Heaven sent

There's an alternate water resource for a city like Melbourne, but at the moment it is literally going down the drain. Harvesting urban stormwater is a bold idea being developed by a multidisciplinary team at Monash University.

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The world is undergoing the largest wave of urban growth in history.

According to the United Nations Population Fund more than half the world's population now lives in towns and cities. In Australia this boom in city living has coincided with what may be the worst drought in 100 years. Communities are experiencing critical water shortages, along with increased flooding, higher temperatures and the degradation of waterways.

Staff in a Monash-led research project believe the time is right to put a bold idea on the table that could produce 20 to 30 per cent of Melbourne's future water needs, potentially eliminating the need for further expansion of the $4 billion Wonthaggi desalination plant as Melbourne's population grows.

Every year almost as much stormwater falls on Melbourne as its citizens use, but only a fraction is captured and reused. Billions of litres of stormwater literally goes down the drain and into Port Phillip Bay, degrading the ecological health of Melbourne streams and the bay.

The Water Sensitive Cities project aims to harness stormwater to overcome water shortages, reduce urban temperatures and improve the landscape and liveability of Australian cities.

"Our cities must become resilient to the climate and social pressures that confront them. We must find new, more integrated solutions that can address the problems thrown up by climate change and population growth," says Professor Ana Deletic from the Department of Civil Engineering.

Serious investment by government and business is required to capture the water, clean it and recycle it for the city's non-drinking water uses. The Monash group believes the time for large-scale stormwater harvesting has come.

"If Melbourne keeps growing, then in 25 years time we will need another desalination plant. Stormwater is cheap for non-drinking uses. If we started to build the infrastructure to capture it, we could have a viable alternative source of water," Professor Deletic says.

The multidisciplinary Monash team comprises researchers from four Monash faculties - Engineering, Arts, Science, and Business and Economics - as well as research groups from urban design company EDAW Australia Ltd, the University of Queensland and the University of Melbourne. The project leader is Tony Wong, a director of EDAW and an honorary professor at Monash.

There are different models, but most involve the capture of stormwater in neighbourhood parks and creeks, letting nature clean it through bio-filtration, then its reuse in toilets, for washing and on gardens. The stormwater treatment systems would also help cool our increasingly hot cities and protect the health of urban waterways.

"When we get the chance to build this new infrastructure, we should take it up. Urban renewal areas could be recycling water into their apartments. Big shopping centres could be capturing water off the roof for toilets and cooling."

In Tel Aviv, Israel, the team has been building a bio-filtration scheme where stormwater is channelled into a natural aquifer where impurities settle out before it is pumped up for reuse. Associate Professor Rebekah Brown, from the School of Geography and Environmental Science, says the biggest impediment is what she calls "institutional".

"Conventional approaches to water supply and urban design are not directed at building a diversity of water sources. There are many levels of social and institutional resistance to change. Our team is developing new governance and policy processes to make stormwater harvesting practical to adopt," Professor Brown said.

Every year almost as much water falls on Melbourne as its citizens use, but only a fraction is captured and reused.

"Just as important as proving the technology is convincing government and the public that this is a practical and achievable idea. There are many positives - flood mitigation benefits, lowering the temperature of cities and healthier waterways, but we need to educate the community about the benefits of the idea."

At Syndal South Primary School (pictured left) in Melbourne's east the theory is being put into practice. Stormwater from the schoolyard as well as the roof is gravity filtered through novel filtration technology before being captured in large underground tanks. The cleaned water is then pumped up to header tanks, providing the school with more than one million litres of water for toilet flushing and irrigation of playing fields. The 370 pupil school is expected to cut its use of mains water by two thirds.

The Monash group is actively lobbying all levels of government as well as land developers to back more demonstration projects. At the same time, the researchers are seeking around $15 million from government and industry to complete research on stream ecology, health risks, sustainable technologies, micro climates, climate change, society and institutions and economic evaluation.

Find out more on the Facility for Advancing Water Biofiltration website.