Dryland salinity is essentially a problem of salt and rising water tables, most obviously expressed in lower landscapes. It is a very apparent management problem in some catchments, but may be currently invisible or minor in others. Deciding whether there is a threat, how large that threat might be, and whether it is cost-effective to invest in management, is the first step in managing salinity at catchment-scale. It is necessary to understand how much salinity there is, where it occurs in the landscape and its risk of expansion. Broad-scale mapping is used for strategic planning and policy-making to help set sensible targets to protect valuable resources at risk, and efficiently allocate limited resources for both research investigations and on-ground investments.

Estimates of dryland salinity collected by the National Land & Water Resources Audit (NLWRA) presented the first comprehensive snapshot of extent and risk across Australia. The NLWRA used regional-scale dryland salinity risk or hazard assessments undertaken by State/Territory agencies drawing on:

• Groundwater levels and trends;
• Known incidence of salinity;
• Soil characteristics; and
• Topography.

It shows about 5.7 million hectares of agricultural and pastoral land at risk of dryland salinity (through shallow water tables), increasing to 17 million hectares by 2050 in the absence of effective action.

The key messages on dryland salinity risk and hazard from the NLWRA are:

• There is no quick fix - salinity can be managed by prevention, treating the cause, ameliorating the symptoms, living with it or a combination of these.
• Salinity management requires knowledge about soil, salt, water and vegetation to be integrated with knowledge about groundwater flow systems.
• Large tropical and sub-tropical areas will have salinity problems if clearing occurs. Broadscale land clearing with little regard for salinity hazard is a recipe to repeat the problems of temperate Australia.
• Assessment of areas identified as having a hazard, particularly areas of extensive clearing in central and southern Queensland, is essential, and would underpin the development and implementation of vegetation management policies and guidelines.

The NLWRA on-line 'make-a-map' facility allows users to examine what information is adequate and what is deficient for their specific purposes. This is particularly important given that the National Action Plan (NAP) for Salinity and Water Quality has devolved many resources directly to the regional level. Decision-makers need to be aware of the wealth of information that exists and where their investment choices can best add value.

At National, State and regional scales, the Groundwater Flow Systems Framework is guiding policy and investment decisions by identifying local, intermediate and regional groundwater flow systems (GFS), helping to determine broadly where the salinity risk is greatest and where management activities are most likely to be rewarded. This approach recognises that there is no 'one size fits all' solution and uses models that help interpret and describe groundwater behaviour at all scales.

Where information on the current extent and risk of spread is limited, the GFS approach has helped to fill gaps. A wide range of models supports salinity planning and management. The CRC for Catchment Hydrology has an on-line �Catchment Modelling Toolkit' with software and documentation on modelling, supported by a school for professional training.

For more information about the current extent of dryland salinity and its risk of spread, go to  Question 1 in Dryland Salinity and Catchment Management - A resource directory and action manual for catchment managers (pdf - 375KB)  (pdf 366Kb)