Australian Natural Resources Atlas

Natural Resource Topics

Salinity - Impacts & Costs - South Australia

South Australia

Location map

Dryland Salinity Impacts : South Australia overview

Table: 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

What, and how much, agricultural land occurs in areas at high risk from dryland salinity?

Table: Estimates of areas (ha) affected in South Australia.
Region 2000 2020 2050
Upper South East 250 500 324 000 409 500
Murray Basin 19 800 29 600 34 000
Eyre Peninsula 20 400 24 000 27 000
Kangaroo Island 5 600 6 500 8 000
Mid North 14 800 18 000 21 000
Yorke Peninsula 13 900 17 500 20 000
Mt Lofty Ranges 1 200 1 400 1 500
Total 326 000 421 000 521 000

One of the fundamental steps in the management of dryland salinity is the determination of dryland salinity its cost to the community and the benefits (or otherwise) of various treatment options. An economic model has been constructed by CSIRO Land and Water (Hajkowicz and Young, 1999) to estimate the cost of dryland salinity through losses in agricultural production.

What biological resources occur in areas of high dryland salinity risk?

Biodiversity

Biodiversity mapping has identified several areas at risk from rising watertables. These include extensive tea-tree shrublands and native grasslands in the Coorong District, and seasonal wetlands and watercourses in the Upper South East. On Kangaroo Island, the viability of sedgeland and tea-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 have also been identified as being at high risk.

Apart from the well known impacts of dryland salinity on agricultural production, it is becoming increasingly recognised that rising watertables can have environmental consequences. A study by Grear and Moyle (2000), funded by the Audit, examined the threats to the biodiversity in the agricultural regions of SA by collecting biological data in a GIS format (vegetation associations, landcover type, threatened species, conservation tenures and wetlands), and then correlating them with similar GIS coverages of depth to watertable and shallow aquifer salinity. Ground-truthing was undertaken in selected areas to accurately determine factors such as dominant vegetation, vegetation health, pre-settlement vegetation systems, hydrology, halophytic species and surface soil/water levels. Results are shown in the table below.

Table: Dryland salinity impacts on biodiversity
Impact Current 2020 2050
Remnant vegn (,000 ha) 18 22 25
Rivers ephemeral (km) 160 190 210
Wetlands (,000 ha) 45 52 57
Wetlands of National Significance 4 4 4

The mapping identified extensive tea-tree shrublands and native grasslands in the Coorong District that are at risk from rising watertables. The conservation significance of much of these habitats is enhanced by close proximity to the Ramsar listed Coorong and Lower Lakes. Seasonal wetlands and watercourses in the Upper South East are at high risk from dryland salinity. Extensive clearance of vegetation and drainage of wetlands in this district has had particularly severe implications for sedgelands and seasonal wetland ecosystems. Those areas remaining are almost all at high risk and have high conservation significance, often recognised by inclusion in the protected area estate.

Similarly on Kangaroo Island, the viability of sedgeland and tea-tree ecosystems protected in conservation parks or vegetation heritage agreements are threatened by extensive areas of shallow saline aquifers. Native vegetation on valley floors and in seasonal swamps on Lower Eyre Peninsula, provide refuge for birds and mammals endemic to the region and have also been identified as being at high risk.

A summary of these findings is presented in the table below, together with the several significant Conservation Parks and Wildlife Reserves which have been identified as having high potential for biodiversity degradation from rising watertables. In addition, numerous Vegetation Heritage Agreement Areas on Eyre Peninsula, the Coorong, Upper South East, Riverland and Kangaroo Island are at risk from a decrease in biodiversity.

Table: Risks to habitat from dryland salinity
Region Habitat Conservation Parks
Upper South East Seasonal wetlands, watercourses Messent and Gum Lagoon
Coorong District Tea-tree shrublands, native grasslands
Lower Eyre Peninsula Native vegetation, seasonal swamps Hincks and Bascombe Well
Kangaroo Island Sedgeland, tea-tree ecosystems Murrays Lagoon

Other areas such as the Murray Mallee and Lower Yorke Peninsula have problems associated with rising watertables, however the paucity of remnant vegetation in these areas lessens the biodiversity risk.

What water resources occur in areas of high dryland salinity risk?

Stream Salinity

South Australia?s climate, with low and highly variable winter rainfall combined with long, hot and dry summers, has resulted in relatively small harvestable water resources, and heavy dependence on the River Murray which is central to the social and economic development of the State. In dry years, it supplies up to 85% of the State?s urban water needs. One of the most significant threats to these resources is deterioration of water quality, in particular increases in salinity.

The causes of dryland salinity are well documented, namely the increase in recharge following clearing results in rising watertables. In the case of streams, lakes and dams, increased hydraulic gradients due to rising groundwater can result in greater movement of saline groundwater into these surface water resources (see figure below).

Two projects were carried out to determine the impacts of dryland salinity on the surface water resources of SA. A brief reconnaissance study of the likely impacts on water resources within SA was carried out by a team from CSIRO Land and Water and the Department for Water Resources, in addition to a groundwater modelling study by the Department for Water Resources and consultants Australian Water Environments to determine salinity increases in the River Murray due to clearing in the Mallee region.

Table: Key assets at risk from dryland salinity in South Australia
Assets 2000 2020 2050
Wetlands (ha) 45 000 52 000 57 000
Rivers ephemeral (km) 160 190 210
Ramsar wetlands (number) 0 0 0
Wetlands of national significance (number) 4 4 4
Main findings:

Increasing stream salinisation is occurring in Tod River (Eyre Peninsula) and Middle River (Kangaroo Island), although in both situations, alternative domestic supplies are available (limited groundwater on EP, desalination on KI), and there is little prospect of increased demand for domestic and stock water. However, there is little opportunity for increased industrial, mining and irrigation supplies in the future, which could have serious consequences for regional development in these areas. Elsewhere within SA, and particularly in the Mt Lofty Ranges, stream salinisation trends are not evident from the available data from catchments that have been monitored.

Perhaps the most widely felt impacts of watertable rise will be felt by the consumers of River Murray water. This resource is of vital importance to SA. Groundwater modelling has suggested that vegetation clearance in the Mallee will result in an increase in salinity of 118 EC by 2050, with an additional cost to consumers of $17.4M/year.

What infrastructure occurs in areas of high dryland salinity risk?

Key assets at risk from dryland salinity in South Australia

Assets 2000 2020 2050
Roads (km) 910 1 260 1 710
Rail (km) 35 40 46
Towns (number) 0 0 2

Most of the infrastructure losses (road and rail) wlil occur in the large areas of affected land over the regional flow systems (Murray Basin). Individual farm dwellings are generally situated on higher ground. The two towns likely to be affected by urban salinity are Tintinara and Coomandook in the Murray Basin.

Further information

South Australian Dryland Salinity Assessment 2000

Link to Map maker to make a map using this information.

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