Spatio-Temporal Analysis of Water Erosion in the Tafna Watershed (Algeria) Using the RUSLE Model and Bias-Corrected Rainfall Data (1983–2023)

Soil erosion poses a significant environmental challenge in semi-arid and Mediterranean regions, jeopardizing the sustainability of land and water resources. This study explores the spatio-temporal dynamics of water erosion within the Tafna watershed in Algeria, which encompasses an area of approximately 7200 km2. Utilizing the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS), the assessment relies on bias-corrected simulated rainfall data that offers consistent spatial coverage over the past four decades (1983–2023). Additionally, the rainfall asymmetry coefficient (Cs) was calculated to evaluate the impact of temporal rainfall variability on soil loss. The results indicate significant spatial and temporal variability; average erosion rates vary from less than 6 t/ha/year in stable areas to 23–27 t/ha/year in steep, sparsely vegetated regions. Overall, soil erosion has increased by approximately 16% during the study period, driven by heightened rainfall aggressiveness and an intensification of erosive potential. Correlation analysis underscores the intricate relationships between rainfall, topography, and erosive dynamics, highlighting the exacerbating effect of irregular rainfall patterns (Cs). These findings underscore the Tafna watershed’s high vulnerability to both natural and human-induced pressures, reinforcing the necessity for differentiated land management and targeted soil and water conservation strategies. The methodology developed in this study provides a transferable approach for assessing water erosion in other semi-arid and Mediterranean watersheds facing similar data limitations and hydro-climatic variability.