Frequency and/or Time Domain HEM Systems for Defining Floodplain Processes Linked to the Salinisation along the Murray River?

Abstract

Geophysical, particularly electrical, methods have the potential to provide detailed spatio-temporal information on the distribution of salinity in soils and groundwater that characterise the floodplains of the Murray River in southeastern Australia, thereby assisting our understanding of floodplain processes. This knowledge can help manage the ecology of these settings, particularly in a time of severe drought when floodplain salinisation, vegetation dieback or health decline is a growing problem. In this paper we examine the relative merits of high resolution helicopter EM technologies for elucidating floodplain processes. Specifically we consider the relative performance of the RESOLVE frequency domain helicopter EM (FDHEM) and the SkyTEM time domain helicopter EM (TDHEM) systems for defining variations in near surface conductivity and sediment salt load across the Bookpurnong Floodplain in the Riverland of South Australia. Results from coincident surveys are reviewed as are strategies for the inversion of these data. Data are examined against available borehole information including sediment chloride content and groundwater conductivity.