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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Salinity - Impacts
Australia
Impacts of dryland salinity: Australian overview
The processes of dryland salinity can operate at landscape or local scale; impacts can occur on-site (farm scale), elsewhere in the catchment or outside the catchment (downstream). The original cause of the change in water entering the watertable (the main driver of salinity) is often distant from where the salinity occurs.
Dryland salinity as an agent of degradation
The impact of dryland salinity as a resource management issue is greatly increased by its off-site effects, its social and economic consequences and-most importantly-the often high level of inputs required and the long timeframes for management to be effective. Dryland salinity is more pervasive than other degradation issues but is also closely linked to them (e.g. causing soil erosion, eutrophication of streams and loss of riparian zone vegetation). Dryland salinity is difficult to manage because of the lasting nature of its effects on soil and water resources, and on the stability of ecosystems.
The main impact of increasing salinity at the farm level is loss of production and income. Other on-farm effects include the decline in capital value of land, damage to infrastructure, salinisation of water storage, loss of farm flora and fauna, and loss of shelter and shade. These effects are magnified at the regional level, where they have a substantial impact on public resources such as biodiversity, water supplies and infrastructure.
Some of the assets at risk as a consequences of shallow watertables are listed in the table below, with estimates of their impact predicted to 2050.
| Asset | 2000 | 2020 | 2050 |
|---|---|---|---|
| Agricultural land (ha) 1 | 4 650 000 | 6 371 000 | 13 660 000 |
| Remnant and planted perennial vegetation (ha) 2,5 | 631 000 | 777 000 | 2 020 000 |
| Length of streams and lake perimeter (km) 2 | 11 800 | 20 000 | 41 300 |
| Rail (km)2 | 1 600 | 2 060 | 5 100 |
| Roads (km)2 | 19 900 | 26 600 | 67 400 |
| Towns (number)3 | 68 | 125 | 219 |
| Important wetlands (number) 1,4 | 80 | 81 | 130 |
1 Data from all States, Qld only for 2050.
2 Data from WA, SA, Vic and NSW, Qld only for 2050.
3 Data from WA, SA, Vic and NSW.
4 Including Ramsar wetlands.
5 Much of the remnant and perennial vegetation reported for each State occurs on agricultural lands.
How much agricultural land occurs in areas at high risk from dryland salinity?
Broadacre cereal crops and traditional pasture species grown in Australia do not tolerate salt and are seriously affected when salts concentrate within the root zone. Total loss of crop and pasture production occurs where groundwaters are close enough to the surface to discharge or concentrate salts; losses may be restricted to reduced yields where groundwater is deeper.
The assessment has indicated that dryland salinity from shallow watertables potentially threatens production from 4.6 million hectares of agricultural land. Under current land use systems and climate, this is expected to at least double by 2050. These estimates also include some areas-mainly in the temperate zone-with persistent waterlogging from shallow watertables. Although salt is ubiquitous in landscapes in agricultural areas, it is acknowledged that not all of these waterlogged lands will become saline. Much of the area at risk is Australia?s most productive land.
The greatest impacts are in the Temperate Semi-arid Slopes and Plains agro-ecological region (Williams et al. in press) which includes the wheat-sheep belt in south-west Western Australia. Significant areas of salinity also occur in the crop-pasture zones of New South Wales, South Australia and Victoria. Major irrigation areas of the Murray-Darling Basin will be affected by the predicted increases in salt concentrations. The loss of productive lands places a burden on remaining lands. Aggregate productivity can only be maintained by increasing production from unaffected lands and/or developing integrated systems that include saltland production. Higher-yielding crops and additional agricultural inputs are seen as part of the solution but come with their own risks. Innovative land use systems are also seen as part of the solution, but these are still in very early stages of identification and development.
| State/Territory* | 1998/2000 | 2020 | 2050 |
|---|---|---|---|
| New South Wales | 180 600 | 580 000 | 1 300 000 |
| Victoria | 665 500 | 1 306 000 | 3 110 000 |
| Queensland | not assessed | not assessed | 2 600 000 |
| South Australia | 326 000 | 421 000 | 521 000 |
| Western Australia | 3 553 000 | 4 182 000 | 6 490 000 |
| Tasmania | 53 000 | 70 000 | 90 000 |
Click here to download and view map in.pdf format (1.2MB)
What environmental resources occur in areas of high dryland salinity risk?
