Salinity

Salinity refers to the concentration of dissolved salts in water or soil. While salt is a natural feature of the Basin — derived from ancient ocean sediments, the weathering of rocks and deposition by rainfall over millions of years — high salinity can reduce crop yields, affect aquatic ecosystems and vegetation and damage infrastructure.

Salinity management is one of the most significant environmental challenges facing the Murray–Darling Basin. If it is not managed appropriately, salinity has serious implications for water quality, plant growth, biodiversity, land productivity and the supply of water for critical human needs.

While salt does accumulate naturally in the Basin, human activities such as irrigation development and land clearing often exacerbate salt mobilisation, causing it to concentrate in certain parts of the landscape.

Managing salinity in the landscape

Water flowing through the river system and out to the sea through the Murray Mouth is the only natural way that salt can leave the Basin.

However, salinity can also be managed through salt interception. Salt interception schemes are an engineering tool used to divert groundwater and drainage water away from the river system.

Under the River Murray operations program, we coordinate joint salt interception schemes to achieve and maintain agreed minimum salinity levels in the River Murray system.

There are currently 18 salt interception schemes in operation, which divert more than half a million tonnes of salt away from the river each year. These schemes are implemented in conjunction with the Basin salinity management 2030 strategy. For more information, see keeping salt out of the Murray or watch the short video: Salt of the earth

Another method of addressing salinity in the landscape is through improved farming systems. The clearing of native vegetation and the introduction of European farming practices has affected the natural water cycle in the Basin. However, improved farming practices have reduced the amount of water entering groundwater systems.

Improved farming methods in dryland areas include:

  • grazing and crop management
  • conservation farming (minimal tillage cropping, precision farming)
  • use of deep-rooted plants (lucerne, saltbush, farm forestry) to minimise the rise of water tables.

In irrigation areas, improved farming methods include:

  • improved irrigation efficiency
  • salinity zoning — establishment of new irrigation development in areas where the impacts are low
  • storage of surface run-off in dams
  • reusing drainage waters for irrigation.

On behalf of Basin governments, we maintain a register of salinity credits and debits to keep account of actions that increase salinity in the river system, so they can be offset by actions, implemented elsewhere in the system, which decrease salinity.

We are also responsible for operation, maintenance and renewal of salt interception schemes that have been constructed over many decades.

Salt interception schemes in operation along the Murray–Darling system
Salt interception schemes in operation along the Murray–Darling system

Water quality and salinity management plan

The Water quality and salinity management plan provides a framework for action to protect and enhance water quality and manage salinity in the Basin.

The plan builds on existing water quality and salinity management agreements and arrangements and sets out objectives and targets to ensure the Basin’s water remains suitable for environmental, social, economic and cultural uses.

This includes salinity targets for management of water flows at 5 reporting sites and water quality targets to inform development of measures as part of water resource plans for improving water quality. The 5 reporting sites include 3 locations along the River Murray at Murray Bridge, Morgan and Lock 6, as well as the Darling River downstream of Menindee Lakes at Burtundy and the Lower Lakes at Milang.

Our role in the implementation of the water quality and salinity management plan includes assessment of:

  • salinity levels against target values at each of the 5 reporting sites
  • achievement of the salt export objective.

The MDBA also:

  • considers flow management targets for dissolved oxygen, blue-green algae and salinity in the system
  • improves knowledge and understanding of threats to water quality to help manage the associated risks
  • makes recommendations about accreditation of water quality management plans developed by the states as part of their water resource plans.

Basin salinity management 2030 strategy

Salinity remains a significant management challenge and poses ongoing environmental, social and economic risks in the Murray–Darling Basin.

Salinity is forecast to continue to increase over time and requires careful ongoing management to prevent a return to the highly saline conditions of previous decades.

The MDBA and Basin governments have a long and successful history of working together to manage salinity in the Basin with a new strategy now developed for the next 15 years.

This strategy, the Basin Salinity Management 2030 (BSM2030), builds on the successes of the Basin Salinity Management Strategy 2001–2015 to deliver a strategic, cost-efficient and streamlined program of coordinated salinity management until 2030.

This program will enable partner governments and their communities to manage salinity, during a period of transition, as Basin Plan water reforms take effect.

Salt interception schemes will continue to be critical for protecting the river system from salinity.

At a state level, existing salinity management arrangements remain in place and regional development can continue with confidence that salinity will be well managed.

The focus of BSM2030 is to:

  • maintain the cap on salinity through the existing Basin salinity target and the existing accountability framework
  • bring environmental water fully into the accountability framework in a practical and pragmatic way
  • explore opportunities to responsively manage salt interception schemes so that operations can be further optimised and costs can be reduced when river salinity is forecast to be low
  • support Basin Plan flow management obligations with regard to the salinity targets for managing water flows
  • support Basin states in managing salinity in their catchments through their land and water management plans that are consistent with their Basin Plan water resource plan obligations
  • develop fit-for-purpose governance arrangements which reduce the frequency of audit, reporting and reviews
  • invest in knowledge to reduce uncertainty and potentially avoid the need for future capital investment in new joint works and measures
  • undertake a major review to ensure the strategy continues to guide effective management of salinity in the Basin.