The billabongs on the Birrarung (Yarra) River floodplains are an integral part of a complex and functioning ecosystem, that through river regulation and pressures of a growing capital city, often do not receive enough water to meet critical ecological needs.
Billabongs are bodies of water formed when a river changes course or after floodwaters go down. The Annulus Billabong on the Birrarung has immense environmental value for the plants and animals that depend on it and is a site of cultural significance for the Wurundjeri Woi-Wurrung people.
The nearby area is also highly valued for recreation including walking and cycling.
In 2021, the Annulus Billabong received a helping hand from water for the environment held by the VEWH as part of the Yarra Environmental Entitlement to support the plants and animals that call it home. The water was delivered to take advantage of high natural flows and to capitalise on the benefits of a 2020 environmental watering.
Image: Annulus Billabong - Birrarung (Yarra) River, by Melbourne Water
Melbourne Water as the waterway manager for the Birrarung River built on information gained from environmental watering the previous year which recommended a follow-up delivery of water for the environment.
The watering aim was to suppress weeds, encourage the growth of native vegetation while stopping the growth of terrestrial species in the billabong, and build a better understanding of the billabong’s watering needs going forward.
Timing the watering to coincide with higher natural flows was a bonus to lift the fill level to where it would likely be in natural flood conditions prior to urbanisation and river regulation - the last time the billabong was full was 2011.
Monitoring during and after the 2021 environmental water delivery was undertaken by Melbourne University and the Wurundjeri Woi Wurrung Cultural Heritage Corporation’s Narrap team, observing exciting results. Watering led to a swift response through an abundance of frogs, ducks and swamp wallabies. Further monitoring in summer as the billabong began to naturally dry showed there was a strong positive response from native vegetation and weed suppression.
These watering events have given the Narrap team and Melbourne Water a great opportunity to see what happens when the Annulus Billabong is filled, and will be important to help determine its watering and management needs into the future.
Image: Djirri Djirri womens dance group at Annulus Billabong celebration event, by Melbourne Water