Using electrical resistivity imaging technique for borehole calibration in selected communities in Asutifi North District, Ghana

Abstract

This study has investigated the use of Electrical Resistivity (ER) technique for siting suitable groundwater points in selected communities within the Asutifi North District of Ghana where borehole drilling success rate has been low, leading to water shortages in the dry season. The study method employed involved 2D Electrical Resistivity Imaging (2D ERI) survey along existing boreholes in the area using the dipole-dipole array and correlating the outputs with existing 1D Vertical Electrical Sounding (1D VES) data and its corresponding borehole logs of the area to delineate the potential groundwater zones. The results from the 2D ERI survey showed the potential groundwater zones to be at depths of 14.7 to 58.9 m with resistivity values ranging from 2.08 to 156 Ωm while that for the 1D VES were at depths of 20 to 60 m with resistivities ranging from 67.10 to 545.28 Ωm. Also, the delineated potential groundwater zones from the 2D ERI showed a positive linear correlation with the observed aquifer zones from the borehole logs at a correlation coefficient (R2) of 0.72, whereas no correlation was observed when the observed aquifer zones from the borehole logs were compared to potential groundwater zones from the 1D VES data. Additionally, the 2D pseudo-sections from the 2D ERI survey aided in categorising the different potential groundwater zones in the area as good, moderate, fair and poor. Thus, the 2D ERI technique provided more detailed information on the subsurface in the area than the 1D VES approach and would be more reliable for subsequent groundwater exploration projects in the area and similar geological terrains.