Abstract
Water erosion is one of the major causes of soil degradation in the world. Among the most negative effects of water erosion is the accumulation of sedimentation in dam reservoirs, leading to a loss of their water storage potential and agro-pedological damage. In the northwest of Morocco, the Bouregreg watershed experiences soil losses every year, that cause a natural imbalance in the ecosystems of the basin and a slowdown in the region’s socio-economic development. These soil losses are reflected in the Sidi Mohamed Ben Abdellah Dam near the mouth of the Bouregreg, by silting up estimated, from a financial point of view, at several million dirhams/year. In order to help better understand and quantify this soil degradation phenomenon, we carried out an evaluation and quantification of the soil losses using empirical universal soil loss equations (USLE) and (RUSLE), by integrating into a Geographic Information System (GIS), layers of information of the main environmental factors involved in the erosive process of the Bouregreg sub-basins (climate, topography, soil, land use). The application of these empirical equations allowed us to identify in a general way, the main factors responsible for the soils water erosion in the Bouregreg watershed. Therefore, the results obtained from these equations show average values of soil loss estimated to 0.94 t/ha/yr and 1.07 t/ha/yr, by applying the USLE and RUSLE methods respectively. On the other hand, the comparison between the values of soil losses estimated in this work by USLE and RUSLE and those of previous works, show relatively small differences. The distribution of the different erosion classes highlights the combined effect of vegetation cover and topography on the variability of water erosion rates in the Bouregreg sub-watersheds