Assessment of erosion, sediment yield, and runoff generating areas in Dirima catchment, upper Blue Nile, Tana Basin, Ethiopia

Soil erosion is a significant issue, particularly in tropical regions such as the Ethiopian highlands, where it drives land degradation. This study focuses on assessing runoff generation areas (RGAs) in the Dirima catchment, located in the upper Blue Nile, Tana Basin, Ethiopia. The main objectives are, evaluate soil erosion, quantify sediment yield and identify potential RGAs. To do this the SWAT + model was used to simulate crucial hydrological processes followed by, calibration and uncertainty analysis. This helps establish the hydrologic model of streamflow dynamics with significant performance metrics including; NSE = 0.84–0.86; KGE = 0.77-0. 87; R²=0. 86 − 0. 87. The analytic hierarchy process (AHP) was used to evaluate the relative importance of runoff generation factors via the Satty principle. The catchment was classified into five runoff generation potential zones: very low (VL), low (L), medium (M), high (H), and very high (VH). The VL category account for 8%,566 mm of runoff and a sediment yield of 33 t/ha/yr. The “L” category, representing 17% with 606 mm of runoff and 53.5 t/ha/yr of sediment yield. The M, category 32% of the catchment, generate 662 mm of runoff. The H and VH category, covering 27% and 16%, which produce substantial runoff of 682 and 690.2 mm, respectively. This indicating critical areas for runoff management. In this category, an annual average sediment loss ranges from 53.5 to 186.5 t /ha/y, severely affects crop production due to nutrient depletion and mass deposition. Therefore, implementing erosion prevention techniques, such as conservation tillage, cover cropping, contour ploughing, and runoff harvesting is vital for sustainable watershed management of the Dirima catchment and similar regions grappling with runoff challenges. This study shows integration of AHP with SWAT + provides a powerful tool to manage erosion which can be adapted and applied worldwide.