Connecting our river environment
Restoring the River Murray’s ecological health through improved delivery of water for the environment.
Aboriginal people are the First Peoples and Nations of South Australia, and the traditional custodians of Country. The River Murray, along with the connected waters and surrounding lands have sustained unique First Nations’ cultures since time immemorial.
The Department for Environment and Water pays respect to the Traditional Owners, their ancestors and their elders past, present and emerging. We acknowledge their deep cultural, social, environmental, spiritual and economic connection to their lands and waters, as well as their rights, interests and obligations for the region and connected waterways.
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Historically, the River Murray experienced variable annual and seasonal water levels in response to prevailing climatic conditions. The river’s ecosystems evolved to thrive in this environment and relied on a variable water regime to remain healthy. This variation included natural wetting and drying cycles where large areas of floodplain and wetlands were inundated when water levels were high, and areas of riverbed were exposed when water levels were low.
When European settlers began using the river as a water source and for commerce, the variable river levels made it difficult for vessels, such as paddle steamers, to navigate the river, and posed challenges when sourcing water for livestock, irrigation, and other activities.
To overcome this unpredictability, locks and weirs were constructed along the river, with 6 locks installed in South Australia. These locks and weirs were important for human purposes but came at a cost to the environment, as they restricted the natural fluctuations in water levels needed to sustain river ecosystem health.
Now, we are using water for the environment to help restore these systems.
A modified river
In the early 1900s, weirs were installed at 14 locations along the River Murray, with all but one (Yarrawonga Weir) including a navigation lock. Six of these weirs are located in South Australia.
The weirs create a series of ‘steps’ in the river, allowing river operators to keep water levels regulated at a consistent height between one weir pool and the next (unless there is a natural flood or high flow event). These sections of river are called weir pools.
Navigation locks are fixed chambers in which water levels can be manually raised or lowered, allowing river vessels to move between weir pools that are at different water levels.
While the construction of the weirs and locks has ensured a more consistent water supply for critical human needs and agriculture, it has heavily reduced the River Murray’s seasonal overbank flows and the availability of water for the environment, which are both required for river ecosystems to thrive.
While Australia’s climate has always been highly variable, a warming trend over the past century has placed additional stress on river health, with some land areas warming approximately 1.5 degrees Celsius.
A decline in rainfall has also been observed since the 1970s, reducing the amount of water available in the Murray-Darling Basin, decreasing flows in the River Murray and reducing the number of natural floods and overbank flows.
These changes, along with river regulation and over-extraction have resulted in the degradation of the river’s wetlands and floodplains, and the decline of keystone flora and fauna species.
Water for the environment
One way of returning flow regime variability to the river is by recovering water for environmental use and managing its delivery for ecological outcomes.
Water for the environment is water allocated purely for environmental purposes, and not for human or industrial extraction. Water for the environment provides many benefits, including keeping the Murray Mouth open, flushing salt from the system and providing additional water to precious wetlands and floodplains, which need a varied flow regime for their ecosystems to thrive.
Healthy river ecosystems have many benefits, including improving water quality, capturing carbon and providing habitat for a range of nationally and internationally listed plants and animals. Healthy lands and waters are also core to the wellbeing of First Nations people.
In South Australia, water for the environment is held by the Murray-Darling Basin Authority, the Commonwealth Environmental Water Holder and the Government of South Australia, who are responsible for deciding when, where and how much water for the environment is required to achieve desired environmental outcomes.
Overbank flows
Overbank flows occur when the river channel is above capacity, causing water to spill over riverbanks, inundating floodplains and wetlands.
High flow events that enable overbank flows are beneficial for the environment because they connect habitats along the floodplain with the main river channel and one another. Such connections enable species to access refuge habitat areas, find breeding partners and recolonise suitable habitats, all of which are important for species’ long-term survival. Flooding also increases food resources for species downstream of the flood location.
Prior to river regulation, overbank flows at the South Australian border occurred more frequently, with high flows of ~80 gigalitres per day (GL/day) that lasted for more than one month, occurring approximately once every 4 years, whereas now they only occur approximately once every 14 years. Similarly, moderate flow events of ~60 GL/day that lasted for at least one month, have reduced from once every 2 years to approximately once every 6 to 7 years.
To more closely mimic the pre-regulation natural water regime variability, water for the environment can be used to increase the frequency and duration of these essential overbank flows.
How is water for the environment delivered?
There are numerous ways water for the environment can be delivered to benefit the reaches and ecosystems in South Australia's River Murray.
Enhanced flows added to a normal operating flow range
When flows are within normal operating range (up to 40 GL/day), the addition of water for the environment, of typically no greater than up to 10 GL/day, can add much needed water to wetlands that are naturally connected to the channel.
Flood inundation modelling and vegetation mapping indicates that there are significant increases in the area of vegetation communities inundated once flows exceed 50 GL/day.
Enhanced flows added to a high flow event (PICTURED)
When natural high flows occur in the channel or overbank but are not quite enough to reach areas that will benefit from additional water, water for the environment can be used to boost flows.
In these situations, adding water for the environment from upstream storages will enhance the flow’s reach and/or duration, therefore achieving greater environmental outcomes for the river, its wetlands and floodplains.
What are the impacts to the community of overbank flows?
When the River Murray is experiencing overbank flows, the community may observe some impacts to infrastructure and access along the river.
These natural overbank flows are a part of life on the river. Communities can find out more information about the impacts of various flow scenarios by visiting the River Murray inundation mapping page .
When River Murray flows reach 60 GL/day, towns along the river are generally unaffected, however the Shack Areas between Cadell and Mannum may start to experience inundation of low-lying roads, access tracks and riverfront land.
The community can use a number of resources to monitor river conditions, including:
South Australia Constraints Measures project
What are constraints?
