Abstract

A total of thirty-two (32) vertical electrical sounding (VES) data were acquired using R 50 d.c. Resistivity meter within the Precambrian basement geology of part of Akure metropolis southwestern Nigeria.  The VES data were interpreted; eight type curves were identified, from the geoelectric section the subsurface was characterized into four lithologies namely topsoil, weathered layer (clay /lateritic clay), weathered / fractured basement and bedrock. Thus, two major aquifers were mapped these are weathered/partially weathered layer and weathered basement/fractured basement aquifers. These aquifers are characterized by thick overburden, found within basement depressions and exhibit moderate to relatively high values of coefficient of anisotropy, λ, (0.97-1.11) with depth. Also, ancient river channel trending approximately NE-SW was mapped. The assessment of the materials above the aquifers showed that longitudinal conductance (S), values ranged from 0.0035 to 0.17 mhos; thus the S values are generally low suggesting that the materials above the aquifers are loose and porous thus having less capacity to protect  aquifers in the study area. Thus the aquifers  are poorly protected, and by implication vulnerable to infiltration.

Key words: Basement aquifer, Dar-Zarrouk parameters, Protective capacity Aquifer Risk.