VEWH - Yarra system

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 Gorge is used to divert water from the Yarra River to Sugarloaf Reservoir.

Tributaries, including Armstrong Creek, McMahons Creek, Starvation Creek, Woori Yallock Creek and the Watts and Little Yarra rivers, influence flow in the upper reaches of the 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. Requests can also be made to cease diversions from the Yarra River at the Yering Gorge Pumping Station, allowing the flow to pass down the whole river system. The priority Yarra River reaches for water for the environment are 2 and 5, shown in Figure 3.2.1. Reach 6 is also a priority in summer and autumn to manage poor water quality upstream of Dights Falls, as flow targets in reach 5 may not be sufficient. Water for the environment delivered to reaches 2 and 5 will help meet flow targets in other reaches. Occasionally, watering actions met naturally in reaches 2 and beyond are not achieved in reach 1 due to the lack of unregulated tributary inflows immediately downstream of Upper Yarra Reservoir. If so, water for the environment can also be used to meet flow targets in reach 1.

The Plenty River rises from the slopes of Mount 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 the Yarra River near Viewbank, east of Banyule Flats Reserve. Yan Yean Reservoir is located off the waterway north of Plenty Gorge, and it receives a flow 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 in the coming years.

System map

Environmental watering objectives in the Yarra River

Protect and increase populations of native fish, including threatened species (such as the Australian grayling, Macquarie perch and river blackfish)

Maintain the population of frogs, particularly on the mid-Yarra River floodplain

Maintain the form of the river channel

Scour silt from riffles and clean cobbles

Provide sufficient rates of carbon and nutrient production and processing to support native fish and waterbug communities

Maintain the population of resident platypus

Maintain and increase the abundance and diversity of waterbugs to support aquatic food webs

Improve water quality in river pools, ensuring adequate oxygen concentration in the water to support fish, crustaceans and waterbugs

Maintain native streamside and aquatic vegetation on the riverbank and in the channels

Increase the growth of threatened wetland plant species to rehabilitate shallow marsh, deep marsh and freshwater meadows on the floodplain and billabongs

Environmental values

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

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 were recorded in recent surveys.

Billabongs are an important feature of the lower Yarra River floodplain between Heidelberg and Dights Falls and in the upper reach around Yarra Glen. The billabongs support distinct vegetation communities and provide foraging and breeding habitat for waterbirds and frogs. Except in times of very high flow, most billabongs are disconnected from the Yarra River.

Traditional Owner cultural values and uses

Melbourne Water is working with the Registered Aboriginal Parties (RAPs) within the Birrarung (Yarra River) system — the Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation, the Bunurong Land Council Aboriginal Corporation and the Taungurung Land and Waters Council Aboriginal Corporation — to develop and strengthen relationships with them and to increase Traditional Owners’ involvement in the planning and delivery of water for the environment.

Melbourne Water is in discussions with each of the Traditional Owner corporations to work towards developing overarching partnership agreements. In terms of environmental water management, the intent is for Traditional Owners to be active partners in the planning, delivery and monitoring of all deliveries of water associated with Birrarung (Yarra River) and the Plenty River.

The part of the lower Birrarung (Yarra River) floodplain included in the environmental watering program is on Wurundjeri Woi wurrung Country upstream of Chandler Highway. The parts of the lower Birrarung (Yarra River) floodplain on Bunurong Country are not currently in the environmental watering program.

In 2021, changes to the RAP boundaries resulted in the lower Birrarung (Yarra River) from just upstream of Moonee Ponds Creek to Port Phillip Bay now falling within the Bunurong Land Council Aboriginal Corporation’s boundaries. The Bunurong Land Council Aboriginal Corporation is working with the Bunurong people to determine the cultural objectives for the Birrarung (Yarra River) on Bunurong Country.

In early 2023, Melbourne Water met with the Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation to discuss 2023-24 priorities for water for the environment on the lower Birrarung (Yarra River) floodplain. The Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation indicated it supports the priorities for the year ahead.

Where possible, Melbourne Water and the Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation work together to link water for the environment on the lower Birrarung (Yarra River) floodplain with cultural outcomes for the Wurundjeri Woi wurrung people. In general, environmental flows management on the lower Birrarung (Yarra River) floodplain aligns with a landscape-scale approach for billabong watering, developed in consultation with Wurundjeri Woi wurrung people. Management of water for the environment (including wetting and drying) at Annulus, Banyule and Bolin Bolin billabongs is closely aligned with Wurundjeri Woi wurrung aspirations.

