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Flows in the upper Barwon River are regulated by the operation of the West Barwon Reservoir upstream of Forrest. Water can be released directly from the reservoir into the west branch, or into the east branch via a diversion channel. The junction of the two branches is near Boundary Creek. Upstream of Birregurra, water can be diverted into the Wurdee Boluc inlet channel, a 57 km, concrete-lined channel that transfers water to Wurdee Boluc Reservoir.

Barwon Water releases passing flows in the order of 1–5 ML per day in both the upper east and west branch (and up to 15 ML per day in September during a wet year) from the West Barwon Reservoir. Flood spills from the reservoir and natural inflows from unregulated and partly regulated tributaries add to the passing flows.

The Upper Barwon River Environmental Entitlement 2018 enables water to be made available for the environment from the West Barwon Reservoir. The entitlement provides an average of 1,000 ML per year and up to 2,000 ML of the total storage capacity at full supply. Water for the environment was first delivered to the upper Barwon in 2018–19. The current entitlement provides only enough water to meet the highest ecological objectives in the upper Barwon east branch (reach 4) and the upper Barwon west branch (reach 3).

Traditional Owners

System map

Environmental watering objectives in the Upper Barwon River

Platypus icon
Maintain the abundance, improve the condition and extend the distribution of platypus populations
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Increase the abundance of waterbugs as a food source for fish, frog and platypus populations
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Maintain water quality for native fish, waterbugs, aquatic vegetation and other water-dependent animals
Maintain the abundance, and improve the breeding and recruitment of migratory fish species including short-finned eels, Australian grayling and tupong, broad-finned galaxias and common jollytail Maintain the abundance, and improve the breeding and recruitment of resident freshwater fish including several species of galaxias, Australian smelt, big-headed gudgeon, Yarra pygmy perch and river blackfish
Plant icon
Improve the condition and extent of native instream vegetation, to provide structural habitat for macroinvertebrates and various fish species Increase the extent and diversity of emergent macrophyte vegetation, to provide structural habitat and stabilise banks Increase the extent and diversity of native riparian vegetation Improve the condition and extent of native floodplain vegetation

Environmental values

The upper Barwon River is home to native fish species including the Australian grayling, river blackfish, short-finned eel, southern pygmy perch, Australian smelt and various galaxias. The system retains some submerged aquatic vegetation, undercut banks, overhanging vegetation and riffle-pool sequences: these provide important habitat for fish and other aquatic animals.

Recent conditions

Total rainfall in the Barwon River catchment was slightly below average during 2019–20 but varied within and between seasons. Significant rain in July and August 2019 filled the West Barwon Reservoir from 26 percent capacity to 60 percent capacity, and rainfall between January and May 2020 was above the long-term average.

Natural inflows maintained an average flow of 50 to70 ML per day at Winchelsea throughout winter and spring 2019 and delivered several high-flow events and freshes including a peak flow of 3,560 ML per day at Winchelsea in mid-July 2019. Water for the environment was used to maintain minimum low-flow targets (up to five ML per day) in the east branch of the upper Barwon River during summer, to maintain water quality and instream habitat for native fish and platypus and to maintain aquatic vegetation. Small freshes up to 15 ML per day were delivered in January and March 2020 to allow fish and other aquatic animals to disperse and maintain vegetation higher up the banks. The recommended fresh of 35 ML per day cannot currently be delivered due to channel constraints.

Traditional Owner cultural values and uses

The Corangamite CMA is working with Eastern Maar and Wadawurrung Traditional Owners to understand opportunities to provide for both groups’ respective cultural values and uses and other aspirations for environmental water management throughout the Barwon system.

The reaches of the Barwon River that can be most influenced by water delivered from the West Barwon Reservoir sit in Eastern Maar Country. Good opportunities exist within these reaches for actively managed shared benefits in the future.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, Corangamite CMA considered how environmental flows could support values and uses including:

  • water-based recreation (such as canoeing, fishing, kayaking and swimming)
  • riverside recreation and amenity (such as bird watching, walking, camping, picnicking and using parks and lookouts)
  • socio-economic benefits (such as diverters for irrigation, domestic and stock uses).

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the upper Barwon River

Potential environmental watering action1

Functional watering objective

Environmental objective

Summer/autumn low flow (continuous 0.5–30 ML/day during December to May)

  • Maintain an adequate depth of permanent water in the channel/pools to support resident fish, platypus and waterbugs
  • Promote the recruitment of native aquatic vegetation
  • Reduce encroachment by terrestrial plants into aquatic zone
  • Provide minimum velocity to maintain mixing in pools
Fish iconPlatypus iconPlant iconWater drop iconInsect icon

Summer/autumn freshes (two freshes of nine to 35 ML/day for two days during December to May: east branch only)

  • Provide longitudinal connectivity with water over riffles to allow fish to move between pools to breed, feed and find new habitats
  • Submerge woody debris and clean hard surfaces to provide breeding substrate
  • Maintain waterbug communities in the dry period by flushing organic matter into the channel to provide food after inundating benches
  • Maintain emergent and streamside vegetation on terraces, the channel edge and lower bank
  • Provide minimum velocity to mix and flush pools

Fish iconPlatypus iconPlant iconInsect iconWater drop icon

Winter/spring low flow (continuous 10–50 ML/day or natural during April to November)

  • Maintain an adequate water depth in the channel/pools to support fish and platypus foraging and breeding habitat
  • Maintain an adequate depth of permanent water in the channel to promote the recruitment of aquatic and streamside plants and to limit the encroachment of terrestrial species
  • Provide minimum velocity, to mix pools

Fish iconPlatypus iconPlant iconWater drop icon

Engagement

Table 2 shows the partners and stakeholder organisations with which Corangamite CMA engaged when preparing the Upper Barwon River 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 Corangamite Regional Catchment Strategy and the Corangamite Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Upper Barwon River system seasonal watering proposal

Partner and stakeholder engagement
  • Upper Barwon Surface Water Advisory Group
  • Land and Water Resources Otway Catchment
  • Barwon Water
  • Department of Environment, Land, Water and Planning Water and Catchments
  • Southern Rural Water
  • Colac Otway Shire Council
  • Landholders on the Upper Barwon Surface Water Advisory Group
  • Recreational users on the Upper Barwon Surface Water Advisory Group
  • Eastern Maar Aboriginal Corporation
  • Wathaurung Aboriginal Corporation
  • Wathaurung Aboriginal Corporation

Page last updated: 24/07/20