Application of 2-dimensional tomography for subsurface lithology imaging and aquifer determination in Etim Ekpo, Southern Nigeria.

Abstract

In recent times, surface water has been seen not to be a good source of domestic water because of impurities from physical, biological and chemical contaminants. The use of geophysical techniques for groundwater exploration and water quality evaluations has increased over the past few years due to the rapid advances in computer software and associated numerical modeling solutions. A 2D electrical resistivity tomographic method was adopted in this study using the Werner electrode arrangement in determining the variation of subsurface resistivity distribution in Etim Ekpo, southern Nigeria. Ten soundings were carried out in the area. The RES2DINV software was used to transform the measured ERT data to an approximate picture of the subsurface resistivity distribution and geometry of the subsurface features. The resistivity values in the area for layer 1(top soil) range from 34.60 Ωm to 2311Ωm while the thickness ranges from 0 to 12 m. For layer 2 (lateritic sand), the resistivity values range from 213 Ωm to 3982 Ωm while the thickness ranges from 5 to 20 m. The resistivity values in the area for layer 3(coarse grained sand) range from 1237 Ω m to 6964 Ω m while the thickness ranges from 17 to 57 m. Three geo-electric layers were delineated (top soil, lateritic sand and the coarse grained sand). This study shows that the groundwater potential within the area is of economic volume.