reconnaissance level of the study almost all reports related to the basin have been reviewed. Section 3 gives the information about water resource development study projects of the basin 1.1 OBJECTIVE The objective of the hydrological study was to estimate the potential water resources of the basin which will be give light to water resource development of the basin. In this aspect the reconnaissance phase of the study started. The major goal of this reconnaissance level of the study ios to :- - gther the available related informations in side and out side of the basin: - reviw the studied projectsinside the basin, - give guidance to the next phase of the study. 2. LOCATION AND PHSYIOGRAPHY Aysha basin situated between 10° to 11° lat and 42 to 43" long The altitude in the basin varies from u 1700m south of the basin to 575 m north of the basin. It is situated in the north-eastern part of the country bordering with Djibouti Republic to the top and right side of the basin, and it is a part of Awash basin. Completely founded in Somali regional state, in Shinile zone Fig 1 shows the tpography of the basin. The area of the basin round to 4312 km2 Streams like Bive Gurger, Kobe. Seblosa. Lasarat. Gerbale and Dbeder are flowing seasonally in the basin with defined river courses Ministry of water resources of Ethiopia 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 sluds departmentBasin map of a 1230000 i ir7'i6" Figure 1. 10*34‘43’ 1170000 ______ International boundary ______ Basin boundary ______ Seasonal stream I io 2 ir ,, 3000 , 43'0* 160000 180000 200000 220000 42*26'29‘ 260000 . 1110000 280000 42.59.9. icon 1:500000 0 10 15 20Dry basins study project /Danakil, Ogaden and Aysha/ 3. OVERVIEW OF PREVIOUS STUDIED PROJECTS Hydrology report, 1999 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 analy sis of all implemented projects w ith 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. Al! identified irrigation and multipurpose aswell as exclusively hy drpower 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 departmentDry basins study project /Danakil, Ogaden and Aysha/ 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 waler resources. Ministry of water resources of Ethiopia 4 Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 3. data availability 3.1 METEOROLOGICAL DATA Hydrology report. 1999 Source of all meteorological data could be NMSA and FAO. In this report no detailed information regarding the climate of the basin is collected. For general information annual value of basin climate 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 be expected. 3.3 SEDIMENT TRANSPORTATION DATA Since the basin have no perennial streams which can be quantified the amount of flow, flow measurement couldnot be done. Beside to this the estimation of sediment transportation from these seasonal streams have been impossible. Ministry of water resources of Ethiopia 5 Basin development studx departmentDry basins study project /Danakil, Ogaden and Aysha/' 4.0 CLIMATE 4.1 GENERAL DESCRIPTION Hydrology repon. 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 cohered by the wet regime in April. In may the bell 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 bell mo\es southwards and this movement is accelerated, leaving the north and central parts dry. Ministry of water resources of Ethiopia 6 Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 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 with 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 daily temperature over the basin amounts to be 24.8 °C. Mean wind speed over the basin is 2.4 m/s, mean 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 a part of Awash basin, regionalization of evaporation based on data collected for Awash master Plan. 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 the masterplan study. Ministry of water resources of Ethiopia 7 Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 5. PRECIPITATION Hydrology report, 1999 The meteorological sen ice agency released an isohyetaJ map 1:2,000,000, which is clearly depicts the rainfall distribution of Ethiopia. According to the map mean annual rainfall in the basin is in the range of 400 mm. Where as in WAPCOS report, based on updated isoheyts, 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 development and to work out correlation between various hydrological parameters e.g. rainfall and runoff. Zone I Rainfall less than 400 mm Zone II Rainfall between 400 and 800 mm Zone III Rainfall between 800 and 1200 mm Zone IV Rainfall between 1200 and 1600 mm Zone V Rainfall between 1600 and 2000 mm Zone VI Rainfall above 2000 mm Aysha basin gets more rainfall in its southern part /zone II/, while the nonh and central part /zone 1/ gets rainfall amounts less than 400 mm. As indicated by different studies, the basin exhibit uniform spatiall disribution of rainfall amount The temporal ditribution of rainfall also shows uniformirty as well. But based on information gathered from settlers of the two tow/ns /Aysha and Dewele/ during field visit to the basin the uroup have able to observe the scarcity of water due to the rarely occurance of rainfall. According to the first hand information the ram fall after some three years. Ministry of water resources of Ethiopia 8 Basin development study departmentDry basins study project ZDanakil, Ogaden and Aysha/ Hydrology report, 1999 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 Minimum density, range/km /gauge/ 2 Temperate Mediterranean and tropical zones Flat areas 600-900 Mountainous areas Small mountainous is lands (<20000km ) Arid &. polar zones 2 100-250 25 1500-100000 In Awash master pian 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. Ministry of water resources of Ethiopia 9 Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 6.0 SURFACE WATER RESOURCE Hydrology report, 1999 in the basin flows seasonal streams like Biye Gurger, Kobe, Seblosa, Lasarat, Gerbale and Dbeder. The climate of the area indicates scarcity of rainfall at low lands, inconsequence of this is small amount of flows. Due to scarcity of drinking water the people in the basin nedds to fetch it from a very far distance Sometimes the supply of water assisted by drilling of boreholes around the villages. In some places pastorialists construct ponds or bircas to harvest rain to give drinking water for their cattle. Hence in 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 rhe basin. The less in amount and rarely flowing of streams of the basin to depend on water resource could be difficult Moreover on the WAPCOS report indicated that the surface water potential of the basin is negligible. Ministry of water resources of Ethiopia 10 Basin development stud) departmentDry basins study project /Danakil, Ogaden and Aysha/ Hydrology report. 