Environmental Assessnment for the Blue Nile Sub-Basin in the Eastern Nile Basin

摘要

The blue Nile sub-basin, located in the middle east of the Eastern Nile Basin, is the largest contributor by 56bcm/year of the Eastern Nile Basin system accounting 67% of the inflow at Aswan, Droughts, intense flooding, and massive erosion, cause major environmental, social and econemic impacts within the basin. Also in the most agricultural areas, yields and irrigation efficiencies are very low, deforestation and land degra dation are severe in some spots, contributing to low soil productivity and increased downstream sedimentation lastly pollution of the water resources from urban and industrial zones is becoming a serious problem.The study assessed the impacts of five pre-dellned concerns namely, freshwater shortage, pollution, habitat and community modification, unsustainable exploitation of fish and other living resources and global change.Currently, freshwater shortage per se does not appear to be a significant problem for the region. However, the impact of the modification of stream flow hasbeen considered severe. This is evidenced by changes in the flow volume of the Nile and its tributaries caused by development activities, notably the construction of dams for hydropower development. Economic development and population growth will increase water demand, and the extensive development of hydropower schemes will significantly alter the hydrological cycle.The impacts of pollution due to sediment load have been considered to be severe. Development activities during the past decade includingdeforestation, grazing and urbanization have caused extensive soil erosion in many parts of the sub basin resuhing in high contents of total suspended solids (mainly suspended sediment) The suspended solids are transported through the basin. 1 he impactsof the loss and/or modification of ecosystems, categorized under the concern of habitat and community modification, have been considered to be severe and are becoming major issues in the region. Modification or loss of the ecosystems has been found to deplete the living resources on which the rural communities depend for their subsistence. Habitat modification was selected as the main priority concern for the Blue Nile .