Determination of aquifer parameters distribution pattern from surficial geophysical measurements in Obot Akara Local Government Area, Akwa Ibom State, Nigeria – A. E. Akpan, A. M. Ekanem, A. A. Sunday, and A. S. Ekine
Surface resistivity data acquired using Schlumberger’s vertical electrical sounding and some geological information have been used to investigate the groundwater resource potential and also characterize the shallow surface aquifers in Obot Akara Local Government Area (LGA) of southeastern Nigeria. Thirty vertical electrical soundings spread across the entire LGA were performed using an ABEM terrameter (SAS 1000 model) with maximum current electrode separation that vary from 800m to 1000m. Both manual and computer modeling techniques were deployed to model the field data. Results show that the shallow surface can be approximated by 3-4-layered subsurface structure with moderate to high resistivity values. Electrical resistivity of the inferred aquiferous layer vary from 3,365Ωm to 55, 799Ωm (mean of 20,187Ωm). Aquifer transmissivity was determined to vary from a minimum of 133.9m3/day around Ikot Amba community to a maximum of 788.0m3/day around Ikwen community (mean of 453.8m3/day). Isoresistivity, isopach and transmissivity maps suggest that the aquiferous layer is inhomogeneous and isotropic with Ikwen community at the centre of major textural discontinuity. An aquiferous sandy layer with poorly sorted textural composition, thickness and type was consequently inferred.