1999 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 II Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ 7.2 MATERIAL AND MAN POWER REQUIREMENT Table 1 Material and equipment requirement for the hydrology section Hydrology report, 1999 No. Item description unit Qty Remark 1 2 3 4 5 6 7 8 9 10 II 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 I'PS Personal items Stationary materials Topo Map Vehicle Set nr nr nr nr nr nr nr 1 1 1 1 1 I 1 1 l/S Set nr 2 1 Can be shared with other sections in water resource group. For all skilled man power w hich are participating in the next phase of the sudy Scale 1 250.000 1 station wagon for super vision 1 pick up for field work Table 2 Man power requirement No Man power Qty. Remark 1 2 3 4 Senior hydrologist Hydrologist Hydrographer Driver 1 1 1 1 Who has an experience on water resource of arid region W ho participated in water resources related projects Who participated in water resources related projects j class driving license and good working experience Ministry of water resources of Ethiopia 12 Basin development study departmentDry basins study project /Danakil, Qgaden and Aysha/ 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 oi 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. Ministry of water resources of Ethiopia 13 Basin development study departmentDry basins study project /Danakil, Ogaden and Aysha/ Hydrology report, 1999 REFERENCES 1. EVDSA, 1990. water resource development Master plan for Ethiopia /water and power consultancy services, India Ltd./, Vol. Ill 2. FAO, 1977. Crop water requirements, food and Agricultural organization and drainage paper No. 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 Awash 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 strategy to combat desertification. Vol. II. 7 WARREDOC. March 1996. International works shop, water resources management in drought prone area, Addis Ababa. 8. WMO. 1994. Guide to Hydrological practices, NO 168, Geneva. Ministry of water resources of Ethiopia 14 Basin development stud} departmentMinistry 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 PE4N V olume IV: Water resources A- H'drolog> B- H> d rogeology C-Danis & Hydropower D-Irrigation |.\.gnculture{Table of cntents 1. Physical description............................................................ 3 2. Geology and geological history..................................... 3 2.1. Quaternary deposit................................................................... 3 2.2. Magdala group.......................................................................... 4 2.3. Amba Aradom formation (upper sandstone)............................. 4 2.4. Afar group................................................................................. 4 3. Hydrogeology of Shinile Zone (Aysha sub-basin)............ 4 4. Water quality......................................................................... 6 5. 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 senes 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. 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 conglomerateFigure 1 Shinile area stratigraphy 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 & congiomerate (Geological map of Ethiopia, V.kazmin 1972). The sandstones are vanegated 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 Chemet, 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 atthe shinile Military camp. The static water level has a range of 11 m to 72 m depth as observed in the record In this Zone it was observed that deep wells seem to have higher yield if productive. The second two types of aquifers have moderate productivity with the geothermal aquifer having high productivity too. These two cover the area found west of Aysha town. In addition, the ground water in these two types of formation has a total dissolved solid of 1500 PPM to 3000 PPM. There are also some strips of moderately productive formations found west of Aysha town. There are a lot of fractures trending east-west that are important for ground water development. The recharge estimate for this zone is 50 mm /year as shown by the Hydrogeological map of Ethiopia In this area there is no geophysical investigation was recorded during this investigation. In general, the dry regions having limited or no drainage have limited water resource that can be used for the society and population of cattle Even though the rainfall in the area is known to be below 500 mm, it is expected that some amount of percolation is possible. Thus, limited resources can be found in the area by performing detail investigation. 4. Water quality It is obvious that dry areas have high evaporation rate, which leads to water containing high concentration of dissolved solids If it is surface water it leaves encrustation like calcrete. When there is rainfall, it percolates down to the ground water system with the dissolved solids. This in turn leads to saline groundwaterIn 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. Hyarogeological 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 eacn 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 0 Prepare contract document for additional test well drilling and test pumping0 Perform pumping test and drill deep wells where there are no representative boreholes to be test pumped. 0 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. 0 Hydrogeological map preparation of the basin. 