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Flows through the Yarra system have become highly regulated due to the construction of water storages that capture natural run-off and allow the controlled removal of water for consumptive uses. Over time, the lower Yarra River has been straightened, widened and cleared of natural debris as Melbourne grew around its banks, with the earliest alterations to its course occurring as far back as 1879. Environmental watering aims to reinstate flows that support ecological outcomes throughout the length of the system.

Environmental water can be released from the Upper Yarra, Maroondah and O'Shannassy reservoirs. Priority reaches for environmental watering are reaches 2 and 5 (see below) and delivery of water to these reaches is also expected to achieve flow targets in neighbouring reaches. The environmental flow reaches in the Yarra system are shown in the below map. In the upper reaches, the system is influenced by tributaries (such as Woori Yallock Creek, Watts River and Little Yarra River). In the lower reaches, urbanised tributaries (such as Diamond Creek, Plenty River and Merri Creek) provide additional water to the Yarra River.

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

Landscape icon
Maintain the form of the river bank and bed
Fish icon
Protect and boost populations of native fish including threatened species (such as the Australian grayling and Macquarie perch)
Insect icon
Restore communities of waterbugs which provide energy, break down dead organic matter and support the river’s food chain
Landscape icon
Scour silt build-up and clean cobbles in the river to ensure fish, platypus and other water animals have healthy habitat pools and places to shelter
Plant icon
Rebuild, strengthen and maintain plant life on the river bank and in the channel, as well as on the upper Yarra floodplains and in the river’s billabongs
Water icon
Boost water quality in river pools, ensuring there is plenty of dissolved oxygen in the water to support water animals and bugs

Environmental values

The Yarra River supports many important environmental values including terrestrial and aquatic vegetation, billabongs, birds, frogs, platypus and several nationally significant native fish species (such as the Australian grayling and the Macquarie perch).

The upper system (reaches 1–3) provides habitat for a range of native fish species including the river blackfish, spotted galaxias and common galaxias and contains good-quality riparian and aquatic vegetation. The lower system (reaches 4–6) contains Australian grayling, Macquarie perch and tupong.

There are several billabongs in the Yarra system which are an important feature of the Yarra River floodplain downstream of Millgrove. The billabongs support a variety of distinct plants, providing foraging and breeding habitat for waterbirds and frogs. Except in very high flows, the billabongs are disconnected from the Yarra River.

Social and economic values

The upper reaches of the Yarra River are an important water supply catchment for Melbourne. There are more than four million people who live in and travel to greater Melbourne and the river provides social and recreational opportunities such as swimming and kayaking, as well as aesthetic appeal for walkers and cyclists. The waterways of the Yarra system (including the Yarra River) hold significance for Traditional Owners and their Nations in the region.

Conditions mid-2016

Dry conditions persisted from 2014–15 into 2015–16 and resulted in low flows falling below target levels at times, as well as an absence of higher unregulated flows in winter/spring. The volume of environmental water required to maintain target low-flow levels was too large, so intermittent freshes (small water pulses) were released during the year to maintain habitat and some movement opportunities for animals.

Four freshes were delivered in 2015–16, one in spring and three over summer/autumn. These releases successfully maintained aquatic plants and habitat for waterbugs and fish. Releases over summer were able to maintain water quality (particularly in reach 6) and environmental water also helped allow fish to move up and down the river.

Given the dry conditions and lack of unregulated flows, higher spring and autumn releases primarily targeting fish (Australian grayling) migration and spawning were not delivered. These higher releases were less important in 2015–16 as they had been delivered in previous years.

Scope of environmental watering

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

Potential environmental watering1

Environmental objectives

Year-round low flows2 (varying rates from 10–350 ML/day)

  • Provide sufficient access to riffle habitat
  • Allow river bank vegetation to dry
  • Limit the growth of fringing/riparian/terrestrial vegetation into the stream channel
  • Maintain and/or rehabilitate in-stream vegetation

Summer/autumn freshes (2–5 freshes of varying rates between 60–750 ML/day for 2–4 days each in December–May)

  • Maintain habitat by scouring sediments and cleaning cobbles in faster-flowing areas
  • Provide suitable habitat and migration opportunities for native fish
  • Promote flood-tolerant vegetation
  • Improve water quality in pools

Winter/spring freshes (2–3 [or more] freshes of varying rates between 100–2,500 ML/day for at least 2–7 days in June–November)

  • Maintain habitat by scouring sediments and cleaning cobbles in faster-flowing areas
  • Promote flood-tolerant vegetation
  • Provide suitable habitat and migration opportunities for native fish
  • Improve water quality in pools

Autumn high flow (1 high flow of varying rates between 560–1,300 ML/day for 7–14 days in April–May)

  • Stimulate Australian grayling spawning

Targeted billabong watering

  • Support native vegetation and improve habitat availability for wetland plants and animals

Spring high flow (1 high flow of 700–2,500 ML/day for 14 days in October–November)3

  • Maintain riffle habitat by scouring sediments and cleaning cobbles
  • Promote flood‐tolerant vegetation growth
  • Promote migration of native fish

1 The magnitude and duration of potential environmental watering depends on the reach being targeted, with the lower range generally occurring in the upper reaches (for example, reach 1) and higher range in the lower reaches (for example, reach 6).

