Sustainable Diversion Limit (SDL) adjustment mechanism and its implementation

​​​The Murray–Darling Basin Plan sets limits on the amount of water available for urban, industrial and agricultural use in the Basin.

These limits are known as Sustainable Diversion Limits (SDLs).


SDLs commence on 1 July 2019 and are set at a Basin-wide, catchment and aquifer scales. The Authority has estimated the Basin-wide SDL for surface water is 10,945 gigalitres per year (GL/y)1. At the catchment scale, SDLs are implemented through Basin States’ water resource plans.

Adjustment mechanism

During the development of the Murray-Darling Basin Plan, Basin water ministers requested the inclusion of an adjustment mechanism in the Basin Plan. This would allow for better social, economic and environmental outcomes than would otherwise be achieved by the Basin Plan.

The Basin Plan (at Chapter 7) provides for a mechanism to adjust the SDLs to achieve equivalent social, economic and environmental outcomes with less water recovery. The mechanism enables adjustment of the Basin-wide SDL (up or down) by no more than 5% (approximately 543GL/y).

Environmental, social and economic outcomes are not to be compromised by this adjustment.


Supply and Constraint Measures

In 2017, the Australian, New South Wales, South Australian and Victorian governments notified a package of 36 supply measure projects under the mechanism.

Supply measures can:

  • reduce evaporation at water storages; or
  • manage environmental water more efficiently through using infrastructure or changing river operating rules.

Some constraints measures, activities which address barriers to delivering environmental water, have also been notified as supply measures.

Taking into account these 36 projects, the Murray-Darling Basin Authority (MDBA) determined a supply adjustment to the SDLs of 605GL/y. This means there is more water available for Basin communities.

On 13 January 2018, the Basin Plan Amendment (SDL Adjustment) Instrument 2017 amended the Basin Plan to reflect the change in SDLs. Combined with changes from the Northern Basin Review, the adjusted SDLs are estimated to be 10,945GL/y. This means we now have an annual Basin-wide surface water recovery target of 2,075GL/y* and 62GL/y of efficiency measures.

* 2,075GL/y = 2,750GL/y (original water recovery target in the Basin Plan 2012) less the 70GL/y adjustment from the Northern Basin Review and the 605GL/y adjustment from the SDL adjustment in the southern Basin

Efficiency Measures

To allow the 605GL/y increase, at least 62GL/y must be obtained through efficiency measures. This keeps the adjustment within the 5% limit set out in the Basin Plan. Efficiency measures are activities that change water use practices and save water.

Read more about Efficiency Measures.

Implementation and delivery

Basin States are responsible for implementing the supply and constraints measures. All projects must be ready to enter into operation by 30 June 2024.

We are providing:

  • up to $1.3 billion to support the implementation of the package of supply measures
  • up to $1.775 billion through the Water for the Environment Special Account for implementing constraints and efficiency measures

Further information

We are also implementing a package of commitments to complement and support the delivery of the Basin Plan.

Check the MDBA website for information on:

1 See section 6.04(2) of the Basin Plan 2012 ​​​
Last reviewed: 15 October 2020
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