Rainwater Harvesting: Efficient Water Use

Rainwater Harvesting Initiative Has Cut Water Consumption from 370 Litres Per Day in Brisbane to 155 Litre

Los Angeles imports 89% of its water. Every year it spends over $350m (£211m) disposing of the perfectly acceptable rainwater that falls upon it, water valued at between $300-400m. At the same time, it spends $785m importing the water it needs from many miles away, a process that uses the largest amount of electricity in California.

Meanwhile, here in the UK, as the climate warms the likelihood of drought is increasing. If the raised beds in my garden are anything to go by, this is turning out to be a very dry summer already.

A recentWater Resources Management paperby researcher Muhammad Rahiz and Professor Mark New, looked at future drought trends and concluded that "both drought intensity and the spatial extent of droughts in the UK are projected by these climate models to increase into the future". The South East of England is of particular concern.

Perhaps we should be looking to places where drought is a more regular fact of life, for inspiration for how to develop a more resilient relationship with water. Although LA may lack a coherent city-wide strategy for rethinking its water system, it doesn't lack people working on solutions. Andy Lipkis has spent 20 years looking at LA in its wider context as a water catchment.

California is currently suffering an historic drought, the worst for 500 years, which has brought to the fore many of the issues thatTreePeople, the organisation he founded over 40 years ago, has been working on for years. With support for widespread conservation slow to emerge, and growing pressure for energy-intensive desalination plants which can cost up to $4bn a piece as the solution, Lipkis visited Australia to see what lessons could be learnt from the country's recent 12-year drought.

Rather than the linear thinking that underpins LA, Australian cities such as Adelaide have started to think of themselves more as forest ecosystems. When rain falls on a forest, the impact of its fall is broken by the trees. An oak tree with a 100ft canopy can hold more than 57,000 gallons of water just in its rootmat, like a sponge, and more in its leaves which act almost as a floating lake.

Flooding downhill is reduced, water is filtered and aquifers are replenished. Could our cities shift their relationship with rainwater in this direction? Rather than seeing rainfall as a problem, might each downpour be the opportunity to capture and store as much of it as possible?

This was the approach taken in Australia. People were incentivised toharvest and store rainwater, with tanks and cisterns being heavily discounted. As a result, 45% of homes in Adelaide now have rainwater harvesting. In Brisbane, average water use fell from 80 gallons per person per day to 33.

In Sydney, the installation of water cisterns is one of the sustainability changes required in order to get planning consent for changes to existing buildings.

Source: The Guardian

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• Conservation
• Water Utility