Upper Barwon River

The Barwon River flows east from the Otway Ranges passing the towns of Forrest, Birregurra, Winchelsea and Inverleigh and the City of Geelong before discharging into Bass Strait at Barwon Heads. The Leigh River and Moorabool Yulluk (Moorabool River) are major tributaries, joining the Barwon River at Inverleigh and Fyansford respectively. Other tributaries including Birregurra, Boundary, Callahan, Dewing, Matthews, Pennyroyal, Deans Marsh and Gosling creeks flow into the Barwon River above Winchelsea. The main storages in the Barwon River catchments are the West Barwon and Wurdee Boluc reservoirs.

Flows in the upper Barwon River are regulated by the operation of the West Barwon Reservoir. Water can be released directly from the reservoir into the west branch, or into the east branch via a diversion tunnel. The junction of the two branches is near Boundary Creek. Downstream of the reservoir, operational 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 from the West Barwon Reservoir. These releases may increase to 15 ML per day in September in a wet year. 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) under particular climatic conditions.

System map

Environmental watering objectives in the Upper Barwon River

Maintain the abundance, improve the condition and extend the distribution of platypus populations

Increase the abundance of waterbugs as a food source for fish, frog and platypus populations

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

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, which provide important habitat for fish and other aquatic animals.

Recent conditions

Rainfall in the Barwon River catchment in 2020-21 was slightly above the long-term average. Wet conditions from August to October contributed high inflows to catchment storages, but West Barwon Reservoir did not fill beyond 70 percent capacity. Allocations against the environmental entitlement increased from 536 ML in July 2020 to 1,000 ML in October 2020.

Operational releases and passing flows maintained low flows in the upper Barwon River throughout most of the year. High- rainfall events delivered several natural high-flow events during winter and spring 2020 and two natural freshes in January 2021. These high flows and freshes provided opportunities for fish and platypus to migrate and likely improved the condition of native vegetation and in-stream habitats. Water for the environment was used to supplement low flows in the west branch of the upper Barwon River as needed, to achieve recommended flow targets during summer and autumn.

Water for the environment in the upper Barwon River was managed in line with an average climate scenario during 2020-21, and all planned watering actions were achieved.

A lack of flow data from key locations has limited the assessment of previous environmental flow releases in the upper Barwon River. A new streamflow gauge was installed on the east branch (near King Creek junction) in 2020, and data from that site will support future environmental flow management.

Traditional Owner cultural values and uses

The reaches of the Barwon River that can be most influenced by water delivered from the West Barwon Reservoir sit in Eastern Maar Country. In February 2020, the Eastern Maar Aboriginal Corporation received Registered Aboriginal Party status under the Aboriginal Heritage Act 2006 over a large portion of land in south-west Victoria including the Barwon River upstream of Winchelsea. The Eastern Maar Aboriginal Corporation was invited to be involved in the development of Corangamite CMA’s seasonal watering proposal, as good opportunities exist within these reaches to support Eastern Maar values and aspirations associated with the waterway.

The Corangamite CMA is working with Wadawurrung Traditional Owners to understand opportunities to provide for cultural values and uses and other aspirations for management of water for the environment in the Barwon River downstream of Winchelsea.

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 birdwatching, camping and walking)
socio-economic benefits (such as domestic and stock uses)

Scope of environmental watering

Table 1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the upper Barwon River

Potential environmental watering action	Expected watering effects	Environmental objectives
Winter/spring low flow (10-50 ML/day or natural) (June to November) (east and west branch)	Maintain connectivity and 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 sufficient flow velocity, to mix pools
Summer/autumn low flow (0.5-5 ML/day from December to May, east branch)	Maintain an adequate depth of permanent water in the channel/pools to provide habitat to support resident and migratory fish, platypus and waterbugs Reduce encroachment by terrestrial plants into the aquatic zone Provide minimum velocity to mix and flush pools
Summer/autumn low flow (30 ML/day or natural from December to May, west branch)	Maintain an adequate depth of permanent water in the channel/pools to provide habitat to support resident and migratory fish, platypus and waterbugs Reduce encroachment by terrestrial plants into the aquatic zone Provide minimum velocity to mix and flush pools
Summer/autumn freshes (two to three freshes of 9-35 ML/day for two days from December to May, east branch)	Provide longitudinal connectivity with water over riffles to allow fish to migrate upstream and fish and platypus to move between pools to breed, feed and find new habitats Submerge woody debris and clean hard surfaces to provide breeding substrate for resident freshwater fish Mobilise sediment and scour algae to maintain waterbug communities in the dry period by flushing organic matter into the channel to provide food after inundating benches for platypus Provide a mosaic of wetted areas to improve emergent and streamside vegetation on terraces, the channel edge and lower bank Provide minimum velocity to mix and flush pools
Summer/autumn freshes (five to six freshes of 50 ML/day for six days from December to May, west branch)	Provide longitudinal connectivity with water over riffles to allow fish to migrate upstream and fish and platypus to move between pools to breed, feed and find new habitats Submerge woody debris and clean hard surfaces to provide breeding substrate for resident freshwater fish Mobilise sediment and scour algae to maintain waterbug communities in the dry period by flushing organic matter into the channel to provide food after inundating benches for platypus Provide a mosaic of wetted areas to improve emergent and streamside vegetation on terraces, the channel edge and lower bank Provide minimum velocity to mix and flush pools

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

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: 22/01/21