Detrimental Role of Selected Soil Properties on Sedimentation of Dam- Reservoir

Abstract

Reservoirs are broadly affected by sedimentation resulting from soil erosion. This study aimed to analyze the detrimental role of selected soil physical properties on the sedimentation of reservoirs, in this case, Washa Dam-Reservoir, Ethiopia; in a view to help the monitoring system. The catchment was divided into square grids of size 300 m by 300 m as a study unit to collect all information for the analysis. Thirty-two years of rainfall data were used to analyze rainfall trends, and estimate runoff through the runoff curve number model. Soil loss was estimated using USLE. the study revealed that the soil is dominated by as high as 49% clay content; pH of 4.6–5.6; and bulk density of 1.4 to 1.6 kg/m³ which is a challenge to plant growth affecting ground cover in turn soil erosion. The average daily runoff was 13.55mm with a runoff coefficient of 26%. The average annual soil loss was 6.9t ha^− 1 y^− 1 producing a yearly volume of sediment 4918.32 tons. The catchment sediment delivery ratio was 26.98% resulting in the maximum sediment of 1.81 t ha^− 1 with a total of 1327.95 tonsediment yield per year forming 8mm thick sediment on average. In conclusion, although the catchment has erosive rainfall and is relatively less conserved, it revealed tolerable soil loss and sediment yield. Except using their separate interrelation, soil properties, and erosion do not show statistical correlation. Therefore, it is recommended to plan interventions by giving priority to grids having sediment-promoting soil factors coupled with paying attention to getting a working relationship between soil properties and sedimentation for a better monitoring system.