Geophysical Investigation of Uke-Ideani and Environs in Southeastern Nigeria

Abstract

Groundwater is an important source of water supply for communities in southeastern Nigeria, and reliable subsurface information is required for effective groundwater exploration and borehole siting. This study presents a geophysical investigation of Uke-Ideani and adjoining areas in Anambra State, southeastern Nigeria, using the electrical resistivity method. Five Vertical Electrical Sounding (VES) stations were occupied using the Schlumberger electrode configuration, with a maximum half-current electrode spacing of 160 m. Field resistance measurements were converted to apparent resistivity values and interpreted to determine subsurface layer resistivities, thicknesses, depths, and inferred lithological units. Geoelectric sections were constructed to assess vertical and lateral variations in lithology and aquifer occurrence. Aquifer parameters, including longitudinal conductance, transverse resistance, hydraulic conductivity, and transmissivity, were estimated from the interpreted geoelectrical data. The results indicate four to five geoelectric layers across the investigated locations, consisting mainly of topsoil, clay, sandy clay, clayey sand, sandstone, and water-saturated sandstone. The principal aquifer units occur within sandstone layers, with aquifer resistivity values ranging from 92.8 to 1539 Ωm. The interpreted aquifer depths vary from 22.6 m at Alor to 97.1 m at Uke, showing spatial variation in groundwater occurrence across the area. Estimated hydraulic conductivity values range from 0.00064 to 0.01077 m/day, while transmissivity values range from 0.0512 to 0.677433 m²/day. These values indicate low to moderate groundwater potential, with Uke, Ojoto, Alor, and Nnobi showing moderate transmissivity and Umuoji showing comparatively low transmissivity. The findings indicate that electrical resistivity sounding can delineate aquifer geometry and support groundwater development decisions in the study area.