Environmental water release for the yarra River
Melbourne Water will deliver a spring fresh environmental water release to the upper reaches of the Yarra River over the next three weeks to freshen up water quality and scour sediments from the river bed after a dry winter.
Up to 6 billion litres of water will be released from Upper Yarra and O’Shannassy reservoirs in late September and early October 2015. Water harvest will be halted in some tributaries at this time to maximise flows.
This environmental water release is designed to flush fine sediment and organic material from the river bed, maintain habitat for bugs and fish life, and support native vegetation.
What are the benefits of this release?
Following the successful recruitment of Australian grayling and Macquarie perch in the river in recent years, the focus of the 2015/16 environmental flows program is protecting the populations of native fish species in the Yarra.
This spring fresh is considered important for scouring sediments and biofilms from the river bed that have accumulated over the recent winter which has been characterised by lower than normal flows. This is important to maintaining key fish habitat in the lead up to summer. This flow will also allow for localised fish movements into habitat that may have been inaccessible during low flow periods.
Species that are expected to benefit from the increased environmental flows include the regionally significant River Blackfish, Australian grayling and Platypus.
Will the releases cause any changes in the surrounding environment?
During this release, river levels in the target area may be up to 10-40 cm higher, which is within the river’s usual level of variance. Detailed planning and close monitoring of water levels during the release period will ensure flooding and erosion do not occur.
Melbourne Water is working with the Victorian Environmental Water Holder (VEWH) and other stakeholders in relation to this release. We will also monitor the response of the river and aquatic life closely following the event to inform future releases.
The VEWH prioritised this water release as part of its Seasonal Watering Plan 2015-16, which aims to improve river and wetland health across the State.