Lower Murray: Locks 8 and 9 Project

Part of the NSW Government’s Sustainable Diversion Limit Adjustment Mechanism (SDLAM) Acceleration Program, the Lower Murray: Locks 8 and 9 Project aims to enhance connectivity across the Carrs, Capitts and Bunberoo creek systems by implementing weir pool operational changes and upgrading associated water infrastructure.

The project is a collaborative initiative, aimed at addressing environmental issues within the Lower Murray, surrounding wetlands and connected creek systems.

About Locks 8 and 9

Locks 8 and 9 are 2 of the 14 weirs and locks constructed on the Lower Murray between 1922 and 1939. They are located downstream of the Murray-Darling junction in southwestern NSW, between Wentworth and the South Australian border.

The weirs regulate river flows by each creating a stable pool of water held at a level several metres above the original river height. The associated locks allow boats to pass from one weir pool to the next. The weir pool at Lock 9 also enables the transfer of water into Lake Victoria via Frenchmans Creek, an anabranch of the Murray River upstream of Lock 9.

While the locks and weirs have provided significant economic benefits, they have also resulted in adverse environmental impacts. In particular, they have impacted the Carrs, Capitts and Bunberoo creek systems, an interconnected group of floodplain waterways isolated from the main Murray channel by fixed crest weirs on the Lock 9 weir pool.

The weirs have reduced the ability of native fish to migrate for breeding, and maintaining constant river heights has reduced the natural wetting and drying cycles needed for many native plant and animal species to flourish.

Project details

The project works include:

• new regulators and fishways within the Carrs, Capitts and Bunberoo creek systems
• changing the operational rules to introduce seasonal variability to operational water levels in the Lock 8 and Lock 9 weir pools.

This will allow intermittent inundations and exposure of river banks and riparian vegetation and will create some fast-flowing habitat and hydrodynamic diversity, conditions known to support fish breeding cycles.

The works and rule changes are scheduled to be operable by December 2026.

The project is being managed along with other proposed changes in river operations and existing environmental infrastructure, such as The Living Murray works at Mulcra Island.

Weir pool operational changes

The Murray-Darling Basin Authority (MDBA) sets the river operating rules maintaining the heights of the Murray River’s locks and weir pools. Historically, under the Murray-Darling Basin Agreement, the Locks 8 and 9 weir pool heights have operated at agreed and consistent levels throughout the year to support river navigation and water pumping.

The proposed operational changes would allow the pools to be raised and lowered seasonally. Levels would be raised in late winter and throughout spring and would be lowered in mid to late summer to reduce water losses from evaporation.

The proposed seasonal operating patterns would, as far as practicable, mimic the natural variations in river height that occurred prior to river regulation and would respond to the natural river conditions occurring at the time. The extent of any raising or lowering would depend on the flow already moving through the river. 

When natural flows are already providing suitable environmental conditions, little or no weir pool manipulation would be required. When natural flows are lower, river operators would temporarily raise the weir pool to replicate a 20,000 ML/day weir pool extent to deliver environmental watering outcomes. When natural flows are higher, river operators would lower the weir pool to support a more natural pattern of seasonal river level variation.

The operational limits of weir pool raising and lowering has been trialled by key government agencies over the past decade and will continue to be refined to achieve the best environmental outcomes with the water available.

The knowledge gained from various environmental watering trials suggests operators of the river could vary the height of the Lock 8 weir pool by up to 0.5 m below and 0.85 m above the current weir pool height of 24.6 m Australian Height Datum (AHD), and the Lock 9 weir pool by up to 0.4 m below and 0.5 m above the current weir pool height of 27.4 m AHD.

These upper and lower levels represent operational limits available to river operators and are not target operating levels.

Approval is now being sought through the MDBA procedures to implement a variable operating pattern with some flexibility to continuously improve the longer-term environmental outcomes for this important river reach.

The project is being managed collaboratively with stakeholders in New South Wales, South Australia and Victoria.

The Lower Murray is rich in cultural and spiritual significance. The Traditional Owners, the Barkandji, Maraura and Kirra Tar Ru people, play a key role ensuring cultural considerations are made throughout the project in line with their Healthy Country Plan.

The Water Group has consulted with local landholders and stakeholders during the design phase of the project through stakeholder and technical advisory groups. As the project progresses into delivery, we are contacting landholders to share updated information about the proposed operational changes.

Modelling

Hydrologic and hydraulic modelling has been undertaken to inform the options assessment, design and operational planning stages for the project. Modelling has been fundamental to validating project feasibility, through considering designs, outcomes, costs and impacts, prior to commencing the design, submission and approval process.

Environmental planning and assessments

View the project's environmental impact assessment.

Learn more about the project through these frequently asked questions and answers.