Salinity - Overview - Western Australia
Western Australia
Introduction
Western Australia has the largest area of dryland salinity in Australia and the highest risk of increased salinity in the next 50 years. An estimated 4.3 million hectares (16%) of the south-west region have a high potential of developing salinity from shallow watertables. This is predicted to rise to 8.8 million hectares (33%) by 2050.
In 2000, the risk is predominantly in the eastern wheat belt in valley floors and adjacent areas. Eastern sections of the northern wheat belt also exhibit high risk. There are some coastal areas at high risk around Bunbury and Donnybrook Sunkland. Salinity expansion by 2050 is mainly in the Great Southern and south coast regions.
The assessment was restricted to the south-west of Western Australia where dryland salinity is widespread. All analysis was based on groundwater depth and trend and the risk of shallow watertables was derived from these two attributes. As dryland salinity is caused by shallow watertables, the risk of salinity is inferred from the risk of shallow watertables. Not all shallow watertables will be saline. Estimates and projected risk areas are based on analysis of existing groundwater levels and trends at a scale of 1:250 000 based on soil systems mapping. There are limitations in the resulting assessment due to gaps in data.
Findings
In south-west Western Australia:
- Groundwater level patterns are dominated by rising or stable trends. No land systems have significant falling trends.
- Of the 4.3 million hectares (16%) of the south-west region potentially at risk from shallow groundwater, 81% is agricultural land.
- Predictions based on current and perceived land uses indicate that approximately one-third of the agricultural areas may be affected by shallow watertables and salinity by 2050.
- Surface water resources in the south-west part of the State are likely to become more saline.
- Approximately 30 000 km of road and rail networks and up 30 major rural towns may potentially be affected.
- Twenty-one of the 54 wetlands located within the agricultural region are potentially at risk of shallow watertables, which may affect wetland health.
- An estimated 1500 plant species will be affected, with 450 possibly subject to extinction.
- Salinisation is likely to reduce fauna species by 30% in affected areas.
- Terrestrial animals will decline significantly (e.g. a 50% reduction in the number of water birds using wheat belt wetlands is anticipated due to the salinity-induced death of shrubs and trees).
- Species richness has already declined with the onset of salinity.
An interim assessment of the annual costs of the consequences of dryland salinity is $664 m. This is based on ?best guess? estimates and does not include any assessment of the costs and benefits of strategies designed to combat salinity impacts on biodiversity.
Key issues
- The most important aspects of salinity investigations in Western Australia will be to determine the impact of different management strategies on groundwater trends at a catchment scale (1:10 000 to 1:25 000) as a basis for improving salinity management.
- Managing groundwater to protect rural towns and associated assets is a major challenge.
Reporting units and case studies
Reporting units
In Western Australia the primary unit for analysis for this assessment was the soil landscape system (see figure and table below). For reporting purposes results have typically been aggregate soil landscape zones or in some case AWRC river basins. For more informaiton on the soil-landscape mapping hierarchy refer to the the Western Australian Dryland Salinity Assessment 2000 report
Click here for a listing of soil landscape zones in the south-west of Western Australia
What are groundwater flow systems?
To understand salinity across the Australian landscape and through time, we need to understand how groundwater systems respond to changing recharge, and how the excess water that results from increased recharge is distributed. The broad distribution of groundwater flow systems in Australia has been mapped using attributes such as elevation, landscape form and geology. The classification groups groundwater systems with similar recharge and flow behaviour, and other measures such as length of flow paths through aquifers, aquifer permeability and driving pressure gradients for groundwater flow. It identifies groundwater flow systems where particular management activities will lead to similar responses and provides a framework for action.
For more detail: move to the Australia?s Groundwater Flow Systems overview
Case studies were implemented in catchments in southern Australia as part of an evaluation of the groundwater flow systems and a catchment water balance approach to identify:
- areas of the catchment where changes in recharge will most affect catchment salinity;
- how much recharge reduction would be required to reduce salinity by a given percentage in an area of salt-affected land;
- land use and farming system options for reducing recharge enough to manage salinity;
- information for an economic analysis of the costs, benefits and viability of the options for change;
- constraints to achieving required change.
