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Up to 400,000 ML per year (long-term average diversion limit) can be harvested from the Yarra system for consumptive use in Melbourne and surrounding areas. The Upper Yarra, O’Shannassy and Maroondah reservoirs harvest water from headwater tributaries, and a pump station at Yering is used to divert water from Birrarung (Yarra River) to Sugarloaf Reservoir.

Flow in the upper reaches of Birrarung (Yarra River) is influenced by tributaries (such as Armstrong Creek, McMahons Creek, Starvation Creek, Woori Yallock Creek, Watts River and Little Yarra River). Urbanised tributaries (such as Olinda Creek, Mullum Mullum Creek, Diamond Creek, Plenty River and Merri Creek) provide additional water to the middle and lower reaches of Birrarung (Yarra River).

Environmental flows can be released from the Upper Yarra, Maroondah and O’Shannassy reservoirs to support ecological processes and environmental outcomes in downstream river reaches and wetlands. The priority environmental flow reaches in Birrarung (Yarra River) are reaches 2 and 5. Water for the environment that is delivered to reaches 2 and 5 will help meet flow targets in downstream reaches.

Plenty River rises from the slopes of Mt Disappointment in the Great Dividing Range about 50 km north of Melbourne. It flows downstream through rural and semi-rural areas and Plenty Gorge before joining Birrarung (Yarra River) near Viewbank, east of Banyule Flats Reserve. Yan Yean Reservoir is located off the waterway, north of Plenty Gorge, and it receives flows from Toorourrong Reservoir via a channel. The Plenty River has not received managed environmental flows before, but there may be opportunities to deliver water for the environment from Yan Yean Reservoir from 2021-22 onwards.

Waterway manager
Traditional Owners
Storage manager
Environmental water holder

System map

Environmental watering objectives in the Yarra River

Fish icon
Protect and increase populations of native fish including threatened species (such as the Australian grayling, Macquarie perch and river blackfish)
Frog icon
Maintain the population of frogs, particularly on the mid-Birrarung (Yarra River) floodplain
Landscape icon
Maintain the form of the river channel

Scour silt from riffles and clean cobbles
Platypus icon
Maintain the population of resident platypus
Plant icon
Increase and maintain native streamside and aquatic vegetation on the riverbank and in the channels

Increase and maintain the growth of threatened wetland plant species to rehabilitate shallow marsh, deep marsh and freshwater meadows on the floodplain and billabongs
Insect icon
Maintain and increase the abundance and diversity of waterbugs to support aquatic food webs
Water icon
Improve water quality in river pools, ensuring adequate oxygen concentration in the water to support fish, crustaceans and waterbugs

Environmental values

The upper reaches of Birrarung (Yarra River) (reaches 1-3) provide habitat for a range of native fish species including river blackfish, mountain galaxias and common galaxias, and have good-quality streamside and aquatic vegetation. Middle and lower reaches of Birrarung (Yarra River) (reaches 4-6) flow through forested gorges, cleared floodplains and some highly-urbanised areas, and support several populations of native fish including Australian grayling, river blackfish, Macquarie perch and tupong. Macquarie perch were introduced to Birrarung (Yarra River) last century, and the population is now considered one of the largest and most important in Victoria.

The Plenty River (reach 9) provides habitat for waterbugs and native fish species (such as common galaxias). Platypus have been detected in the Plenty River in the past, but none have been recorded in recent surveys.

Billabongs are an important feature of the Birrarung (Yarra River) floodplain between Millgrove and Yering Gorge and in the lower reaches around Banyule Flats near Heidelberg. The billabongs support distinct vegetation communities and provide foraging and breeding habitat for waterbirds and frogs. Except in very high flows, most billabongs are disconnected from Birrarung (Yarra River).

