Saline areas

Salinity and water are inextricably linked. Because of this salinity is affected by climate variability which can tend towards extremes in NSW. In drought periods groundwater levels are usually lower, particularly where there is no irrigation. Dryland salinity caused by rising groundwater may improve, but because there are reduced flows in the rivers, the EC level, or concentration of salt, may be worse. Although the relationship between flow and EC is not nearly as strong as between flow and salt load. Many factors influence EC levels but salt load is driven by water flow.

In wet periods, especially after a drought breaks, salt loads are likely to spike as large amounts of salt, held in soils during a drought, are mobilise by much higher levels of surface and groundwater. These high salt loads will tend to taper off as the flows decrease. During these flood periods the EC in rivers may improve because of the dilution effect of the higher flows, but the EC may also rise due to much higher levels of salt being introduced to the river, or saline soils being eroded during the flood.

It is therefore important that predictions about salinity also consider climate variability. Both are natural processes that impact on how we manage land use. Just as landholders and urban planners need to plan for water availability, they also need to plan for and manage variable salinity.

Dryland salinity

In 1999, a report by the Prime Minister's Science, Engineering and Innovation Council (PMSEIC, 1999) estimated the area of land affected by salinity in NSW varied from 120,000 hectares to 174,000 hectares. The report described areas affected by salinity and potentially salt-affected land area for each State and Australia as a whole. It showed that although NSW had only 5% of the land currently affected by dryland salinity in Australia, it had almost 50% of the potentially affected land.

The National Dryland Salinity Assessment 2000 (National Land and Water Resources Audit 2001) reported that approximately 181,000 hectares of land in NSW had shallow watertables or was affected by dryland salinity. It was estimated that this area could potentially increase to 1.3 million hectares by 2050. In NSW over 90% of the areas affected by dryland salinity occur in five catchments - the Murray, Murrumbidgee, Lachlan, Macquarie and Hunter rivers. In coastal catchments, the Hunter and Hawkesbury-Nepean river catchments have the most extensive areas of existing dryland salinity or shallow groundwater.

Known areas of major concern in relation to dryland salinity are:

  • A north-south belt near Canberra, taking in the Yass River Valley;
  • The south-western part of the Lachlan River Catchment;
  • East of Wagga Wagga in the Murrumbidgee River Catchment; and
  • East of Dubbo in the Macquarie River Catchment.

Irrigation salinity

Irrigation salinity is estimated to affect 320,000 hectares, or 15% of irrigated land. About 70-80% of irrigated land in NSW is threatened by rising watertables and associated salinity problems (EPA, 1997). The areas at greatest risk from irrigation salinity are in the:

  • Murrumbidgee River Irrigation Areas in the vicinity of Griffith, including the Mirrool, Yanco and Colleambally Irrigation Areas;
  • Murray Irrigation Areas around Deniliquin, including the Berriquin, Deniboota and Wakool Irrigation Districts; and
  • Jemalong Irrigation District, west of Forbes.

Urban salinity

Although urban development can create a high salinity risk, towns and cities are often located in areas prone to salinity. These areas are usually at lower positions in the landscape, such as floodplains, in valley floors, or at the foot of a ridge.

In NSW, many towns and cities are currently affected by urban salinity. The predictions are that this will get steadily worse over the next 50 years if nothing is done (NLWRA 2001).

Urban salinity is of concern in Western Sydney, the Hunter and in many other rural towns in NSW including (in alphabetic order) Blayney, Boorowa, Canowindra, Condobolin, Cootamundra, Cowra, Crookwell, Dubbo, Forbes, Grenfell, Gunnedah, Harden-Murrumburrah, Junee, Lake Cargelligo, Leeton, Orange, Parkes, Queanbeyan, Tamworth, Wagga Wagga, Wellington, Yass and Young.

Many councils are making a commitment to manage urban salinity, but much more needs to be done.

River salinity

The report Salinity Predictions for NSW Rivers in the Murray-Darling Basin (Murray-Darling Basin Ministerial Council - MDBC 1999) provides important information on river salinity. Of particular interest are the current and predicted salt loads and salinity levels for the years 1998, 2020, 2050, and 2100 for the major inland rivers in NSW.

Marked increases in salinity are predicted for most rivers over these periods, in a "business as usual" scenario. The Lachlan, Murrumbidgee and Namoi Rivers show the largest increase in total salt loads, while the Bogan, Macquarie and Namoi show the largest increase in salinity. For example, water salinity in the Bogan River is predicted to rise from approximately 700 EC units in 1998 to almost 2000 EC units in 2050. Likewise, it's predicted the Macquarie River will rise from approximately 600 to 1700 EC units over the same period. The World Health Organisation's recommendation for safe drinking water is 800 EC units.

Salinity in catchments

Regionally specific salinity information includes:

Central West

Murray/Murrumbidgee

Sydney Metropolitan

Hunter

Page last updated: 26 February 2011