River-borne NanoTEM survey for location of salt accession to the River Murray at Loxton

Abstract

As part of an ongoing commitment to the reduction of salt accession to the River Murray in South Australia, the South Australian Department for Water, Land and Biodiversity Conservation (DWLBC) is engaged in a series of investigations to determine the feasibility of the construction of salt interception schemes (SIS). An integrated multi-disciplinary approach has been adopted to develop an understanding of the hydrogeological processes, which is essential for effective scheme design. To assist in identifying areas of salt accession, a river-borne NanoTEM survey was conducted in September 2003. Previous work at the Waikerie SIS highlighted the success of the river-borne Transient Electro-Magnetic (TEM) technique. These systems can provide valuable information and understanding of salt accession to the River Murray. Traditional methods, such as river EC measurements and Run of River (RoR) EC surveys, have revealed that the Loxton and Bookpurnong reaches of the river receive substantial salt loads. These techniques provide limited spatial resolution, whereas the river-borne TEM has exceptional spatial resolution with soundings every 5 to 10 metres. A total of 80 km of data over a 37 km stretch of the River Murray was collected near the townships of Loxton and Bookpurnong. The survey results correlate well with recent RoR data, sediment core ground-truthing and groundwater model flow budget results.