Recent conditions

Rainfall in the Birrarung (Yarra River) catchment in 2020-21 was above the long-term average, and tributary inflows significantly contributed to flow in Birrarung (Yarra River) and the Plenty River throughout the year. O’Shannassy Reservoir was offline for most of the year for maintenance, so most flow from the O’Shannassy River catchment passed directly into Birrarung (Yarra River). Maintenance work at Upper Yarra Reservoir required operational releases to Birrarung (Yarra River) during September and October 2020. These operational releases replaced the need for environmental flows that were planned during that time. The operational releases were adjusted where possible to align with environmental flow needs, and they largely met the expected watering effects.

In Birrarung (Yarra River), natural rain events combined with the larger-than-normal inflows from the O’Shannassy River and operational releases from Upper Yarra Reservoir achieved most of the planned watering actions for 2020-21. As a result, only a small portion of available water for the environment was used in 2020-21, and there is a large carryover volume for 2021-22. Water for the environment was released in conjunction with a natural fresh in May 2021 to support Australian grayling migration and spawning. In the Plenty River, natural rain events achieved most of the high-priority planned watering actions. An opportunity to supplement winter/spring low flows with water for the environment could not occur, due to poor water quality and valve delivery constraints at Yan Yean Reservoir.

Yering Backswamp has received water for the environment annually since 2013. Wet conditions in early May 2020 primed the site for a series of top-ups using water for the environment in late May, June and July. Wet conditions in August maintained water levels, which helped support water-dependant vegetation and aquatic animals. The wetland was allowed to gradually dry out by December, in accordance with the site’s management plan. Annulus Billabong last filled in 2011 by an overbank flow from Birrarung (Yarra River), and it held water until 2012. Water for the environment was delivered to the site for the first time from October to December 2020 to support the growth of threatened wetland plant species and provide habitat for frogs, waterbugs and eels. This delivery was undertaken safely and successfully during a COVID-19 lockdown period, providing great recreational opportunities for many local visitors. Bolin Bolin was filled in 2017 with a combination of overbank flows and environmental watering. Drying at the site since has resulted in the return of terrestrial and exotic plant species. Overbank flows in August 2020 partially filled Bolin Bolin wetland, and further watering is planned in 2021-222 to improve vegetation outcomes.

Monitoring is showing that upgrades to the Dights Falls fish ladder in November/December 2020 are allowing more native fish to move between the Birrarung (Yarra River) estuary and the freshwater reaches. At Yering Backswamp, Melbourne Water has initiated a monitoring program to understand how bat species use the site as water levels vary. Monitoring by Melbourne Water, the Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation’s Narrap team and citizen scientists indicated that the new watering actions at Annulus Billabong supported at least four frog species.

Traditional Owner cultural values and uses

Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation and Melbourne Water are working towards an overarching partnership that will frame the relations and obligation between the two organisations. The intent is to embed Wurundjeri Woi wurrung as active partners in the planning, delivery, and monitoring of all works associated with Birrarung (Yarra River).

Melbourne Water has also made initial contact with Bunurong Land Council Aboriginal Corporation and Boon Wurrung Foundation to discuss environmental watering in the Yarra system.

Increasing the involvement of Traditional Owners in environmental water planning and management, and ultimately providing opportunities to progress towards self-determination within and beyond the environmental watering program, is a core commitment of the VEWH and its agency partners. This is reinforced by a range of legislation and policy commitments (for example the Water Act 1989, the Victorian Aboriginal Affairs Framework, Water for Victoria (2016)) and, in some cases, agreements under the Traditional Owner Settlement Act 2010.

Where Traditional Owners are more deeply involved in the planning and/or delivery of environmental flows for a particular site, their contribution is acknowledged in Table 1 with an icon. The use of this icon is not intended to indicate that these activities are meeting all the needs of Traditional Owners but is incorporated in the spirit of valuing that contribution, and indicating progress towards this objective.

