Effect of Climate Change on Sea Water Intrusion in the Essaouira Basin Coastal Aquifer

Groundwater serves as a vital source of potable water for domestic and drinking purposes in various regions globally. However, rising sea levels have led to the encroachment of saltwater into coastal underground aquifers, resulting in a degradation of water quality over time. In the context of the hydrogeochemical examination conducted, it was observed that the groundwater within the Plio-quaternary aquifer exhibits a composition characterized by Cl–Ca–Mg and Cl–Na elements. Specific ionic ratios, such as Br/Cl (approximately 1.5–1.7‰) and Na/Cl (approximately 0.86), in addition to relatively weak values for Mg/Ca and SO4/Cl ratios, signify the initiation of seawater intrusion into the freshwater reserves of the Plio-quaternary aquifer within the Essaouira basin. This incursion of seawater is substantiated by ionic ratios and is further validated through stable isotopic analysis. By leveraging the combined information from oxygen-18 contents and chloride concentrations, the degree of mixing between seawater and freshwater in the Plio-quaternary aquifer is estimated to range from 12.8 to 15.9%. Furthermore, the stable isotopes approach has shed light on the source of recharge for the Plio-Quaternary and Turonian aquifers, indicating that these aquifers are primarily recharged by Atlantic-origin precipitation with limited evaporation effects. However, it is evident that these freshwater resources have undergone contamination due to the intrusion of seawater.