Water erosion is a major threat to land resources and agricultural productivity in semi-arid Mediterranean environments. This study aimed to identify the main factors driving water erosion in the Nfifikh watershed (Morocco) and to assess spatial variations in erosion susceptibility using a combination of the PAP/CAR qualitative model and Geographic Information Systems (GIS). Spatial data, including ASTER-DEM, land use, vegetation cover, and lithological maps, were analyzed alongside field observations to map erosion vulnerability. The PAP/CAR methodology was applied in three stages—descriptive, predictive, and integration—to classify the watershed into stable and unstable zones and to evaluate areas at low, moderate, high, and very high erosion risk. Results indicate that 55.96% of the watershed exhibits high to very high erosion potential, primarily concentrated in downstream agricultural areas and slopes exceeding 20%. Sheet erosion dominates (87.77% of the basin), while rill and gully erosion occur in areas with sparse vegetation and moderates to steep slopes. Approximately 35% of the watershed is highly sensitive, while protective vegetation covers less than 35% of the area, failing to coincide with the most vulnerable zones. High erosion risk areas overlap with regions of intensive agriculture and higher population density, confirming that erosion susceptibility is driven by both natural factors and human activities. These findings provide a reproducible spatial framework for targeted soil and watershed management interventions. The integration of GIS with the PAP/CAR model enables the identification of priority zones for conservation, contributing to sustainable land use planning. This study offers new insights into the spatial dynamics of water erosion in semi-arid Mediterranean watersheds and demonstrates the value of combining cartographic modeling with field verification for environmental management.