Assessment of soil loss and erosion risk using RUSLE in the Saguling Dam Reservoir Catchment, Indonesia

This study aimed to estimate soil loss and identify high-erosion-risk areas in the Saguling Dam reservoir catchment using the Revised Universal Soil Loss Equation (RUSLE), as the catchment faces serious issues of soil erosion, water pollution, and reservoir sedimentation. Input data were prepared by considering the spatial and interannual variability of rainfall erosivity and land cover conditions. The simulation estimated a total soil loss of 19,662,905 tons in 2020 under long-term average rainfall conditions. Reflecting changes in land cover over time, the average annual soil loss was calculated as 5.28, 8.19, and 8.02 tons/ha/year for 1989, 2000, and 2020, respectively. High-erosion-risk areas were primarily concentrated in valleys and steep slope croplands directly connected to these valleys, with a notable overlap with LS factor values ranging from 12 to 17.2. The Cisangkeuy, Cirasea, and Citarik catchments, located in the southern and eastern parts of the area, were identified as the most vulnerable to soil loss. Under wet rainfall conditions, rainfall erosivity increased significantly, resulting in an estimated doubling of high-erosion-risk areas compared to those identified under dry conditions. An effective soil conservation strategy should focus on managing steep slope croplands, while also considering the spatio-temporal variability of factors influencing soil loss.