Victoria
The area predicted to be at risk from shallow saline watertables is approximately 670 000 ha. This could increase to over 3 million hectares within 50 years. Between 8% and 18% of the State's agricultural land is predicted to fall into the high salinity risk category, with up to a further 47% in the moderate-risk category under the worst-case scenario. High-risk areas are concentrated in the Goulburn-Broken and North Central regions in northern Victoria and the Glenelg-Hopkins and Corangamite regions of southern Victoria (Table 9).
Figure 5
Current salinity risk areas are based on mapping of land affected by dryland salinity at 1:25 000 scale and analysis of groundwater levels at a scale of approximately 1:250 000. Mapping was based on the nine-second digital elevation model for Victoria and work undertaken for the Murray Darling Salinity Audit, for much of northern Victoria. Large contiguous areas of forest or woodland (mostly public land) were excluded from the analysis due to the lack of groundwater data and generally low threat of salinisation. Future salinity risk is based on current risk areas and analysis of groundwater trend information. Worst- and best-case trend values were calculated based on relatively wet and dry climatic sequences, respectively. Information on salinity risk and potential impact presented generally represents the worst-case trend scenario.
More specifically, the major areas of land that are either currently affected by dryland salinity and/or are predicted to have shallow watertables are:
- the Dundas tablelands of south-west Victoria;
- parts of the western Victorian basalt plains;
- the break of slope between the uplands of the Great Dividing Range and the northern Victorian riverine plain in north-eastern and north-central Victoria;
- the middle and lower reaches of the Loddon riverine plain;
- agricultural land on the eastern fringe of the Sunset Country in north-west Victoria;
- the lower Wimmera river floodplain;
- the floodplains of the Avon and Richardson rivers; and
- coastal areas of south Gippsland.
Figure 6.
Table 9.Areas* (ha) of land predicted to have shallow watertables for catchment management authority regions in 1998, 2020 and 2050 in Victoria.
|
CMA Region |
1998 |
2020 worst-case |
2050 worst-case |
|
Corangamite |
51 200 |
213 300 |
499 100 |
|
East Gippsland |
1 800 |
1 800 |
19 100 |
|
Glenelg?Hopkins |
144 500 |
429 600 |
947 200 |
|
Goulburn?Broken |
123 600 |
193 500 |
739 800 |
|
Mallee |
60 700 |
63 500 |
74 400 |
|
North Central |
124 300 |
176 500 |
401 400 |
|
North East |
40 400 |
48 000 |
68 100 |
|
Port Phillip |
8 500 |
43 200 |
134 100 |
|
West Gippsland |
14 100 |
14 000 |
70 600 |
|
Wimmera |
96 400 |
122 500 |
160 800 |
|
Total |
665 500 |
1 305 900 |
3 114 600 |
* Area excludes irrigation and urban areas and those with substantial contiguous forest or woodland coverage.
Findings
Table 10. Assets at high risk from salinity from shallow groundwater and under the worst-case scenario in Victoria.
|
Asset |
Current |
2020 |
2050 |
|
Agricultural land (ha) |
555 000 |
1 170 000 |
2 800 000 |
|
Perennial vegetation (ha) |
6 200 |
11 830 |
24 280 |
|
Railways (km) |
131 |
303 |
952 |
|
Freeways and major roads (km) |
808 |
1 541 |
3 597 |
|
Other roads (km) |
3 088 |
6 513 |
17 326 |
|
Length of stream or perimeter of wetlands (km) |
10 121 |
18 146 |
34 599 |
|
Towns (number) |
10 |
21 |
63 |
|
Ramsar wetlands* (number) |
4 |
5 |
8 |
* Coastal wetlands have not been included in those at risk.
- Potential future impacts on cropping land are concentrated in the North Central and Goulburn-Broken regions, while impacts on grazing land are greatest in the Glenelg-Hopkins, Goulburn-Broken and Corangamite regions of the State.
