Sustainable groundwater supply in semi-arid dune fields: hydrochemical constraints and freshwater-lens variability in Médanos, Buenos Aires, Argentina

Abstract

Groundwater quality and quantity are critical in semi-arid regions, where it is often the sole water source. This study focuses on Médanos (Villarino district, Argentina), which relies on a phreatic aquifer within an eolian dune field. Water quality varies with well location and depth due to hydrochemical stratification. This study aims to determine the hydrogeological conditions and limiting factors of the aquifer in the area, using well surveys, in situ measurements, physicochemical analyses, and electrical resistivity tomography (ERT). Results identify a freshwater lens, characterized by electrical conductivity generally below 1000 μS/cm in recharge zones, overlying saline groundwater. Electrical conductivity shows spatial variability, with lower values in central and southwestern preferential recharge areas and higher values toward discharge sectors. ERT results reveal significant variations in freshwater thickness and identify paleochannels as preferential targets for groundwater abstraction. Analysis of existing well fields demonstrate the strong influence of well depth and placement on both yield and water quality, with the La Mascota field presenting the most favorable conditions. The results highlight the combined role of hydrochemical constraints and freshwater-lens variability in controlling groundwater exploitation and emphasize the need for strategic well placement to ensure a sustainable water supply for the town of Médanos.