Groundwater potential evaluation and aquifer characterization using resistivity method in Southern Obubra, Southeastern Nigeria

Geo-electric soundings were made in 18 different locations in Southern Obubra area to obtain depth to aquifer units, and thickness of aquifer units. The simulated results of the 18 VES points reveal the presence of 4–5 geo-electric layers. The top layer comprises clay, sand, siltstone intercalations. Layers underneath the top soil are the silty shale, shale, water saturated shaly sandstone and sandstone aquifer. The area is also characterized with high depth to sandstone aquifer which varies from 100m to 240m. This can be attributed to the thick water saturated shaly sandstone in the area. However, at the extreme of North Eastern part of the study area, depths to aquifer are at about 3m to 40m, with VES location 15 having a thickness of about 17m. Aquifer thickness in the study area varies from 17m to 120m. VES No.12 has the highest aquifer resistivity value (689Ωm) in the study area, with depth to aquifer and aquifer thickness of about 200m and 100m respectively. VES 12 is along the Cross section CC¹. Therefore, Aquifer resistivity value along the cross section varies from 689Ωm to 66.94Ωm. The transmissivity varies between 3.5x10⁻²m²/s to 4.68x10⁰m²/s, above the aquifer units in the study area is a widely distributed thick saturated shaly sandstone layer. Borehole construction in the area must be preceded by a detailed geophysical survey with current electrode spacing of at least 600m to 800m.