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Prerequisite policy measures

Water entitlements for the environment are used by environmental water holders to improve the health of our rivers, wetlands and floodplains and the plants and animals who depend on these for their survival. They are now a permanent part of water management in the Basin.

Prerequisite policy measures are legislative and operational rule changes that improve the use and accounting of water for the environment in the southern-connected Murray–Darling Basin.

These policy measures ensure there are secure and enduring water management arrangements for the efficient and effective use of water for the environment and provide greater flexibility in how this water can be used.

The policy measures include:

  • Instruments that account for and protect ‘return flows’ of water for the environment: A portion of the water used in an environmental event may return to the river as a ‘return flow’. The measures account for these flows, allowing the water to be protected through crediting arrangements, and used for environmental purposes downstream.
  • Instruments that allow ‘piggybacking’ on unregulated events: This means water for the environment can be released on top of other unregulated flows such as natural flooding. Environmental water holders are able to specify which storage, or dam, their water order is delivered from. As a result, important environmental outcomes can be achieved through piggybacking on an unregulated event while the water is travelling to its planned destination, making the best use of water available for the environment.

Implementation of these policy measures does ensure that reliability of water for entitlements are not adversely affected.

These measures have been made through:

  • state legislative changes
  • amendments to local water sharing plans
  • changes to regulations and operational manuals.
Policy measures came into effect before 30 June 2019. Basin states have demonstrated that water for the environment can piggyback on an unregulated event, and be re-credited, to ensure the planned outcomes are achieved.


These measures are adaptable. A forward work program of appropriate review and refinement will ensure the continued improvement of the efficient and effective use of water for the environment.

In the northern Basin, improved arrangements for using environmental water will occur through the ‘toolkit measures’ and other northern Basin initiatives.

Assessing prerequisite policy measures

As of 1 July 2019, prerequisite policy measures were considered to be in effect. The Murray–Darling Basin Authority (MDBA) has assessed the measures and determined that they are in effect. Members of the Independent River Operations Review Group have also undertaken an independent review of the assessment. Read the MDBA’s position statement on prerequisite policy measures.

The New South Wales, Victorian and South Australian state governments have been working to implement the measures and have each used various approaches to consult their stakeholders.

Further refinements of the policy settings will continue as part of the adaptive management approach to improving environmental water arrangements in the Basin.

Read more information about the assessment of prerequisite policy measures.

Updated: 03 Dec 2021