Hydrogeological and hydrochemical characterization of the Turonian aquifer in the Matmata and Menzel El Habib regions for groundwater quality assessment

The Gabès region, located in southeastern Tunisia, is characterized by a semi-arid climate, with a mean annual rainfall of approximately 198.9 mm. Under these hydrologically constrained conditions, groundwater is the primary source of water for domestic, agricultural, and industrial uses. The Turonian aquifer represents one of the main groundwater reservoirs in the region and plays a strategic role in drinking water supply, irrigation, and industrial activities. Sustainable management of this resource requires a thorough understanding of its geometry, hydrodynamic behavior, and hydrochemical quality. In this study, 24 groundwater samples were collected from the Turonian aquifer. The analyses included standard physico-chemical parameters such as temperature, pH, electrical conductivity (EC), and the major ions: Na⁺, K⁺, Ca 2 ⁺, Mg 2 ⁺, HCO₃⁻, SO₄ 2 ⁻, CO₃ 2 ⁻, and Cl⁻. The hydrochemical results indicate that water–rock interactions are the dominant processes controlling the evolution of groundwater chemical facies. Saturation indices calculated for selected minerals, together with the strong correlations observed between major ions (Cl⁻, SO₄ 2 ⁻, Na⁺, and Ca 2 ⁺) and total dissolved solids (TDS), suggest that groundwater mineralization is primarily governed by the dissolution of evaporitic minerals, mainly halite, gypsum, and/or anhydrite. Multivariate statistical analysis using Principal Component Analysis (PCA) allowed identification of the main geochemical processes controlling groundwater composition. The results show that groundwater chemistry is shaped by a combination of evaporite dissolution and cation-exchange processes with the geological matrix, which significantly contribute to the hydrochemical evolution of the Turonian aquifer.