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Rosslynne Reservoir is in the upper reaches of Jacksons Creek near Gisborne, and it 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, environmental flow reaches 6 and 7 shown in the system map below). 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
Landscape icon
Maintain channel morphology
Platypus icon
Maintain platypus population
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 has experienced below average rainfall since the summer of 2016–17, and inflows to Rosslynne Reservoir in 2019–20 continued to track well below average. The VEWH did not purchase allocation from licence holders in 2019–20, due to low water availability in the Maribyrnong system.

The dry conditions meant that winter/spring low-flow, winter/spring and summer/autumn freshes were not achieved in 2019–20. Summer/autumn low flows were achieved in reach 6, but only partially achieved in reach 7 (below Riddles Creek) by passing flows delivered under Southern Rural Water’s bulk entitlement. These flows prevented poor water quality conditions and maintained suitable habitat and food resources for small-bodied native fish, waterbugs and platypus.

Traditional Owner cultural values and uses

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

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). This includes repeating the outcomes of watering in 2019–20, where releases into the upper reaches of the Maribyrnong helped maintain healthy habitat and improve water quality.

Scope of environmental planning

Table 1 Potential environmental watering actions and objectives for the Maribyrnong River

Potential environmental watering action

Functional watering objective

Environmental objective

Summer/autumn low flow (four to six 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 fresh (one to five freshes of 20–40 ML/ day for up to seven days during December to May)

  • Flush pools to maintain water quality
  • Scour substrates to remove fine sediment
  • 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 iconMountain iconsPlatypus iconPlant iconInsect iconWater drop icon

Winter/spring low flow (20–40 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
  • Scour substrates to remove fine sediment
  • Provide passage for small-bodied native fish and platypus between habitats

Fish iconMountain iconsPlatypus iconPlant iconInsect 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
  • Friends of Holden Flora Reserve
  • Friends of the Maribyrnong Valley Inc.
  • Jacksons Creek Eco-network
  • Department of Environment, Land, Water and Planning | Water and Catchments
  • Southern Rural Water
  • Western Water
  • Environment Protection Authority
  • Port Phillip and Westernport Catchment Management Authority
  • Licenced diverters from the Maribyrnong River at Keilor
  • Melbourne University – research collaborators
  • Monash University
  • Arthur Rylah Institute (Department of Environment, Land, Water and Planning)
  • Boon Wurrung Foundation
  • Bunurong Land Council Aboriginal Corporation
  • Wurundjeri Woi-Wurrung Cultural Heritage Aboriginal Corporation

Page last updated: 24/07/20