Moroccan Climate in the Present and Future: Combined View from Observational Data and Regional Climate Scenarios

The impact of climate change on water availability in the Middle East and the Upper Jordan catchment (UJC) is investigated by dynamic downscaling of ECHAM4 time slices and subsequent hydrological modelling. Two time slices (1961–90 and 2070–99) of the global climate scenario B2 of ECHAM4 were dynamically downscaled with the meteorological model MM5 in two nesting steps of 54 km and 18 km resolution. The meteorological fields were used to drive a physically based hydrological model, computing in detail the surface and subsurface water flow and water balance of the UJC.

Results of the joint regional climate-hydrology simulations indicate mean annual temperature increases up to 4.5° C and 25 % decreases in mean annual precipitation in the mountainous part of the UJC. Total runoff at the outlet of the catchment is predicted to decrease by 23 %, and is accompanied by significant decreasing groundwater recharge.