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Up to 400,000 ML per year (long-term average diversion limit) can be harvested from the Yarra River 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 the Yarra River to Sugarloaf Reservoir.

Flow in the upper reaches of the Yarra River is influenced by tributaries (such as Armstrong Creek, MacMahons 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 the 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 the Yarra River are reaches 2 and 5, shown in Figure 3.2.1. Water for the environment that is delivered to reaches 2 and 5 will help meet flow targets in downstream reaches.

Waterway manager
Storage manager
Environmental water holder

System map

Yarra System
Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

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)
Landscape icon
Maintain the form of the river channel.

Scour silt build-up in riffles and clean cobbles.
Landscape icon
Maintain the population of resident platypus
Plant icon
Increase, strengthen and maintain native riparian and aquatic vegetation on the riverbank and in the channel, as well as on the upper Yarra floodplain and in the billabongs along the river
Insect icon
Protect and increase communities of waterbugs, which break down dead organic matter and support the river’s food chain
Water icon
Improve water quality in river pools, ensuring adequate dissolved oxygen concentration in the water to support fish, crustaceans and waterbugs

Aboriginal environmental outcomes

Traditional owners
Traditional Owners have specifically identified Aboriginal environmental outcomes associated with these watering actions

Environmental values

The upper Yarra River (reaches 1–3) provides habitat for a range of native fish species including river blackfish, mountain galaxias and common galaxias, and has goodquality riparian and aquatic vegetation. The middle and lower Yarra River (reaches 4–6) flows through forested gorges, cleared floodplains and some highly-urbanised areas, and supports several populations of native fish including Australian grayling, river blackfish, Macquarie perch and tupong. Macquarie perch was introduced to the Yarra River last century, and the population is now considered one of the largest and most important in Victoria.

Billabongs are an important feature of the 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 the Yarra River.

Recent conditions

Inflows to the main Yarra River storages were slightly below average in winter 2018 and representative of a dry year from spring 2018 through to autumn 2019.

Environmental flows were used to achieve two winter/spring freshes, with the aim of scouring sediments to improve riffle habitat within the river to create opportunities for fish to lay eggs. The freshes also favour flood-tolerant native vegetation on the banks of the river.

Two summer freshes were also delivered, to maintain habitat and enable localised fish movements, as well as to improve water quality in deep pools.

A planned autumn high flow was not delivered, as recent modelling indicated that the Dights Falls fishway was less effective when flow exceeded 1,000 ML per day. Water for the environment was instead used to deliver the second winter/spring fresh (at flows which facilitate movement through the fishway) and to target vegetation objectives. Works will be undertaken in 2019–20 to improve the function of the Dights Falls fishway.

Water for the environment was used to fill Yering Backswamp and the Willsmere and Burke Road billabongs in spring, to maintain water-dependent vegetation and aquatic animals. This is the first time Willsmere and Burke Road billabongs have received water for the environment. Monitoring of water levels, water quality and frogs by the Wurundjeri Land and Compensation Cultural Heritage Council will inform future management of these billabongs.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the Yarra system

Potential environmental watering action Functional watering objective Environmental objective

Summer/autumn low flows (varying rates from 80 – >350 ML/day during December to May)

  • Minimise the risk of stratification and low dissolved oxygen in pools through mixing
  • Maintain habitat for fish, macroinvertebrates and platypus
Fish iconPlatypus iconInsect icon
Water drop icon

Winter/spring low flows (varying rates from 200 – >350 ML/day during June to November)

  • Minimise the risk of stratification and low dissolved oxygen in pools through mixing
  • Maintain access to habitats for fish, macroinvertebrates and platypus
  • Wet bank vegetation to promote growth

Fish iconPlatypus iconPlant iconInsect icon
Water drop icon

Summer/autumn fresh (up to three freshes of 80–750 ML/day for two to four days during December to May)

  • Flush pools in the low flow season to prevent a decline in water quality
  • Scour sediment and biofilm from gravel in riffles and pools to maintain
    habitat quality for fish and macroinvertebrates
  • Provide opportunities for localised movement of fish, macroinvertebrates 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 fresh of 560–1,300 ML/day for seven to 14 days during April to May)

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

Fish iconMountain icons

Winter/spring freshes (two freshes of 700–2,500 ML/day
for three to seven days during June to September)

  • Scour sediment and biofilm from gravel in riffles to improve spawning opportunities for Macquarie perch
  • Inundate native riparian vegetation on the banks of the river to promote growth

Fish iconMountain iconsPlant icon

Winter/spring high flow (one high flow of 700–2,500 ML/day
for 14 days during June to November)

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

Fish iconMountain iconsPlant icon

Bankfull (flows in 2,700–5,000 ML/day for two days any time)

  • Mobilise sediment to minimise the development of bars and islands in the river channel
  • Prevent the encroachment of terrestrial vegetation into the channel
  • Engage floodplain billabongs
  • Entrain organic material into the waterway

Mountain iconsPlant icon

Billabong watering

Yering Backswamp (partial or complete fill in autumn and
winter/spring)

  • Water to support the growth of threatened wetland plant species and encourage the regeneration of spreading aquatic herbs
  • Provide habitat for frogs and macroinvertebrates
Frog iconPlant iconInsect icon

Banyule Billabong (partial or complete fill in winter/spring)

  • Water to support the growth of threatened wetland plant species to rehabilitate shallow marsh, deep marsh and freshwater meadows
  • Provide habitat for frogs, macroinvertebrates and eels
Fish iconFrog iconPlant iconInsect iconcracked 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
  • Environment Victoria
  • Yarra River Keeper
  • Arthur Rylah Institute
  • Environment Protection Authority
  • Port Phillip and Westernport CMA
  • Yarra Valley Water
  • Individual landholders
  • Banyule City Council
  • Boroondara City Council
  • Manningham City Council
  • Nillumbik City Council
  • Yarra Ranges Shire Council
  • Parks Victoria
  • Melbourne Water Service Delivery
  • Victorian Environmental Water Holder
  • Department of Environment, Land, Water and Planning
  • Paddle Victoria
  • Native Fish Australia
  • Warburton Holiday Park
  • Whitehorse Canoe Club
  • VRFish
  • Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation
  • Melbourne University – research collaborators
  • Monash University