Morocco is facing an alarming decline in surface water supplies, which is severely impacting dam reserves due to climate change and a scarcity of rainfall. The El Makhazine dam, located in the north, is crucial in supplying 800 Mm3 annually of water, and the irrigation of 34,000 ha in the Loukkos perimeter. The study and monitoring of water and sediment discharge are urgently needed to plan anti-erosion interventions, thus ensuring the sustainability of regional water resources. This study has achieved innovation by applying the Soil and Water Assessment Tool (SWAT) model to the basin using high-resolution data. These data include climate, flow, and sediment concentration from 1979 to 2019, topographic data, land use data from a high-resolution Sentinel image, and soil data from laboratory analyses. The SUFI2 algorithm was used to simulate the hydrological process in the basin. In contrast, the SWAT-CUP program calibrated and validated the model over two distinct intervals (1979–2002 and 2003–2019). The model utilized 23 sensitivity parameters to control flows and sediments, assessing reliability through statistical indices such as NSE, PBIAS, and R². The results were used to analyze the basin's water yield and calculate the water balance, revealing a predominance of evapotranspiration and surface runoff. Erosion rates and sediment load ranged from 5.36 to 99.86 t/ha/yr, with an average of 29.33 t/ha/yr. The sub-watersheds were prioritized and ranked based on their erosion rates, with a focus on implementing erosion control interventions. The results of the Best Management Practices simulation indicated that terracing was the most effective practice for the region, resulting in a 64.8% reduction in erosion. The model has demonstrated effectiveness in simulating watershed development and simulating practices to reduce dam siltation. This document is a valuable guide for planners in hydrological management in northern Morocco.