2.5 River basins in Ethiopia Good morning/afternoon. I would like, before I begin, to thank the search committee for giving me this opportunity. I have been enjoying my visit so far very well. My presentation is titled ‘observations, modeling and scaling: the three pillars of hydrology’.

2.5 River basins in Ethiopia The country has 12 river basins. The total mean annual flow from all the 12 river basins is estimated to be 122 BMC

Potentially irrigable area in ha(%) 2.5 River basins in Ethiopia 2.5.1 River Basins River Basin Catchment area (Km2) Annual Runoff BCM*(%) Specific discharge (L/second/km2) Potentially irrigable area in ha(%) Irrigated area in 2002 in ha Blue Nile 199,812 52.60(43.1) 7.8 760,000(28) 30,000 Baro-Akobo 74,100 23.60 (19.3) 9.7 600,000(22.1) ** Omo-Gibe 78,200 17.9 (14.7) 6.7 248,000(9.1) Tekeze 89,000 7.63 (6.0) 3.2 Genale-Dawa 171,050 5.8 (4.8) 1.2 300,000(11) 8,850 Rift Valley 52,740 5.6 (4.6) 3.4 47,600(1.8) Awash 112,700 4.6 (3.8) 1.4 206,000(7.6) 69,900 Wabe Shebele 200,214 3.15 (2.6) 0.5 355,000(13.1) Afar-Danakil 74,000 0.86 (0.7) 0.0 Mereb 5,700 0.26 (0.2) Ogaden 77,100 0.00 Aysha 2,200 Northern Rivers 200,000(7.4) Total 1,136,816 122.00(100) 2,716,600(100) 197,000 River Basins ,annual runoff, and specific discharge *Billion cubic meters **No data available Sources: Kloos and Legesse (2010).

2.5 River basins in Ethiopia Hydropower (technical) potential of Ethiopia, 75% dependable surface water availability, and number of potential hydropower sites , by river basin. River Basin Technical potential (GWh/yr) 75% dependable surface water (BCM) Potential hydro power sites Blue Nile 78,820 51.48 132 Baro-Akobo 18,880 8.51 39 Omo-Gibe 36,560 14.46 23 Tekeze 5,930 5.73 15 Genale-Dawa 9,270 4.58 Rift Valley 800 4.36 6 Awash 4,470 4.1 43 Wabe Shebele 5,440 2.34 18 Aysha * 0.57 Total 160,170 96.13 299 *No data available

2.5 River basins in Ethiopia all basins are drained by rivers that flow across international boundaries or into lakes except Rift valley and Afar Danakil four major rivers in the western highlands : Blue Nile, Baro-Akobo, Tekeze, and Omo Gibe. Accounts 83 % of the total runoff from all catchments Their basins cover only 38% of the total area of the country Blue Nile generates half of all surface water 52.6 BCM.

2.5 River basins in Ethiopia main river basins in the central and eastern parts of the country: Awash, Wabie Sheble, and Genale-Dawa occupy about 43% of the countries area, their combined runoff constitute only about 11% of the total runoff generated within the country. River flow throughout Ethiopia is highly seasonal with far-reaching implications for water accessibility, the economy, dams, ecosystems, and flooding..

2.5 River basins in Ethiopia The dry/wet season ratios of the flow volume of: Blue Nile, Tekeze, Awash, Wabe Sheble and Genale Rivers vary from about 1:20 to 1:15, with peaks extending from June to October or November, after the end of the main rains. Even the Omo and other rivers originating in the most humid part of the south western highlands, although having relatively larger dry season flows and longer flood periods, are characterized by significant seasonal fluctuations.

2.5 River basins in Ethiopia Inter annual flows also fluctuate significantly with rainfall. Despite the continuous food and water insecurity, less than 5% of the potential irrigable land and 1% of the hydropower potential have been developed. Nevertheless, increasing utilization of streams, springs, and lakes in drought-prone areas for irrigation and domestic purposes and climatic change are already contributing to local water insecurity.

