Effects of Land Use Changes on Soil Erosion and Sedimentation of Dams in Semi-Arid Regions: Example of N’Fis Watershed in Western High Atlas, Morocco

Abstract

In Morocco, water resources management has become a challenging request due to the arid climate of the region and the growing population, the water reservoir studied in this work is an example of solutions proposed by the Moroccan government to face this issue. However, the Lalla Takerkoust reservoir is subject to the sedimentation problematic related to soil c classified as severe in the corresponding watershed. We have applied the RUSLE and the SEDD model over two periods to understand the impact of land use change on potential c erosion as well as the suspended sediment yield SSY. Results show a decrease in the the potential soil erosion risk (42.87 t/ha/yr in 1987 to 36.59 t/ha/yr in 2009) and suspended sediment yield SSY (6.52 t/ha/year 1987 to 4.03 t/ha/year in 2009), allowing us to conclude that the green policies adopted by the Moroccan government; especially the one concerning the vegetation cover, have a direct influence on reducing erosion phenomenon, thus, sedimentation of dames. Those results were confirmed by the observed sedimentation obtained from a series of bathymetric campaigns (from 6.52 t/yr in 1987 to 4.03 t/yr in 2009) leading us to conclude that the use of alternative datasets in GIS-based models can give valuable estimations enabling the understanding of the relation of spatial distribution of vegetation-soil erosion-sedimentation in dams, even for a region characterized by lack of data. This study proves also, that rational green strategy of water and vegetation can have a long-term positive effect on dams’ lives.