2 Low flows are generally provided by passing flows under the environmental entitlement but during dry conditions it may be necessary to supplement low flows using environmental water.

3 A spring high flow will only be achieved with significant unregulated flow due to release constraints in the upper reaches of the system. However, ceasing harvesting at Yering during a natural high flow may assist in the desired flow being achieved.

Scenario planning

Watering actions across all scenarios are similar in 2016–17. Given the dry conditions, the autumn high flow and billabong watering did not occur in 2015–16, making them high-priority watering actions in 2016–17, including in dry conditions. Sufficient environmental water will be available to deliver these actions under all planning scenarios, due to the high security of the environmental entitlement in the Yarra system.

Less environmental water is expected to be required under average and wet conditions as natural flows following rainfall contribute significantly to meeting the environmental flow objectives. An additional spring high flow is planned under these conditions. Under wet conditions, priorities such as billabong watering may occur naturally.

A minimum of 3,000 ML carryover into 2017–18 is required (in addition to the 17,000 ML annual entitlement) to deliver the highest-priority flows if dry conditions continue into the following year.

Table 2 Potential environmental watering for the Yarra system under a range of planning scenarios

Planning scenario

Dry

Average

Wet

Expected river conditions

  • Low streamflows year-round
  • Lack of unregulated freshes and high flows
  • Minimum passing flow requirements not likely to meet low-flow requirements
  • High winter flows with small storages likely to spill
  • Unregulated flows may provide some freshes but duration and/or magnitude will likely be less than target flows
  • High winter and spring flows with good variability
  • Unregulated flows over summer/autumn will provide freshes and possibly high flows
  • Some natural inundation of billabongs may occur

Expected availability of environmental water

  • 22,000 ML carryover
  • 17,000 ML allocation
  • 39,000 ML total

Potential environmental watering

  • Summer/autumn low flows
  • Summer/autumn freshes
  • Winter/spring low flows
  • Winter/spring freshes
  • Autumn high flows
  • Targeted billabong watering
  • Summer/autumn low flows
  • Summer/autumn freshes
  • Winter/spring low flows
  • Autumn high flows
  • Targeted billabong watering
  • Winter/spring freshes
  • Spring high flows

Possible volume of environmental water required to achieve objectives

  • 32,000 ML
  • 24,000 ML
  • 8,000 ML

Priority carryover requirements

  • 3,000 ML

Risk management

In preparing its seasonal watering proposal, Melbourne Water considered and assessed risks and identified mitigating strategies relating to implementing environmental watering. Risks and mitigating actions are continually reassessed by program partners throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

Communities in the Melbourne region are involved in decisions about the Tarago, Yarra and Werribee river systems through each system's Environmental Water Advisory Group.

Who is engaged and how

Recreational users

Through formal advisory groups coordinated by Melbourne Water, representatives of recreational user groups are engaged. Advisory group members receive notifications about planned environmental water deliveries via the community bulletin.

For recreational users, safety related to higher water levels are a key concern.

On occasion, Melbourne Water informs recreational users directly about environmental watering (such as the Werribee fishing club or Canoes Victoria).

Environment groups

Representatives of environment groups are engaged through formal advisory groups coordinated by Melbourne Water. Advisory group members receive notifications about planned environmental water deliveries via the community bulletin.

Melbourne Water has informal relationships with various environment groups (such as Landcare, Birdlife Australia, Yarra Riverkeepers, Environment Victoria and Waterwatch) and meet with these groups on an as-needs basis.

Some groups, such as Waterwatch, share monitoring information with Melbourne Water.

Landholders/farmers

Through the Yarra Diversions newsletter, diversions licence holders receive information and updates on environmental watering.

Landholders and farmers are engaged through formal advisory groups coordinated by Melbourne Water. Advisory group members receive notifications about planned environmental water deliveries via the community bulletin.

Traditional Owners

Melbourne Water is doing a collaborative project with the Wurundjeri Tribe Land and Compensation Heritage Council and the Victorian Environmental Water Holder to document the Wurundjeri cultural values in the Yarra river system. The aim of this project is to increase understanding of values that can be supported with environmental water to achieve shared benefits for Aboriginal people from environmental watering (Aboriginal environmental outcomes).

Councils

Through formal advisory groups coordinated by Melbourne Water, Council representatives (from various local councils across region) are engaged. Advisory group members receive notifications about planned environmental water deliveries via the community bulletin.

Melbourne Water publishes an annual two-pager for each Council about activities undertaken in their catchment, including delivery of environmental flows.

General public

Melbourne Water communicates and engages with the general public through their website, media releases and Facebook and Twitter. Melbourne Water community bulletins are posted on their webpage, Facebook and Twitter, and issued to media contacts.