A Review on Reservoirs Sedimenation Problems in Ethiopia

Abstract

Environmental impacts and long-term morphological changes on the natural water course and mainly through soil erosion (water erosion) due to human intervention, the reservoirs handled by sedimentation. Soil erosion and sedimentation are natural phenomena involved in landscape formation. Cumulative sediment yield is influenced by the combination of factors including soil erodability, soil textural class, organic matter content, watershed area, topography and vegetation cover. In Ethiopia, accelerated sedimentation in reservoirs providing hydroelectric power and irrigation water has resulted in loss of these intended services. The frequent power-cuts and rationing-based electric power distribution recently experienced in the country are also partially attributed to the loss of storage capacity of hydroelectric power reservoirs. Sediment derived from soil erosion and delivered to rivers is a major source of various environmental problems such as sediment deposition in river channels and reservoirs which deteriorates water quality. Sedimentation is a critical pollutant in surface waters that adversely affect water quality and contains other important contaminants including nutrients, pesticides and heavy metals. Some minerals transported with sediments like Cu, Pb, As and Hg are extremely toxic even in small concentration and affect quality of water in dams for various purposes. The suspended solids in the eroded material increases the raw water turbidity (i.e., water becomes muddy and physically dirty),which increases water treatment costs.