Exploring deeper groundwater in a dolomite aquifer using telluric electric frequency selection method geophysical approach

Several Telluric Electric Frequency Selection Method (TEFSM) geophysical equipment is now available for groundwater exploration. However, case studies on its application in different hydrogeological settings are limited. This study investigates the TEFSM geophysical approach's application to identify groundwater potential sites for drilling production boreholes in a dolomite aquifer in South Africa. Field tests comprised geophysical surveys using the TEFSM approach to collect vertical and horizontal electrical potential difference profile data from four sites. Evaluation of the potential difference profile data before borehole drilling indicated that two sites had groundwater potential. Two sites were therefore prepared for drilling. Corroboration of the survey data and drilling lithology show that the TEFSM investigated up to 230 m depth and delineated the thickness of the dolomite aquifer from 170 m to 210 m. The dolomite aquifer was delineated based on low EPD contrast ranging from 0.042 to 0.083 mV. The ability of the TEFSM to delineate the dolomite aquifer at a depth of 170–210 m highlights the technical capability of the approach in exploring deeper aquifers that are important to meet the rising demand for freshwater. More research is necessary to establish the EPD ranges of aquifer lithology in different hydrogeological settings. It will assist in the interpretation of the data by field practitioners to optimise the application of this TEFSM technology in groundwater investigations.