Characterization of Subsurface Lithology and Aquifer Parameters Using Vertical Electrical Sounding (VES) for Groundwater Development in Igbo-Imabana, Southern Nigeria
Vertical Electrical Soundings (VES) using Schlumberger array was carried out at fifteen (15) different points to evaluate aquifer characteristics within Igbo-Imabana, Abi L.G.A of Cross River State. Resistivity meter and its accessories were used for data acquisition. The maximum current and potential electrode distance were 400 m and 20 m respectively. The field data were interpreted using Interpex software and three to five geo-electric layers encountered within the study area. The dominant curve type was H followed by K. From the result, geo-electric layers delineated were sandstone, clay, saturated sandstone, sandy shale, clayey shale, and shale with average apparent resistivity values of 2249.94 Ωm, 2.86 Ωm, 365.28 Ωm, 222.69 Ωm, 14.60 Ωm and 59.02 Ωm respectively. The top geoelectric layer was dominantly lateritic topsoil, with variation in degrees of compaction and having an average resistivity of 876.33 Ωm with depth and thickness generally less than 5 m. The calculated aquifer parameters hydraulic conductivity (Kc), transmissivity, longitudinal conductance, and transverse resistance from the VES results show ranges values; 3.86×10–4 to 4.69×10–2 m/day, 2.95×10–3 to 2.82 m2 /day, 2.95×10–3 to 2.81 Ωm and 484.33 to 19444.83 Ω2 m respectively. The aquifer thickness and depth values range from 3.60 m to 68.05 m and 5.20 m to 76 m respectively. The study reviewed that the area is made of heterolithic/heterogenou lithofacies, confined aquifer(s), shallow and deep aquifer. Also, from the models and aquifer parameters, the area is characterized by semipervious materials. This integrally explains why the area have have low transmissivity and majority of boreholes drilled in the area failed.