Résumé
The objective of this study was to simulate the evolution of soil erosion in a semi-arid mountainouswatershed (225 km2, High Atlas Mountains, Morocco) under different scenarios of climate and land usechange to the end of 21st century. Erosion plots monitored over four years showed spatially contrastedresults. Most of the soils produced from 0.015 to 2.5 t/ha/y, whereas badlands produced350 t/ha/y The average sediment yield measured at the outlet during the same period wasapproximately 4 t/ha/y.The STREAM distributed erosion model was parameterized using these field measurements (infiltrationrates and runoff sediment concentrations). The results showed an overall agreement between themodelled and measured annual cumulative sediment yields.Simulations of the ARPEGE meteorological model were used for the 1960-1990 and 2070-2100 periods.The changes between these two periods were downscaled using three different methods,decreasing annual precipitations by 10-14%, although with more rainfall in summer and fall. Climatechange alone increased sediment yield by 4.7-10.1%. However, simulations showed that land usechanges might potentially induce much larger changes in erosion (up to 250%), approximately proportionalto the evolution of the extension of badlands.