Résumé
Over the past decades, drought has become a major concern in Morocco due to the strong importance of agriculture in the economy of the country. In the present work, the standardized precipitation index (SPI) is used to monitor the evolution, frequency and severity of droughts in the High Atlas basins (N'Fis, Ourika, Rhéraya, Zat and R'dat), located south of Marrakech city. The spatiotemporal characterization of drought in these basins is done by computing the SPI with precipitation spatially interpolated on the catchments areas. The Haouz plain, located downstream of these basins, is strongly dependent on water provided by the mountain ranges, as shown by the positive correlations between the Normalized Difference Vegetation Index (NDVI) in the plain and the SPI 3-month, 6-Month and 12-Month in the High-Atlas catchments. On the opposite, no strong correlations are found with piezometric levels due to intensified pumping for irrigation in the recent decades. To evaluate the climate change impacts on drought occurrence, we calculated a relative SPI index, to estimate future droughts with the projected precipitation (2006-2100) of high-resolution CORDEX regional climate simulations, under 2 emission scenarios (RCP 4.5 and RCP 8.5). These models show a decrease in precipitation towards the future up to -65% compared to the historical period. In terms of drought events, the future projections indicate a strong increase in the frequency of SPI events below -2.