Spatial modelling incorporating AEM data to show the effects of manipulating flow regimes and groundwater lowering options over the Chowilla floodplain, SA

Abstract

Along the floodplains of the Murray River in south eastern Australia, where the saline groundwater system is particularly close to the surface, evapotranspiration concentrates salt resulting in extensive salinisation, vegetation dieback or health decline. In many floodplain areas, ecologically important woodland species that inhabit the floodplain are dying from soil water salt concentrations that often exceed those of seawater. To better manage this problem and to protect the ecology and biodiversity on the floodplains along the river, a range of management strategies are being employed. Modelling tools are integral to their development, but key to their effectiveness is the availability of detailed biophysical data. In a study focussed on the Chowilla Floodplain in South Australia, WINDS, a spatial model that examines soil water availability was employed to show the possible effects of manipulating flow regimes and groundwater lowering options across the whole of the floodplain. We examined the value of using biophysical parameters derived from the helicopter electromagnetic (HEM) data, specifically groundwater conductivity and salt storage for specific zones in the saturated, capillary and unsaturated parts of the floodplain, as a basis for making vegetation health assessments or predictions at any particular time. The procedure for deriving this information in 3D is discussed.