Abstract

  
  Lake Tana Located in the Northern part of Ethiopia, with an area of 3156 km2, accounts for 50 percent of the total inland water area of the country and source of the Blue Nile River, which contributes about two thirds of the total flow of water in the Nile. Lake Tana has unique diversity both in fauna and flora and it is the only undamaged natural laboratory in the world where unique flock of Cyprinids is found. However, recent developments in the region around the Lake have cast doubt on the sustainability of the resource. Major threats are population pressure, deforestation coupled with sediment loading and rapid growth of the town of Bahir Dar. The objective of this paper is to generate information on the effect of sediment load in biotic and abiotic component of the Lake's ecosystem and propose management options for policy makers. Environmental, physical, chemical and biological parameters were measured and interaction between different factors was analysed.
  The catchment area of the Lake (16,500 Km2) has dendritic type drainage network and experiences a soil loss rate ranging from less 5 to more than 250 tons per hectare per year. On some major tributary rivers, turbidity of the water increased from 40 NTU during dry season to 400 NTU during rainy season. The conductivity dropped during the rainy season indicates that the sediment contains more fine sediment (clay) and high organic matter. Increase in turbidity following the rainy season resulted in a decline of plankton production and blooming of weeds. Integrated community based catchment management is recommended for sustainable development of the Lake resource.