A constraint is anything that reduces the ability for water to flow to where it is needed, such as floodplains and wetlands.
Constraints can include physical restrictions, such as roads, low-lying bridges, crossings or impacts to private land, as well as regulatory restrictions such as river rules or operational practices. These constraints mean the river system is not operating as effectively as it could be.
What is the SA Constraints Measures project?
The SA Constraints Measures project (SA Constraints) is part of the Government of South Australia’s commitment to deliver the Murray-Darling Basin Plan. The project aims to achieve environmental benefits and community resilience at flows of up to 80 GL/day at the South Australian border.
SA Constraints is removing constraints, or barriers, to the delivery of water for the environment, to improve the health of the South Australian River Murray channel, floodplains and wetlands.
While the main goal of relaxing constraints is to provide greater scope for environmental flows to floodplains and end-of-system, SA Constraints will also improve access to the river and facilities for water managers, communities and landholders during natural high flow events.
In 2013, the Constraints Management Strategy – 2013 to 2024 (the Strategy) was produced by the Murray-Darling Basin Authority to identify the physical, operational and management constraints that are affecting delivery of water for the environment for 7 key areas across the Basin, including the River Murray in South Australia.
SA Constraints is one of numerous projects that Basin states are collaborating on as part of the Strategy, to improve the movement of flows through the system and into the South Australia.
SA Constraints has achieved milestones including:
- investigating the use of small overbank flows to connect floodplains more frequently to achieve healthier ecosystems
- investigating impacts of small overbank flows on communities and property
- identifying infrastructure improvements that will reduce impacts of small overbank flows
- engaging stakeholders to incorporate their local knowledge in operational decision-making.
SA Constraints is also assessing current river management practices, resulting in updated policy and operational procedures that support enhanced flow delivery into South Australia for better environmental outcomes.
SA Constraints Measures Early Works infrastructure projects
To address the physical constraints impacting the delivery of water for the environment, SA Constraints has identified a number of river sites for potential upgrades. These upgrades would remove constraints to flow and support community resilience to more frequent higher flows. Some of these sites were selected for construction as part of the SA Constraints Measures Early Works project, which is scheduled for completion by 30 June 2025.
The interactive map below shows the sites being delivered as part of the Early Works project in partnership with the South Australian National Parks and Wildlife Service, local government and irrigations trusts.
SA Constraints Measures Early Works project sites
Click on the site thumbnails in the lefthand menu to see what is being done at each site. You can either scroll through the images or click on the site markers on the map for more detail.
River Murray native plants, animals and fish
The River Murray and its floodplains provide vital habitat for a diverse but declining population of plants, fish, turtles, birds and countless other important animals such as insects, yabbies, frogs and snakes.
The SA Constraints Measures project will benefit these species by restoring more frequent overbank flows to mimic the conditions these plants and animals evolved to thrive in.
Let’s take a look at 2 of these important species, the southern bell frog and the regent parrot.
Regent Parrot
The regent parrot is a floodplain reliant bird and the species’ long-term recovery has been identified as benefitting from increased water for the environment and overbank flows.
Regent parrots are brightly coloured, medium-sized birds that can be recognised by their red beak. They feed on seeds, buds, and flowers of understory plants such as saltbush, and insect larvae. Male regent parrots are a bright golden-yellow colour, with a green back and patches of yellow, blue and red on their wings. Female and juvenile birds have similar patterns but are greener around the head and body.
Most regent parrots nest in old, large river red gums located within the floodplain, which have hollows created by missing limbs.
The regent parrot is listed as vulnerable under the South Australian National Parks and Wildlife Act 1972, with river regulation and agricultural practices causing substantial loss of nesting and foraging habitat, and adding to the decline in population.
Southern bell frog
Native across south-eastern Australia, including River Murray wetlands, the southern bell frog is a brightly coloured green and gold frog, spotted with black or brown patches and a pale green stripe along the middle of their back.
The southern bell frog is most active throughout their breeding season in spring and summer (both day and night), and they have been known to move up to one kilometre in 24 hours in search of food and mates.
Relatively large in size, southern bell frogs can grow up to 10 cm in length and can often be seen basking in the sun or gathering in groups under reeds at the edge of wetlands.
Once one of the most common frog species throughout the River Murray wetlands and slow-moving waterways, southern bell frog populations have significantly declined due to modifications to wetlands, including altered flow regimes and prolonged droughts greatly reducing their habitat areas.
The southern bell frog is now classified as endangered under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and vulnerable under the South Australian National Parks and Wildlife Act 1972.
Water for the environment is known to benefit southern bell frog populations by helping to maintain complex wetland vegetation and water regime variability that support the species' vital habitat.
Where to from here
Enhanced flows are required to maintain the landscape that both local communities and visitors enjoy, and the delivery of the SA Constraints Measures project will contribute to building more resilient communities through improved opportunities for recreation, tourism, lifestyle and amenities during periods of higher flow.
SA Constraints will also contribute to achieving First Nations cultural objectives through the protection of cultural heritage sites and facilitation of cultural watering opportunities.
SA Constraints Measures project alignment
SA Constraints is closely aligned with the Enhanced Environmental Water Delivery project (EEWD), which seeks to develop new forecasting and planning tools and streamlined processes for coordinated system-wide river operations in the Southern Connected Basin. The connection between the 2 projects aims to maximise downstream and system-wide connectivity and enhance environmental outcomes to address both physical and operational barriers to enhanced environmental flows.
The Department for Environment and Water has a number of other programs that are working towards sustaining the River Murray, its wetlands, floodplains and the ecosystems they support. These include:
The South Australian Constraints Measures project is being delivered by the Government of South Australia and funded by the Australian Government as part of the Murray-Darling Basin Plan.
