Erosion spatial distribution mapping and sediment yield estimation using RUSLE and Arc GIS of Ayigebire watershed, North Shewa zone of Amhara region, Ethiopia

Abstract

Soil erosion and sedimentation are the major threats to Ethiopia’s economy by impacting the productivity of agricultural land and shortening the life of dams. Ayigebire watershed was one of the most erosion-susceptible watersheds in Menz Gera district of Ethiopia. At the outlet, there was a soil dam (Godebe soil dam) which covered 12.7 ha. The dam was designed for irrigation purposes wishing to serve 378 households on 68 ha of land. However, the dam was facing a huge challenge of siltation due to the soil erosion brought from the upper reaches of the watershed. Therefore, the purpose of this study was to identify the erosion-affected area and to estimate the watershed's annual sediment yield delivered to the dam. The study used rainfall, DEM and satellite image data obtained from different sources. The result shows the annual soil loss of the watershed was 47 tons ha⁻¹ yr⁻¹. The regions along the drainage lines were identified as erosion hotspot areas and they contribute 76.6% of soil loss. The estimated annual sediment washed from the watershed and reached the Godebe soil dam was found to be 8710 m³ (60969 m³) since the time the dam became operational). From the finding, it could be concluded that the watershed was highly vulnerable to soil loss above the tolerable soil loss limit of the country i.e., 10 tons ha⁻¹ yr⁻¹. Therefore, it’s recommended the high erosion and sediment-producing areas along the waterlines and side banks of the dam get priority for management.