Billabong icon

Watering planned and/or delivered in partnership with Traditional Owners to support cultural values and uses

There are a large number of places of tangible and intangible cultural significance for the Wurundjeri Woi wurrung people on the lower Birrarung (Yarra River) floodplain. Where possible, Melbourne Water and the Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation will work together to link water for the environment with cultural outcomes for Wurundjeri Woi wurrung.

A recent example is a vegetation monitoring and water quality monitoring project at the billabongs with the Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation’s Narrap Team, The University of Melbourne and Melbourne Water. The group has been out monitoring the vegetation watering outcomes and held an on-Country knowledge-sharing day to discuss learnings. Monitoring is underway at Annulus Billabong following a delivery of water for the environment in 2020-21, and similar work will likely be undertaken in 2021-22.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, Melbourne Water considered how environmental flows could support values and uses including:

  • water-based recreation (such as kayaking, canoeing, fishing and swimming)
  • riverside recreation and amenity (such as walking, running, cycling, camping and birdwatching)
  • community events and tourism (such as the Moomba Festival and the Inflatable Regatta)
  • socio-economic benefits (such as diverters for irrigation, domestic and stock uses, and Melbourne’s water supply).

Scope of environmental watering

Table 1 Potential environmental watering actions, expected watering effects and associated environmental objectives for Birrarung (Yarra River), the Plenty River and Yarra billabongs

Potential environmental watering action Expected watering effects Environmental objective

Birrarung (Yarra River)

The highest-priority reaches for Birrarung (Yarra River) are reaches 2 (upper Birrarung) and 5 (lower Birrarung); water delivered to these reaches generally benefits other reaches

Winter/spring low flow (June to November)

Reach 2: 200 ML/day
Reach 5: 350 ML/day

  • Physically mix pools to minimise the risk of stratification and low oxygen
  • Maintain access to habitats for fish, waterbugs and platypus
  • Wet bank vegetation to promote growth
Fish iconPlatypus iconPlant iconInsect iconWater drop icon

Winter/spring fresh(es) (one to two freshes for three to seven days during June to November)

Reach 2: 700 ML/day
Reach 5: 2,500 ML/day

  • Scour sediment and biofilm from gravel in riffles to improve spawning opportunities for Macquarie perch
  • Wet native streamside vegetation on the banks of the river to promote growth
  • Provide cues for upstream migration of juvenile migratory fish (e.g. Australian grayling and tupong)

Fish iconMountain iconsPlant icon

Spring high flow (one high flow for 14 days in September)

Reach 2: 700 ML/day
Reach 5: 2,500 ML/day

  • Scour sediment and biofilm from gravel in riffles
  • Provide prolonged wetting to favour flood-tolerant native vegetation in the streamside zone
  • Provide cues for upstream migration of juvenile migratory fish (e.g. Australian grayling and tupong)
  • Trigger spawning of Macquarie perch

Fish iconMountain iconsPlant icon

Summer/autumn low flow (December to May)

Reach 2: 80 ML/day
Reach 5: 200 ML/day

  • Physically mix pools to minimise the risk of stratification and low oxygen
  • Maintain access to habitats for fish, waterbugs and platypus

Fish iconPlatypus iconInsect iconWater drop icon

Summer/autumn fresh(es) (one to three freshes for two to four days during December to May)

Reach 2: 350 ML/day
Reach 5: 750 ML/day

  • Flush pools to prevent a decline in water quality
  • Scour sediment and biofilm from gravel in riffles and pools to maintain habitat quality for fish and waterbugs
  • Provide opportunities for the localised movement of fish and platypus
  • Wet the banks of the river to maintain flood-tolerant vegetation on the banks

Fish iconMountain iconsPlatypus iconPlant iconInsect iconWater drop icon

Autumn high flow (one high flow for seven to 14 days during April to May)

Reach 2: 560 ML/day
Reach 5: 1,300 ML/day

  • Cue the migration of Australian grayling
  • Scour sediment and biofilm from gravel in riffles and pools to maintain habitat quality for fish and waterbugs

