GIS-Based Model for Vulnerability and Seawater Intrusion Risk Assessment by Combined Chemical Indicators and GALDIT Tools: The Case of a Coastal Aquifer in Monastir, Tunisia

Due to an increase in population and agricultural activities in coastal areas, seawater intrusion is a major threat to the rapidly depleting groundwater resources around these areas. This research was refined with local inputs to study one of the most sensitive Tunisian coastlines, Monastir. With the aim of tackling the groundwater degradation problem, an approach combining a survey of some dissolved ions and the Geographical Information System (GIS)-based hydrogeological index, named the GALDIT method, was applied to evaluate the aquifer’s vulnerability, as a technique for assessing seawater intrusion potential. This allowed to prepare thematic maps for seawater indicators and to develop a final vulnerability map. The derived map illustrates that the most affected areas in our case are the coastal zones of the aquifer and the northeastern part in the proximity of the Moknine sabkha, having the highest GALDIT Index, between 70 and 90. This study aims to propose some agricultural policies to conserve groundwater resources and groundwater management alternatives for this coastal aquifer. It could also serve as a scientific basis for sustainable groundwater planning and management in Monastir.