Significant water events
During the 2011–12 year rainfall across the Melbourne region was generally above-average and, in parts of the southern area of the Melbourne region, rainfall was the very much above average (see Climate overview). As a result, streamflows in two of the major rivers significantly exceeded the long-term mean annual flow (see below). Above-average rainfall also translated into significant runoff into Melbourne's surface water storages, and the average storage volume was above 85% of total storage capacity at the end of 2011–12 year (refer to the Water resources and systems Surface water note for more information). Similar wet conditions were recorded across the state of Victoria, allowing continued recovery of storage volumes in the Thomson Reservoir following a prolonged period of drought.
In addition to the improvement observed in Melbourne's storage volumes, the prevailing wet conditions resulted in high allocations of surface water resources in the Melbourne region (see line item 21.1 Surface water allocation announcements) and the qualification of rights to water (see discussion below).
Rights may be suspended, reduced, increased or otherwise altered after a water shortage has been declared under section 33AAA(2) of Victoria's Water Act 1989. There were no qualification of rights in the Melbourne region during the 2011–12 year, likely the consequence of continued wet conditions and recovery of storage levels.
More information on qualification of rights is available on the water.vic.gov.au website.
During the 2011–12 year, annual flow in the Yarra and Bunyip rivers was well above the mean annual flow (Table W1). In contrast, annual flow in the Werribee and Maribyrnong rivers was well below the mean annual flow.
|River||Period of record||Mean annual flow (ML)||2011–12 flow (ML)||2011–12 as % of mean annual flow|
Figures W1, W2, W3 and W4 show the total monthly flows for the Yarra, Bunyip, Maribyrnong and Werribee rivers respectively.
Figure W1 Chart of monthly flow for the Yarra River compared to long-term values for the region
Figure W2 Chart of monthly flow for the Bunyip River compared to long-term values for the region
Figure W3 Chart of monthly flow for the Maribyrnong River compared to long-term values for the region
Figure W4 Chart of monthly flow for the Werribee River compared to long-term values for the region
Major water initiatives
Major projects relating to water supply augmentation in the region include the Wonthaggi desalination plant and the Melbourne to Geelong pipeline. The Melbourne-Geelong pipeline is being built to enable the transfer of water from the Melbourne system, including Thomson and desalination sources, to Geelong. The pipeline is scheduled to begin operation in the 2012–13 year, with Barwon Water entitled to take 16,000 ML/year.
Construction of the Wonthaggi desalination plant continued throughout the 2011–12 year. Upon completion it will be operated by a private consortium and will supply water to the Melbourne region. The plant is scheduled to produce up to 150 GL/year. The project will be delivered through a public-private partnership with the AquaSure consortium. Once operational, Degrémont Thiess Services will be responsible for the operation and maintenance of the plant and pipeline to July 2039.