Fish iconMountain icons

Plenty River

Winter/spring low flow
(20 ML/day during June to November)

  • Physically mix pools to minimise the risk of stratification and low oxygen
  • Maintain access to habitats for fish and waterbugs
  • Wet bank vegetation to promote growth

Fish iconPlant iconInsect iconWater drop icon

Winter/spring freshes (four freshes of 70 ML/day for three days during June to November)

  • Scour sediment and biofilm from gravel in riffles
  • Provide access to habitats for fish and waterbugs
  • Wet native streamside vegetation on the banks of the river to promote growth

Fish iconPlant iconInsect iconWater drop icon

Summer/autumn low flow (10 ML/day from December to May)

  • Physically mix pools to minimise the risk of stratification and low oxygen
  • Maintain access to habitats for fish and waterbugs

Fish iconPlant iconInsect iconMountain icons

Summer/autumn freshes (four freshes of 55 ML/day for two days)

  • Flush pools to prevent a decline in water quality
  • Scour sediment and biofilm from gravel in riffles and pools to maintain habitat quality for fish and waterbugs
  • Provide opportunities for the localised movement of fish
  • Wet the banks of the river to maintain flood-tolerant vegetation on the banks

Fish iconMountain iconsPlant iconInsect iconWater drop icon

Yarra billabongs

Annulus Billabong (partial fill in winter/spring)

Billabong icon

  • Wet the wetland bed for up to three months to support the growth of threatened wetland plant species to rehabilitate shallow marsh, deep marsh and freshwater meadows
  • Provide habitat for frogs, waterbugs and eels
Fish iconFrog iconPlant iconInsect icon

Bolin Bolin (partially fill in winter/spring)

Billabong icon

  • Wet the deepest part of the wetland to about 100-150 cm to provide habitat for frogs, waterbugs and eels
  • Wet the remaining area of the wetland to about 50-100 cm to support the growth of threatened wetland plant species and encourage the regeneration of spreading aquatic herbs
Fish iconFrog iconPlant iconInsect icon

Yering Backswamp (complete fill in autumn/ winter/spring)

  • Wet the deepest parts of the wetland to about 80 cm to provide habitat for fish, frogs and waterbugs
  • Wet remaining areas of the wetland to about 40-60 cm to support the growth of threatened wetland plant species and encourage the regeneration of spreading aquatic herbs
Fish iconFrog iconPlant iconInsect icon

Engagement

Table 2 shows the partners and stakeholder organisations with which Melbourne Water engaged when preparing the Yarra system seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Port Phillip and Western Port Regional Catchment Strategy and Melbourne Water's Healthy Waterways Strategy.

Table 2 Partners and stakeholders engaged in developing the Yarra system seasonal watering proposal

Partner and stakeholder engagement
  • Cannibal Creek Water Monitoring Group
  • Environment Victoria
  • Friends of Mt Cannibal Flora and Fauna Reserve
  • Friends of Robin Hood Reserve
  • Independent community members
  • Native Fish Australia
  • Waterwatch Coordinators
  • Department of Environment, Land, Water and Planning
  • Melbourne Water (Service Delivery)
  • Southern Rural Water
  • Aboriginal Victoria
  • Baw Baw Shire Council
  • Cardinia Shire Council
  • Commissioner for Environmental Sustainability Victoria
  • Environment Protection Authority Victoria
  • Parks Victoria
  • Port Phillip and Westernport CMA
  • Victorian Fisheries Authority
  • Individual landholders
  • Glen Cromie Reserve
  • Local anglers
  • VRFish
  • Aquatic Pollution Prevention Partnership
  • Arthur Rylah Institute (Department of Environment, Land, Water and Planning)
  • Australian Platypus Conservancy
  • Cesar Australia
  • Melbourne Water subject matter experts
  • Research collaborators at Melbourne University
  • Boon Wurrung Foundation
  • Bunurong Land Council Aboriginal Corporation
  • Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation

Page last updated: 22/01/21