Spatio-temporal variations in floodplain soil/sediment conductivity: Great Darling Anabranch

Abstract

SUMMARY Spatio-temporal information on the distribution of salt in floodplain soils and groundwater is integral to effective floodplain management strategies along the Great Darling Anabranch in NSW. Geophysical technologies have the potential to provide detailed spatial information on the variability of salt stored in the near surface and for monitoring surface water -groundwater interactions across the floodplains, and in particular looking at the spatial controls on those processes. The research sought to examine the role of hydrogeophysical methods in monitoring changes in floodplain sediment condition, linked to ecological investigations. A two stage investigation, to examine the role of a low cost, near surface, geophysical method for monitoring changes across several sites located adjacent to the Anabranch. It represented a short term spatio-temporal investigation of inundation on salt in the floodplain. Our results clearly show changes in the near-surface conductivity distribution at the sites surveyed. These changes are attributed to variations in the flows over the year, pumping of groundwater and changes in vegetation. The survey shows that EM techniques are a useful tool in aiding our understanding of floodplain processes resulting from changes in flows along the Anabranch and can be applied in other floodplain environments as a lowcost survey to observe changes in conductivity in the near surface. It is an effective method to monitor variations in conductivity in the floodplains due to changes in environmental flows and can aid in understanding changes in sediment conditions and be used to validate floodplain processes, contributing to ecological investigations of river floodplains.