Coupled RUSLE-SWPT morphometric characterization of soil erosion under land use change and climate projections in the Upper OMO Gibe Basin
摘要
Soil erosion threatens land productivity, water resources, and hydropower sustainability in the Upper Omo Gibe Basin (UOGB), Ethiopia. This study quantified soil erosion dynamics, assess land use/land cover (LULC) changes and climate variability, and prioritized erosion-prone sub-watersheds to support targeted soil and water conservation planning. A GIS-based Revised Universal Soil Loss Equation (RUSLE) model was applied to estimate soil loss for 1991, 2006, and 2020 LULU series. LULC changes were analyzed using multi-temporal satellite imagery obtained from the USGS Earth Explorer and processed in ERDAS Imagine. Sub-watershed prioritization was conducted using the Sub-Watershed Prioritization Tool (SWPT) based on morphometric and topo-hydrological parameters. Future climate conditions were assessed using Regional Climate Models under RCP 4.5 and RCP 8.5 emission scenarios. The results show significant expansion of agricultural and settlement areas at the expense of forest, shrubland and bare land. Classification accuracies ranging from 72 to 86.4%, with kappa coefficients between 0.67 and 0.84. Mean annual soil loss increased from 25.47 t ha−1 yr−1 in 1991 to 36.72 t ha−1 yr−1 in 2020, exceeding tolerable soil loss limit. Projected temperature increases ranged from 1.5 to 2.2 °C relative to the baseline period, while rainfall showed reductions of up to 31.8%. Erosion hotspot analysis identified SW1, SW3, SW4, and SW5 as highly vulnerable sub-watershed, with SW1 and SW3 ranked as top conservation priorities. Overall, the integrated GIS-based RUSLE-SWPT framework effectively identifies erosion hotspots and guide’s sustainable watershed management to protect the downstream Gibe III hydropower reservoir.