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

Abstract

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. It is particularly important as an aid to our understanding of the links between surface flow manipulation, groundwater pumping and artificial recharge on soil salinity and floodplain vegetation health. 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 Great Darling Anabranch in NSW. It represented a short term spatio-temporal investigation of inundation on salt in the floodplain either in response to flooding or environmental flows. The results clearly show changes in the conductivity distribution at the sites surveyed. These changes can be attributed to variations in the flows over the year, pumping of groundwater and changes in vegetation. The survey showed that EM techniques are a useful tool in aiding our understanding of floodplain processes resulting from changes in flows along the Anabranch and could be applied in other floodplain environments as a low cost 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 can be used to validate floodplain processes, contributing to ecological investigations of river floodplains.