The risk of water erosion between the vulnerability of environmental balances and prospects for sustainability: The case of the El Abed watershed (north-eastern Morocco)

Abstract

The objective of this work is to study water erosion phenomenon in El Abed watershed in North Eastern Morocco. With this in mind, we have analyzed the quantitative and qualitative information available on the one hand, and on the other hand, we have carried out field measurements by rain simulation (60 mm/h during 10 mn). Soil loss was estimated using the universal soil loss equation (USLE). The qualitative analysis based on the inventory of the various forms of water erosion showed a strong morphodynamic activity, characterized by diffuse and concentrated streaming, gullying and side extensions of valleys. The quantitative analysis of soil losses using USLE model made it possible to estimate that 4,7% of the watershed surface area are strongly eroded and that average specific degradation is estimated to be 6,4 t/ha/an. Measurements of rain simulation tests showed clear differences between the various land uses. Indeed, runoff coefficient is low on the vegetation covered plots of and the plots cultivated parallel to contour lines. On the other hand, runoff coefficient is high on steeply bare soils. The amount of detached soil varied from 0.014 t/ha for the covered plots to 2.9 t/ha for the steeply bare soils. It should be underlined that the extent of water erosion in El Abed watershed is due to its natural settings, but also to anthropic activities (cultivation and overgrazing).

 Keywords: Water erosion, USLE, El Abed watershed, Morocco