In this example, a resistivity investigation was carried out to map the groundwater surface. The measurements were undertaken to provide an ERT (Electrical Resistivity Tomography) dataset. The differences in resistivity clearly show the groundwater aquifer as a low resistivity zone between high resistivity dry top–soils and an undulating bedrock at 10 to 35 meters below ground.
In this example, a TEM investigation was undertaken in an arid region where there was potential for the aquifer to be quite deep – hundreds of meters below the surface. A large loop and high current was used to allow for significant penetration depth from the TEM system.
It was possible to identify three main layers: a low resistivity top layer of clays and silt, underlain by the local bedrock with relatively high resistivity but which gave way to higher conductivity zone once within the water table.
It is often beneficial to combine different geophysical methods to get the best resulting picture of the groundwater condition. For instance: