The Sustainable Diversion Limit Adjustment Mechanism (SDLAM): Murray-Darling Basin Plan

The Sustainable Diversion Limit Adjustment Mechanism (SDLAM) (Glossary) is a way to change the 2,750 gigalitres (GL) sustainable diversion limits target if we can achieve similar or even better environmental outcomes for the rivers, wetlands and birds and fish using less water. It’s a provision written into the 2012 Basin Plan and agreed by Basin States and the Commonwealth.

This process helps to achieve the Basin Plan’s social, economic and environmental outcomes.

Using less water

The Murray-Darling Basin Plan’s 2,750 GL target is only enough to protect low-lying floodplains. A different solution is needed to reach the mid- to upper-levels of the floodplains.

The Basin Plan was developed to achieve environmental outcomes for the river and its floodplains: it’s about more than just the amount of water.

Using infrastructure to deliver water to high value sites, and changing the way dams and rivers are managed, can help us achieve better environmental outcomes with less water. In many cases, environmental works like flow regulators, pumps and channels are the only way to get water to many of the sites that need it. This approach works when there is not enough water to flood wetlands naturally. In some areas, options to ease delivery constraints are also being investigated to allow higher flows down the river. Creating the large flows required to flood these areas naturally would need massive volumes of water and would damage private land and public infrastructure, such as bridges and roads.

Large-scale environmental works have been completed as part of the Living Murray Program and are already delivering results at Chowilla Floodplain, Gunbower Forest, Hattah Lakes, Koondrook-Perricoota Forest, Lindsay Island and Mulcra Island. We are seeing improvements in vegetation health, successful waterbird breeding, and increases in fish populations: see Victoria’s Basin Plan report card.

Cowanna and Brickworks Billabongs Merbein Common, image credit DELWP

Offset projects

Each of the Basin states (Glossary) submitted proposals for offset projects. Water Ministers from each of the Basin states and the Commonwealth agreed to 36 projects in June 2017. Victoria is a proponent or co-proponent of 22 of the 36 agreed projects.

These “offset projects” mean that better outcomes can be achieved using less water. The Murray-Darling Basin Authority has determined that water recovery target can be reduced by 605 GL through these projects. This means:

Better off with SDLAM

The Federal Government allowed an amendment using the SDLAM to reduce the 2,750 gigalitres (GL) target by 605 GL to 2145 GL in May 2018.

The 605 GL amendment:

• reduces the amount of water for the environment we need to recover, and
• improves the environmental benefits in the Basin.

The 605 GL offset projects have been assessed by all five Basin states and the Murray-Darling Basin Authority (MDBA). CSIRO modelling has shown that the projects will deliver outcomes equivalent to 605 GL of environmental water flows.

The Basin’s floodplains are better off with this amendment:

• we will achieve the same environmental benefits with 605 GL less environmental water needed,
• environmental needs for the mid- to upper-floodplain will be met using environmental infrastructure, even in dry periods,
• all of South Australia's targets set for Coorong, Lower Lakes and Murray Mouth will continue to be achieved.

In some cases, the environmental works projects are the only way sites can be watered, no matter how much water farmers give up under the Basin Plan. The environmental works will protect these places during droughts and under a drier future; they secure the community’s investment in water recovery.

When the Basin Plan was developed, all Basin governments agreed to having a SDLAM to allow for less water to be recovered but still achieve the same environmental outcomes. In 2017, it was agreed that the SDLAM target would be reduced by up to 650 GL. The 605 GL adjustment is within the agreed amount.

Securing the benefits of SDLAM

The Basin Plan requires that environmental works and measures (supply measures) should only be recognised as providing environmental outcomes up to 544 GL. Above 544 GL, additional water recovery is required, at a ratio of 1:1 with environmental works and measures (known as the 5% rule, as 544 GL is equal to 5% of the Basin-wide sustainable diversion limit).

Because the Sustainable Diversion Limit Adjustment was determined to be 605 GL, Basin jurisdictions are required to recover 62 GL of water to satisfy the 5% rule. Efficiency measures that recover this water need to be socio-economically neutral or positive.

Victoria’s projects towards recovery of the 62 GL

Victoria’s Northern Water Infrastructure Prospectus – Continuing to deliver the Basin Plan was published in October 2018 and submitted to the Commonwealth Government. The Prospectus delivers on the Victorian Government’s commitment (made at the Murray-Darling Basin Ministerial Council meeting on 8 June 2018) to identify up to 9 GL of water savings projects for Commonwealth Government investment to contribute to the 62 GL of additional water recovery required to satisfy the 5% rule.

Download Victoria's Northern Water Infrastructure Prospectus — Continuing to Deliver the Basic Plan (PDF, 7.6 MB) or Accessible Version (DOCX, 40.3 KB).

The prospectus was developed in line with Water for Victoria’s principles for public investment in rural water infrastructure and is focused on:

• irrigation channel upgrades
• improving irrigation system viability
• pipelining for efficient stock and domestic supplies

The Victorian Government committed $1.05 million to complete the five business cases outlined in the prospectus and where the business cases justify investment, capital funding will be sought from the Commonwealth.

In March 2021, Victoria secured Commonwealth funding to commence the $177.5 million GMW Water Efficiency Project, which is delivering off-farm infrastructure works across the Goulburn Murray Irrigation District, including the modernisation or decommissioning of more than 250 km of channels and upgrading or rationalising more than 1,000 outlets. This project will recover 15.9 gigalitres (GL) long term average annual yield (LTAAY) of water for the environment by treating system losses.