Efficacy of Geophysical Techniques for Groundwater Exploration in the Volta Basin, Northern Region of Ghana

Abstract Groundwater, traditionally extracted from hand-dug wells and boreholes is the main drinking water source in the Northern Region of Ghana. Many boreholes have been constructed in the region to increase accessibility to potable water mainly as part of rural water supply projects where borehole siting has to be relatively cheaper.  These projects have resulted in low success rates of borehole drilling because of the application of inefficient and simple geophysical techniques supposed to be cheaper. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. The surveys were conducted at stations of existing dry and positive boreholes. Results show that the three geophysical techniques are efficient to identify groundwater accumulation zones. The ERI, EKS and 222Rn are efficient to identify discontinuities, calculate hydraulic conductivity of discontinuities and identify areas of water circulation respectively. It is recommended that the ERI be used to obtain discontinuities and weak zones for drilling on rural water supply projects in the VB. The EKS and 222Rn should be conducted to evaluate these features when high yield boreholes are required.   Keywords: Geophysical Techniques, Volta Basin, Borehole Drilling, Success Rates