Using natural resource inventory data to improve the management of dryland salinity in the Great Southern, Western Australia

The synoptic assessment of salinity risk and the likely costs and benefits associated with various management options is crucial to natural resource management decision-making in southern Australia. A variety of methods have been proposed and tested for assessing various aspects of salinity risks and costs, but no large region of Australia has ever had a comprehensive risk assessment across the range of biophysical and economic issues with forecasts of the effectiveness of different levels of intervention. This National Land and Water Resources Audit Implementation Project (referred to locally as Salt Scenarios 2020, or SS2020 for short) attempted to provide such an assessment (at a scale of around 1:100,000). The existing methods of monitoring and predicting salinity (based on variables derived from widely-available Landsat TM data and existing contour data; albeit with improved variable extraction from the DEMs) are being applied to the rest of the agricultural area of WA as part of the Land Monitor Project, funded in part by NHT. Collecting accurate contour data (2-metre) is a major part of the NHT project. This Audit project was proposed to allow other fundamental data sets, and especially groundwater levels from bore-hole data, to be used to significantly improve predictions in lower-rainfall areas as well as refine the predictions in the high rainfall areas. The Great Southern is an area of considerable economic and environmental value populated by 60,000 people. In 1996, it was estimated that about 30% of the cleared land and associated vegetation and water resources are at risk from becoming salt-affected over the next 30 years unless high-water use farming systems and farm forestry are adopted over large parts of the region(Ferdowsian et al., 1996). Four key questions arise with respect to the future of this region as affected by dryland salinity: •How large will the problem eventually be under current land practices? How large might it be in the year 2020? •What is at risk if the area under threat grows that large? •To what degree can we change the eventual extent of salinity with land use alternatives that are both feasible and available? •What are the costs and benefits of intervening with these alternative land uses? Ultimately, the SS2020 Project aimed to provide some guidance to state, regional and local planners and managers regarding salinity risk in the Great Southern. The analyses underpinning this guidance were based on similar data employed by NLWRA projects under Theme 2 – Dryland Salinity