Flows in the River Murray System vary widely depending on a range of factors, including rainfall, inflows, evaporation, and demand for water for human use.
At any given time, water flowing through the river is destined for various uses, including irrigation, industry, communities, the environment, and meeting South Australia’s flow entitlement. The exact mix of these flow components is determined by demand and water availability, amongst other factors.
The graphic below is indicative of how water flow is managed throughout the seasons across a typical year.
- River operations focus on managing dam storage levels and river system for the following water year
- River flows are relatively stable
- Medium demand for consumptive use (irrigation, industry, communities)
- Water for the environment flows are low
- Dam storage levels decline
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- River operations focus on capturing inflows from tributaries and meeting early season demand*
- River flows are highly variable
- Lowest demand for consumptive water (irrigation, industry, communities)
- Water for the environment flows increase
- Dam storage levels increase
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- River operations aim to capture water inflows and manage dam storage levels for summer demand*
- Increasing demand for consumptive water (irrigation, industry, communities)
- River flows are highly variable
- Water for the environment flows are highest
- Dam storage levels increase due to higher inflows
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- River operations focus on managing water supply to meet large system demand*
- River flows are relatively stable
- Highest demand for consumptive water (irrigation, industry, communities)
- Water for the environment flows decrease
- Dam storage levels decline
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* including meeting South Australia's flow entitlement.
Water for the environment
Overall, water for the environment is a small percentage of the total water used in the Murray–Darling Basin. Across the past 5 years the volume of water for the environment used under water entitlements has averaged 18% of the total water used in the Basin.
Importantly, water held for the environment uses the same entitlement framework as consumptive users. In any given year the amount of water available for delivery to key environmental sites is determined based on the same rules that apply to all other consumptive water uses.
Types of water for the environment
Water for the environment can be categorised as:
- 'Planned' environmental water – water that flows through the river system that is typically managed through rules outlined in state water resource plans and is used to improve the health of the environment.
- 'Held' environmental water – is water that is held by government agencies and is delivered where and when it is needed in the river system. It is water that is allocated to relevant government agencies through water licenses for environmental use.
Flows in the River Murray system
Information in the figure above is for the month of April 2023 and may not include recent rainfall or delivery of water for the environment in the River Murray system. Information in this figure is an average estimate over the past month and formal accounts from Basin state governments may vary. Water for the environment in the figure above represents water that is held by environmental water holders, through entitlements. Other water that flows through the river can also achieve environmental outcomes.
River flow information
The April flow to South Australia comprised of water for South Australia’s entitlement, ADF, unregulated flow, traded volumes and water for the environment. Water for the environment consisted of water delivered from the Goulburn-Broken, Murrumbidgee and Lower Darling Rivers.
For the latest information on water for the environment, see the River Murray weekly report.
Intended environmental outcomes
Water for the environment takes time to move through the system. Water from past watering events is still moving through the River Murray as return flows. Environmental water holders can also use water for the environment by extracting allocations directly from the river. These allocations are often used for small-scale watering events rather than having water delivered from a storage.
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Location
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Return flows used
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Intended environmental outcomes
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| Goulburn River |
n/a |
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increase the abundance of aquatic and flood-tolerant plants in the river channel and on the lower banks to provide shelter and food for animals and stabilise the riverbank
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maintain populations of turtles
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protect and increase populations of native fish
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maintain abundant and diverse waterbug communities to support riverine food webs
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| Lower Broken Creek |
n/a |
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provide habitat for native fish, platypus, rakali, turtles and waterbugs
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support the movement and recruitment of fish
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| Campaspe River |
n/a |
- protect and increase populations of native fish, including increased longitudinal connectivity for improved habitat
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protect the resident platypus population
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increase the extent of in-stream aquatic plants
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increase the diversity and biomass of waterbugs
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maintain water quality in deep pools and prevent stratification in summer
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| Loddon River |
n/a |
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maintain an adequate depth in pools for aquatic plants and to provide habitat for waterbugs, fish and rakali (water rats)
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maintain water quality
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support the growth of in-stream and fringing non-woody vegetation
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| Gunbower Creek |
No |
- maintain and improve populations of large-bodied native fish (such as Murray cod)
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| Great Darling Anabranch |
n/a |
- maintain native fish populations, with particular focus on the dispersal of golden perch from Lake Cawndilla to the Murray
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| Lower Darling-Baaka River |
No |
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improve dissolved oxygen levels and water quality,
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improve habitat for native fish with aim to minimise the risk of further large-scale fish deaths.
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Sharing River Murray water
For more than 100 years, the states have been sharing the waters of the Murray. The Murray–Darling Basin Agreement sets out the rules negotiated and agreed by New South Wales, South Australia, Victoria and the Australian Government.
The Murray–Darling Basin Authority (MDBA) facilitates the sharing of River Murray water based on the agreed rules. The MDBA determines releases in the River Murray System to meet expected demands from the states. A range of scenarios are considered and these are used to guide operations for the year. As the year unfolds the scenarios and options are updated and operations amended accordingly.
Identifying how much water is available to the states takes into consideration stored water and seasonal weather conditions. Of the available water the MDBA determines conveyance water, critical human water needs and reserve for the next season before it shares water to the states. Each state has developed its own set of entitlement licences and rules around how to allocate their share of water. This means allocations, water orders and delivery of water all work in a different way from state to state.
