South Australia
Dryland salinity affects approximately 370 000 ha of land and wetlands in South Australia, in addition to 84 000 ha of primary (or natural) salinity. Under current land use and groundwater trends this is predicted to increase by 60% in 50 years.
The largest area affected by dryland salinity in South Australia is in the Upper South East, where the rising regional watertable in the limestone aquifers of the Murray Basin is intersecting the land surface (Table 14).
Table 14.Estimates of areas (ha) of agricultural land affected in South Australia.
|
Region |
Primary |
Secondary |
Total |
|
Upper South East |
22 500 |
250 500 |
272 000 |
|
Murray Basin |
16 700 |
19 800 |
36 500 |
|
Eyre Peninsula |
35 200 |
20 400 |
55 600 |
|
Kangaroo Island |
500 |
5 600 |
6 100 |
|
Mid North |
300 |
14 800 |
15 100 |
|
Yorke Peninsula |
8 000 |
13 900 |
21 900 |
|
Mt Lofty Ranges |
1 200 |
1 200 |
|
|
Total |
84 000 |
326 000 |
410 000 |
Figure 8. Dryland salinity risk in South Australia 2000
Estimate of salt-affected lands and risks was based on field survey at scale of 1:100 000. Projection for 2050 was based on extrapolation of field survey and groundwater trend data from representative catchments across the agricultural regions. The South Australian estimates of current extent cannot be compared directly to other States as they are better estimates of affected land than exist for the other States. The figures for 2050 are considered comparable to other State 2050 projections.
Findings
Table 15 Key assets at risk from dryland salinity in South Australia.
|
Assets |
2000 |
2020 |
2050 |
|
Agricultural land (ha) |
326 000 |
421 000 |
521 000 |
|
Remnant vegetation (ha) |
18 000 |
22 000 |
25 000 |
|
Wetlands (ha) |
45 000 |
52 000 |
57 000 |
|
Rivers ephemeral (km) |
160 |
190 |
210 |
|
Roads (km) |
910 |
1 260 |
1 710 |
|
Rail (km) |
35 |
40 |
46 |
|
Towns (number) |
0 |
0 |
2 |
|
Ramsar wetlands (number) |
0 |
0 |
0 |
|
Wetlands of national significance (number) |
4 |
4 |
4 |
Figure 9. Dryland salinity risk in South Australia 2050
- Because most of the groundwater trends are strongly controlled by rainfall, levels have been falling throughout southern South Australia for the past two to three years due to well below average winter rainfalls with some drier catchments experiencing falling groundwater levels since 1993.
- Increasing stream salinisation is occurring in the Tod River (Eyre Peninsula) and Middle River (Kangaroo Island). Elsewhere, particularly the Mt Lofty Ranges, trends are not evident from the available data.
- Groundwater modelling suggests that vegetation clearance in the Mallee will cause salinity to increase by 115 µS/cm by 2050 at Morgan, costing consumers an additional $16.5 m each year.
- Biodiversity mapping has identified several areas at risk from rising watertables. These include extensive ti-tree shrub lands and native grasslands in the Coorong District, and seasonal wetlands and watercourses in the Upper South East. On Kangaroo Island, the viability of sedge and ti-tree ecosystems protected in conservation parks or vegetation heritage agreements are threatened by extensive areas of shallow saline aquifers, while on Lower Eyre Peninsula, native vegetation on valley floors and in seasonal swamps has been identified as being at high risk.
An interim assessment of costs (Table 16) to agricultural production represents 1_2% of the State-wide gross margin from production on all agricultural land.
Key issues
- The guarantee of good quality water into the future is the major issue for South Australia. There is very limited, often no, scope to further develop water supplies within the State. Water from the Murray is essentially the only option for improved supplies apart from the more expensive option of desalinisation of salt water. Long-term guarantees from the other States in the Murray Darling Basin are essential for South Australia.
- Managing and preferably preventing the predicted salt inflows from the cleared Mallee region in South Australia (and to a lesser extent Victoria) will be a major challenge requiring very long time leads and integrated approaches.
- Development of industries based on saline resource will require emphasis.
Table 16.Interim total costs of dryland salinity ($m/year) in South Australia.
|
Impacts |
2000 |
2020 |
2050 |
|
Losses in agricultural production |
26.1 |
34.0 |
42.0 |
|
Road and rail maintenance |
17.1 |
23.5 |
30.5 |
|
Building maintenance |
1.2 |
1.4 |
1.9 |
|
Costs of increase in Murray River Salinity |
0 |
8.3 |
16.7 |
|
Total cost |
44.4 |
67.2 |
91.1 |
Government response
A whole-of-government approach to managing the growing salinity problem in South Australia has been adopted with the formation of the State Salinity Committee, consisting of seven agency heads. This body has overseen the formulation of the overarching policy statement Directions for Managing Salinity in South Australia and the more specific South Australian River Murray Salinity Strategy and the State Dryland Salinity Strategy(Government of South Australia 2000a, 2000b, 2000c).
The State Dryland Salinity Strategy aims to reverse the trend of rising salinity and to minimise, and where possible prevent, damage to water resources, the environment and to infrastructure. Management options include:
- reducing recharge (usually with the aid of deep-rooted perennial vegetation);
- utilising discharge (usually with salt-tolerant plants or in industries that can use saline water); and
- disposal of surplus water (usually by drainage).
Key points to emerge from the strategy
- Whole-of-catchment management is required.
- Significant new investment will be needed to support individuals and communities.
- Costs of salinity are borne by the whole community and therefore managing salinity is the responsibility of everyone.
The strategy recommends:
- support for on-ground works;
- developing partnerships with affected communities;
- improving knowledge; and
- commitment to action.
Significant action is already being undertaken to combat the impacts of dryland salinity through the Upper South East Dryland Salinity and Flood Management Plan, (Natural Resources Council of South Australia 1993) with associated drainage, revegetation, farm redevelopment and environmental initiatives.
The Coorong and Districts Local Action Plan (Coorong District Local Action Plan Committee 2000)and associated on-ground works has become a national model: a local community-led implementation of significant on-ground works to increase rainfall utilisation and reduce salinity threats. Similar projects are emerging in other parts of South Australia.
A more difficult challenge is in dealing with the increased recharge from rainfall onto dryland farming areas in the Mallee region which will cause significant saline discharges into the Murray River.
Table of Contents for the Australian Dryland Salinity Assessment 2000
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