Geo-electrical investigation of the groundwater potential of Ogidi and environs, Anambra State, South-eastern Nigeria

Abstract

The electrical resistivity method was used to determine the groundwater potential of Ogidi and its environs. Thirteen soundings were carried out at thirteen different locations using the ABEM terrameter (SAS 1000), and adopting the Schlumberger configuration with maximum current electrode spacing of 1000 m. The lithologic logs for the boreholes were used to delineate the geologic sections. The results revealed six to nine geo-electric layers comprising laterite, clayey sandstone, sandstone, water-saturated sandstone and shale. The water-saturated sandstone forms the aquiferous unit. This unit was found to have resistivity values ranging from 363Ωm to 9107Ωm. It is deeply seated in some areas with a depth of 33.2–103 m. It was observed that the hydraulic conductivity varies between 0.001 and 0.066 m/day, while the transmissivity values vary between 0.01 and 4.7 m2/day. Among all the VES points studied, it was observed that VES 1 has the highest transmissivity value and the highest aquifer thickness. In view of the foregoing, it is expected that water will flow more from aquifer in VES 1 since groundwater flow from an aquifer is directly proportional to transmissivity.