Water for weir pools
When locks and weirs were installed, the River Murray’s natural and highly variable water regime were disrupted, with the now regulated water levels greatly reducing the opportunities for drying of riverbanks and higher areas to be inundated.
Wetting and drying cycles are essential for a healthy river environment, and to aid in restoring the river system, we now actively manage the weirs (called weir pool manipulation) to create greater variation in water levels to connect floodplain habitats with the creeks and the river channel.
Goals for weir pool manipulation and the delivery of water for the environment are decided in consultation with Traditional Owners and local communities, and based on scientific advice, investigations and monitoring.
Our goals help deliver the following Basin Plan objectives:
- Protect and restore water-dependent ecosystems of the Murray-Darling Basin
- Ensure water-dependent ecosystems are resilient to climate change and other risks and threats.
The long-term aim is to restore floodplains to healthy conditions.
How water delivery works
Weir pool manipulation involves using the River Murray weirs for improved environmental outcomes, including through the use of water for the environment.
Weir pool manipulation includes:
- Weir pool raising (WPR)
WPR increases inundation of upper riverbanks and low-lying floodplains supporting a greater diversity of plants and wildlife.
As the water rises invertebrates flourish attracting small fish and birds such as spoonbills and ducks. Native plants such as river red gum, black box, river coobah, lignum and a range understorey plant species benefit from much needed water.
- Weir pool lowering (WPL)
WPL can help to support faster flowing water in the river channel, which supports native fish and transport seeds and other nutrients.
Lower water levels allow vegetation to grow in the exposed areas, while decomposing aquatic plants become a food source for invertebrates which are in turn eaten by wading birds and other wildlife.
Water levels are raised and lowered at controlled rates of between 2 to 5 cm a day. Once the target level is reached, it is typically maintained for 30 to 60 days.
The level of weir pool manipulation that can be achieved at each weir varies. Limited weir lowering is currently able to be undertaken. Weir manipulation events are only undertaken in consultation with river users.
Timing
We undertake annual planning based on the ecological needs of the River Murray and its floodplains and wetlands. Decisions are based on monitoring results, assessments of river flow and water quality, recent flow history, and the availability of environmental water.
This guides our decisions on how and when to raise or lower weir pools, to vary water levels each year, with changes not always following a set pattern.
Access to the area
River conditions including water levels frequently change with changing flows, and river management including weir manipulation.
Any activities on the River Murray should always be carried out with caution. Weir pool manipulation is undertaken in consultation with river users.
Does watering work?
Long-term scientific monitoring tracks the ecological condition of the floodplain in connection with the goals listed above. Monitoring informs decision-making around how we manage delivery of water for the environment.
The weir pool monitoring program includes trees, lignum understorey vegetation, fish, frogs, waterbirds, groundwater and water quality.
Highlights from 2023-24 ecological monitoring
Plants
Across all weir pools, the health of river red gum and black box trees improved slightly, with no tree loss recorded.
Weir pool lowering supported the recruitment of vegetation on exposed soils.
Fish
The lowerings reduced available wetland habitat for the introduced common carp, which were observed in very large numbers during the 2022 flood.
Birds
29 sites along the 6 weir pools were monitored. They supported approximately 6,167 waterbirds, including 43 different species including:
Musk duck, Australasian darter, intermediate egret, great crested grebe, and spotless crake.
Four listed migratory birds were observed including the common greenshank, caspian tern, crested tern and sharp-tailed sandpiper.
Frogs
All 7 species of frogs were heard calling, including the endangered Southern bell frog at one site.
How can I stay informed?
- Sign-up to receive the weekly River Murray Flow Report via email for information on when water levels will rise, expected water level depths and the expected duration. View previous reports
- Visit Marine Safety SA to view the latest information on boating safety and latest news from Marine Safety SA.
- Get involved in environmental water planning
