ENVIRONMENTAL WATER IN THE UPPER BARWON TAKES A DETOUR

Corangamite CMA manages an environmental water entitlement from the West Barwon Reservoir, receiving 3.8% of inflows (approximately 1,000ML/yr).  This water is released into both the East and West Branches of the Barwon River to improve waterway health, including water quality, in-stream habitat and riparian vegetation.   

In October 2025, flood modelling showed that releasing environmental water through the river’s natural channels could contribute to flooding on multiple private properties on both the East and the West branch of the Upper Barwon.  For releases of environmental water to continue in these areas, Corangamite CMA need to gain permission from affected property owners.  As this consultation process takes time, it was unlikely to be completed in time for the 2025/26 dry season (December to May).   

After assessing several options with Barwon Water and the Victorian Environmental Water Holder, a preferred solution was identified using existing infrastructure to bypass properties where river flow is restricted willow infestations, invasive grasses and historic changes to the river channel.   The chosen option uses the Barwon-Colac transfer system (Gerangamete pipeline) and Wurdee Boluc Inlet Channel to deliver environmental water to the East branch downstream of Callahans Creek and upstream of the East and West branch confluence.   This pipeline is normally used to transfer water from West Barwon Reservoir to Colac when local water storages are low.  

While a suitable alternative release point could not be found for the West Branch, the new arrangement has successfully delivered environmental water to the East Branch and downstream reaches of the river, including areas around Birregurra that can stop flowing during dry periods. 

Corangamite CMA will continue talking with landholders along the East and West branches of the Upper Barwon River about the flood mapping results. Feedback from landholders, along with assessments of river and floodplain environmental values, will help identify future options to improve environmental water delivery and river health in the Upper Barwon.

HIGHLIGHTS FROM THE 2025/26 WATER YEAR 

• The scour point on the Gerangamete pipeline was used to deliver environmental water to the east branch for 35 days over the dry season.  
• A total of 111 megalitres of environmental water was delivered from West Barwon Reservoir.   
• Barwon Water and Corangamite CMA staff worked collaboratively throughout the delivery period.  
• Corangamite CMA was able to maintain a good relationship with the landholder who owned the property alongside where the scour point was located and landholders downstream of the scour point.  
• Feedback from a landholder with property downstream of the confluence of the East and West branch suggested that expected cease to flow conditions during a particularly dry period was averted mainly due to releases of environmental flow.

If you would like more information on Water for the Environment, please contact Rose Jackson on rose.jackson@ccma.vic.gov.au or 0459 835 628

Or visit our web page: Upper Barwon River - Corangamite Catchment Management Authority