2.5 River basins in Ethiopia Many springs dried up within the last few decades in Hararge Highlands, lakes Haramaya and Adele disappeared in 2006 due to (Alemayehu,et al., 2007). a combination of environmental degradation siltation, and over pumping

2.5 River basins in Ethiopia 2.5.2 Lakes , Reservoirs and wetlands Lakes Ethiopia has 11 fresh and 9 saline lakes, 4 crater lakes and over 12 major swamps or wetlands Majority of the lakes are found in the Rift Valley Basin. The total surface area of these natural and artificial lakes in Ethiopia is about 7,500 sq.kms. The majority of Ethiopian lakes are rich in fish.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Most of the lakes except Ziway, Tana, Langano, Abbaya and Chamo have no surface water outlets, i.e., they are endhoric. Lakes Shala and Abiyata have high concentrations of chemicals and Abiyata is currently exploited for production of soda ash. With the exception of Lake Tana, the largest Ethiopian lakes are located in the Rift Valley.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes The weir constructed from 1995 to 1997 regulates the water level and outflow of Lake Tana to increase generation of electricity through the Tis Abbay II hydropower plant on the Blue Nile. Although the use of Lake Tana was not, unlike other lakes, regulated by environmental laws until recently, the level of exploitation of its water resources, particularly for irrigation, was insignificant in the past.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes However, Lake Tana and its tributaries have been selected for irrigation development and hydropower production. A notable development is the Tana-Belse growth pole, which is expected to stimulate integrated water resources development programs as part of the Nile Basin Initiative.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Of the 10 largest Rift Valley Lakes, Shala, Abiyata, Abe and Beseka are salt lakes, Turkana, Langano, Awasa, and Chamo have brackish water (between 1 and 2g/l salt) and only lakes Ziway and Abaya have freshwater.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Rising water level in lakes Abaya, Chamo, and Awassa have been associated with increasing silt load deposited by their tributaries in the lake beds, a result of watershed degradation.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Lake Beseka expanded more than 10-fold between the 1950s and 2005, largely due to a combination of increased groundwater inflow related to geo-tectonic activity and drainage water from nearby Abadir irrigation farm.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Increasing soda ash extraction from Lake Abiyata and ongoing Large-scale irrigation development around Lake Ziway catchment are significantly reducing their volumes.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lakes Lake Abe’s water level also declined, by two thirds since the 1930s, due to large scale irrigation development in the Awash Valley

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Reservoirs Four large Reservoirs have been created by Koka, Finicha, Melka Wakena and Gilgel Gibe I dams At least five additional reservoirs (Tekeze in Tekeze Basin, Tendaho and Kessem in the Awash, Koga near Lake Tana, and Gibe III in the Omo Basin are expected to be filled by 2012.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Reservoirs The new Millennium Dam for the development of hydroelectric power is under construction on Blue Nile River near to the border of Sudan in Benishangule Region. The dam is planned to create an artificial reservoir which has a capacity of 63 BMC (about 2 times of Lake Tana storage). After the completion of the dam it is planned to produce 5250MW power.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Lake Tana in the north-western highlands, the largest lake in Ethiopia, is about 3000 to 3500 km2 an estimated storage volume of 28 km3. The major tributaries, including the Gilgel-Abbay, Ribb, Gumara, and the Megech contributes more than 93% of the inflow into the lake

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Wetlands Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. Various researchers and investigators have attempted to document the wetlands of Ethiopia but no comprehensive inventory has been made.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Wetlands Although little is known about the impact of agricultural and urban development on Ethiopia’s wetlands (Abebe,2003), an estimated 35% of the largest wetland area of Ethiopia, in Ilubabor Region had been developed to agriculture by 1999 (Hailu,2003), and pent-up demand for wetland cultivation in that region is threatening their sustainability (Mulugeta, 2004).

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Wetlands Only one wetland area, in the Omo River Delta in Lake Turkana, has increased in recent years (by more than 500sq.kms), due to silt inflow from the Omo River and decreasing lake levels, but its future is threatened by dam construction.

2.5 River basins in Ethiopia Lakes , Reservoirs and wetlands Wetlands Although some policies specifically address wetlands, no national wetlands policy exists and none of the country’s wetlands are covered by a conservation and management plan

2.5 River basins in Ethiopia Groundwater Resources System Little reliable information exists on the volume, location and quality of groundwater resources estimation of the groundwater potential of Ethiopia is complicated by the complexity of its geology.

2.5 River basins in Ethiopia Groundwater Resources System Based on the scanty knowledge available on groundwater resources, the potential is estimated to be about 2.6-13.5 BMC annually rechargeable resource. More than two thirds of the estimated utilizable groundwater potential is in the Blue Nile Basin and around 90% is in the western half of the country.