- Potential impacts of shallow watertables and dryland salinity on physical infrastructure, particularly roads and rail, are predicted to more than double by 2050. These changes, particularly for the road network, would be expected to greatly increase the maintenance costs incurred by State and local government.
- Shallow watertables are predicted to increase under more than 30 000 ha of land surrounding the Ramsar wetlands of the Western District lakes during the next 20 years.
- Wetlands in the Goulburn-Broken and Corangamite regions are expected to be the most affected, with over 40% of wetlands in each region predicted (in the worst-case scenario) to be in landscapes with shallow watertables by 2050.
- The number of rare or threatened plant and animal species whose habitat is located in shallow watertable areas is expected to increase substantially: plant species from 122 to between 196 and 346, and animal species from 269 to between 317 and 485.
- A two- to 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. Much of the increase is predicted for the Goulburn and North Central regions, and under the worst-case trend scenario, for the Glenelg and Corangamite regions. If realised, this change would result in increased groundwater discharge to streams, greater salt wash off and increased stream salinity and salt load.
- Stream salinity increases westwards across northern Victoria (to the Avoca River). Flow-weighted salinity (Table 11) in the lower Loddon and Avoca Rivers either already exceeds or is predicted to exceed Murray Darling Basin Commission benchmarks for water quality (800 and 1500 µS/cm).
Table 11. Current and predicted future flow-weighted stream salinity (µS/cm) at the end of the major Murray Basin river systems in Victoria.
|
Location |
Current |
2020 |
2050 |
|
Goulburn River upstream of Murray River |
134 |
136 |
231 |
|
Broken River upstream of Murray River |
114 |
231 |
968 |
|
Campaspe River upstream of Murray River |
595 |
600 |
606 |
|
Loddon River downstream of Kerang Weir |
871 |
883 |
903 |
|
Avoca River downstream of Marshes |
1 444 |
1 468 |
2 216 |
|
Wimmera River upstream of Lake Hindmarsh |
680 |
684 |
691 |
Water quality is more variable across south-west Victoria and does not have a consistent pattern of increasing salinity either westwards or downstream. Flow-weighted salinities in several of the major rivers (e.g. Barwon, Leigh, Woady, Yalloak, Hopkins, Wannon) already exceed Murray Darling Basin Commission benchmarks and are generally greater than for streams in northern Victoria.
Agricultural costs are predicted to increase from approximately $27 m each year to between $77 m and $166 m. Losses from pasture and cropping account for 95% of the current (predicted) loss in gross margin, and between 80% and 82% of the loss in predicted gross margin in 2050.
Key issues
- Management of stream salinity is perhaps the most important issue for Victoria. The issue is significant because of the State's obligations to the Murray Darling Basin Salinity Strategy as well as potential impacts on irrigation, urban and industrial use and on aquatic ecosystems.
- Implementation targets for the catchment management authorities will require considerable technical support to integrate the latest information from the Audit and Murray Darling Basin salinity audits, and to set up appropriate monitoring processes.
Government responses
The Victorian Salinity Program was established in 1987 with the release of Salt Action Joint Action. Under this program, dryland salinity management plans, strategies, or land and water management plans were prepared for major catchment areas of northern and south-west Victoria between the late 1980s and mid 1990s. They focus on dryland salinity but recognise the links to other natural resource issues. Government has accepted all plans and strategies and they are being implemented.
Catchment management authorities have been created and given responsibility for overseeing the plans, leading to further integration of salinity with other natural resource issues.
The State Government has recently prepared a revised salinity management framework for Victoria. Regional salinity management plans and strategies will be reviewed and second generation plans prepared by September 2001. Reviews will consider: the progress of the plans against specified targets for works; the progress of works towards achieving desired catchment health outcomes; the validity of the assumptions on which the plans were based; and new information that contributes to a better understanding of the dryland salinity problem.
It is expected that the reviews, particularly for the Murray Basin catchments, will recommend an approach to salinity management based on the protection of specific social, economic or environmental assets and the achievement of targets for catchment health outcomes.
Table of Contents for the Australian Dryland Salinity Assessment 2000
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