0 Finally the report compilation should be made.’2J0OT0 J QKOOO I ICJO’OC” ftJtooo HOMO |CIND Jtensive aquifers with intergranular permeability c High productivity Moderate productivity JtENSIVE AQUIFERS 11TB High productivity jquiFtis iiti High productivity Loi productivity FRACTURE AND/OR KaRSTIC PERMEABILITY HYDROGEOLOGICAL SYMBOLS - . Faults - - - - - - > Groundwater movement,inferred direction Disappearance point of intermittent stream FRACTURE PERMEABILITY Hz i |caLIZED *QVIFIRS WITH Low productivity PRACTURB and intergranular permeability base information - - - - - - - - international boundary _ _ _ _ _ Basin boundary _ _ _ _ Road River Roil 1 T ||N geothermal areas.common occurence of thermal groundwater ? practured volcanic ROCKS aNO subordinate uncoisolidated Town_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF WATER RESOURCES Moderate or nigh productivity OiT! SC I LI I IIO HO nvwAnnex 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 Equipment (Type of equipment Amount 1 (Stereoscope 1 2 Compass 3 3|Altimeter ~31 4 GPS (Navigation) 3 5iWater Bottle 3 6 Hammer 3i 7 Latest Computer with accessories 2 8 Field water sample analysis kit 1 9 Resistivity instrument 1 10 Seismic instrument 1 11 Land cruiser 2 Soft wares Type of equipment Amount 1 Satellite image processing 1 2 Resistivity interpretation 1 3 Seismic interpretation 1 4 Water quality analysis 1 5 Ground water flow modeling 1 Field equipment Type of equipment Amount 1 Tent with accessories 3 k Ll 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 2000 2001 Task Name______________________ Hydrogeological survey Remote sensing analysis well inventory Water sample collection Geophysical Survey Test pumping on existing bore Preparation of contract docun Drill aditional wells Drilling and test pumping sug Analyse the field data Hydrogeological map Preparati Final report Preparation Remote sensing expet I Hydrogeologist Water quality expert I Geophysicist Hydrogeologist Drilling crue Hydrogeologist Hydrogeologist Hydrogeologist Figure 3: Tentative work schedule Tor Somali Regional StateTentative work schedule of Dry Basin in Somali Regional StateReferences 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 Waler 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 Volume IV: Water resources A- Hydrology B- Hydrogeology______ C-Dams & Hydropower D-Irrigation |.\.gnculturg]FEDERAL DEMOCRATIC OF ETHIOPIA MINISTRY OF WATER RESOURCES AYSHA BASIN INTEGRATED DEVELOPMENT MASTER PLAN PROJECT RECONNAISSANCE PHASE DAM AND HYDROPOWER October 19991 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------------------------------------------------------------------------------------------- 6 2Aysha 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 1 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 ma si on the high lands where Biyo Kobe and Biyo Gurgus dry streams commencing place and 450 m a s i. 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 3The 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 1 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 4 Detailed work program for the Second Stage investigation 51 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 ruies house, sub-surface dams and accessibility 8 carryout seismicity, tectonic, geophysical survey for foundations at proposed dam sites 9 Investigation for construction materials 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 6Ministry 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 Volume IV’: Water resources A- Hydrology B- Hydrogeology C-Dams & H) dropower D-Irrigation. [Agriculture]Aysha Dry Bann Master Plan Project Reconnaissance Irrigation & Drainage Report Table Of Contents Abbreviations 1. Introduction............................................................................................................. 1 2. Back Ground......................................................................................................... 1 3. Objectives.............................................................................................................. 3 4. Study Approach & Methodology.......................................................................... 3 5. Institutional & Policy Aspects...............................................................................4 6. Need For Development..........................................................................................7 7. Description Of The Study Area.......................................................................... 8 7.1. Location & accessibility............................................................................... 8 7.2 Topography & Land Feature.........................................................................8 7.3 Climate.............................................................................................................. 9 7.4 Water Resource...............................................................................................9 7.5 Agriculture, Land Use & Land Cover......................................................10 7.6 Soils.................................................................................................................. 10 7.7 Socio- Economic Aspects.............................................................................. 11 8. Existing Irrigation Development Practices.......................................................... 11 9. Potentials For Irrigation Development................................................................ 12 Page Possible .Areas Of Small Scale Irrigation Development Sites................................... 14 10. Previous Studies Reviewed ................................................................................15 11. Data Gaps Of The Study..................................................................................... 15 12. Conclusion & Recommendation........................................................................ 17 13. .Annexes I. Field Trip Report....................................................................................................19 II. Terms Of Reference For The 1st Phase Study....................................................... 28 III “ " .................................... " ........................................ 29 14 References......................................................................................................................................... 