The Wadi Ouergha watershed faces significant challenges due to erosion, which directly impacts sedimentation rates and reduces the water storage capacity of the El Wahda dam, a crucial infrastructure for the region. This study aims to prioritize the sub-watersheds most vulnerable to erosion, which pose a direct threat to the dam’s efficiency. Through morphometric and hypsometric analysis, the research evaluates the geomorphological evolution, hydrological characteristics, and erosion risks within the sub-watersheds. The results indicate that sub-watersheds SW 6, SW 7, and SW 11 are the most at risk, with high drainage densities and advanced erosion stages, demanding immediate intervention. Sub-watersheds SW 2, SW 3, SW 4, SW 5 and SW 7 are identified as moderately vulnerable but still require erosion control measures to prevent long-term degradation. The findings underscore the need for targeted soil management and conservation efforts in these priority areas. This study introduces a novel integration of spatial analysis with statistical methods, incorporating weighted compound factors (WCF) and quartile analysis to prioritize sub-watersheds according to their vulnerability. This method enables a data-driven classification, establishing a structured framework for conservation priorities. Through combined numerical rankings and spatial mapping, decision-makers gain a clear visualization of high-risk areas, facilitating more targeted watershed management and optimized resource allocation.