Hydrogeophysical delineation of aquifer vulnerability in parts of Nkalagu area of Abakaliki, se. Nigeria

In this study, Vertical Electrical Sounding (VES) method was employed in evaluating aquifer protective capacity/vulnerability of the study area. For the study, 20 VES survey was conducted using the Schlumberger configuration with maximum electrode spacing of 200 m. The evaluation of aquifer protective capacity was based on the following Dar- Zarrouk parameters: longitudinal conductance (S), transverse resistance (T), longitudinal resistance (ρL), and average transverse resistance (ρt). Results obtained from VES data suggested that the layer model ranges from 3 to 6 layers, it was observed that curve HK was the dominant curve type with 37% when compared to other curve types. Findings from S revealed that aquifer protective capacity ranges from poor to very good category and the middle part of the study area with high S value showed the area with high aquifer protective capacity when compared to other parts of the study area, high Tr value was observed in northwest part of the study area, such area could be referred to an area with high groundwater potential, map of ρL showed contour interval of 500 Ω-m that demarcates the study into saline, brackish and freshwater aquifer and high ρt value was observed in northwest and southwest part of the study. Plots from aquifer geometric properties; aquifer thickness, aquifer resistivity and aquifer conductivity range from 12.3 to 116.5 m, 150.6 to 498.6 Ωm and 0.0810^–3 to 5.510^–3 respectively. Contour maps of iso-resistivity revealed that as AB/2 increase with depth from 6 to 150 m the area becomes shaly.