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Flows in the River Murray System

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.

Seasonal flow in the River Murray System, highlighting that water for environment flows are lower in summer-autumn, and higher in winter-spring.

  • 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
  • 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
  • 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
  • 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

* 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. 

The volume of water for the environment used under water entitlements has increased slightly over the past five years, as more water became available. The average use over this period was 20.4 per cent 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

Flows in the River Murray System infographic for June 2021

Information in the figure above is for the month of June 2021 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 June flow to South Australia comprised of water for South Australia’s entitlement, as well as traded volumes and water for the environment. Delivery of water for the environment consisted of small volume delivered from the Broken and Campaspe rivers.  Hattah Lakes also received water for the environment. 

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.

Location

Return flows used at site

Intended environmental outcomes

River Murray channel downstream of Yarrawonga weir n/a
  • increase water depth in the River Murray channel
  • provide habitat and food for large-bodied native fish in the River Murray and unregulated anabranches in Barmah–Millewa Forest
Whymoul Creek No
  • provide habitat for native fish, waterbirds and southern bellfrogs
  • maintain river red gum health
Goulburn River n/a
  • protect and boost native fish numbers
  • improve habitat for small-bodied native fish and maintain waterbug communities
  • increase growth of water-dependent plants in the river channel
  • encourage seed germination on the riverbanks to help stabilise the banks
Loddon River n/a
  • maintain an adequate depth in pools for aquatic plants and to provide habitat for waterbugs, fish and rakali (water rats)
  • provide continuous flow through the reach, to maintain water quality
Campaspe River n/a
  • provide habitat to help protect and boost native fish
  • maintain resident platypus numbers
Gunbower Creek No
  • maintain breeding habitats and food resources for native fish including Murray cod
Gunbower Forest No
  • maintain feeding and refuge habitat for waterbirds, small-bodied native fish, turtles and frogs
  • maintain water depth to support wetland plants to grow and germinate
Pyramid Creek Yes
  • maintain connectivity between pools
  • provide habitats for native fish and waterbugs
Hattah Lakes Yes
  • filling of selected wetlands following a drying period to stimulate growth of aquatic plants
  • improve the condition of river red gums
  • provide important refuge and feeding habitat for waterbirds
Lindsay, Mulcra and Wallpolla islands (Lake Wallawalla and Wallpolla Horseshoe) No
  • provide shallow-water, open-water and shoreline habitat to provide foraging habitat and breeding opportunities for frogs, yabbies, waterbirds and turtles
Lower Broken Creek n/a
  • maintain pool habitat for native fish and waterbugs
  • access to food and habitat for platypus and in-stream vegetation
Lower Darling n/a
  • small increase to baseflows to improve the condition of the Lower Darling (Baaka)
  • provide extra food and habitat to help support young fish to grow including Murray cod and golden and silver perch
Lake Limbra, Chowilla Floodplain Yes
  • provide healthy wetland refuge habitat for a range of native plants and animals
Lower Murray wetlands No
  • provide healthy wetland refuge habitat for a range of native plants and animals
Lower Lakes, Coorong and Murray Mouth Yes
  • maintain barrage releases to support native fish migration through barrage fishways
  • reduce salinity in the Coorong, supporting the Coorong food web

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.

Updated: 09 Jul 2021