Hydrogeophysical Delineation of Coastal Aquifer Systems Using Electrical Resistivity Imaging in Selected Coastal Communities of the Niger Delta, Nigeria

Abstract

An integrated hydrogeophysical investigation was conducted to delineate coastal aquifer systems and assess groundwater potential in selected coastal communities of the Niger Delta, Nigeria. Ten Vertical Electrical Sounding stations and five Two-Dimensional Electrical Resistivity Tomography profiles were acquired using an ABEM Terrameter SAS 1000. Apparent resistivity data were interpreted with IPI2Win and RES2DINV software, while hydraulic parameters, Dar-Zarrouk parameters, reflection coefficient and coefficient of anisotropy were derived from the interpreted resistivity models. Four principal geoelectrical layers were identified: sandy topsoil, clay, sandy clay and freshwater-bearing sand aquifers. Aquifer resistivity ranged from 485 to 622 Ωm, and aquifer thickness varied from 52.4 to 74.6 m at depths of 25.2–30.9 m. Longitudinal conductance values of 0.62–0.76 mhos indicated moderate to good aquifer protective capacity, while transverse resistance values of 25,414–46,401 Ωm² suggested favourable transmissive conditions. Estimated hydraulic conductivity ranged from 12.5 to 18.0 m day⁻¹, with transmissivity values of 655–1,343 m² day⁻¹. Reflection coefficient values of 0.31–0.45 and coefficient of anisotropy values of 1.36–1.72 indicated moderate to very high groundwater potential. The integrated interpretation indicates that the aquifers have favourable storage and transmission characteristics for groundwater development. However, their low elevation and proximity to the Atlantic coastline require continuous monitoring and regulated abstraction to limit seawater-intrusion risk.