Use of WQI and Isotopes to Assess Groundwater Quality of Coastal Aquifers (Essaouira, Morocco)

In the aquifers located along the Morocco coast, high mineralization of the groundwater is caused by dissolution processes of evaporitic rocks and carbonates and human impact from agriculture. The aim of the present work was to assess the origin and groundwater quality in the coastal aquifer of Essaouira synclinal basin. Therefore, 28 groundwater samples were used in the calculation of the Water Quality Index (WQI) during the period of March 2019. Eleven physico-chemical parameters were taken into account for the calculation of the WQI. The results obtained showed that the WQI values range from 110 to 890. The results obtained indicate that poor groundwater quality was specially found in the downstream part of the study area due to several factors such as the dissolution of evaporite minerals (e.g. gypsum, halite, and anhydrite), the use of pesticides and sea water intrusion. In addition, oxygen 18 (¹⁸O) and deuterium (²H) showed that the aquifer of study area is recharged by rapid infiltration (without evaporation) of meteoric waters ascribed to oceanic precipitation. Results obtained showed that this basin is sensitive and vulnerable to any climatic variation and therefore climate change.