Water resources at risk
The most significant off-site impact of dryland salinity is the salinisation of previously fresh rivers. This affects the supply of drinking and irrigation water, with serious economic, social and environmental consequences for rural and urban communities (e.g. in Western Australia, many of the surface water resources are already too saline for domestic use and further deterioration will challenge future supplies).
Increased salt concentrations also change the habitats of aquatic fauna in wetland, stream and riparian zone systems.
- Predictions from Western Australia show that the length of streams affected by salinity may double over the next 50 years, posing risks for riparian zones and water quality. Surface water resources in the south-west of the State are likely to become more saline.
- In Victoria, a possible three-fold increase in the length of stream or perimeter of reservoir, lake or wetland located in areas of shallow watertable is predicted over the coming 50 years. If these changes are realised, increased saline discharge could be expected into streams and surface water bodies.
- In South Australia, where water resources on the Lower Eyre Peninsula and Kangaroo Island have been degraded by salinity, there is little opportunity for increased industrial, mining or irrigation water supplies. This may have serious consequences for regional development in these areas.
- Nationally, the predicted deterioration in the quality of Murray River water indicates the magnitude of the problem. The salinity audit of the Murray-Darling Basin (MDBC 1999) suggested that in the absence of remedial action, the median salinity in the Murray River at Morgan was estimated to increase by about 25% over the next 50 years as a result of increased salt inflows from irrigation and dryland districts. Stream salinity in the Murray exceeds World Health Organization levels for potable water for about 10% of the year. Salinity levels in the Murrumbidgee River are increasing at between 0.8% and 15% each year, depending on where measurements are made.
- The Murray-Darling Basin Commission Salinity Audit also suggests that in the upper part of the Basin, the Macquarie, Namoi, Bogan, Lachlan and Castlereagh rivers will exceed the 800 µS/cm (sometimes referred to as EC units) threshold for water within the next 50 years. Some will also exceed the 1500 µS/cm threshold for irrigation within 100 years.
A high correlation between major areas of dryland salinity and areas where the water quality guidelines have been exceeded also occurs (see map below).
Click here to download and view map in.pdf format (930 KB)
To compile an overview of surface water salinity guideline exceedances within Australia?s river basins, the following definitions were used:
- ?major? issues occurred where guideline exceedances were calculated to occupy greater than a third (33%) of a basin area;
- ?significant? issues occurred where guideline exceedances were calculated to occupy greater than 5% but less than 33% of a basin area;
- ?not significant? issues occurred where monitoring coverage was greater than 50% of a basin area; and observed guideline exceedances represented less than 5% of a basin area.
- ?undetermined? issues occurred where monitoring coverage was less than 50% of a basin area; and observed guideline exceedances represented less than 5% of a basin area.
| Asset | 2000 | 2020 | 2050 |
|---|---|---|---|
| Length of streams and lake perimeter (km) 2 | 11 800 | 20 000 | 41 300 |
| Important wetlands (number) 1,3 | 80 | 81 | 130 |
1 Data from all States, Qld only for 2050.
2 Data from WA, SA, Vic and NSW, Qld only for 2050.
3 Including Ramsar wetlands.
Biodiversity
The greatest threat posed by dryland salinity to biodiversity is from the loss of habitat-both on land and in water. Dryland salinity has severely affected many areas in riparian zones because they occupy the lowest parts of the landscape where much of the saline groundwater is released to the surface. The natural vegetation of such areas has been destroyed or damaged, and this is causing major changes to the landscape and its biodiversity, including destruction of remaining natural habitat in many agricultural areas and fragmentation of wildlife corridors.
