Groundwater Exploration in the Granitic Rock Formation of Komenda/ Edina/ Eguafo/ Abirem District Using Integrated Geophysical Techniques

Abstract

Geophysical investigations were carried out in six communities in the granitic rock formation of Komenda/Edina/Eguafo/Abirem (KEEA) District of the Central Region of Ghana with the aim of delineating groundwater potential zones, drilling the selected sites and subsequently compar-ing the geophysical results with those of the drilling and subsequently to provide potable water for the beneficiary communities of the district. The geophysical methods employed included elec-tromagnetic profiling, short resistivity profiling and resistivity sounding using the Schlumberger Array. The findings of the survey indicates apparent conductivity ranging between 7 mS/m and 30 mS/m with a mean value of 10.00 mS/m ±0.02% and the apparent resistivity of the crystalline basement granitic rock is between 287.5 Ωm at Saaman and 2198.4 Ωm at Anwewmu-Kissi with a mean value of 1317.4 Ωm ±0.4%. Out of the five (5) boreholes drilled, three(3) were success-ful with a success rate of 60% which indicates moderate groundwater potential as it depends largely on fractures to enhance groundwater development. Only two sites produced dry wells at drilled depths of 69.0 and 76.0 m as predicted by the geophysical results. The results revealed a lithology that consists of laterite, clay, sandy-clay and slightly-to-highly weathered granite or gneiss as the regolith. Groundwater was generally found at the depth of 20.0-55.0 m. The sur-face geophysical results were correctly validated by the drilling results which confirms geophysi-cal exploration technique as a vital scientific tool required for borehole siting.