Quantification of water erosion using empirical models RUSLE and EPM in the Rheraya basin in the High Atlas of Marrakech

Soil loss caused by water erosion constitutes a major issue that generate environmental and other several problems. The objective of this work is to quantify and assess the risk of erosion in the region of the Rheraya basin3 and to estimate the rate of soil loss and to characterize the main criteria involved in the evolution of water erosion in the basin. The study revealed that the combined presence of streams, crossing easily eroded surfaces, slopes, as well as anthropogenic action, aggravated the phenomenon. The empirical RUSLE4 and EPM5 models combined with GIS and remote sensing6 were adopted to characterize this rate in the region. The RUSLE model evaluated the rate of soil loss produced by sheet erosion, based on the aggressiveness of the rain, soil erodibility, the vegetation cover, the length and the inclination of the slope as well as the anti-erosion practices in the basin. The "EPM" model estimated the rate of erosion and soil losses caused by water erosion in general. It is based on the mapping and the combination of six parameters which are: average temperature, average annual precipitation, slope, erosion state, land use and soil resistance to erosion. Results showed that the erosion rate using Rusle model varies between 0 and 188 t/ha/year with an average annual soil loss of 46, 85 t/ha/year. The results of the application of the EPM model showed that the average annual of soil loss is 103 t/ha/y with values extending between 0 and 200 t/ha/y. These results exposed that the areas upstream represent a very high risk of erosion, so they can surely aid to manage and reduce soil erosion in the High Atlas mountains.