Modeling soil erosion using RUSLE and GIS at watershed level in the upper beles, Ethiopia

Abstract

Soil erosion by water often described as the most worst form of land degradation with serious environmental and socioeconomic ramification, which accelerated by human-induced activities and impacts agricultural productivity, water resources sustainability, and ecological conservations. Despite, the significant amount of research on the topic, location-specific soil erosion studies are still limited in Ethiopia, particularly in the study region. Therefore, this study investigates the spatial pattern of soil erosion risk and map the annual soil loss rate in the Upper Beles watershed of the Blue Nile Basin, Ethiopia. The Revised Universal Soil Loss Equation (RUSLE) model, coupled with geographical information system (GIS), has been adopted for soil loss estimation. The respective model factors were derived from rainfall, soil, land use/cover, and digital elevation model data. The raster layers of rainfall erosivity, soil erodibility, topographic, cover management, and conservation practices were processed and multiplied together in the GIS platform. The order of magnitude of the estimated soil loss was within the range of zero in bare areas and watercourses to well over 50 t ha−1 yr−1 in degraded slope and steep mountain areas. The resulting average annual soil loss was founded to be 13.2 t ha-1 yr-1, which exceeded the soil loss tolerances of Ethiopia's northern highlands. Based on soil erosion risk's spatial distribution, 58.2% of the watershed has suffered soil loss less than 5 t ha−1 yr−1. Result shows that high soil erosion prevails at steep slopes and mountainous areas with no vegetation covers and extensively cultivated areas. The RUSLE and GIS-based approach provides a reliable estimation of soil loss that helps identify the priority area for effective planning and implementation of sustainable soil management practices to reduce soil erosion, particularly for the sustainability of the Grand Ethiopian Renesance Dam (GERD) located at the downstream.