Murray River floodplain salt storage
Abstract
In the Victorian Mallee, it is estimated that large volumes of salt are being carried toward the Murray River by regional groundwater flow. However, recent work indicates that only a small percentage of this salt is actually discharging directly to the river. The fate of the remaining salt is unknown. One possible explanation is that it is being stored in the unsaturated zone in the floodplain. Understanding the location, transport mechanisms and the potential of mobilisation of salt in the floodplain has significant implications for the ongoing management of both the Murray River and the health of the floodplain. This paper discusses the establishment of salinity monitoring sites which aim to increase understanding of salt accumulation and mobilisation processes in the floodplain environment. Three locations were selected within the floodplain zone of the Victorian Mallee. A series of temporary transects, running perpendicular to the river, were established in 2004 at each of the three study areas. EM38 and EM34 surveys, vegetation mapping and selective soil salinity sampling was undertaken along each transect.
Digital globe satellite imagery was captured contemporaneously with the field program. Analysis of the data sought to establish a relationship between the vegetation health and salinity data gathered in the field with vegetation canopy density analysis undertaken on the satellite images. A second phase of field work, in 2006, involved repeat geophysical and vegetation surveys and the recapture of Digital Globe imagery. The results indicate soil salinity varies significantly between and within sites. Vegetation distribution and health correlated well with soil salinity and both were influenced by floodplain geomorphology. A promising relationship was identified between observed vegetation health and the canopy density results that were obtained through remote sensing. Although further development is required the results suggest that the analysis of the Digital Globe images has the potential to provide valuable information on vegetation health and soil salinity across large tracts of the floodplain.
Authors
Simon Fulton, Greg Hoxley, Ian Sluiter & Georgina Race