Aquifer Vulnerability Investigation Using Geoelectric Method in Parts of Sapele Local Government Area of Delta State, Nigeria

Abstract

The electrical resistivity survey has been used in the determination of the overburden protective capacity in Amukpe area of Delta State, Nigeria. Nineteen Schlumberger vertical electrical soundings (VES) were carried out with maximum electrode separation of 1000m. The data were presented as VES curves interpreted quantitatively by computer iteration using the Resist Software to obtain the first order geoelectric parameters. Three geoelectric layers namely the topsoil, laterite/clayey sand and sand (medium to coarse grained) were delineated from the survey. The topsoil has resistivity values ranging from 43 to 1067Ăm and thickness varying
from 0.8 to 1.6 m. The second geoelectric layer is composed of clayey sand and laterite with resistivity values ranging from 77 to 644 Ăm and thickness varying from 3.8 to 6.7 m. While the third geoelectric layer represents the aquiferous unit with resistivity values ranging from 200 to 1067 Ăm diagnostic of sand (fine to coarse grained). The interpreted geoelectric data correlated with lithologic logs of a borehole drilled in the study area. The overburden protective capacity in an area was evaluated by utilizing the total longitudinal unit conductance values. The generated longitudinal conductance map showed poor protective capacity (<0.1mhos) in all parts of the study area. The low value of the protective capacity makes the aquifer in the study area vulnerable to contamination especially hydrocarbon in the event of pollution.

Keywords: Protective capacity, Amukpe, Geoelectric, Pollution.