Hydrogeophysical and Hydrogeological Characterization of Groundwater in Parts of the Benin Formation, Akwa Ibom State, Nigeria: Implications for Sustainable Water Resource Management

This study investigates the hydrogeophysical and hydrogeological characteristics of groundwater within Nigeria’s Benin Formation, aiming to support sustainable water resource management. Through 80 Vertical Electrical Soundings (VES) using a Schlumberger array, the study identified three key subsurface layers: topsoil with high resistivity (1,200–5,000 Ωm), an unsaturated zone (1,500–2,000 Ωm), and main aquifer units (1,000–3,500 Ωm), predominantly composed of medium to coarse-grained sands and gravels. The dominant resistivity curve types are KH, HK and KQ (63%), which indicates a high-energy sedimentary terrain with mainly sandy formations or unconsolidated sediments with a mixture of clayey formations. These curve types indicate an alternating layer of conductive (clay) and resistive (sand) materials, reflecting a heterogeneous subsurface. This sand-clay intercalation provided for the unconfined and semi-confined auriferous units. The sandy aquifer units, located at depths between 20 and 75 meters, exhibit high groundwater potential, particularly in the central and northern parts of the Formation. Groundwater flow analysis indicated a predominant north-to-south direction, influenced by regional topography and subsurface lithology, with key recharge zones identified in the northern and central regions. The findings underscore the need for the protection of these recharge zones and careful management of extraction rates to maintain groundwater sustainability. This combined method, which uses both geophysical surveys and hydrogeological analysis, presents a complete framework for the management of groundwater in the Benin Formation.