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Rosslynne Reservoir is in the upper reaches of Jacksons Creek near Gisborne and is the only major storage in the Maribyrnong catchment. The reservoir has a release capacity of 20 ML per day, which significantly constrains the environmental outcomes that can be achieved in the Maribyrnong system. Water for the environment is primarily used to support environmental outcomes in Jacksons Creek between Rosslynne Reservoir and the confluence with Deep Creek (that is, the environmental flow reaches 6 and 7). These two reaches are described as upper and lower Jacksons Creek respectively.

The VEWH does not hold an environmental entitlement in the Maribyrnong system, and it relies on opportunistic, temporary trade to meet demands. Melbourne Water and the VEWH work with local diversion licence holders to purchase unused water when it is available to support environmental outcomes. This arrangement is negotiated each year, and it only occurs with the agreement of all parties involved.

Waterway manager
Traditional Owners
Storage manager

System map

Maribyrnong system

Environmental watering objectives in the Maribyrnong River

Fish icon
Protect and increase populations of native smallbodied fish
Platypus icon
Maintain platypus population
Landscape icon
Maintain channel morphology
Plant icon
Maintain and improve the condition, abundance, diversity and structure of instream and streamside vegetation
Insect icon
Support a wide range and high biomass of waterbugs, to break down dead organic matter and support the river’s food chain
Water icon
Maintain water quality, particularly oxygen concentrations

Environmental values

The upper Maribyrnong catchment contains areas of intact streamside vegetation, which provide important habitat for native fish including migratory short-finned eels, common and ornate galaxias, flathead gudgeon, tupong and Australian smelt. A large population of waterbugs provides abundant food for a significant platypus population in several reaches in the Maribyrnong system.

Recent conditions

The Maribyrnong catchment had above-average rainfall during winter and spring 2020, leading to high soil moisture and above-average tributary inflows downstream of Rosslynne Reservoir. Conditions remained near-average for the remainder of the year, but inflows to Rosslynne Reservoir were well-below average during 2020-21, and the storage remained below 30 percent capacity. The VEWH did not purchase allocation from licence holders due to low water availability in the Maribyrnong system, meaning no water for the environment was available for use in 2020-21.

The wetter-than-average conditions in the catchment below Rosslynne Reservoir meant winter/spring low flows in reach 7 were partially met by tributary inflows. Local rainfall runoff and passing flows (delivered by Southern Rural Water’s bulk entitlement) met most of the summer and autumn low-flow watering actions recommended for reaches 6

and 7 and two summer/autumn freshes in reach 7. These flows maintained water quality and suitable habitat and food resources for native fish, platypus and waterbugs, despite the lack of environmental water.

Traditional Owner cultural values and uses

Melbourne Water has made initial contact with the Boon Wurrung Foundation, Bunurong Land Council Aboriginal Corporation and Wurundjeri Woi wurrung Cultural Heritage Aboriginal Corporation to discuss environmental watering in the Maribyrnong system.

There are more opportunities for Melbourne Water and the VEWH to work with the Traditional Owner groups to identify and better integrate cultural values and their flow requirements into the environmental watering program on an ongoing basis.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, Melbourne Water considered how environmental flows could support social values such as community connection and amenity, by planning flows that will maintain healthy habitat and improve water quality.

Scope of environmental planning

Table 1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Maribyrnong system

Potential environmental watering action

Expected watering effects

Environmental objectives

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

  • Wet the in-stream vegetation and streamside benches to support the growth of native plants and to limit encroachment by terrestrial plant species
  • Prevent fine sediment settling and smothering waterbug habitat
  • Provide passage for small-bodied native fish and platypus between habitats
Fish iconPlatypus iconPlant iconInsect icon

Summer/autumn low flow (6 ML/day during December to May)

  • Maintain waterbug habitat by providing suitable depth over riffles, maintaining pools and inundating large woody debris
  • Provide passage for small-bodied native fish and platypus between habitats

Fish iconPlatypus iconInsect icon

Summer/autumn freshes (two to three freshes of 40 ML/day for seven days during December to May)

  • Flush pools to maintain water quality
  • Prevent fine sediment settling and smothering waterbug habitat
  • Wet the in-stream vegetation and streamside benches to support the growth of native streamside plants and to limit encroachment by terrestrial plant species
  • Provide passage for small-bodied native fish and platypus between habitats

Fish iconPlatypus iconPlant iconInsect iconWater drop icon

Engagement

Table 2 shows the partners, stakeholder organisations and individuals Melbourne Water consulted when preparing the Maribyrnong 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 Maribyrnong system seasonal watering proposal

Partner and stakeholder engagement
  • Environment Victoria
  • Friends of Holden Flora Reserve
  • Friends of the Maribyrnong Valley Inc.
  • Independent community members
  • Jacksons Creek EcoNetwork
  • Native Fish Australia
  • Waterwatch Coordinators
  • Department of Environment, Land, Water and Planning
  • Melbourne Water (Service Delivery)
  • Southern Rural Water
  • Western Water
  • Aboriginal Victoria
  • Commissioner for Environmental Sustainability Victoria
  • Environment Protection Authority Victoria
  • Hume City Council
  • Maribyrnong City Council
  • Moonee Valley City Council
  • Parks Victoria
  • Port Phillip and Westernport CMA
  • Victorian Fisheries Authority
  • Victoria Police
  • Licensed diverters from the Maribyrnong River at Keilor
  • Atlas Ecology Pty Ltd
  • Blackbird Cruises

Page last updated: 22/01/21