The rainfall across the central region varied between systems in 2021-22. Rainfall in the Tarago, Upper Barwon and Moorabool systems was close to the long-term average, while the Yarra, Werribee and Maribyrnong systems had above- average rainfall. This is the second consecutive year of average or above-average rainfall in the central region, and some reservoirs in all systems other than the Maribyrnong spilled during 2021-22. These spills and other natural inflows met many planned environmental flows in the Tarago, Yarra, Werribee, Moorabool and Upper Barwon systems and some planned watering actions in lower Jacksons Creek in the Maribyrnong system. The VEWH purchased water from licence holders in the Maribyrnong system to deliver environmental flows in Jacksons Creek.
The Bureau of Meteorology has forecast above-median rainfall and temperatures during autumn, winter and spring 2022 across the central region. With full or near-full storages in most systems from 2021-22 and a wet outlook for the start of 2022- 23, most systems are likely to have significant water holdings. Large carryover volumes and secure water allocations will allow a wide range of watering actions to be delivered in the Yarra, Tarago and Werribee systems under all climate scenarios to build on environmental outcomes achieved over the last two years.
Further inflows to Rosslynne Reservoir in winter and spring 2022 are likely to create an opportunity to purchase water to deliver environmental flows in the Maribyrnong system, although outcomes in upper Jacksons Creek continue to be limited by infrastructure delivery constraints.
Options for delivering water for the environment in the Moorabool and Barwon systems in 2022-23 will be heavily influenced by local climatic conditions due to their smaller and more variable environmental allocations. Larger flows in the Moorabool and upper Barwon systems rely on significant contributions from local rainfall and are therefore only likely to be achieved under average or wet climatic conditions. Natural inflows will also have a significant bearing on low flows and freshes in
the Moorabool and upper Barwon systems, and summer and autumn flows may need to be delivered at the lower end of their recommended range to conserve available environmental supply if those seasons are dry. Delivery of water for the
environment in the lower Barwon wetlands is not affected by annual allocations of water for the environment, and the proposed fill in winter/spring and partial drawdown in summer/autumn should be possible under all climate scenarios if river levels allow.