A desalination plant to provide water for Adelaide is “inevitable”, SA Premier Mike Rann told parliament today.

Based on interim reports from an advisory desalination working group, the government’s preference is to build a 50 gigalitre desalination plant and expand the Mt Bold Reservoir, the premier said in a press statement.

The two projects could cost more than $2.5 billion, Rann said. Cabinet will make a final decision in November, after the working group submits its final report. The desalination plant would supply about 25% of Adelaide’s water, Rann said. It would take five years and cost more than $1.4 billion to build, and would be located on a site that would allow it to eventually be doubled in size.

Greens MLC Mark Parnell said desalination should be “last choice technology”. If the plant goes ahead, it should be powered by 100% new renewable energy, he said.

Meanwhile, WA Premier Alan Carpenter today said the Water Corporation would begin advertising for the supply of 200 gigawatt hours (GWh) a year of renewable energy to power the Binningup desalination plant.

Up to 40GWh of this could be supplied through technologies not yet commercially proven, such as wave power and geothermal energy, rather than through already proven technologies such as wind farms. Binningup, the state’s second desalination plant, is expected to be up and running in 2011.