Bonacci Water
27 October, 2008
It’s still raining in Melbourne!

Melbourne’s future water supplies and the lack of rain in the area continue to be topics of lengthy discussions in the media.

Dr Peter Coombes, director of Bonacci Water, has spent many hours researching these topics and has found that the current rainfall sequences vary widely across Melbourne and in a number of regions are in fact NOT the worst on record. At most locations in Melbourne, current rainfalls are consistent with the long term cycles of natural variation in rainfall. Research shows that at all locations in Melbourne, there are sufficient depths of annual rainfall, even during low rainfall years, for rainwater tanks to provide significant yields. Figure 1 shows the annual rainfall (mm/yr) for the greater Melbourne region. Figures 2, 3 and 4 show the rainwater yield/water demand (kl/yr) and rainfall (mm/yr) for the Melton, Geelong and Yarra Ranges areas respectively.

Rainwater tanks have also featured extensively in the media in recent months. In an article published in The Age on 27 August 08, Peter discussed opportunities for Melbourne’s households to partner with authorities in managing our water future. He stated that ‘rainwater tanks benefit society in many ways. For a start, they reduce dependence on water supply from centralised sources (such as dams and inland rivers) and assist with the management of stormwater run-off.’ It is important to note that rainwater tanks alone won’t solve the water crisis, but as part of a water-wise strategy, rainwater tanks help to reduce our reliance on tap water.

Peter also stated ‘our water future involves a far greater range of challenges, all of which require greater understanding of detail. We need to move away from the natural human response to generalise a problem that is perceived to be too complex. We need to embrace this complexity in order to fully understand the opportunity and find better solutions. There is a role for everyone — the state, citizens and the water monopolies. Similarly there is a need for a wide range of water solutions — from rainwater tanks to dams.’

Research indicates that rainwater tanks can provide a reasonably consistent level of service that will supplement demands for mains water. Rainwater tanks have potential to supplement demands for water supplies and to manage urban stormwater runoff. The benefits of rainwater tanks apply at different scales, to householders, various agencies and the environment. Figure 5 shows the rainwater yield (kl/yr) across the greater Melbourne area based on 50m2 roof with a 5k rainwater tank. Conversely, Figure 6 shows the reduction of property stormwater runoff (%) across the greater Melbourne area based on 50m2 roof with a 5k rainwater tank.

For more information about rainfall statistics, the use of rainwater tanks or any other water related issues, please contact Dr. Peter Coombes on 03 9418 4000 or pcoombes@bonacciwater.com