Application of Integrated Geophysical Methods for Groundwater Exploration in El Azreg Basin, Northern Mauritania

The El Azreg region in Zouerate, Mauritania, a key iron ore–producing area, faces acute freshwater scarcity due to arid climatic conditions and increasing industrial demands of SNIM (Société Nationale Industrielle et Minière). This study applies an integrated geophysical approach combining electromagnetic (EM), gravity, and electrical resistivity surveys (1D VES, HEP, and 2D ERT) with borehole data to characterize the basin's hydrogeological framework. EM data identified high-conductivity anomalies (>90 mS/cm) corresponding to fractured dolomite aquifers controlled by NE–SW-trending fault systems that act as preferential groundwater pathways. Gravity anomalies revealed fault-controlled structural blocks that compartmentalize the aquifer system within the ~500-m-thick Infracambrian succession. Electrical resistivity imaging delineated the vertical and lateral continuity of key stratigraphic units, with the fractured dolomitic sequence (Char Group) emerging as the primary aquifer, extending 50-120 m in thickness with moderate resistivity (50–500 Ωm) and enhanced secondary porosity. The overlying quartzitic sandstones act as regional hydraulic barriers, while the basement provides limited storage in fracture networks. Aquifer productivity is maximized at intersections of vertical faults with horizontal lithological contacts, creating dual-porosity conditions optimal for groundwater storage. Despite significant reserves, long-term sustainability is threatened by localized salinization along fault corridors from natural and anthropogenic sources. The results demonstrate the effectiveness of integrated geophysics in delineating complex aquifer systems in arid environments and underscore the need for managed aquifer recharge, structural control studies, and policies that balance industrial growth with environmental protection and community water needs.