Parameter variations for the sandy aquifers in northern parts of Akwa Ibom state, Southern Nigeria

Abstract

The subsurface sandy aquifers in the in northern parts of Akwa Ibom State, Southern Nigeria were studied to see how homogenous or otherwise the aquifer parameters could be. The parameters considered in the present study were lithologic composition of the aquifer, depth of occurrence, thickness and aquifer resistivity. Vertical Electrical Sounding (VES) using Schlumberger electrode configuration was the choice array used in data collection. Forty five (45) points were electrically sounded across the study area to obtain information on the electrical signatures of the subsurface layers. Both manual and computer aided methods were used in the analysis of the acquired field data. Interpreted results showed great variability of the aquifer parameters. Aquifer lithological make-up varied markedly from fine/coarse grained sand to clayey sand as one approached the northern parts of the study area. Deep seated/confined aquifers reaching an interpreted drill depth of about 110 m were also found northwards compared to an interpreted drill depth of about 22.7 m inland. Most of the aquifers encountered were prolific with some reaching a thickness of over 60 m. Aquifer resistivity values varying between 71.8 Ωm to 28,413.0 Ωm were also obtained within the study area. The study concluded that, the varied inhomogeneity of the explored subsurface indicated that the area of study is a transition zone between the Pliocene-Pleistocene Benin formation/Coastal plain sand and the Middle Eocene Bende-Ameke Group.