Lock 3 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.
As part of the program, 3 ecologically important sites in the South Australian Riverland were identified for increased investment as part of SRE in November 2020. 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.
As one of the 3 identified sites, the Lock 3 Reach project focuses on improving environmental outcomes in the reach with river infrastructure and operational investments.
Located near Overland Corner, Lock 3 controls 85 kilometres of the River Murray and contains the most diverse range of flow conditions of all the South Australian River Murray weir pools.
The reach connects many significant water bodies, including Lake Bonney, Banrock Station and Wachtels Lagoon, and is the heart of many Riverland townships, including Loxton and Barmera, which rely on the river for critical human water needs, irrigation, industry, cultural use and tourism.
SRE Lock 3 Reach project
There are multiple key threats causing ecological decline in the Lock 3 Reach, including reduced frequency and duration of floodplain inundation, floodplain and wetland salinisation, loss of variability in water levels, and obstructions to fish passage. The SRE Lock 3 Reach project aims to address these threats by investigating options and investing in infrastructure works and/or channel remediation at sites shortlisted by the Lock 3 Master Plan. Investigations will also explore capacity and outcomes associated with weir pool manipulation (WPM) of the Lock 3 Reach and the resulting raising and lowering of lakes and wetlands.
What are we doing and why?
A key focus of the Lock 3 Reach project is generating beneficial outcomes for native fish by restoring hydraulic diversity, improving opportunities for movement between different habitat types and increasing availability of food resources. The project will contribute to enhanced environmental outcomes on a local scale, which will complement environmental watering activities made possible under the Basin Plan.
Additional objectives considered by the Lock 3 Master Plan and SRE are:
- improvement of river operation flexibility
- improved management of the effects of salinity on the River Murray
- maximisation of future benefits from the Constraints Management Strategy (delivered under the Basin Plan).
The project will be implemented across the following components:
Wetlands and Creeks Investigations and Investment
This component will investigate and invest in infrastructure works and/or channel remediation at crucial floodplain and wetland sites. The works will focus on improving the sites’ function and integrate their operations with any proposed weir pool manipulation (WPM) events and future high flows.
The sites that have been prioritised for further investigations are:
DEW is investigating the feasibility of options at these sites for operational investments that will help improve the health of the Lock 3 Reach and connectivity between the river and floodplain.
As a part of these investigations, supporting activities will include but are not limited to, ecological investigations, topographic and bathymetric surveys, hydrodynamic modelling and groundwater assessments. All site options will be evaluated via rigorous assessment to decide the final design/s that will move to construction stage.
Wetland site landholder and manager insights and knowledge will play an instrumental role throughout the program, by improving ecological and cultural knowledge and co-designing management and potential infrastructure solutions.
This component will also investigate options to improve the function of the Katarapko Creek Stone Weir structure.
Updates will be published here as the project progresses.
Weir Pool 3 Raising and Lowering Investigations
Prior to the construction of locks and weirs, the River Murray experienced greater naturally occurring water level variability. Changing the operation of locks and weirs has been identified as a way to help restore some of the river’s flow variability, with benefits of weir pool raising and weir pool lowering including improved vegetation health and recruitment, improved water quality, and creating variable flowing water habitats.
The Weir Pool 3 Raising and Lowering Investigations component will look at the possible environmental opportunities and risks of weir pool raising and weir pool lowering within the reach, comparative to the investment required to enable weir pool manipulation of Lock 3 outside of normal operating ranges. Investigations will explore weir pool manipulation capacity and outcomes, including potential benefits for lakes and wetlands such as Wachtels Lagoon, Loch Luna and Lake Bonney. This will include assessments of existing infrastructure operability during increased variability in water levels.
Investigations will be extensive and include:
- pump survey assessments and engagement
- non-pump infrastructure (e.g. boat ramps, moorings, etc.) survey assessments and engagement
- bathymetric surveys to assess navigational hazards (sand bars etc.)
- Lock 3 stability assessments (in partnership with SA Water)
- ecological surveys (including fish, native vegetation, and acid sulphate soils)
- modelling scenarios to inform best management of salinity risks associated with Lake Bonney
- ongoing cultural and heritage surveys.
Community and stakeholder engagement will continue to occur throughout the life of the project.
More information about this component can be viewed in the Lock 3 Master Plan: Weir Pool 3 Reach.
Fish and Vegetation Surveys
The Sustaining Riverland Environments (SRE) program have undertaken baseline surveys of the native and non-native fish and vegetation in and around Lake Bonney and Loch Luna between February and April 2023. These surveys were delayed due to the recent floods and have been undertaken to increase understanding of how the fish and vegetation might be influenced by more variable water levels.
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
- SA River Murray Flow Report
- Constraints Management Strategy
- Murray-Darling Basin Authority
- Murray-Darling Communities Investment Package
- MDBA Water Recovery Strategy
- South Australian Riverland Floodplains Integrated Infrastructure Program (SARFIIP)
- The Ramsar Convention on Wetlands
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.
