Groundwater recharge assessment combining a water balance model with chemical and isotopic tools in a Mediterranean environment: case study from Kasserine, Central West Tunisia

Groundwater recharge assessment in semi-arid Mediterranean regions is challenging due to irregular rainfall, climate variability, and increasing human pressures. The Sidi Marzoug-Sbiba basin (central-western Tunisia), an agricultural area dependent on groundwater, provides a case study of a multi-aquifer system. This study integrates a water balance model, hydrochemical indicators (TDS, NO3−, SO42-, and water facies), and stable (δ18O, δ2H) and radioactive (3H, 14C) isotopes to investigate recharge, groundwater flow, and water quality. Results indicate that the Mio-Plio-Quaternary (MPQ), Miocene, and Cretaceous aquifers are mainly recharged by high-elevation rainfall during the wet season (November-April), with limited evaporation. Groundwater flows regionally from the Sidi Marzoug syncline toward the Sbiba plain, accompanied by increasing mineralization and residence time. Faults and fractured outcrops facilitate recharge and lateral hydraulic connectivity. Isotopic evidence highlights modern recharge upstream and older groundwater downstream. These findings highlight the value of integrated approaches for assessing recharge and supporting sustainable groundwater management.