- In Western Australia, at least 1500 plant species will suffer from dryland salinity, with 450 of these possibly subject to extinction. Fauna species are likely to be reduced by 30%.
The impacts of salinity on aquatic habitats have been less well studied and are more difficult to assess than those on land-based habitat such as woodlands and riparian vegetation.
- Approximately 80 important wetlands including those of national and international significance have been affected or are at risk of damage from dryland salinity in all States. Information on the full extent and degree of impacts is very sparse. In the Murray-Darling Basin, major wetlands of the Macquarie Marshes, Great Cumbung Swamp, Avoca Marshes and Chowilla Floodplain will suffer impacts from rising salinity.
Remnant vegetation, plantation forest and areas rehabilitated to perennial vegetation in Western Australia, Victoria, South Australia and New South Wales (see table below) are under threat due to rising watertables. The biggest threat in South Australia is to coastal lowlands of the upper south-east. In Victoria and New South Wales the threats are mainly to remnant and planted vegetation in agricultural lands.
| State | Current | 2020 | 2050 |
|---|---|---|---|
| New South Wales | 7 000 | 32 700 | 81 000 |
| Victoria | 6 000 | 11 800 | 24 300 |
| Queensland | n/a | n/a | 92 000 |
| South Australia | 18 000 | 22 000 | 25 000 |
| Western Australia | 600 000 | 710 000 | 1 800 000 |
| Total | 631 000 | 776 500 | 2 022 300 |
What infrastructure occurs in areas of high dryland salinity hazard?
Large decreases in the lifespan of road pavement occur when groundwater levels rise to within 2 m of the pavement surface. Salt also destroys the properties of bitumen and concrete structures. Road and bridge damage caused by shallow, saline groundwater is a major cost at all levels of government.
- Estimates are that high watertables potentially affect about 34% of State roads and 21% of national highways in south-west New South Wales, with damage costing $9 m each year for classified roads (Douglas 1997).
- Main Roads Western Australia estimated that in 1997, salinity affected 500 km of main roads and that this was likely to double within 20 years (McRobert et al. 1997).
Structures associated with communication and gas pipelines are subject to a similar fate. Wagga Wagga is one of the worst affected towns in New South Wales, experiencing salinity-induced damage to roads, footpaths, parks, sewage pipes, housing and industry (Bugden 1997). Salinity is also present in other provincial cities and towns in New South Wales and Victoria (e.g. Dubbo, Forbes, Cowra, Booroowa, Bendigo) as well as Western Sydney.
Predictions suggest that approximately 30 rural towns in Western Australia will be threatened by rising saline watertables by 2050, leading to damage to roads, recreation facilities and buildings; and difficulties with public utilities such as water supplies and waste management systems. In Victoria, predictions are that more than 60 towns will be at risk from shallow watertables.
Increased flood risks are also a consequence of shallow watertables in Western Australia (Campbell et al. 2000), and this is resulting in increased flood damage to roads, fences, dams, agricultural land and wetlands.
| Asset | 2000 | 2020 | 2050 |
|---|---|---|---|
| Rail (km)1 | 1 600 | 2 060 | 5 100 |
| Roads (km)1 | 19 900 | 26 600 | 67 400 |
| Towns (number)2 | 68 | 125 | 219 |
1 Data from WA, SA, Vic and NSW, Qld only for 2050.
2 Data from WA, SA, Vic and NSW.
Further information
- Australian Dryland Salinity Assessment 2000 report
- National Technical Overview Report of the State-based dryland salinity assessments
- Dryland Salinity Evaluation and Monitoring Report
- Australian Groundwater Flow Systems Technical Report
- National Dryland Salinity Program
- National Action Plan for Salinity and Water Quality
Australian Dryland Salinity Report
Link to Map maker to make a map using this information.
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