31 15. Map Ministry of Water Resorces River Bsm Development Studies Department January 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 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. MOA 18. NGO 19. NRDEP 20. PET 21. REST 22. SERP 23. SCF 24. SAERT 25. WAPCOS 26. WWCE 27. WWDSE ABBREVIATIONS 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 nterpnse Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Master Plan Project Reconnaissance Irrigation A 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 our 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 invoked 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- iiminary 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. Ministry ofV/ater Resorces River Bsin Development Studies Department January 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation A Drainage Report 2. Back Ground 2 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 ai 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 Hfc, 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 Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 3 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basm Master Plan Project Reconnaissance Irrigation A Drainage Report 4. Study approach & Methodology 4 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, m 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 made only to areas that were accessible. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation A 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-boundary rivers shall be governed by international treaties. Utilization of tributaries of trans- rcgjonal or trans-boundary 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 only 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 arc 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 Ra^nn Master Plan Project Reconnaissance Irrigation A 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) arc 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 ph 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. iii) Water Works 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) Prime Minister 's office, desk of the Somali Region. It is involved in the follow up of for the study; design and supervision of small irrigation projects, in support of the region's development activities. Ministry of Water Resorces River Bsm Development Studies Department Junuary 2000Aysha Dry Basm Master Plan Project Reconnaissance Irrigation & Drainage Report_________________ 7 Regional governments:- Through the following appropriai 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 agnculture 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 6. Need for Development 8 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 7. Description of the Study Area 7.1. Location & Accessibility 9 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 laL 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 Bivo 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 pan 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 pan and some undulating land feature composing of various dry stream courses dissecting through, on the other parts. Ministry ofWater Resorces River Bsrn Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 7.3 Climate 10 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 under-ground 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. 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 11 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 N2 which is permanently not suitable with several physical limitation for irrigation development. A small part of the central basin and southern areas are classified as S2. moderately suitable 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 January 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 7.7 Socio- Economic Aspects 12 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 km 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 13 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 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. Ministry of Water Resorces River Bsm Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation &. Drainage Report 14 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 fanning 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report Possible areas of small scale Irrigation development Sites 1. Irrigation from Kobe stream 15 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 masl. 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.l. A diversion at elevation 1050 m.a.s.l. 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.l 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 Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Master Plan Project Reconnaissance Irrigation A Dramage Report 3. Irrigation from the other streams 16 The other dry streams shown on the topo-map, namely; Gerbale, Lasarat, Scblola, Delad and Debcdcr are 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 UA 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 reliable. Ministry of Water Resorces River Bsm Development Studies Department h^mary 2000Aysha Dry Ra<m Master Plan Project Reconnaissance Irrigation & Dramage Report 11. Data Gaps of the Study 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 data 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. Ministry of Water Resorces River Bstn Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report - 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. 18 Ministry of Water Resorces River Bsm Development Studies Department Junuary 2000Aysha Dry R*nn Master Plan Project Reconnaissance Irrigation A Drainage Report______________ 19 Conclusion & Recommendation The study results shown above reveal that the whole basm area is in great shortage of water resources. This water shortage problem coupled with the severe chmatic 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 erratic distribution partem, 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 concentratcdh 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 Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 20 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report Field Trip Report 1. Introduction 1.1 General 21 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, ail 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. Ministry of Water Resorces River Bsm Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 1.2 Group members The group members participated in the field trip consist of the following staff of the project. 