Understanding Seawater Intrusion by Hydrochemical Parameters and Stable Water Isotopes Along the Coastal Alluvial Aquifers of the Essaouira Basin, Morocco

The agricultural and domestic water supply of Essaouira’s coastal region depends on groundwater resources drawn from the Turonian aquifer. However, due to seawater intrusion and anthropogenic activities, the water supply of coastal aquifers is frequently threatened by salinization. To investigate this matter comprehensively, the present study involved the collection of a total of 34 water samples during the year 2020, with the inclusion of results from 2019 samples. This study used hydrochemical parameters along with stable water isotopes (δ18O and δ2H) to infer salinization processes. The major ions chemistry showed that the groundwater of the Plio-Quaternary aquifer belongs to Cl-Ca-Mg and Cl-Na water types. The ionic ratios, i.e., Br/Cl ≈ 1.5 to 1.7‰, Na/Cl close to 0.86, Mg/Ca and SO4/Cl showed that the seawater begins to invade the freshwater of the Plio-quaternary aquifer of Essaouira basin. The presence of evaporation and maritime intrusion and the contribution of recent precipitations to aquifer recharging were demonstrated by stable water isotopes (δ18O and δ2H). The results show that most of the groundwater samples are saline due to the intrusion of Atlantic Ocean seawater in the coastal aquifer. Hence, an immediate imperative arises for the implementation of an integrated approach to water resource management within this region, employing contemporary methodologies and technologies, in order to secure their enduring viability.