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Lock 6 Reach

Background

Announced in September 2020 as part of the Australian Government’s Murray-Darling Communities Investment Package, the $37.6 million Sustaining Riverland Environments (SRE) program implements projects focused on improving the condition of the lower River Murray channel, floodplain and wetland ecosystems, with the aim of recovering native fish populations and providing flow on benefits for SA Riverland communities. The program will help achieve a healthier River Murray system for stronger communities, better recreation and more profitable industries, while also stimulating jobs and economic growth in the Riverland region.

In November 2020, 3 ecologically important sites in the South Australian Riverland were identified for increased investment as part of SRE. The objectives of the 3 site projects are to:

improve environmental outcomes in the Lock 3 Reach with river infrastructure and operational investments
restore natural river patterns in the Lock 6 Reach
reinstate natural habitat conditions in the Bookmark Creek complex.

SRE Lock 6 Reach project

The Lock 6 reach spans from near Lake Victoria, NSW through to just upstream of Murtho in SA. It supplies water to the iconic Chowilla Creek and floodplain and is critical to the operations of the Chowilla environmental regulator. It is home to many iconic and endangered native species and is of significant cultural importance to the First Peoples of the River Murray and Mallee Region.

Building on the South Australian Riverland Floodplains Integrated Infrastructure Program (SARFIIP), the SRE Lock 6 Reach project will focus on enabling an increase in weir pool lowering within the reach. Changing the operation of locks and associated weir pools has been identified as a way to help restore more natural river patterns in the River Murray. This is known as weir pool manipulation (WPM) and can include weir pool raising (WPR) or weir pool lowering (WPL).

To achieve this, current constraints to WPL are being assessed and a range of mitigation measures will be implemented, including assisting irrigators to upgrade their infrastructure to better manage water off-takes at periodic lower water levels. The project will also assess impacts to non-pump infrastructure (e.g. boat ramps, moorings, etc.) and navigation constraints associated with periodic lower water levels.

Why are we doing this?

By increasing the capacity for WPL in Weir Pool 6, the project aims to achieve the following environmental outcomes:

Increased lotic (faster flowing water) habitat in the river channel and some connected anabranches, to support recruitment and survival of Murray cod.
Promote downstream drift of flow-cued fish (golden and silver perch) eggs and larvae by undertaking WPL during specific flows and seasons.
Promote recruitment of river red gums and other woody vegetation in riparian areas, including creek systems, by undertaking sequences of WPR to wet sediments, and WPL to dry them.
Improved and more widespread ecological benefits from coordinated management of a more variable water regime in the Lock 6 and Lock 7 reaches, and the Chowilla and Lindsay-Wallpolla complexes.
Improved and more widespread environmental outcomes from increased hydraulic diversity in the weir pool, including increased connectivity for native fish and other biota that prefer fast-flowing habitats or variable water levels.
Increased likelihood of European carp eradication in managed wetlands by undertaking WPL before closing regulators, to enable native fish to exit the drying wetland before disconnection occurs.
Partial or complete drying of wetlands (managed or not) without losing connectivity, leading to enhanced matter transport, native fish dispersal and other processes.
Enhanced social, economic, and recreational benefits associated with improved amenity and condition of high value wetlands/floodplains.

What have we already done?

Weir pool lowering trials and investigations

SARFIIP has been able to undertake WPL planning, trials and investigations for Locks 1 to 6 and is in the process of finalising the optimal WPL depth that best balances the benefits and risks.

The Department for Environment and Water (DEW) first trialed lowering of water levels in the River Murray between Locks 2, 5 and 6 in 2018. This trial explored the benefits and challenges of varying water levels in the river, with the aim of reinstating variability to water height to benefit the riverine environment.

Following the success of these initial trials, DEW has since implemented WPL events in all weir pools.

Pump surveys

Following the 2018 trial, DEW engaged a contractor to undertake an irrigation pump infrastructure survey between Locks 6 and 7 to:

identify all irrigation pump infrastructure
determine how irrigation pump infrastructure would function under varying water levels
determine the potential impacts to irrigation pump infrastructure under water level variations.

The survey results identified that capacity was limited to 18 cm below normal pool level (NPL) and irrigation pump infrastructure would require upgrading to ensure continued water access during a WPL of up to 60 cm below NPL at Lock 6.

Irrigators in the Lock 6 Reach have been engaged regarding available grants for pump upgrades, with offtake protection (fish screens) also being offered as part of the grant.

What are we doing?

The SRE Lock 6 Reach project aims to deliver the following:

Irrigation pump infrastructure upgrades to enable business continuity during increased water level variability.
Infrastructure upgrades to ensure ongoing access (including recreational) to the river during periods of weir pool lowering.
Increased irrigator and community resilience to periods of low flow or weir pool lowering.

Infrastructure upgrades will be facilitated by DEW through the issuing of grants to interested and eligible pump owners beginning in 2024.

DEW will communicate these events in advance.

More Information

Get involved

We are committed to working with First Nations people, local communities and the broader South Australian community throughout the life of the SRE program.

Subscribe to the River Murray SA newsletter for updates and SRE engagement opportunities.

Contact us

Email us at dew.sreprogram@sa.gov.au
Call the Department for Environment and Water (DEW) on (08) 8204 1910.

Department for Environment and Water (DEW) social media

Resources

Other SRE project pages

Weir pool manipulation

Other resources

The Sustaining Riverland Environments Program is a $37.6 million program funded by the Australian Government through the Murray-Darling Basin Authority and delivered by the Government of South Australia through the Department for Environment and Water.