Sedimentation in the Koka Reservoir, Ethiopia

Ethiopia is one of the few African countries that have great potential for producing hydroelectricity and irrigation development. The estimated total hydropower potential of Ethiopia is about 30-40GW; of this vast potential, only 1% has been utilized up to now and more than 87% of the country's electricity out put is generated by hydroelectric facilities. Koka is the first large hydroelectric power plant established in Ethiopia. It was commissioned in May/June 1960 followed by Awash II and III cascade power plants and currently all the above three power plants supply about 26% of Ethiopian's power production. According to a recent bathymetric survey, the capacity of Koka Reservoir has been reduced from 1667 Mm(3) in 1959 to 1186 Mm(3) in 1998. The loss on total capacity over 38 years is 481 Mm(3) i.e., 28.9% of the total storage volume. The average annual loss of capacity is 0.74%. In this article it is attempted to discuss the impact, extent and alternative measures to prolong its service life.