Fast-sampling EM Applied to the River Murray and Surrounding Floodplains in Australia

Accurate, high resolution images of the top 10 to 50 metres of the earth’s surface potentially provide insights into the underlying hydrogeology that help us to understand, for example, the distribution of saline groundwater in the subsurface, or subtle changes in the distribution of clays in the top ten metres. This paper reviews the use of a commercially available fast-sampling TEM system in use in the surrounds of the River Murray system in southeastern Australia. This system has been used to collect data in a fairly standard TEM mode, i.e. discrete stations at fixed intervals along a line. Additionally results are shown using the system in a modified configuration, with much smaller transmitting and receiving antennae towed behind a boat, for example, with data collected in conjunction with a GPS in a “continuous” mode. This type of data provides a continuous electrical cross section with data points as close together as five metres apart, to a depth of at least ten metres.