Delineating groundwater aquifer using geo-electrical data: A Case Study of Ogwashi-Asaba Formation in Anambra State of Nigeria

Abstract

The residents of Anambra State in South East of Nigeria has experienced failure of public water scheme, resort has been made to rainwater and majorly groundwater resource for daily water use. This study seeks to delineate the groundwater aquifer and subsurface structures of Ogwashi-Asaba formation to ascertain the potential for good water source for the study area. The formation spans through several towns such as Onitsha, Oba, Orafite, Nnewi, Ozubulu, Utuh, Ihembosi, Ihiala, Ukpor, Okija, Azia, Orsumoghu, Ubuloisizo, and Iseke. Thirty (30) Vertical Electric Sounding (VES) stations were used in the assessment and delineation of the groundwater potential and subsurface structures using Schlumberger configuration. Aquifer parameters assessed includes depth, longitudinal conductance, hydraulic conductivity, transmissivity, refection coefficient and fractured contrast. The data of the aquifer parameters were plotted using Surfer software. The results revealed that the subsurface section consists of four to seven geo-electrical layers, the aquifer parameters varied from 89.9 m – 217.5 m, 0.006442338 mhom - 1.036379385 mhom, 0.002669441 m/day - 1.561045959 m/day, 1.0918 m²/day- 16 m²/day, 0.0865694-0.9982744, and 0.02841167 - 0.84065551 for Depth, Longitudinal Conductance, Hydraulic Conductivity, Transmissivity, Refection Coefficient and Fractured Contrast respectively. The data obtained from the variability of aquifer characteristics from the various towns in Ogwashi-Asaba geological formation will be a veritable tool in utilizing the groundwater resource of the study area.