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The Murray–Darling Basin Agreement

Water is a precious and limited resource that needs to be shared for the benefit of Basin communities, farmers and the environment. The Murray–Darling Basin Agreement (the Agreement) is a long-standing arrangement that aims to share water in the southern Basin and outlines the rules for the way the River Murray is managed and operated.

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Water sharing arrangements of some kind have been in place for a century

The Murray–Darling Basin Agreement sets out rules and plans for dividing the water in the River Murray to support a reliable supply of water for communities and environments along the River Murray across New South Wales, South Australia and Victoria. Before water is available for the states, system demands must be met. These include conveyance water (water that is needed to deliver water) and reserves for the following year.

The first version of the water sharing agreement was signed in 1914 when New South Wales, South Australia and Victoria came together to make sure water in the River Murray was managed in an agreed way, to leave South Australia with enough water.

Basin state governments and the Australian Government have all signed the Agreement, and each state contributes funding for managing the River Murray based on its level of water use.

The Agreement has been updated and amended from time to time by the Ministerial Council, ensuring it meets current needs. An example of this is when updates were made to address problems identified during the millennium drought. In 2008, the Agreement was incorporated into the Water Act (2007).

Elements of the Agreement

For more than 100 years the states have been sharing River Murray water.

There are a number of key elements to managing the River Murray. These include:

  • critical human water needs – states set aside water for core human needs such as drinking, food preparation and hygiene. Critical human water needs are a practical measure to help safeguard communities in drought.
  • system demands (conveyance water) – conveyance water is the water needed to keep the system running. It includes water lost to evaporation and through seepage. It can vary through the year and between years depending on river flows and climate. Without it, water could not be delivered.
  • water in reserve – most river catchments are operated so that a certain amount of water is kept in reserve. In the River Murray system, water is set aside to assist with system needs for the following year. Some water is set aside at the start of the water year, and some is set aside progressively throughout the year.
  • water delivery – the MDBA delivers water through the river to entitlement holders who have placed water orders through the states. This can be for consumptive use or water for the environment. There are several challenges in delivering water to where it needs to go and the MDBA and other water managers must plan for and manage these challenges. These include how long it takes water to travel, the amount of water that will be lost along the way, and physical constraints.
  • assets – under the Agreement the MDBA is responsible for overseeing the construction, operation and maintenance of the physical assets – the dams, weirs and locks used to store water and regulate flows in the River Murray system.
  • water sharing defines an agreed approach between Basin states for how water is shared.

Sharing the water in the River Murray

The MDBA is legally responsible for sharing water under the Agreement. It acts as an independent body to make sure each state gets the water it is entitled to from the major River Murray storages (the Hume and Dartmouth Dams), as well as the Menindee Lakes.

Water shares are not simply a volume made available to each state each year. Inflows to the system change every year which changes the water available to the states and likewise water available for allocations. What doesn’t change is the formula for calculating how much water each state receives. 

Victoria and New South Wales each receive:

  • 50% of water flowing into the Hume Dam
  • 50% of water flowing into the Dartmouth Dam
  • 50% of water flowing in the Kiewa River
  • 50% of water in the Menindee Lakes when Menindee is considered a shared resource.

Menindee is a shared resource when the volume held exceeds 640 GL and stays as a shared resource until the amount of water falls below 480 gigalitres, Menindee is then a New South Wales resource until the lakes reach 640 gigalitres again.

South Australia receives a specific volume (currently 1,850 gigalitres) which it can rely on each year, except when forecast reserves are low.

Victoria and New South Wales each provide half of South Australia’s share from the water they have in the system.

A flow diagram of the River Murray system

South Australia’s storage right

As a result of the millennium drought, an important element of South Australia’s water security framework, the South Australian Storage Right, was incorporated into the Agreement.

South Australia can defer and store part of its annual entitlement in River Murray storages, such as Dartmouth and Hume Dams and Lake Victoria to meet critical human water needs and / or private carry over.

The MDBA’s role in implementing the Agreement

The Agreement means the MDBA is responsible for:

  • calculating how much water is in the River Murray system and informing New South Wales, Victoria and South Australia of their ‘share’
  • delivering water to entitlement holders in the River Murray system
  • managing water in most of the River Murray system, and
  • maintaining water infrastructure in the River Murray system.

The MDBA is responsible for calculating each state’s share of water in the River Murray system, while Basin state governments allocate water within each water catchment, depending on how much water is available. The MDBA is not involved in deciding on the amount of water to allocate to entitlement holders.

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Updated: 17 Sep 2021