VEWH - Werribee system

The four reaches in the Werribee system that can receive water for the environment are Pyrites Creek between Lake Merrimu and Melton Reservoir (reach 6), the Werribee River between Melton Reservoir and the Werribee Diversion Weir (reach 8), Werribee River between the Werribee Diversion Weir and Werribee Park Tourism Precinct (reach 9) and the Werribee River estuary below the Werribee Park Tourism Precinct.

Environmental flows that target environmental objectives in reach 9 and the estuary are delivered from Melton Reservoir and therefore also benefit reach 8. Water for the environment released from Lake Merrimu is re-harvested in Melton Reservoir, where it can be held and released at an appropriate time to achieve environmental objectives in the lower Werribee River.

Werribee pie chart

Proportion of water entitlements in the Werribee system held by private users, water corporations and environmental water holders on 30 June 2020

System map

Environmental watering objectives in the Werribee River

Protect and increase populations of native freshwater fish species, including galaxiids and Australian grayling.
 Protect and increase populations of black bream in the estuary

Maintain the health and increase the cover of in-stream, streamside and estuary plants.
 Limit the spread of terrestrial plants, and promote the recruitment of native water-dependent plant species on the banks and benches of waterways

Maintain channel beds and pool habitats.
 Maintain clean substrate surfaces to support biological processes

Maintain native frog populations

Maintain the platypus population

Maintain and enhance the population of waterbugs, to break down dead organic matter and support the river’s food chain

Maintain oxygen and salinity levels in pools

Environmental values

The Werribee system supports a range of native fish, including Australian grayling, river blackfish, flathead gudgeon, short- finned eel, tupong, Australian smelt, several species of galaxiids and a large population of black bream in the estuary. Several species of frogs, a diverse waterbug community and platypus inhabit the upper and lower reaches. The freshwater-saltwater interface of the Werribee River estuary is a regionally significant ecosystem due to the many aquatic plants and animals it supports, and it provides nursery habitat for juvenile freshwater and estuarine fish species (such as black bream).

Traditional Owner cultural values and uses

Melbourne Water is working with the Registered Aboriginal Parties within the Werribee system – the Wadawurrung Traditional Owners Aboriginal Corporation, the Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation and the Bunurong Land Council Aboriginal Corporation – to strengthen relationships and increase Traditional Owners’ involvement in the planning and delivery of water for the environment. As of June 2023, an overarching partnership agreement was near completion between Melbourne Water and Wadawurrung Traditional Owners Aboriginal Corporation to frame relations and obligations between the organisations. Melbourne Water was also in discussions with Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation and the Bunurong Land Council Aboriginal Corporation to work towards developing a similar partnership agreement. The intent is for Traditional Owners to be active partners in the planning, delivering and monitoring water for the environment associated with Wirribi Yaluk/Weariby Yallok (Werribee River).

All three Registered Aboriginal Parties in the Werribee system were involved in the upper Wirribi Yaluk/Weariby Yallok (Werribee River) environmental flows study, completed in 2022-23.

The Bunurong Land Council Aboriginal Corporation is working with Bunurong people to determine the cultural objectives for Weariby Yallok (Werribee River) on Bunurong Country. There are concerns about low flow in the lower reaches and that fish of cultural importance to the Bunurong are not supported by the flow and are restricted in movement. This concern may be partially addressed through the implementation of Action 8-10 in the Central and Gippsland Region Sustainable Water Strategy, which aims to improve fish passage and the delivery of water for the environment to the lower Weariby Yallok (Werribee River) on Bunurong Country.

The Wadawurrung Traditional Owners Aboriginal Corporation has reviewed the environmental values of the Wirribi Yaluk (Werribee River) system. It has identified environmental values that also have cultural significance to Wadawurrung Traditional Owners, which the table below shows. However, further work is required to understand how potential environmental watering actions can improve these cultural values.

Reach	Extent	Key environmental values with cultural significance to the Wadawurrung
8	Wirribi Yaluk (Werribee River)
9	Wirribi Yaluk (Werribee River) between Wyndham Vale and Bluestone Ford
Estuary	Werribee River downstream of Bluestone Ford

Social, recreational and economic values and uses

In planning the potential environmental watering actions in Table 3.5.1, Melbourne Water considered how environmental flows could support values and uses, including:

water-based recreation (such as canoeing, fishing, kayaking and swimming)
riverside recreation and amenity from urban cooling (such as camping, walking, cycling and picnicking)
community events and tourism (such as Werribee Zoo).

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 3.5.1 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 1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Werribee system

Potential environmental watering action	Expected watering effects	Environmental objectives
Pyrites Creek (targeting reach 6)
Winter/spring/summer low flow (2 ML/day or natural during June to December)	Provide sufficient water depth in riffle habitats for macroinvertebrates native fish Maintain habitat for frogs at the margin of the stream channel Provide sufficient water depth to support the growth of flood-tolerant vegetation within the stream channel Provide sufficient water depth to allow for native fish to move between pools
Winter/spring freshes (three to five freshes of 30-40 ML/day for two days during June to November)	Provide sufficient water depth in riffle habitats for macroinvertebrates native fish Maintain habitat for frogs at the margin of the stream channel Provide sufficient water depth to support the growth of flood-tolerant vegetation within the stream channel Provide sufficient water depth to allow for native fish to move between pools
Spring high flow (one high flow of 70-130 ML/ day for one to two days during September to October)	Maintain access to food and habitat for waterbugs, native fish and frogs * Increase the growth and recruitment of in-stream vegetation At 130 ML/day, the effects above plus: inundate the full width of the channel and high backwaters to flush accumulated organic matter and promote the growth and recruitment of streamside vegetation
Lower Werribee River (targeting reaches 8, 9 and estuary)
Winter/spring low flow (up to 80 ML/day during June to November)	Provide flow to allow fish to move upstream past natural and artificial barriers Facilitate the downstream movement of diadromous fish to the estuary Drown terrestrial plant species and support the growth and recruitment of water-dependent streamside vegetation Maintain permanent pools and increase the extent of habitat for waterbugs, fish, platypus and frogs Maintain flow through pool habitats to allow mixing or suppression/ dilution of saline groundwater
Winter/spring freshes (two to four freshes of 350 ML/day for three days during June to October)	Support the growth and recruitment of water-dependent streamside vegetation Flush silt and scour biofilms and algae from substrates on the stream bed and maintain pools and channel dimensions Provide movement cues and enough flow for fish to move upstream past natural and artificial barriers Maintain water quality and quantity of food and habitat for waterbugs and platypus Wet depressions adjacent to the stream that frogs can use for breeding
Summer/autumn low flow (10 ML/day during December to May)	Maintain habitat for in-stream and water-dependent streamside vegetation Maintain access to habitat and improve water quality for native fish, frogs, platypus and waterbugs Maintain flow through pool habitats to allow mixing or suppression/dilution of saline groundwater intrusion
Summer/autumn freshes (three to five freshes of 135-215 ML/day for one to two days during December to May)	Increase the growth and recruitment of water-dependent streamside vegetation Flush silt and scour biofilms and algae from substrates on the stream bed and maintain pools and channel dimensions Maintain access to habitat and improve water quality for native fish, frogs and platypus Provide enough flow for native fish to move downstream past natural or artificial barriers Maintain the quality of water within pools by dispersing azolla and blue- green algae blooms

Page last updated: 01/12/22