Prospecting for Groundwater in the Bawku West District of the Upper East Region of Ghana Using the Electromagnetic and Vertical Electrical Sounding Methods

Abstract

An integrated approach involving the Electromagnetic (EM) and Vertical electrical sounding (VES) survey methods, has been used to locate potential drilling sites to find groundwater for twenty (20) rural communities in the Bawku West District of the Upper East Region of Ghana. The EM method involved the use of the Geonics EM 34-3 equipment to obtain traversing data for the horizontal dipole (HD) and vertical dipole (VD) modes at station intervals of 10 m for a 20 m coil separation. The EM survey provided subsurface information relating to positions of high electrical conductivity anomalies which presumably pointed to locations for groundwater structures. As a follow up, the VES was carried out with respect to the anomalous positions, using the dipole-dipole configuration with the McOhm-EL resistivity meter. The VES enabled the estimation of the depth of the weathered layer to the bed rock. The results of the VES data were interpreted quantitatively by modeling using IX1D V.3 software. The study identified prospective sites for drilling of bore-holes to provide potable water for the communities. Results for the VES suggested that the aquifer zones in the area under study are mainly deeply weathered and fractured. The lithology for some of the recommended drilled points correlated well with the results obtained from the EM and VES investigations. The aquifer depth was found to be between 10 and 40 m with an average value of 21.5 m. The depth of the basement rock from the surface was 21.4 m. The estimated yield of the boreholes drilled within the area was between 10 and 500 litres/min with an average value of 136.8 lit/min. the success rate was found to be about 95%. The integrated use of EM and VES surveys has been found to be very successful in locating groundwater resources for the rural communities with the area studied.