Sediment Hotspot Identification and Evaluation of Best Management Practices under Future Climate in the Beressa Watershed Ethiopia

Abstract

Abstract Intensifying climate extremes under future scenarios are expected to exacerbate soil erosion, with widespread impacts on food security, water quality, and ecosystem stability. These shifts may compromise the effectiveness of soil and water conservation measures, particularly in erosion-prone regions of the Ethiopian Highlands. However, evidence remains limited on how CMIP6 climate projections influence sediment yield and the performance of best management practices (BMPs). This study assessed the impacts of climate change on sediment yield and evaluated BMP effectiveness under CMIP6 scenarios (SSP245 and SSP585) using the Soil and Water Assessment Tool (SWAT) in the Beressa watershed, Ethiopia. Model performance was strong, with R² values of 0.83 and 0.88 and NSE values of 0.78 and 0.85 for streamflow during calibration and validation, respectively. For sediment, R² and NSE values were 0.73 and 0.69 during calibration, and 0.75 and 0.68 during validation. Extreme rainfall events accounted for nearly half of the interannual variability in sediment yield. Projections indicate increased sediment yield and expansion of hotspot areas under future scenarios. Terracing reduced sediment yield by 48–51%, conservation agriculture by 30–33%, and contour farming by ~20%, while combined practices achieved up to 60% reduction. Terracing and combined BMPs markedly expanded areas below the tolerable soil loss threshold (11 Mg ha⁻¹ yr⁻¹), increasing stable zones by 48–61% across climate scenarios. In years dominated by extreme rainfall, soil and water conservation measures experience reduced efficiency and increased maintenance demands, with associated resource and cost implications. These findings highlight the need for climate-resilient, integrated land management strategies to sustain ecosystem services in the Ethiopian Highlands.