Appraisal of aquifer protective capacity and groundwater potential using the vertical electrical sounding technique in Illah, Delta State, Nigeria

Groundwater is a critical resource in Illah, Delta State, where surface water is unreliable. This study aims to evaluate groundwater potential and aquifer properties using geoelectric methods, with a particular focus on Dar-Zarrouk parameters. Thirteen Vertical Electrical Sounding (VES) surveys were conducted using the Schlumberger array. Derived parameters, including resistivity, thickness, and Dar-Zarrouk indices, were analysed to characterise the aquifers’ hydraulic properties. Four to five geoelectric layers underlie the study area. Aquifer resistivity ranged from 124–2499 Ω·m, thickness from 3.4–57.9 m, and transmissivity from 27.54–468.99 m²/day. VES 4, VES 1, and VES 7 were identified as high-potential sites. Longitudinal conductance values (0.0038–0.2949 Ω⁻¹) indicated that most aquifers had poor to moderate protective capacity. High transmissivity zones with moderate overburden protection, such as VES 4 and VES 1, are ideal for borehole development. VES 2 and VES 9 had low transmissivity, suggesting low productivity. Spatial variations reveal Illah’s complex hydrogeological structure influenced by the Imo Formation. Geoelectrical sounding and Dar-Zarrouk analysis offer a cost-effective approach for aquifer evaluation in Illah, facilitating data-driven groundwater resource planning. The integration of resistivity and Dar-Zarrouk parameters provides a robust geophysical framework for aquifer zoning in data-scarce rural settings.