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Melbourne’s desalination plant is just one part of drought-proofing water supply

One of Melbourne’s drinking water reservoirs at 30% capacity in 2010. At the time of writing, the dam is 60% full. Melbourne Water/Flickr, CC BY-NC-ND

Melbourne’s desalination plant is just one part of drought-proofing water supply

Water has now been ordered from the Victorian desalination plant. The plant was built at the end of the millennium drought to provide security against drought. But once built, it then rained and rained.

Since then many have seen the desalination plant as a white elephant – an unnecessary expense that has burdened Victoria with debt. Indeed, it seems to have been demonised as something evil.

However, with dry weather over the past two years, water storages have begun to decline, both in Melbourne and particularly in regional Victoria. The desalination plant was built to be used in times of water shortages, and the Victorian government has now deemed it time to order water.

The order is being made to reduce the possibility of water restrictions in Melbourne and to negate the need for Melbourne to take water from the Goulburn system and so allow more water to be made available to localities such as Bendigo and Ballarat.

The cost of drought

Desalination membranes at Melbourne’s desalination plant. Stephen Greay

It has now been six years since the millennium drought ended and it can be hard for city residents to remember the impact of drought on their lives.

To give one example, we conducted a study on the social impact of water restrictions on sportsgrounds during the drought. This study found that 70% of people used sports grounds, either for organised sport or informal relaxation, and that all users were adversely affected by the drought.

The most severely affected were those at women’s, disabled and junior sporting clubs, which were of low priority for irrigation. These groups were forced either to cancel their activities because of the hard playing surfaces or to reschedule their events and find other locations to play their sport. This became a major disruption to the lives of many people during the 13-year drought.

This was just one way that water restrictions and drought affected our lives. When water storage levels were etched in our minds through public billboards and television weather reports, neighbours were asked to report people who used water contrary to the restrictions, car washes became a growth industry, and communities were parched and brown. I am now enjoying my garden, which has sprung to life in recent years, and will be happy if we can avoid such water restrictions again.

For regional Victorians the impact of drought was greater. For them, the reminders of drought are already to the fore following several dry seasons. Parts of Victoria have received less than 50% of average annual rainfall for the past two years. Farmers are reducing the number of cattle on the land.

Water from the desalination plant will be delivered to regional Victoria via the state’s rivers and pipe networks that make up the water grid.

Alternatives?

Some may argue that other sources of water such as dams, storm water harvesting and water recycling would have been better alternatives. However, all require significant investment and none are likely to be fully utilised during wetter periods. This has been one criticism of desalination, but is simply an outcome of reducing risk in a variable climate.

Storm water harvesting is often promoted as being a cheaper alternative to desalination, but a recent water industry article on the cost of such harvesting has estimated costs of A$10-25 per kilolitre (1,000 litres) when used as a substitute for drinking water. This compares to costs of A$2-3 per kL for desalinated water. Turning the desalination plant on adds up to an extra A$12 a year on Victorian water bills.

Perhaps one alternative that is worth considering is recycling waste water for drinking water supplies. This is currently against Victorian government policy, which the two major parties support.

Victoria uses recycled water for irrigation, in toilets and clothes washing, but such schemes require homes to receive water through a second pipe. These second-pipe systems are more costly to build and manage.

Recycling water for drinking avoids these costs, as you simply use the same pipe that supplies water from dams. The technology to recycle water for drinking is also well established and can be delivered to existing homes.

Given Melbourne has access to desalinated water that we are only just starting to use, it is unlikely Melbourne will need to consider recycling water for drinking in the near future. However, regional communities may like to have this option, and I believe this option should be allowed.

Australia’s rainfall patterns are among the most variable in the world, and prolonged periods of dry weather are normal. However, climate change predictions indicate longer, more severe periods of dry weather.

Indeed, one of my climate change colleague has suggested that climate change does not occur in a constant, slow progression, but rather through step changes. If this is the case, then the next drought will be more severe and the need for climate-independent water supplies more pressing.

Faced with this scenario, the desalination plant is a good investment and we should use it when it is needed.