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.

Using an adaptive Mamdani fuzzy inference system model (MFSIM), the purpose of this paper is mainly to assess and rank the assessment and ranking of water quality for irrigation occurring in the Hammamet-Nabeul (Tunisia) shallow aquifer. This aquifer is under Mediterranean climate conditions and affected by intensive and irrational agricultural activities. In the current study, the Mamdani fuzzy logic-based decision-making approach was adapted to classify groundwater quality (GW) for irrigation. The operation of the fuzzy model is based on the input membership functions of electrical conductivity (EC) and sodium absorption ratio (SAR) and on the output membership function of the irrigation water quality index (IWQI). Validation of the applied MFISM showed a rate of about 80%. Therefore, MFISM was shown to be reliable and flexible in quality ranking for irrigation in an uncertain and complex hydrogeological system. The results demonstrated that water quality contamination in the aquifer is affected by the overlaying of three types of negative anthropogenic practices: the excess use of water for irrigation and chemical fertilizers, and the rejection of partially treated wastewater in some areas. The implemented approach led to identifying the spatial distribution of water quality for irrigation in the studied area. It is considered a helpful tool for water agri-environmental sustainability and management.

Degraded groundwater quality, characterized by elevated salinity and nitrate concentrations, poses significant public health concerns, particularly for vulnerable populations such as children. High content of nitrate in drinking water may lead to non-carcinogenic health risks, highlighting the urgent need for sustainable groundwater management strategies to protect both human health and environmental integrity. This study assesses the suitability of groundwater resources in the Regueb Basin for irrigation and drinking purposes, with particular attention paid to nitrate contamination. The Irrigation Water Quality Index (IWQI) indicates considerable spatial variability in groundwater quality, with values varying between 15.86 and 89.55 and a median of 41.69, reflecting differing levels of suitability for irrigation across the basin. Similarly, the Drinking Water Quality Index (DWQI) ranges from 149.16 to 982.42, with a median value of 445.71, suggesting significant concerns regarding groundwater suitability for drinking purposes. The health risk assessment (HHRA) based on the Nitrate Pollution Index (NPI) and the nitrate hazard quotient (HQ__nitrate) reveal substantial risks to human health. NPI values vary between 0.45 and 5.5, with a median of 1.65 indicating varying levels of nitrate pollution. The HQ__nitrate results show that all groundwater samples (100%) pose health risks for children (HQ > 1). For women, 75.61% of HQ values exceed the safe threshold, affecting approximately 80% of the study area, whereas for men, 48.48% of HQ values exceed 1, impacting about 36.67% of the area. Overall, these findings highlight the urgent need for effective groundwater management strategies to mitigate nitrate contamination and ensure the safe and sustainable use of the groundwater resources in the Regueb Basin.