Water management is one of the critical challenges facing humanity due to increasing demand and limited resources resulting from the rapid growth of population, urban planning, agricultural and industrial sectors. Hydrological modeling is one of the key solutions used by researchers for estimating and monitoring the spatial and temporal variability of water resources in a watershed. This paper aims to evaluate the Soil & Water Assessment Tool (SWAT) performances and simulates the water cycle components of El Grou watershed (3504 km2), one of the main basins in the landscape hydrology of Morocco. It points to the need for developmrent of better model input data sets in Africa which are unlimted available when they are crucial for a detailed study of water resources. The model was built under ArcSWAT, and all other processes such as sensitivity analysis, calibration (10 years) and validation (4 years) were done with SWAT-CUP software using the SUFI-2 algorithm. The coefficient of determination (R2), the Nash–Sutcliffe efficiency (NSE) and the square error (RSR) were used to evaluate model performances. The results show that calibration and validation are considered very good, with R2 and NSE >0.81 and RSR <0.5. The hydrological regime of the El Grou watershed points out a predominance of evapotranspiration (75%). Moreover, soil erosion estimation for the period (2000-2015) indicates a low to medium potential of soil erosion with an average of 11.3 t/ha/year.