Enhancing groundwater resources through managed aquifer recharge: A SWAT application in arid southeastern Tunisia

Study region: The Triassic aquifer of Sahel el Ababsa in the Jeffara plain, southeastern Tunisia, lies in an arid region facing growing water scarcity due to climate and land-use pressures. Study focus: This study applied the Soil and Water Assessment Tool (SWAT) to simulate hydrological processes and evaluate the impact of Managed Aquifer Recharge (MAR) structures, including traditional Water Harvesting Techniques (WHTs), on groundwater recharge. Two SWAT models were developed for the pre-implementation (1971-1990) and post-implementation (1991-2020) phases of the Tunisian Strategy for Water and Soil Conservation (SWSC). Model calibration using observed discharge and potential evapotranspiration (PET) showed satisfactory performance (R2 = 0.72, NSE = 0.63 for discharge; R2 = 0.79, NSE = 0.72 for PET) with validation also satisfactory (R2 = 0.69 and NSE = 0.62 for discharge; R2 = 0.82 and NSE = 0.75 for PET). New hydrological insights: SWAT successfully reproduced groundwater recharge under natural conditions, consistent with previous studies in southern Tunisia, and quantified the additional recharge induced by MAR structures. Results demonstrate that rainwater-based MAR significantly enhances aquifer recharge and confirm SWAT's suitability for simulating water balance in arid environments. The water balance shifted from 74 % Actual Evaporation (ET), 5 % recharge, and 21 % outflow before SWSC to 82 % ET, 7.2 % recharge (including recharge wells), and 13 % outflow after SWSC implementation. In the calibrated Koutine watershed, WHTs induce an estimated + 5 % increase in groundwater recharge.