But the Department of Environment approval for the Water Corporation Southern Seawater Desalination Project comes with 23 strict conditions to preserve habitat and protect wildlife, including whales, the black cockatoo and western ringtail possum.

The desalination plant, Western Australia’s second, will provide more drinking water for a growing population.

It will also ease pressure on the Gnangara Mound, north of Perth, currently the city’s most important drinking water source.

Water Corporation spokesman Phil Kneebone said: “This is one of the major planks in our ambition to reduce our take form the Gnangara system to a permanently sustainable level.

“For the water supply in general, it means that we will be able to keep up with continuing growth.”

The corporation says the plant in Binningup, near Bunbury, in the state’s south west, will secure WA’s water supply for the next 10 years boosting it by almost 20 per cent.

Construction is expected to start this month with the plant operating from 2011.

Spanish-led consortium, Southern Seawater Alliance, has signed a 25-year contract to build and operate the new plant.

Once complete, it will produce up to 50 gigalitres of drinking water a year with the potential to increase to 100.

Opponents of the scheme at Binningup are disappointed but not surprised by last month’s (June) approval.

Maree Dilly, of the Binningup Desalination Action Group, said: “I guess I’m disappointed that neither the State nor the Federal Ministers for the Environment seemed to accept that a relatively pristine piece of ocean and near ocean land is a suitable place for what is really a fairly dirty industry.”

The government approval conditions include a requirement to preserve and revegetate almost 47 hectares of habitat at the plant site and protect listed orchid species along the pipeline.

They also require exclusion zones during marine construction with a qualified marine mammal observer to watch for any whales or turtles.

If any listed marine species are spotted, work must stop until the species has been out of the zone for at least half an hour.

If any blasting is necessary a marine management plan must be prepared in advance with restrictions applying on when and how it can take place.

Meanwhile, green groups are urging the West Australian government to use renewable energy to power the plant.

Piers Verstegen, director of the Conservation Council of Western Australia, said: “The opportunity is there to make sure that the second desalination plant is genuinely powered by renewable energy so we don’t see another major spike in carbon emissions resulting from our water supply system.”

David Gibbs

Action inspires action. Stay ahead of the curve with sustainability and energy newsletters from edie