Projecting the impacts of climate change-induced droughts on crops and water in a North-African watershed

Abstract:

North Africa region is considered among the most vulnerable regions regarding climate change impacts. Most of future climate’ related studies are predicting an increase of dryness in this region. Providing data about the potential responses of different vital processes to future extreme events (such as drought) will help in designing the fitting adaptation strategies. In this study, the basin-scale model SWAT (Soil and Water Assessment Tool) was forced by downscaled CORDEX climate projections (RCP4.5 and RCP8.5) to assess the impact of 2030-2050 droughts on hydrology and rainfed wheat yields in Bouregreg watershed(9656 km²) in Morocco. Simulated rainfall over the study watershed were used to calculate 12 months Standardized Precipitation Index (12-SPI). Several drought events with different intensities across sub-basins have been identified in the 2030-2050 period under both RCPs. In comparison with the baseline situation, drought episodes are expected to be of higher durations especially under the pessimistic emission scenario (RCP8.5). During dry years, dramatic decrease of water resources availability has been simulated (more than -60% in some scenarios) with uneven impacts across the study catchment. The most vulnerable sub-basins to drought were identified for very specific management plans. Yields of rainfed wheat crop should drop (up to -70% in some scenarios) during the extreme dry years with lower extent in sub-basin with high elevation or those located close to the ocean.The adopted methodology in this study offers a comprehensive framework by taking benefit of the physical distribution feature of SWAT model and the statistical representation of different drought indices to forecast future droughts and their spatial extent within Bouregreg watershed.