Increasing the involvement of Traditional Owners in environmental flows management and progressing opportunities towards self-determination in the environmental watering program is a core commitment of the VEWH and its agency partners. This is reinforced by a range of legislative and policy commitments, including the Water Act 1989, the Victorian Aboriginal Affairs Framework, the 2016 Water for Victoria, the 2022 Central and Gippsland Region Sustainable Water Strategy, the 2022 Water is Life: Traditional Owner Access to Water Roadmap, 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 3.2.1 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 used in the spirit of valuing that contribution.

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

There are many places of tangible and intangible cultural significance for the Wurundjeri Woi wurrung people and the Bunurong people on the lower Birrarung (Yarra River) floodplain.

A monitoring project continues at the billabongs with the Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation’s Narrap (‘Country’) Unit, the University of Melbourne and Melbourne Water. The group has been monitoring vegetation and water quality outcomes from environmental flows and held an on-Country knowledge-sharing day in 2022 to discuss learnings. The intent is to further the role and leadership of the Wurundjeri Woi Wurrung people in managing the billabongs, including vegetation management, research and being partners in decision-making processes.

In 2023-24, filling Bolin Bolin Billabong in the average and wet scenarios will provide an exit strategy for eels that have entered the billabong while connected with Birrarung (Yarra River). The Narrap Unit suggested this watering action to support the landscape-scale approach to watering floodplain billabongs. The Narrap Unit will collaborate on Bolin Bolin water delivery and monitoring, depending on the unit’s availability in 2023-24.

Social, recreational and economic values and uses

In planning the potential environmental watering actions in Table 3.2.1, 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 birdwatching, camping, picnicking, cycling, running and walking)
community events and tourism (such as the Moomba Festival and the Inflatable Regatta)
socioeconomic benefits (such as for diverters for irrigation, stock needs and domestic use: water levels and water quality can rely on the delivery of water for the environment, particularly in summer).

Scope of environmental watering

The term ‘environmental watering’ refers to the active delivery of water for the environment to support particular environmental objectives by altering the flow in a river or the water level in a wetland. While other terms are also used to describe the delivery of water for the environment, ‘environmental watering’ is deliberately used here and in seasonal watering statements to ensure consistency in the legal instruments that authorise the use of water for the environment in Victoria.

Table 3.2.1 describes the potential environmental watering actions in 2023-24, their expected watering effect (that is, the intended physical or biological effects of the watering action) and the longer-term environmental objectives they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 3.2.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Yarra system

Potential environmental watering action	Expected watering effects	Environmental objectives
Yarra River The highest priority reaches for the Yarra River are reaches 2 (upper Yarra River) and 5 (lower Yarra River); water delivered to these reaches generally benefits other reaches
Winter/spring low flow (June to November) Reach 2: 80-350 ML/day Reach 5: 350-750 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
Winter/spring freshes (two freshes for three to seven days during June to September) Reach 2: 700 ML/day Reach 5: 1,300 - 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) Entrain organic material to support carbon cycling
Winter/spring high flow (one high flow for three days during June- September) Reach 1: 300 ML/d	Scour sediment and biofilm from gravel in riffles Provide prolonged wetting to favour flood-tolerant native vegetation in the streamside zone Entrain organic material to support carbon cycling
Spring high flow (one high flow for 14 days during September to October) 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 Entrain organic material to support carbon cycling
Summer/autumn low flow (December to May) Reach 2: 80 ML/day Reach 5: 200 ML/day Reach 6: 300-450 ML/day	Physically mix pools to minimise the risk of stratification and low oxygen Maintain access to habitats for fish, waterbugs and platypus
Summer/autumn freshes (three freshes for two 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
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
Yarra billabongs
Bolin Bolin Billabong (fill in spring/summer)	Fill the wetland to full supply level to engage the inlet/outlet channel to the Yarra River as an exit strategy for eels Allow to draw down to support the growth of threatened wetland plant species and encourage the regeneration of spreading aquatic herbs Maintain a permanent pool to provide habitat for frogs, waterbugs and any remaining eels
Yering Backswamp (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

Page last updated: 01/12/22