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Sustainable diversion limit adjustment mechanism

The Basin Plan sets sustainable diversion limits, which is how much water can be used in the Murray–Darling Basin, while leaving enough water to sustain natural ecosystems.

To provide flexibility, the Basin Plan includes a mechanism to adjust sustainable diversion limits in the southern Basin. The mechanism requires a suite of projects to be implemented – some projects allow Basin Plan environmental outcomes to be achieved with less water. This means that more water can remain in the system for other users, including households, industry and irrigated agriculture. Other projects improve water use so it's more efficient.

The Basin Plan limits the amount that sustainable diversion limits can be adjusted. The adjustment mechanism means the limit can only be adjusted up or down by a maximum of 5% (approximately 543 GL).  

The sustainable diversion limit adjustment mechanism

View a short video on what it is and how it works.

The adjustment mechanism works in two parts. Supply projects, which include some constraint projects, aim to improve water infrastructure and river operating rules. There are also efficiency projects, which improve water delivery systems, including urban and on-farm infrastructure.

Supply projects

Supply projects are improved ways to manage the Basin's rivers to more efficiently deliver water for the environment. Projects include environmental works, such as building or improving river or water management structures and changes to river operating rules, which achieve environmental outcomes, with less water.

Community input is critical to the ongoing detailed design and implementation of these projects.

Once projects move into the design phase Basin state governments will work with local communities and affected landholders to ensure these projects consider local needs.

Constraints projects

Constraints projects aim to overcome some of the physical barriers that impact delivering water in the system. Constraints projects can include changes to physical features such as crossings and bridges. They can also change river operating practices and rules. They could allow water managers more flexibility in releasing and moving water through the system.

No changes to flows will occur until all third party impacts have been resolved in consultation with affected communities. 

Efficiency projects

Efficiency projects are activities that change water use practices and save water for the environment.

Projects can include upgrading irrigation systems, lining water delivery channels or installing water meters, along with water productivity improvements in manufacturing or irrigated agriculture, or changes to urban water management practices to reduce water.

Efficiency projects aim to provide 450 GL more water for the environment.

These projects need to have positive or neutral socio-economic impacts on Basin communities and industries.

Efficiency projects work with supply projects to achieve the outcomes of the Basin Plan. Funding for supply projects will be reliant on Basin state governments delivering efficiency projects. The confirmation of the supply projects in Australian Parliament has triggered the beginning of new efficiency projects.

How the adjustment to sustainable diversion limits is determined

In consultation with Basin governments, the Murray–Darling Basin Authority (MDBA) has developed an assessment framework, to assess how much water is being saved through the Sustainable Diversion Limit Adjustment Mechanism projects. This assessment framework has been used to calculate and recommend a new sustainable diversion limit.

The framework is complex and includes components such as computer (hydrological) models, hydrological indicator sites, limits on hydrological change and ecological equivalence scoring.

This framework has been trialled and thoroughly reviewed by independent experts and found to be scientifically rigorous and fit for purpose. Basin governments were also extensively involved in the development of the framework and the Basin Officials Committee agreed it was fit for purpose.

The Basin Officials Committed noted at the time of the determination that the MDBA had received advice from independent experts on ecology, river operations and hydrologic modelling that the modelling process and application of the assessment framework was technically sound.

The framework compares project outcomes with the Basin Plan and applies tests during the comparison, to ensure the outcomes of the Basin Plan are achieved.

The MDBA's sustainable diversion limit adjustment mechanism assessment (draft determination) was available for public comment from 3 October to 3 November 2017. Read the summary of feedback report.

Reporting on progress

It is important to monitor the integrity of sustainable diversion limits and the operation of the Sustainable Diversion Limit Adjustment Mechanism.

Updates on progress are regularly provided, through both quarterly and annual reporting, and there have also been independent status reports.

Annual reporting by the MDBA focuses on assessing whether reasonable progress is being made, and that projects are on track to deliver the outcomes committed to. It includes progress of the overall package of projects, including both efficiency and supply measures and the program as a whole. Particular attention is given to the more complex projects that require further design and community consultation, and subsequently have higher delivery risks. These include the Menindee Lakes Water Saving Project, constraints projects, and the multi-jurisdictional Enhanced Environmental Water Delivery project.

Further to annual reporting, Indec Pty Ltd was commissioned by the Department of Agriculture, Water and the Environment to provide a high-level assessment of the status of the Sustainable Diversion Limit Adjustment Mechanism (SDLAM) program. The subsequent Indec independent status assessment report was published in April 2021.

In addition, quarterly reporting aims to provide a regular overview of progress through publication of a quarterly dashboard compiled through information supplied by state governments.

Roles and responsibilities

The Murray–Darling Basin Authority (MDBA)

The MDBA has multiple functions relevant to the Sustainable Diversion Limit Adjustment Mechanism. This includes regulatory roles in:

  • reconciliation
  • technical support
  • project delivery.

These functions overlap in responsibility and, in some cases, are interdependent.

The MDBA will maintain the highest standards of probity in undertaking these functions to maintain the integrity of the Authority’s multiple roles (including decision-making).

The MDBA is responsible for developing the sustainable diversion limit adjustment assessment framework to assess how much water is being saved through supply projects.

The MDBA determined the sustainable diversion limit adjustment volume in September 2017, based on the package of projects notified by the Basin Officials Committee to the MDBA. In February 2018, this adjustment was proposed and adopted as an amendment to the Basin Plan by the Australian Government Minister responsible for water. 

The MDBA provided technical analysis of the projects to support Basin state governments with project feasibility studies and business cases. This is in line with the phased process agreed to by all Basin governments.

The MDBA will continue to play a key role in monitoring the integrity of sustainable diversion limits and the operation of the Sustainable Diversion Limit Adjustment Mechanism. Assumptions about projects within the MDBA's modelling are considered a base-line for the projects. Projects will continue to evolve with community input, along with technical knowledge and on-the-ground practicalities.

Any changes after further design and community consultation is reported at regular intervals. The MDBA will conduct assurance on projects which will inform the Authority on whether to undertake a formal reconciliation prior to 30 June 2024.

The impact of any changes will be assessed through the MDBA's reconciliation process in 2024. The Basin Plan includes the option to re-evaluate the SDL adjustment, should it determine it is appropriate to do so.

The Sustainable Diversion Limit Adjustment Mechanism Reconciliation Framework identifies the legislative framework and approach to reconciliation as required under the Basin Plan.

Basin state governments

Basin state governments are responsible for developing and assessing sustainable diversion limit adjustment projects. Projects are developed and assessed according to the phased process agreed to by all Basin jurisdictions.

Basin state governments are responsible for delivering the projects at a local-level, including consulting with communities and detailed project design and implementation. Basin governments are aware of a range of issues and opportunities in regards to proposed projects and plan to incorporate these into implementation activities over the coming years.

Australian Government

Projects are assessed and funded by the Australian Government.

Sustainable adjustment mechanism timing

Date Stage of process
  • Basin governments nominated supply projects – 30 June 2017
  • MDBA completed assessment of proposed package and developed the final sustainable diversion limit adjusment amounts – July 2017
  • Sustainable diversion limit adjustment released for public consultation – October 2017
  • Proposed adjustment to the sustainable diversion limit tabled in Federal Parliament.
  • The adjustment to sustainable diversion limits was passed by both houses
  • Basin governments will consult with communities on the design and implementation of the projects
2020 to 2024
  • Approved projects are progressively implemented until June 2024


Updated: 17 Nov 2021