The lower Oued El Kart watershed, situated in the north of Morocco, on the Mediterranean side of the eastern Rif, is characterized by a semi-arid bioclimate and rare and irregular rainfall. The obtained result shows that the watershed loses an average of 14,7 t/ha/year. To evaluate this dynamic and the losses of soil it engenders, we have preceded the integration of the EPM model (Erosion Potential Method) of GAVRILOVIC in a GIS. The maximum loses are 138,8 t/ha/year and minimum are 0,01 t/ha/year. Total annual loses of the watershed of the Oued El Kart low an average of 205 800 t/year (Erosion in the plot). The results analysis of this model has permitted, also using a GIS, to determine the factors that control the water erosion and which are in order of importance: the soil protection (vegetation), erosion types, soil erodibility, the precipitations, the slope, and temperature. It should be noted that the used methodology of the EPM model applies to various types of erosion.