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Advice on legislation or legal policy issues contained in this paper is provided for use in parliamentary debate and for related parliamentary purposes. This paper is not professional legal opinion.
Briefing Paper No. 07/2000 by Stewart Smith
Salinity refers to the presence of excessive quantities of salt in soils and water and relates to the concentration of salt on the land and its accumulation in water systems. In Australia large amounts of salt are stored in the landscape, in soils, rocks and weathered material. With European settlement in Australia, the water balance has changed. Native vegetation with a variety of deep-rooted perennial plants and trees has been replaced by large areas of shallow-rooted plants. Woodlands and forests have been replaced with crops such as wheat and clover paddocks.
The result of this tree clearing and cropping is that more water is reaching the water table, and the water table is rising. As the water table rises, it mobilises the salts stored in the landscape. In NSW salinity is generally grouped into three categories. These are: dryland salinity; irrigation salinity; and urban salinity.
Recent national estimates suggest that 2.5 million hectares of land are affected by dryland salinity. As the process of salinisation is temporal, current trends in the process of salinisation indicate that the amount of land affected by salts will increase in the future.
In NSW, the area of salt affected land is reported to be 120,000 hectares. However, this figure is likely to be an underestimate. If current patterns of land use and ground water rise continue, NSW could face up to 7.5 million hectares of salt affected land by 2050.
The major irrigation areas in NSW are all now threatened by rising water tables. Some research indicates that approximately 70-80% of all irrigated land in NSW is threatened by rising watertables and associated salinity problems. Overall, in 1995 an estimated 15% of the irrigated land in NSW had high watertables, and soil salt levels exceeded the level where salinity becomes a problem in 9% of irrigated land. Water tables are rising at the greatest rate (100-500 mm per year) in the south-eastern parts of the Murray Darling Basin.
More recently, off-farm damage by salting has become apparent, with numerous inland communities reporting the presence of high watertables and an increase in the number of salt seeps. The high watertable and increase in soil salt levels has accelerated the deterioration in public infrastructure such as roads and sewerage systems, and damaged private infrastructure.
Salinity, and especially dryland salinity, is diffuse, widespread and often has indirect impacts. As such, it is impossible to calculate its overall effect on the nation. However, it is has been estimated that the capital loss of land due to salinity nationwide is approximately $700 million, with lost production estimated at $130 million annually.
Both the Commonwealth and State Governments, as well as local communities, have been active in the development of strategies and plans to combat salinity. These activities include a NSW government sponsored ‘Salinity Summit’, the outcomes of which are summarised in the paper.