The Tarago River catchment received above-average rainfall in winter and spring 2020, which delivered significant inflows into the storage. Tarago Reservoir filled and spilled in October 2020, January 2021 and April 2021. The Tarago environmental entitlement received its full allocation — 3,000 ML share of storage — in July 2020, and use throughout the year was replenished by frequent inflows. Opportunistic use of water held under the Tarago Reservoir airspace agreement contributed significantly to planned environmental watering actions. Rainfall also contributed to flows in the Tarago and Bunyip rivers downstream of the reservoir.
Natural inflows and storage spills maintained the recommended low flows in the Tarago River throughout much of 2020-21, and they also delivered five winter/spring freshes and three summer/autumn freshes. Water for the environment was used to deliver an additional winter/spring fresh in September 2020 and one summer/autumn fresh in January 2021.
Water for the environment was managed in line with an average climate scenario throughout 2020-21. All planned potential watering actions were met. Melbourne Water delivered a winter/spring high flow in September using environmental water held under the airspace agreement. This temporary arrangement between the VEWH, the storage manager and other entitlement holders allows the VEWH to save its share of inflows in spare reservoir capacity if its share of storage is full. This can help reserve enough environmental water to provide for some of the higher flow requirements that VEWH would otherwise not have sufficient water for.
The high flow improved water quality downstream of the reservoir and provided opportunities for the upstream migration of juvenile native fish species including Australian grayling, common galaxias and tupong. It is the first time since 2012-13 that water for the environment has been used to deliver a winter/spring high flow in the Tarago River.
Water for the environment was used to deliver a summer/ autumn fresh at the end of January to flush sediment and organic material from the river bed. The fresh coincided with a public holiday, which improved conditions for riverside campers and other visitors. An autumn high flow may be delivered using water for the environment in May 2021 to cue Australian grayling to spawn.
Between 1,500 and 2,000 ML of water for the environment will be carried over in the Tarago system to help meet critical priorities in 2021-22 including summer and autumn freshes and an autumn high flow.