Modeling soil erosion severity and sub-watershed prioritization in the Middle Omo-Gibe River basin of Ethiopia: an integrated RUSLE, geospatial, and field survey approach

Soil erosion poses significant global challenges across socioeconomic and environmental domains. This study introduces an integrated methodology for soil loss estimation and modeling soil erosion severity in the Middle Omo-Gibe River (MOGR) basin of Southern Ethiopia. The research has employed the Revised Universal Soil Loss Equation (RUSLE) model alongside geospatial techniques, farmers' perception, and field-based survey. Results indicate a mean rainfall-runoff erosivity of 855.49 MJ mm/ha/h/year and the mean soil erodibility is 0.36 Mg/ha/MJ mm in the river basin. Over half of the basin exhibits strong slope gradients, with topographic factors ranging from 0 to 72.14. The estimated mean annual soil loss is 38.38 t/ha/yr, with 42% of the basin area surpassing the accepted erosion limit (i.e., > 10 t/ha/yr). About 54% of sub-watersheds in the river basin exhibit high to very severe soil loss, including ten sub-watersheds classified as extremely severe, with soil loss rates greater than 100 t/ha/yr. Additionally, the rate of soil loss calculated for the watershed agrees well with the results of farmers' perception, the experimentation outputs of soil physico-chemical properties, and the findings of previous studies. The finding underscores a robust framework for assessing soil erosion and facilitating informed decisions for sustainable use of land resources and conservation across various river basins in Ethiopia.