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Salinity
Salinity is a key natural resource management issue for Australia. Preliminary assessments have suggested that up to 5.7 million hectares of the agricultural and pastoral zones have a high potential for developing salinity problems. This report is available from Land and Water Australia.
To manage salinity more strategically, it is necessary to know the locations of salt stores in the landscape, whether these are likely to be mobilised by groundwater and the extent to which they may pose a risk to assets such as agricultural lands, water quality, the environment and infrastructure.
Work undertaken by BRS suggests that at least for eastern Australia:
- salt is much more localised in the landscape than previously thought, and only represents a salinity risk if it is likely to be mobilised; large areas are essentially salt free
- airborne electromagnetic mapping (AEM) can be used in conjunction with other information to define the location and quantity of salt in the landscape and how it might move under certain land and water management practice conditions
- specific management interventions can be tailored to individual situations, substantially reducing the cost of managing salinity and minimising potential disruption to agriculture.
Compilation of initial results from 10 of BRS’ study sites in eastern Australia has resulted in the development of a regional framework identifying areas where further investigation of salinity hazard is warranted. Only a small proportion of this area is likely to be affected by salinity. Detailed examination of 2.85 million hectares by BRS has identified that 25 percent is underlain by salt. A significantly smaller proportion of this salt is likely to be moved by water into soils or streams where it can cause salinity problems. Broadly, these regions are located within areas of typically very gentle topography with average annual rainfalls between 500 and 850 mm and locally may have saline soils.
A first step towards establishing which catchments are likely to have a salinity problem is to undertake systematic sampling of stream salinities. This approach, together with the compilation and analysis of pre existing water quality and groundwater data, helps identify sub catchments contributing major salt loads. The results provide catchment management authorities with early information to identify sources of freshwater for protection, and to make salinity mapping investment decisions for National Action Plan implementation. The salt producing areas within these sub catchments can then be targeted for detailed airborne electromagnetic mapping, hydrogeological modelling and the development of management options.
Systematic stream sampling undertaken with the community has been used to identify the sources of salt within the Mid Macquarie (NSW) and Billabong catchments, providing information to locate salt stores for subsequent AEM mapping. In the Billabong (southern NSW) catchment, stream sampling, followed by AEM and other mapping, and modelling has led to the development of local land management options which could substantially reduce the export of salts to the Murrumbidgee River.
Location of BRS Salinity Investigations
Salt mapping in the Billabong Creek catchment
National Action Plan (NAP) for Salinity and Water Quality
Jugiong Creek - Community Stream Sampling Project
Contact
Scott Macaulay
Email: Water Sciences