Barwon Water releases passing flow 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. When the reservoir holds more than 40,000 ML, all the natural flow is passed down the east branch between January and March. Flood spills from the reservoir and natural inflows from unregulated and regulated tributaries add to the passing flow in the west branch. Regulated and unregulated tributaries add to the passing flow in the east branch.
The Upper Barwon River Environmental Entitlement 2018 enables water for the environment to be made available 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 River in 2018-19. The current entitlement provides only enough water to meet the highest-potential environmental watering actions in the upper Barwon east branch (reach 4) and the upper Barwon west branch (reach 3) under particular climatic conditions.
Proportion of water entitlements in the Upper Barwon River held by private users, water corporations and environmental water holders on 30 June 2020