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Groundwater (GW) studies have been conducted worldwide with regard to several pressures, including climate change, seawater intrusion, and water overexploitation. GW quality is a very important sector for several countries in the world, in particular for Tunisia. The shallow coastal aquifer of Sfax (located in Tunisia) was found to be under the combined conditions of continuous drop in GW and further deterioration of the groundwater quality (GWQ). This study was conducted to identify the processes that control GWQ mainly in relation to mineralization sources in the shallow Sfax coastal aquifer. To perform this task, 37 wells are considered. Data include 10 physico-chemical properties of groundwater analyzed in water samples: pH, EC, calcium (Ca), sodium (Na), magnesium (Mg), potassium (K), chloride (Cl), sulfate (SO4), bicarbonate (HCO3), and nitrate (NO3), i.e., investigation was based on a database of 370 observations. Principal component analysis (PCA) and hydrochemical facies evolution (HFE) were conducted to extract the main factors affecting GW chemistry. The results obtained using the PCA model show that GWQ is mainly controlled by either natural factors (rock–water interactions) or anthropogenic ones (agricultural and domestic activities). Indeed, the GW overexploitation generated not only the GWQ degradation but also the SWI. The inverse distance weighted (IDW) method, integrated in a geographic information system (GIS), is employed to achieve spatial mapping of seawater intrusion locations. Hydrochemical facies evolution (HFE) results corroborate the seawater intrusion and its spatial distribution. Furthermore, the mixing ratio showed that Jebeniana and Chaffar–Mahares localities are characterized by high SWI hazard. This research should be done to better manage GW resources and help to develop a suitable plan for the exploitation and protection of water resources.

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The coastal aquifers system of Sfax Agareb Chaffar Mahres (Southern Sfax) located in the central east of Tunisia is well known for population growth and industrial development. These industrial and agricultural developments have led to the degradation of water quality. In this study, DRASTIC and GALDIT models were integrated with geographical information system (GIS) tools, in order to assess the aquifers vulnerability to pollution and the seawater intrusion risk. These methods use different parameters explaining the different results in the vulnerability degrees in the Aghereb-Chaffar-Mahres aquifer system. The vulnerability map to contamination as well as vulnerability to seawater intrusion showed three classes of vulnerability: low, moderate and high, depending on the intrinsic properties. In addition, the risk map showed three risk classes: low, moderate and high depending on hydrogeological characteristics, land use, distance from the coast and human impacts in the majority of the study area. GIS is used to manage, manipulate and analyze the necessary geographical data used in the different vulnerability methods. These maps could serve as a scientific basis for sustainable land use planning and groundwater management in Southern Sfax.