Climate change impact on water resource in semi-arid environment: Example of Essaouira basin (Morocco)

As is the case for basins of arid and semi-arid zones, the Essaouira Basin is likely to be at high risk of water scarcity due to climate change. The Essaouira Basin, which is the subject of this study, is located on the Atlantic coast of Morocco, southeast of the city of Essaouira. It is characterized by a semi-arid climate with annual rainfall of around 300 mm and average temperatures of 20°C. Looking at the importance of this basin for the groundwater supply of the Essaouira City and neighbouring clusters, this article considers the potential effect of climate change on water resources in this area. A series of piezometric maps was prepared (1990-2016) and the hydrochemical study of the water shows that they have a Na-Cl type facies in 1990, 1995 and 2009 and Mg-Ca-Cl type in 2015. This evolution is the result of cation exchange following the exceptional precipitation of 2015. The isotopes18O,2H,3H and14C were analyzed during the campaigns of 1996, 2006 and 2007. The local meteoric water line close to the global meteoric water line characterizing precipitation of oceanic origin was determined. The results of this work show: i) the existence of a depression in the piezometric level during dry years (e.g. 1995) and a modest recovery during wet years (e.g. 2004 and 2009), ii) a deterioration of the water quality away from the Wadi Ksob (recharge zone of the aquifer), and iii) that the recharge the aquifer depends on rainfall. © 2018, Institut National de la Research Scientifique. All rights reserved.