Praying for stormy weather

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An Australian town is turning to stormwater harvesting to augment its potable water supply. It could be the shape of things to come.

The inland city of Orange in New South Wales is looking to become the first in Australia to augment potable water supplies through a stormwater harvesting scheme.

The city council currently provides 11,000m3/d of potable water to its 15,600 properties from two dams, but could source a significant proportion of its future supply from stormwater. John Boyd, acting director for technical services in the city of Orange, told GWI that “the council hopes that in an average year, stormwater harvesting will supply up to 2,000 megalitres [5,500m3/d] of water”.

The first component of the scheme is the construction of a weir and a new 200,000m3 dam. Funded on an equal share basis by the NSW government and the Orange City Council, the contracts for this AUD5 million (USD4 million) part of the project were awarded to JK Williams earlier this month. Contracts for the supply of pipes, pumps and power have also been awarded, and the project is expected to be operational by March 2009, in time to catch the winter rains.

Although there are other stormwater harvesting projects in Australia, including large-scale systems currently being installed in Adelaide and Melbourne, water from these schemes is intended only for use in parks and non-domestic environments.

The Orange scheme will harvest water from around the city, then treat it and supply it as drinking water to the local population of 40,000.

One of the key reasons stormwater harvesting is possible in Orange is the high level of treatment provided by council’s state-of-the-art filtration plant, which was installed in 2005. The latest stormwater initiative has attracted substantial interest from other regional councils, who are watching the outcome closely.

Community support for the scheme has been strong, with city residents keen to see the council proceed as quickly as possible. There have, however, been protests from farmers and irrigators downstream, who expressed concerned that they might receive less water as a result of the harvesting. Their fears seem to be unfounded.

“We expect to harvest about 10% of all the runoff,” Boyd told us. “We’ll set up some gross pollutant traps to remove litter and sediment-type pollutants, trap the water and transfer it into storage to allow settlement. Then we’ll put it into our main dams, where it will be treated as part of the normal water supply.”