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The Sustainable Diversion Limit Adjustment Mechanism (SDLAM) is a way to change the 2,750 gigalitres (GL) sustainable diversion limits target if we can achieve similar or even better environmental 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.
Read about the environmental benefits.
Using less water
The current 2,750GL target was only enough to protect low-lying floodplains. We needed a different solution that reached the mid-to upper-levels of the floodplains.
The Basin Plan focuses on environmental outcomes for not just the rivers, but its floodplains too. And it’s about more than just the amount of water. So we can deliver water to high value sites, we needed new infrastructure.
We could achieve better outcomes with less water by changing the dams and river management. 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 naturally flood wetlands. In some areas, we've investigated options that allow higher flows down the river. This can ease many of the delivery constraints.
The large flows needed for the mid-to-upper floodlands would need massive volumes of water. This would damage private land and public infrastructure, such as bridges and roads.
We've completed large-scale environmental works as part of the Living Murray Program. These changes are already delivering results at:
- Chowilla Floodplain
- Gunbower Forest
- Hattah Lakes
- Koondrook-Perricoota Forest
- Lindsay Island
- Mulcra Island
We are seeing improvements in vegetation health, successful waterbird breeding, and increases in fish populations. Read Victoria's Basin Plan report card.
Each of the Basin states submitted proposals for offset projects.
In June 2017, the water ministers and the Australian Government agreed to 36 projects. Victoria is a proponent or co-proponent of 22 of the 36 agreed projects.
These offset projects mean that we can achieve better outcomes using less water. The Murray-Darling Basin Authority (MDBA) determined that a 605GL reduction of the water recovery target was possible through these projects. As a result, we can achieve better outcomes for the environment and communities with less water.
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
- improves the environmental benefits in the Basin.
CSIRO modelling showed that the projects can deliver outcomes equal to 605 GL of environmental water flows.
The Basin’s floodplains are better off with this amendment:
- Achievement of the same environmental benefits with 605 GL less environmental water needed.
- New infrastructure means we can meet environmental needs for the mid- to upper-floodplains. This is the case even during dry periods.
- Achievement of all targets in South Australia's Coorong, Lower Lakes and Murray Mouth.
Before the offset projects, how much water farmers gave up under the Basin Plan wouldn't have mattered. The water still wouldn't have reached where it needed to be. In some cases, the environmental works projects are the only way water can reach those sites.
The environmental works will protect these places during droughts and a drier future. These offset projects secure the community’s investment in water recovery.
During the Basin Plan's development, all Basin states agreed to have an SDLAM. This allowed for less water recovery but still achieved the same environmental outcomes. A 2017 agreement reduced the SDLAM target 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 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 SDLAM 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
In October 2018, we published Victoria’s Northern Water Infrastructure Prospectus – Continuing to deliver the Basin Plan. It was also submitted to the Australian Government.
The Prospectus delivers on the Victorian Government’s commitment to identify up to 9 GL of water savings projects for Australian Government investment. We made this commitment made at the Murray-Darling Basin Ministerial Council meeting on 8 June 2018. to contribute to the 62 GL of additional water recovery required to satisfy the 5% rule.
We developed the prospectus in line with Water for Victoria’s principles. These principles for public investment in rural water infrastructure focus on:
- irrigation channel upgrades
- improving irrigation system viability
- pipelining for efficient stock and domestic supplies.
The Victorian Government committed $1.05 million toward completing 5 business cases in the prospectus. Where the business cases justify investment, capital funding will be sought from the Australian Government.
In March 2021, Victoria secured this funding to begin the $177.5 million GMW Water Efficiency Project. This project delivers off-farm infrastructure works across the Goulburn Murray Irrigation District, which includes:
- 250 km of modernised or decommissioned channels
- 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.
Modelling the outcomes
Modelling shows the SDLAM projects deliver large improvements for the whole river system. This analysis used pre-Basin Plan conditions for comparison.
The ecological elements score* in some reaches is slightly lower compared with the 2,750 GL scenario. Although the reduction is only 1-3%, so it’s considered statistically and ecologically insignificant.
*The ecological elements score used a calculation method from the CSIRO. The score considers ecological outcomes for birds, fish and vegetation in each river reach.
Environmental works will be used on large floodplain sites like Gunbower Forest, Hattah Lakes, Lindsay and Wallpolla Islands. They will also be used to water smaller floodplains all along the river.
As well as making sure the floodplains are healthy at the sites with environmental works, SDLAM delivers all the environmental benefits to the river and floodplains that would have been achieved under the 2,750 GL scenario.
Coorong, Lower Lakes and Murray Mouth
Many people are particularly concerned about the declining health of Coorong, Lower Lakes and Murray Mouth due to high salinity and low water levels.
The water available for these sites has substantially increased compared to pre-Basin Plan conditions, and they remain a priority. Under the SDLAM scenario, all flow and salinity targets set by South Australia will be met and in some cases exceeded.
Modelling the offsets
The Murray-Darling Basin Authority is responsible for modelling and determining how much water recovery can be offset by the projects, while achieving equivalent environmental outcomes.
More information on how this process was undertaken can be found in the 2017 Draft Determination Report.
The Victorian government supported this process throughout and also commissioned, with the NSW government, an Independent Expert Panel to review the offsets mechanism and provide a better understanding of how it works. The report helped to ensure that decisions about offsets were based on the best available information, including expert advice.
Northern Basin Review
In 2017, the Murray-Darling Basin Authority proposed a number of amendments to the Basin Plan process linked to the Northern Basin Review. This included a recommendation that the water recovery target for the Northern Basin be reduced from 390 gigalitres (GL) to 320 GL.
The proposed amendments to the Murray-Darling Basin Plan were subsequently disallowed by the Senate in February 2018.
Governments and the MDBA have committed to there being no negative impacts on triple bottom line outcomes in the southern basin as a result of the Northern Basin Review. If any negative impacts are identified, they will be addressed by the MDBA as part of the established review processes for the Basin Plan.
Page last updated: 27/09/23