Melbourne Water has adaptively managed environmental water, including delivering flows on behalf of the Victorian Environmental Water Holder in accordance with the Seasonal Watering Plan for water dependent values in the Werribee. 

During 2022/23, 2,248 ML was delivered to the Werribee system. The Werribee River (Wirribi Yaluk) experienced wet conditions with unregulated catchment flows contributing to the achievement of low flow targets throughout the year. The lower Werribee also benefited from enhanced releases through Southern Rural Water’s Bulk Entitlement - 15 ML/d from Melton Reservoir (May to Aug 2023) and 10 ML/d from Werribee Diversion Weir (January to June 2023).

In the Werribee River Middle sub-catchment water for the environment was delivered to Pyrites Creek (Reach 6,) from Merrimu Reservoir. Deliveries comprised two spring/summer freshes and two spring/summer high flow events. These flows maintain channel form, habitat and vegetation, and allow for fish movement between pools.

In the Werribee River Lower sub-catchment (below Melton Reservoir (reaches 8 and 9) and into the estuary) 1308ML water for the environment was delivered to achieve five summer/autumn freshes, and one winter low flow event. Freshes and high flows improve habitat, maintain vegetation and support platypus, fish and frog populations in accordance with the Seasonal Watering Plan. The winter low flow event was delivered during June to trigger the downstream migration of Tupong (a native fish species).