The future of stormwater - a forgotten resource?
Friday, 24 June, 2011
Why is it that in the world’s driest continent we continue to throw away one of our most abundant water sources that goes right past our doors? Stormwater, we tend to ignore it until it runs through our houses or overflows our streets and then we only see it as a nuisance, but, for a more sustainable future, we need to reacquaint ourselves with the forgotten cousin of the water cycle.
In this country, various agencies have responsibility for the management of stormwater, including local governments, state agencies, water companies and catchment management authorities. The challenge is that each one manages it usually for only one or two issues, that being flooding and, in the last decade or so, for quality. But is this sufficient? While this year’s strong La Nina episode has pushed the last drought out of the current collective consciousness, it was only in 2007 and 2008 that some cities were on the brink of running dry. During that time, some very interesting schemes were proposed such as major wastewater recycling networks, desalination and new dams. However, only in Adelaide was stormwater being actively utilised at a large scale as an alternative water source through their various aquifer storage and recovery schemes. So why isn’t it being used more often and what does stormwater offer us?
Well, obviously, it can be a source of water. Yes, it contains some nasties, so it is probably not going to be easy to make it into drinking water, but there are many uses for non-potable water, such as toilet flushing, watering gardens, landscaping areas, as part of outdoor artworks and aesthetic features, dust suppression and others. We also get it for free; that is, we don’t have to spend lots of money on building and operating infrastructure to produce it, unlike desalinated water or treated wastewater. It still may require treatment but that treatment, through features such as streetscape biofilters, vegetated swales, rain gardens and wetlands, can also form part of the aesthetic of the built environment, indeed it can even be part of the built environment itself. Green roofs, quite common in Europe, America and some parts of Asia, are now being applied in this country along with green walls (basically walls with gardens in them), rainwater tanks in wall cavities, formalised rain gardens and other features and these have been incorporated in more and more new buildings. We even have software that can help us model all of these things (MUSIC and the new Urban Developer products developed by the eWater CRC).
Another important feature of stormwater, when it is integrated into the built environment, is its ability to cool down the urban heat island. Several researchers, especially through groups such as the Centre for Water Sensitive Cities at Monash University, are investigating how stormwater can be managed to assist in this. Other researchers based in Melbourne and Brisbane are also investigating how the integration of various stormwater treatments into buildings and on individual lots can help to reduce the high frequency of stormwater runoff into creeks and streams from urban areas because, while the quality of stormwater can be quite poor (and in some cases worse than raw sewage), the research shows that it is the increase in the frequency and intensity of flows when catchments are urbanised which causes some of the biggest impacts to stream health. This is due to the increased amount of stormwater from all of the hard surfaces (roof areas, roads, car parks, paving, concrete etc) and our efficient ways of delivering it straight to the streams through pipes and culverts.
So what of the future for stormwater? There are two areas that we really need to focus on, namely, our recognition of stormwater as a resource and also to embrace it in our buildings, structures and landscapes so that we can use it to help manage several issues at once. In some of our cities, there are some councils and government agencies that are prepared to encourage this, but for the vast majority, especially in our biggest capital, there continues to be a mire of legislation and planning controls that specifically inhibit more creative ways of using stormwater. This is our biggest hurdle for the future of stormwater, not technology, not science, but good governance and good planning that encourages, rather than discourages, sustainable management of this valuable resource.
*Tony Weber is the National Practice Leader - Water Quality looking after the water quality discipline area across BMT WBM’s Australian operations and has over 22 years’ experience in the water industry. Since joining the company, Tony has worked on a large range of water-sensitive urban design, integrated water management, water quality and stormwater management projects, including WSUD conceptual and detailed design, urban lake management, strategic policy and planning, catchment modelling and water-quality monitoring.
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