Skip to content

Close to Tullamarine Airport, Jacksons Creek (flowing from the west) and Deep Creek (flowing from the north) join to form the Maribyrnong River. The river runs south through Yarraville in inner Melbourne before meeting the Yarra and flowing into Port Phillip Bay. Rosslynne Reservoir is the only major storage in the Maribyrnong catchment, located in the upper reaches of Jacksons Creek.

The priority river reaches for environmental watering in the Maribyrnong system are reaches 6 and 7 (upper and lower Jacksons Creek respectively) downstream of Rosslynne Reservoir. The release capacity of 20 ML per day from Rosslynne Reservoir is a significant constraint on the outcomes that can be achieved by environmental deliveries.

The VEWH does not hold an environmental entitlement in the Maribyrnong system. Over the past three years, Melbourne Water and the VEWH have worked with local diversion licence holders to purchase unused water that can then be delivered specifically for environmental outcomes in the system. This arrangement is negotiated each year and will only occur with the agreement of all parties involved.

Environmental watering objectives in the Maribyrnong River

Fish icon
Allow for small-bodied fish passage through the system
Insect icon
Maintain self-sustaining waterbug populations and suitable habitats
Water icon
Maintain water quality by flushing pools
Plant icon
Maintain or restore in-stream vegetation and reduce invasive terrestrial vegetation populations

Environmental values

The upper Maribyrnong catchment contains areas of relatively 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 diverse community of waterbugs and a significant

Social and economic values

The Maribyrnong River is located in the western suburbs of Melbourne and provides water (primarily from Rosslynne Reservoir on Jacksons Creek) to urban and rural users. Recreational opportunities such as boating, fishing, cycling, walking and picnicking in the adjacent parklands are popular. The waterways of the Maribyrnong system hold significance for Traditional Owners and their Nations in the region.

Conditions mid-2016

Since 2012 rainfall and run-off into the waterways of the Maribyrnong system have been decreasing with drier conditions. The lack of flow in the waterways has resulted in poor water quality in Jacksons Creek, particularly over summer below Rosslynne Reservoir. Environmental water has been released from the reservoir to freshen up the creek and prevent low oxygen levels in the water causing problems for fish, waterbugs and platypus. Without environmental water, the condition of the animals and plants in Jacksons Creek would have continued to decline.

Over summer and autumn low dissolved oxygen levels can occur, causing stress to aquatic animals, and prolonged very low flows can negatively impact in-stream plants. In 2015–16, 300 ML of water was delivered in two freshes (small pulses of water) to Jacksons Creek, primarily to maintain water quality to protect aquatic animals and in-stream plants in dry conditions.

Scope of environmental watering

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

Potential environmental watering1

Environmental objectives

Summer/autumn low-flow freshes (up to 3 events of 20–40 ML per day for up to 4 days) in December–May

  • Maintain water quality by flushing pools
  • Support in-stream vegetation
  • Provide passage for small-bodied native fish

Low flows (4–6 ML per day continuously) in December–May

  • Maintain self-sustaining waterbug populations and pool run habitats

Winter/spring low flows (20–40 ML per day continuously) in June–November

  • Maintain or restore in-stream vegetation and disturb invasive terrestrial vegetation populations
  • Maintain channel morphology
  • Allow for small-bodied fish passage through the system

1 The range in flow requirements represent the target flow requirements for reaches 6 and 7.

Scenario planning

Under drier climate scenarios, any available environmental water would be delivered to protect or maintain aquatic habitat in Jacksons Creek through the delivery of low-flow freshes and, under drought conditions, delivery of low flows. These deliveries aim to ensure the in-stream plants and animals have refuge to survive.

Under average and wet conditions it is expected unregulated flows will contribute to meeting the flow objectives. Environmental water could still be beneficial for filling in gaps between unregulated events or to continue small-scale unregulated events for a longer duration.

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

Planning scenario

Drought

Dry

Average

Wet

Expected river conditions

  • Minimal unregulated flows
  • Passing flows ceased
  • Low volumes of unregulated flows
  • Passing flows partially to fully meet low flows
  • Unregulated flows partially meet most objectives
  • Passing flows partially to fully meet low flows
  • Unregulated flows meet most objectives
  • Passing flows partially to fully meet low flows

Potential environmental watering

  • Summer/autumn low flows
  • Summer/autumn low-flow freshes
  • Summer/autumn low-flow freshes
  • Summer/autumn low-flow freshes
  • Winter/spring low flows
  • Summer/autumn low-flow freshes
  • Winter/spring low flows

Volume of environmental water required to achieve objectives

  • 300 ML
  • 300 ML
  • 600 ML
  • 600 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.