22 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 include: - 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 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 23 In the overall reconnaissance visit which have been found accessible, only a small portion of the total basin area have been visited. The major travel route include the following. I) Addis Abeba - Jijiga ii) Jijiga - Dire dawa iii) Dire Dawa- Aysha - Deweie. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 24 2.1 Visited Government Offices Offices Region Zone Town 1 Water, Mines & Energy bureau Somali - Jijiga 2 SERP 44 - 44 j 3 Agricultural Bureau 44 - 44 4 44 44 44 Shinile Dire Dawa 5 ESRDF 44 - 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. V Offices Region Zone Town 1 OXFAM Somali - Jijiga 2 Save the Children Fund Uk-(SCF) 44 44 - 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 II N° Site Region Zone Wereda n Elbaye Somali Jijiga Jijiga Biyo Kobobe stream 44 Shinile Aysha Aysha 44 ** | 4 Dewele 44 44 " -------------------------- Dewele 1 Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 4. Government Officials Contacted 25 Place Name Official Post Office l Jijiga Giday Irrigation Team leader Water Mines & Energy 2 44 Siyoum Agronomist Agricultural Bureau 3 44 Mohammed Project officer ESRDF 4 44 - Project Coordinator OXFAM 5 44 - 44 44 SCF 6 DireDawa Elias Mohamed Head of Zones Office Agriculture Bureau 7 44 Yideg Area Coordinator LWF,Diredawa 8 44 Awlachew Abe be Technical Section head 44 44 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 w et 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 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report 26 - 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 Basm 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 Bsm Development Studies Department Junuary 2000Aysha Dry Basin Master Plan Project Reconnaissance Irrigation & Drainage Report Annex- II Terms of Reference for the Reconnaissance Phase study of the Dry Basin Integrated Development Master plan Study Project IRRIGATION AND DRAINAGE 28 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 availability, 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basm Master Plan Project Reconnaissance Irrigation & Drainage Report Annex- II Terms of Reference for the Reconnaissance Phase study of the Dry Basin Integrated Development Master plan Study Project 28 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 availability, 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 co 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. Ministry of Water Resorces River Bsin Development Studies Department Junuary 2000Aysha Dry Basm Master Plan Project Reconnaissance Irrigation & Drainage Report 29 Annex III THE DRY BASIN INTEGRATED DEVELOPMENT MASTER PLAN STUDY PROJECT TERMS OF REFERENCE FOR PHASE n 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 available. 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, e.Lc 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. All 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 be 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 cstiniatcd\calculatcd 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 evaporation & transpiration (evapo-transpiration demand), additional supply from effective rainfall, other water demands like leaching etc. - Computation of crop water requirement of possible cropping pattern and cropping intensity. 8. After comparing all conventional systems of irrigation (gravitational, pressurized) to be applied for each proposed scheme, appropriate irrigation sy stem shall be selected. 9. From selected potential areas, projects shall be prioritized according to priontizahnn criteria for pre-feasibility studies.The selection criteria shall be stated bv the consultant and will be approved by the client.? •% Aysha Dry Basin Master Plan Project Reconnaissance Irrigation A Drainage Report The prefeasibility studies contain, 10. Layouts and preliminary designs of the irrigation systems (at scale of 1:20,000), canals and other hydraulic structures have to be carried out for eachsclected sites of the prc-feasi ty level study. AH alternative designs shall be presented alongside with the most economical 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 (topographic and canal sections) shall be prepared at required scales with one meter contour interval and detail design of sample blocks shall be carried 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 ternary 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. Studies regarding small scale irrigation development projects shall be conduct with the following points of emphasis. - Inventory of existing studies, constructed schemes or those under construction regarding small scale irrigation projects shall be identified using 1:50,000 scale topo-maps and aerial photographs. - Each small scale irrigation sites shall be visually inspected as far as possible. - Design and costing of the proposed schemes shall be earned out. 16. AU requ^ed consecutive reports of the study out put mccption report, progress report draft & final reports as well as necessary drawing shall be prepared and submitted according to agreements to be made. 30 «^oramg D D „,»t r\i ~ TiAysha Dry Basin Master Plan Project Reconnaissance Irrigation &. Drainage Report—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 Reports, Rome. 5. IPS, 19998 Resource Potential Study for Industrial Development in the Afar National Regional State, Vol. IX', Minerals, Energy and Water Resource sscssment, 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 Regjonal State. Addis Abeba. 7. REST, 1998. Feasibility Study Report for the Raya Valley Agricultural Development Project, Vol IL, Water Resources Annex-D Irrigation Development. Plan 8. WAPCOS & EVDS.A, 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 Junuary 2000
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