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Salinity

Salinity refers to the concentration of salts in water or soil and is a major issue for the Murray–Darling Basin. While salt is a natural feature of the Murray-Darling Basin’s landscapes and rivers—high salinity can reduce the amount of crops that can be grown, affect the health of plants and animals, damage buildings and other infrastructure, and impact the quality of water used by people.

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

Land clearing and water intensive farming methods have resulted in underground water tables (groundwater) rising closer to the surface. This has brought more salt into the river system.

Increased water use by communities and industry (including farming) has reduced river flows, leaving less water to dilute salt in rivers or flush it out to sea.

Salt is a natural feature of the Murray–Darling Basin’s landscapes and rivers. It is derived from ancient ocean sediments, the weathering of rocks and from rainfall over millions of years.

Managing salinity

The only natural way that salt can leave the Basin is by flowing down the river and out to sea through the Murray Mouth in South Australia.

Since the late 1960s, there has been a concerted effort by governments and communities to manage the impact of salinity on people and the environment. The Basin salinity management 2030 strategy has been in place since 2015, and outlines how Basin governments are working together to address salinity and meet agreed targets. Good progress has been made and the work continues.

River salinity can also be managed through salt interception schemes, which are an engineering tool used to divert groundwater and drainage water away from the river system. Smarter land management and improved farming practices are also addressing the problem of salinity in the Basin.

There are currently 15 salt interception schemes which divert approximately half a million tonnes of salt away from the river and adjacent landscapes each year. These schemes are implemented in conjunction with the Basin Salinity Management 2030 strategy. 

Development and land management

Smarter development can prevent water tables from rising and can keep saline groundwater from reaching plant roots. Methods include:

  • improving irrigation efficiency
  • updating irrigation infrastructure
  • salinity zoning — establishment of new irrigation development in areas where the impacts are low.

Improved farming methods in dryland areas include:

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

Measuring salinity

Salinity is measured by passing an electric current through a water sample. The presence of salt in the water increases its electrical conductivity (EC), indicating a higher salinity level.

The electrical conductivity of drinking water is usually less than 800 EC, however, sea water is more than 50,000 EC. The Murray–Darling Basin Authority measures salinity at various locations along the River Murray.

Salt interception schemes in the River Murray system

Salt that is already moving through groundwater is intercepted before it reaches the rivers.

These systems are known as salt interception schemes and consist of a series of bores located near rivers, connected to disposal basins by a network of pipes.

The intercepted groundwater is diverted to disposal basins where salt is harvested or deposited in areas that pose less risk to rivers, farm land and natural environments.

There are currently 15 salt interception schemes in the Basin, which divert more than half a million tonnes of salt away from the rivers and adjacent landscapes each year.

Under the River Murray joint venture program, we are also responsible for operation, maintenance and renewal of salt interception schemes that have been constructed over many decades. We coordinate the operation of salt interception schemes to achieve and maintain agreed salinity levels in the River Murray system.

Locations of MDB salt interception schemes

SALT INTERCEPTION SCHEME LOCATIONS (JOINT OPERATED)
1. Waikerie 2A 6. Bookpurnong 11. Buronga
2. Waikerie (Lock 2) 7. Pike 12. Mallee Cliffs
3. Waikerie 8. Murtho 13. Upper Darling
4. Woolpunda 9. Rufus River 14. Barr Creek
5. Loxton 10. Mildura-Merbein 15. Pyramid Creek

On behalf of Basin governments, the Murray–Darling Basin Authority (MDBA)  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.

This accountability by Basin governments ensures on-going management of salinity in the basin to reduce adverse impacts on industries and the environment.

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.

The MDBA also:

  • makes recommendations about accreditation of water quality management plans developed by the states as part of their water resource plans
  • 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.

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.
Updated: 16 Dec 2019