Geoelectrical and Hydrogeochemical Assessment of the Groundwater Potentials of Ehandiagu, Enugu State, Southeastern Nigeria

Geoelectrical, hydrogeochemical investigations were carried out in order to determine the groundwater potentials of Ehandiagu in Enugu state, southeastern Nigeria. Ehandiagu is underlain by the Nkporo Shale, which is a low permeability formation. Four vertical electrical sounding (VES), employing the Schlumberger electrode configuration, was carried out in the study area, with a maximum electrode separation of 580m. The VES data were modeled with the IPI2 WIN software. The VES curves were predominantly of the QH type. The lithologic succession consists of lateritic top soil, weathered bedrock, fractured shale (the aquifer) and compact carbonaceous shale. Results show that the depth to water ranges between 6.82m and 20.7m while aquifer thicknesses range between 8.95m and 26.26m. The depth to water obtained from hand-dug wells varies between 6.20m and 15.18m. Aquifer hydraulic conductivity and transmissivity were calculated to be 2.62 x 10 ^-3 m/day and 4.31 x 10^-2 m^2/day respectively. These parameters were used to classify the aquifer as moderately good to poor aquifer. Hydrogeochemical analysis of groundwater samples collected from twelve (12) hand-dug wells in the study area reveals that weathering is the major process that controls the groundwater chemistry and the water type is Sodium-Potassium-Bicarbonate. The concentration of heavy metals (Mn, Fe, Pb) were found to be above the acceptable limits for potability and the SO4^2- concentration is very low, probably due to sulphate reduction. Both sulphate reduction and high heavy metal concentration suggest a geochemical reducing environment.