The Effect of the Sediment Accumulation in Reservoirs: Case of the Roseires

Abstract

This study is especially about the effect of sediment accumulation in Roseires dam reservoir. It is situated along the Blue Nile reach between the dam site and the Ethiopian border. The dam is located in the vicinity of the Damazin city, approximately 500 km south of Khartoum, with drainage area 290 km2, length 75 km, volume 3.024x109 m3 at top water level 480 m and 7.4x109 m3 at level 490 m after dam heightening. The main objective of this study is to assess the sediment accumulation rate in the Roseires dam reservoir. The historical data and information of the previous bathymetric surveys carried at Roseires dam reservoir, which include those carried in years 1976, 1981, 1985, 1992, 2005 and 2007 were used. Comparison of accumulated silt volumes deposited among the different surveys was\ obtained. The case study revealed that the sediment deposition in the Dam Reservoir reduced its capacity (from 3.024 milliard m3 to 1.92089 milliard m3 after fourty one years of operation (1966-2007)). It was clearly depicted during the 41 years that there is increase in the silt deposit with time at all reduced levels and decrease in siltation rate with time at all reduced levels.