Evaluation of the Magnetotelluric TC 150 instrument for geophysical groundwater exploration

Abstract

Freshwater is the most important resource for life on planet Earth. This natural resource is, however in great danger of being depleted and polluted to an irreparable extend. As surface water is currently the main source of fresh water, scientists explore for new sources that can lighten the load on surface water systems. Groundwater is an easy substitute for surface water. Scientific studies has thus shifted focus from surface water to exploration of groundwater sources. Geophysics is one of the methods that are commonly employed during groundwater exploration projects. Three well-known methods in the subject of geophysical groundwater exploration were employed during this study. These three methods include Electrical Resistivity (ER), Electromagnetic (EM) and Magnetic (MAG). Common geological structures that will be focussed on during the employment of these three methods for groundwater exploration include hard-rock crystalline basement terrains. These terrains are very popular in geophysical groundwater exploration projects due to secondary permeability and porosity which occur within faults, fractures, dyke contacts and deeply weathered zones. The three instruments that were chosen to carry out the measurements of the above methods include the ABEM Terrameter LS 2, the EM 34-3 and the Proton Memory Magnetometer (G5). Accurate and successful results of the above-mentioned methods can be obtained by using the methods together, in order to compare the results. As Geophysical surveys tend to be very expensive, certain groundwater exploration projects do not have the budget to employ more than one instrument for a particular study. It is thus very important to determine the success of various methods when employed to survey a dolerite dyke for groundwater exploration purposes. As a result, this study focused on employing the above-mentioned instruments to determine their success in delineating a known dolerite dyke. Upon the successful completion of the fieldwork, the data of each instrument were processed into contoured maps (making use of Surfer 14 software) and 2D graphs. By analysing the various results that were retrieved by the three instruments, it was concluded that the ABEM Terrameter LS 2, The EM34-3 and the Proton Memory Magnetometer (G5) were successful in delineating the dolerite dyke. These instruments were successful as they produce results that were clear and comparable with one another.