Salt is a part of the landscape of NSW and in some rivers and aquifers high salinity levels are natural. For example, salinity levels in groundwater aquifers can range from that of rainwater to more than ten times that of sea water. The rate of release of salt into our soils and water sources can be accelerated by tree clearing, intensive irrigation and discharge of saline wastewaters from industry, mines and sewerage treatment plants and climate fluctuations. Over-extraction from an aquifer can also cause intrusion from surrounding saline water.
Salinity is the presence of soluble salts and in water is conveniently measured by its ability to transmit an electric current (electrical conductivity or EC). However, the method is not foolproof, and needs to be supplemented with chemical analysis. Water for drinking should ideally have a salt concentration less than 800 μS/cm (microsiemens/centimetre) and levels greater than 1000 μS/cm EC can cause problems for the irrigation of some crops and can damage aquatic ecosystems at higher concentrations.
We have learned that climate can influence stream salinity by causing cyclical mobilisation over decades. Studies over the years suggest that steep catchments in high rainfall areas are less likely to have salinity problems. Flat catchments in low rainfall areas are more vulnerable.
A salinity audit of the Murray–Darling Basin published in 1999 predicted that salinity levels were rising and could cause serious problems for water use and the environment within 20 to 50 years. As a result the NSW Government developed the NSW Salinity Strategy in 2000. This recognised that to slow down the increase in salinity, we need to:
- protect and manage our native vegetation
- use our land so less water goes into the groundwater table
- use water more effectively and efficiently
- use engineering solutions
- make better use of land affected by salt
- focus our efforts on priority salinity hazard landscapes.
Shortly after the NSW Salinity Strategy, The Murray Darling Basin Ministerial Council agreed in 2001 to the Basin Salinity Management Strategy (BSMS). The BSMS established river salinity targets for each tributary valley within the Murray Darling basin. These targets were intended to reflect the shared responsibility between the valley communities and between the States. The BSMS also established an accountability framework to monitor and assess the salinity impact of changes in land and water management. These changes are relative to a baseline condition.
The NSW Office of Water is also operating and constructing a number of salt interception schemes in south western NSW.
In this section
- Salt interception schemes