What is Water for the Environment?
As Melbourne’s population has grown, many of its rivers and wetlands have been significantly modified to provide water for communities. In some rivers, up to half of the water that would have naturally flowed in them is diverted each year to provide water for homes, farms and industry.
To address this, Water for the Environment has been set aside in some reservoirs and dams that is then released into rivers and billabongs to improve their health and protect environmental values.
Melbourne Water works with the Victorian Environmental Water Holder (VEWH) to manage and release Environmental Entitlements from reservoirs to improve the health in four of Melbourne’s waterways: Werribee, Maribyrnong, Yarra and Bunyip-Tarago Rivers.
Why is Melbourne Water preparing a Seasonal Watering Proposal?
Melbourne Water develops a Seasonal Watering Proposal according to our statutory obligation under the Water Act 1989. This document assists VEWH to develop the Victorian Seasonal Watering Plan. This annual planning document outlines what environmental water releases will occur in the following year (July to June).
Sometimes the need for environmental water is higher than the water available to use. It’s therefore important to consider where water is most needed and how it can be used most efficiently to achieve the best environmental outcomes.
Water for the Environment delivered in 2023/24
During the past six months the Werribee catchment has experienced below-average rainfall resulting in low seasonal stream flows across all reaches. In accordance with the Seasonal Watering Plan, environmental water was delivered to Pyrites Creek from Merrimu Reservoir (reach 6) to provide a baseflow of 2 ML/d in October through to the end of November. Three spring fresh events (35 ML/d for two days) and one spring high event (70 ML/d for one to two days) were also delivered.
These flows played a crucial role in supporting the growth and recruitment of riparian vegetation. Furthermore, they contributed to flushing silt and scouring biofilms, thereby improving water quality. Importantly, these actions improved habitat and migration opportunities, benefiting native fish, frogs, and waterbugs within the ecosystem.
High inflows into Werribee system storages have resulted in increased passing flows for the lower Werribee River (Wirribi Yaluk). Melton Reservoir has been spilling nearly continuously since August 2023 which has resulted in some flow pulses in the lower Werribee River. These high flows have met some of the environmental watering targets reducing the need to deliver water for the environment.
Summer/autumn freshes are planned into reaches 8 and 9 (lower Werribee River).
Key environmental values supported by Water for the Environment
- native fish, including estuarine black bream
- platypus
- water quality, including dissolved oxygen and salinity
- frogs
- native vegetation (in-stream, streamside and estuary)
- channel and pool habitats
- waterbugs
Opportunities for shared benefits are also incorporated into planning and watering decisions, if they do not compromise environmental outcomes. Planning is currently occurring to undertake a Cultural Values Assessment for the Werribee River with Wadawurrung and Wurundjeri Woi Wurrung Traditional Owners.
Potential Watering Actions
We plan for all climatic scenarios, below are the proposed environmental watering actions for the Werribee River in 2024/25 under an “average” year scenario:
- Spring freshes (reach 6 - Pyrites Creek)
- Spring high flow (reach 6 - Pyrites Creek)
- Winter/spring/summer low flows (reach 6 - Pyrites Creek)
- Summer/autumn freshes (reach 9 - lower Werribee River & estuary)
- Winter/spring freshes (reach 9 - lower Werribee River and estuary)
- Summer/autumn low flows (reach 9 - lower Werribee River and estuary)
Learn more and provide feedback on the 2024/25 Seasonal Watering Proposal
Engagement with Traditional Owners, local communities, management authorities and scientists is integral to understanding both the ecological values of waterways and how water for the environment can also provide a range of shared benefits including cultural, recreational and economic.
You are also invited to attend an online information session 11.00am-12.30pm on Wednesday 31st January. Register your attendance here.
Provide your feedback via a three question survey
If you would like a copy of the Melbourne Water Seasonal Watering proposal or would like to contribute to its development, please contact us at: EnvironmentalWater@melbournewater.com.au
I acknowledge the Traditional Owners of country throughout Victoria and Australia and pay my respects to them, their culture and their Elders past, present and future. Melbourne Water and its partners recognise the intersection between environmental flow objectives and Aboriginal cultural outcomes. We acknowledge the benefit of genuine, enduring partnerships with Aboriginal people in planning and managing water for the environment.
Platypus photo credit Doug Gimesy