Salinity - Overview - New South Wales
New South Wales
Introduction
Approximately 180 000 ha of land have shallow watertables or are affected by dryland salinity in New South Wales. Over 90% occurs in five catchments-the Murray, Murrumbidgee, Lachlan, Macquarie and Hunter rivers. The Hunter and Hawkesbury-Nepean river catchments have the most extensive areas of existing dryland salinity or shallow groundwaters of New South Wales in coastal catchments.
Within the Murray-Darling Basin, the area predicted to be at risk will increase from approximately 152 000 ha to 1.3 million hectares by 2050, a greater than eight-fold increase.
Areas of risk are based on groundwater levels and air photo interpretation. The merged data, at a nominal scale of 1:250 000, show actual areas where dryland salinity or watertables less than 2 m have been measured. For the extent map, every delineated area is underpinned by either air photo data or by one or more groundwater bores. Therefore, the area at risk is regarded as conservative due to limitations in the spatial coverage of air photo and bore data. A number of techniques to spatially extrapolate these data to infer potential areas at risk were trialled but were considered scientifically or statistically inadequate. Estimates of impacts are based on areas at risk having groundwater levels of less than 2 m. An impact assessment based on groundwater less than 5 m and rising was considered inappropriate. Total areas affected with groundwater less than 5 m and rising have been presented, but only for improved consistency with other States.
Findings
- Groundwater trends are dominated by rising or stable trends. No groundwater flow system under dryland agricultural systems has a significant falling trend.
- Large areas of the Western Slopes, the Hunter Valley and the Sydney Basin already have saline groundwater within 2 m of the surface.
- Within the Murray-Darling Basin, areas affected by shallow watertables will increase four-fold over the next 20 years, and eight-fold over by 2050.
- Of the 152 000 ha of land at risk from shallow groundwater within the Murray-Darling Basin, 93% is agricultural land.
- The area of agricultural land within the Murray-Darling Basin that is affected by shallow watertables will increase from the current 142 000 ha to almost 1.2 million hectares by 2050.
- Forecasted scenarios indicate that areas of conservation and remnant vegetation affected by shallow watertables will increase twelve-fold over the next 50 years.
- Areas of forest affected by shallow watertables could potentially increase seventy-fold over the next 50 years.
- In-stream saltloads are forecast to increase by at least a factor of two in most Murray-Darling Basin catchments by 2050. In some catchments, it is predicted that river EC levels will more than exceed international drinking water guidelines.
- An estimated 954 ha of built-up areas within the Murray-Darling Basin are affected by shallow watertables. This could increase to over 3600 ha by 2050.
Key issues
- Development of acceptable and achievable performance targets for major catchments contributing to dryland salinity will be a major challenge. This will require very considerable technical and process support to regional community groups.
- Development of economically viable and socially acceptable management options for many areas will be extremely difficult because of the nature of the groundwater systems controlling the salinity.
Reporting units and case studies
Reporting units
The results of the New South Wales Dryland Salinity Assessment 2000 are reported by the major catchments of the Murray Darling Basin and selected coastal catchments (Richmond, Clarence, Bellinger, Manning, Hunter, Hawkesbury/Nepean, Georges/Cooks and Deua).
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 catchments in New South Wales was Upper Billabong, New South Wales - a local and intermediate groundwater flow systems in variably weathered fractured rocks in connection to regional flow system in alluvial aquifers
Further information
- New South Wales 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
- New South Wales Department of Land and Water Conservation
- National Dryland Salinity Program
- National Action Plan for Salinity and Water Quality
State strategy
NSW Government 2000, NSW Salinity Strategy: Taking on the Challenge, NSW Department of Land and Water Conservation, Sydney.
Key references
Australian Surveying and Land Information Group (1997). Geodata Topo-250K Infrastructure Theme. Department of Administrative Services, Canberra.
Bureau of Rural Sciences (2000). 1996/1997 Land Use of Australia. Report for the National Land and Water Resources Audit.
Coram, J.E, Dyson P.R., Houlder P.A. and Evans W.R. (2000). Australian Groundwater Flow Systems contributing to Dryland Salinity. Bureau of Rural Sciences. Report for the National Land and Water Resources Audit.
Department of Land and Water Conservation (1999). Salinity Predictions for NSW Rivers within the Murray-Darling Basin. CNR99.048, Sydney.
Department of Land and Water Conservation (2000). Taking on the Challenge: NSW Salinity Strategy. Sydney.
Hutchinson, M.F. (1999) ANUSPLIN V4.0. Centre for Resource and Environmental Studies. The Australian National University, Canberra
New South Wales Dryland Salinity Assessment 2000
Link to the Map Maker to make a map using this information.
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