Erosion represents a significant environmental challenge in southeastern Morocco. This arid and semiarid region experiences notably heavy rainfall, followed by prolonged periods of drought. This alternation of climate events creates an accelerated erosion cycle that affects fragile soils. The present work aims to apply existing models and analysis techniques to identify areas highly vulnerable to erosion, propose solutions against soil degradation, and protect downstream water accumulation zones, which play a vital role in ensuring the sustainability of these fragile ecosystems. To do this, we used a multicriteria analysis based on a geographic information system (GIS). The study area is the upper watershed of the Guir Wadi, one of the southeastern watersheds in Morocco. This area has recently been characterized by constructing a large surface water storage dam (Kaddoussa; 220 Mm3 capacity), which plays a vital role in water mobilization. The study shows that 1.2% of the area is at low erosion risk, indicating moderate fragility. On the other hand, the majority (96%) falls into the medium fragility category, presenting moderate erosion risks. Furthermore, 2.8% is highly exposed to water erosion, requiring immediate action. In addition, large areas within the site are subject to heavy erosion, with erosion levels ranging from 30 to 250 tonnes per hectare per year. This research was carried out with a view to action research and ensuring that decision-makers took ownership of the results. The results should contribute to the integrated management of water resources in this highly vulnerable region, where population growth and climate change make water resources the main factor limiting human and economic development.