The case study catchment in Western Australia was Lake Warden - a local and regional groundwater flow system in alluvial sediments and deeply weathered rocks
The case study region was Great Southern - a local and intermediate flow systems in deeply weathered rocks
Further information
- Western Australia Dryland Salinity Assessment 2000 report
- Australian Dryland Salinity Assessment 2000 report
- National Technical Overview Report of the State-based dryland salinity assessments
- Australian Groundwater Flow Systems Report
- Agriculture WA
- National Dryland Salinity Program
- National Action Plan for Salinity and Water Quality
State strategy
Government of Western Australia 2000, Natural Resource Management in Western Australia, The Salinity Strategy.
Government of Western Australia 1996, Salinity Action Plan.
Key references
Argent R.M. (1999). AgET Water Balance Calculator, Version 2.0 Technical Reference. Agriculture WA.
Argent, R.M. (2000). Catcher. A Catchment rainfall, runoff and recharge calculator. User Manual, Agriculture WA.
Bureau of Meteorology, WA (2000). Some comments of Aspects of Rainfall Trends and Variability in the South-West of Western Australia. Internal Report.
CALM (1999). CALM Biodiversity Survey of the Agricultural Zone. September 1999 Status Report.
Dames and Moore - URS (2000). The economics of predicted rising groundwater and salinity in Merredin townsite - Draft Report. Rural Towns Program project subtitled as Economic Impact Study. Prepared by Dames and Moore - URS.
DNRE (1997). Know Your Catchments, Victoria 1997: An assessment of catchment condition using interim indicators. Department of Natural Resources and Environment, Victorian Catchment and Land Protection Council and Environment Protection Authority.
English, V. and Blyth, J. (1999). Development and application of procedures to identify and conserve threatened ecological communities in the South West Botanical Province of Western Australia. Pacific Conservation Biology, Vol 5, pp124-138.
Evans, F. (2000). Land Monitor salinity risk prediction. Dumbleyung and Mt Barker regions. CSIRO CMIS Task Report No. 2000/45.
Ferdowsian, R., George, R., Lewis, F., McFarlane, D., Short, R. and Speed, R. (1996).
The extent of dryland salinity in Western Australia. In Proc. 4th National Workshop on the Productive Use and Rehabilitation of Saline Lands, Albany, March 1996, pp. 88-89.
George, R., Clarke, C., Hatton, T., Reggiani, P., Herbert, A., Ruprecht, J., Bowman, S. and Keighery, G. (1999). The effect of recharge management on the extent of dryland salinity, flood risk and biodiversity in Western Australia. Preliminary computer modelling, assessment and financial analysis. WA Salinity Council.
Isbell, R.F. (1996). The Australian Soil Classification. Australian Soil and Land Survey Handbook, Volume 4. CSIRO Publishing, Collingwood, Victoria.
McConnell, C. (2000). Predicted land use changes in the agricultural areas of WA and the resulting impact on the extent of dryland salinity. Resource Management Technical Report No. 201. Natural Resource Management Services, Agriculture WA.
McRobert, J., Foley, G., Shayan, A. (1997). An investigation of the Impact of waterlogging and salinity on the road asset in WA. Main Roads Western Australia, CR 6033, October 1997.
Nulsen B. (1998). Groundwater trends in the agricultural area of Western Australia.
Resource Management Technical Report No 173. Natural Resource Management Services, Agriculture WA.
Nulsen, B. and Evans, R. (1999). Dryland Salinity. National Land and Water Resources Audit.
Shao, Q., Campbell, N.A., Ferdowsian, R. and O?Connell, D. (1999). Analysing trends in groundwater levels. CSIRO CMIS Technical Report CMIS 99/37.
Schoknecht, N. (1999). Soil Groups of Western Australia. A guide to the main soils of Western Australia, Edition 2. Natural Resources Assessment Group, Agriculture Western Australia, Resource Management Technical Report No. 193.
Short, R. (2000). A Conceptual Hydrogeological Model For The Lake Warden Recovery Catchments Esperance, WA. Resource Management Technical Report No. 200. Natural Resource Management Services, Agriculture WA.
WAWA (1995). Jurien Groundwater Area Management Plan. Water Resources Division, Water Resources Planning and Allocation Branch, Water Authority of Western Australia. Report No. WG202.
WRC (1999). Status and Trends of Stream Salinity in South Western Australia. Unpublished, Water and Rivers Commission.
Western Australian Dryland Salinity Assessment 2000
Link to the Map Maker to make a map using this information.
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