Water demand versus supply in a Mediterranean Arid Region : current and future challenges

This research aims at establishing an integrated modelling framework to assess the impact of climate change on water supply and demand across an arid area in the western Haouz plain in Morocco. Five General Circulation Models (GCM) are used to evaluate future water resources availability under Representative Concentration Pathways (RCP4.5 and RCP8.5 emission scenarios). The projected crop water demand and irrigation water demand were analysed using Aquacrop software, taking into account the impact of climate change on both reference evapotranspiration and crop cycle lengths. The future water balance is simulated by means of Water Evaluation And Planning (WEAP) Tool, including several socioeconomic and land use scenarios under RCP4.5 and RCP8.5. The results reveal an important decrease in net precipitation with an average of -36.2% and -50.5% under RCP4.5 and RCP8.5, respectively. In terms of water balance, the “business as usual” scenario would lead to an increasing of unmet water demand of about +22% in the 2050 horizon and to an increased depletion of the water table that could reach 2m/year. Changing water management and use practices remains the only solution to ensure sustainable water use and deal with the projected water scarcity.