Groundwater Responses to Climate Change in a Coastal Semi-arid Area from Morocco; Case of Essaouira Basin

Abstract

During the last decades, a decrease in precipitation and an increase in air temperature are observed from arid and semi-arid areas. Therefore, changes in the water resource balance are expected. In this context, this study aimed to identify the climate change effects on groundwater from the Essaouira basin (southwestern Morocco). The average precipitation is about 300 mm/year and the temperatures oscillate around 20 °C. The climate study showed that the precipitation and the air temperatures show a general downward trend (~12%) and an upward trend (~1.5 °C), respectively. The decrease in recharge and recurrent drought episodes caused a continuous decrease in groundwater level. The hydrogeochemical approach indicates that (i) the groundwater facies was mainly of the Na–Cl type from 1990 to 2009, and Mg–Ca–Cl for 2015, (ii) a degradation of groundwater quality with an increase in salinity (80–3500 mg/L) that resulted from the dissolution of evaporate minerals and seawater intrusion. The concentration of 18O, 2H are determined, the local meteoric water line (LMWL) close to the global meteoric water line (GMWL) characterizing ocean precipitations is determined. The ground waters of Essaouira basin are very sensitive to any variation in the natural recharge, this makes them very vulnerable faced with the climate change. The results of this study should be taken in consideration for the future water management in this region.