Effects of vegetation dynamics on the silting rate and the availability of water in Makhazine dam (Morocco)

Abstract

This paper describes the D-RUSLE model (Dynamic Revised Universal Soil Loss), a modified version of classic RUSLE, which takes into account the variability of rain erosivity and land cover, to provide a more precise estimate of the soil potential erosion. In order to precisely model the potential soil erosion rate at the scale of the Loukkos watershed (~1619 ha), we carried out a spatio-temporal monitoring of rain erosivity and vegetation dynamics for two periods (1999-2008) and (2008-2013). In particular, we used time series of NDVI, derived from satellite multi temporal data to calculate C factor of land cover. By integrating C factor estimated in this manner into D-RUSLE model, we estimated in a detailed and reliable way the potential soil loss and the long term seasonal variations of terrestrial cover. The results show that mean specific degradation in Loukkos watershed is 22.56 t/ha/yr. for the first period (1999-2008) and 40.58 t/ha/yr. for the second period (2008-2013), with a delivery rate (SDR) of 22.19 %. They also highlight that the amount of sediments delivered to the dam reservoir is regarded as high compared to the bathymetric value observed of 20.05 t/ha/yr. and 38.44 t/ha/yr., respectively for the first and the second period.

Keywords: Siltation, Delivery Rate, Modeling, D-RUSLE, Remote Sensing, Vegetation Dynamics.