Climate Change Impact on Aquifer System of Essaouira Basin during the Past 4 Decades (Morocco)

Since the 50s, many changes are observed in the climate of the globe, the warming of the atmosphere and the ocean, the decrease in the extent of snow and ice, and rising sea levels. In addition to the demographic pressure, the Maghreb countries are suffering from the drought, which accentuates the phenomenon of desertification and soil erosion, as well as their salinity, which leads to the salinization and depletion of water resources. In Morocco, the climate change leads to the erosion of the soil under the effect of desertification resulting in siltation of reservoirs and the increased salinization of soil and water resources. The Essaouira basin, which is the subject of this study, is located at the Western extremity of the High Atlas to the Southeast of the Essaouira city; between 31°20' to 31°30'N and between 9°00' to 9°46'W. The basin is characterized by a semi-arid climate with average annual rainfall of around 300 mm·year-1 and an average temperature of 20°C. Considering the importance of the aquifer in Essaouira in the supply of the region's groundwater, a study was conducted to assess quantitatively and qualitatively the impact of climate change on water resources in this area. The aquifers present in this region are one of cenomano-turonian upstream and plio-quaternary downstream, separated by the diaper of Tidzi. A piezometric map of the basin was made (1990-2009) and the hydrochemical method of the waters shows that they present a facies Na-Cl with an electrical conductivity ranging from 700 to 7000 μs/cm. The isotopic tracers like 18O, 2H, 3H and 14C were analyzed to determine the age of groundwater, and a right local meteoric close to the right meteoric world characterizing the precipitation of oceanic origin has been determined. The Essaouira basin turns out to be very vulnerable and sensitive to climate change because its recharge is entirely dependent on the rainwater. These results should be taken in consideration for the future water management in the region.