Spatiotemporal Changes in the Hydrochemical Characteristics and the Assessment of Groundwater Suitability for Drinking and Irrigation in the Mornag Coastal Region, Northeastern Tunisia

Hydrogeochemical properties and groundwater quality assessment are very important for the effective management of water resources in arid and semiarid regions. The present investigation is a spatiotemporal analysis of groundwater quality using both chemical analysis and water quality indices (WQIs) in the Mornag Basin in northeastern Tunisia. The results exhibit that the Mornag shallow aquifer is dominated by chloride–sodium–potassium water facies, which progress over time toward chloride–sulfate–calcium and magnesium water facies. This may highlight that the mineralization of groundwater, which increases in the direction of groundwater flow, is primarily controlled by a natural process resulting from the dissolution of evaporative minerals and cation exchange with clay minerals relatively abundant in the study area. The anthropogenic activities represented by the return flow of irrigation water, the recharge by wastewater, and climate change also have a key role in groundwater contamination. The temporal evolution in %Na and SAR over the last three years in the Mornag aquifer shows an increasing trend that makes them unsuitable for irrigation. These findings highlight the need for assessing water quality in mapping local water resource vulnerability to pollution and developing sustainable water resources management.