Utilizing airborne electromagnetic data to map groundwater salinity and salt store at Chowilla, SA

Abstract

The Chowilla floodplain in South Australia is part of the Bookmark Biosphere Reserve with wetlands supporting a wide range of plants and animals, and has provided recreational opportunities to the general public (MDBC, 2006). However, the threats from saline groundwater and salt accumulation at the surface, combined with the overall low rainfall and the lack of natural flooding events in the recent past, have had a negative consequence for vegetation health, especially the river red gums. Information on the spatial patterns of groundwater salinity and the near surface (top 15 m) salt stores in the floodplain is integral to our understanding of floodplain hydrological processes that may be active in the Lower Murray Basin of Australia. This information can be used to help develop appropriate remedial activities for the management of ecologically important wetlands and in particular assist in the maintenance of a healthy vegetation community. A helicopter-borne electromagnetic (HEM) survey was conducted across the floodplain in conjunction with a validation drilling and borehole geophysical logging program. Based on the laboratory results from cored sediments and their pore fluids, we report on the salinity and salt store models calculated from the inverted HEM data.