CANBERRA: An irrigation farm larger than Singapore and sucking up billions of litres of water each year has been bought by Australia's government to help save one of the country's most vital rivers from a slow death and climate change.

Toorale Station, a cotton farm covering 910 sq km (351 sq miles) in the west of New South Wales state, was sold to the national and state governments for almost US$19 million, one day before it was set to go to auction.

The purchase will allow 20 gigalitres -- equivalent to 20,000 Olympic swimming pools -- to be returned each year to the ailing Darling River, which is one of two streams flowing through the Murray-Darling basin, home to almost half the nation's farms.

"Returning this water to the Darling will begin to turn around the long-term decline of this once great river," Climate Change Minister Penny Wong said on Thursday. The Toorale Station is a historic grazing and cropping property on the junction of the Darling and Warrego Rivers, near Gundabooka National Park and the town of Bourke.

But large irrigation farms, some capable of using more water than contained in Sydney Harbour, are accused of exacerbating a long-running drought that has already wiped more than A$20 billion ($16 billion) from the A$1 trillion economy since 2002. The Murray-Darling basin, an area the size of France and Germany, accounts for 41 percent of Australia's agriculture and provides A$21 billion worth of farm exports to Asia and the Middle East.

Wong, whose centre-left government has begun a A$3 billion buy-back of farm licences to release more water back into rivers, said Toorale would become parkland, but its water alone would not save critically endangered lakes downstream in South Australia state. But Green groups said the purchase would be a huge boost to the parched Murray-Darling.

"It means that the Warrego River in New South Wales will now be running free and it's a significant boost to the Darling system, which of course then boosts the whole system," Australian Greens Senator Rachel Siewert said.

The property, previously owned by the Clyde Agriculture conglomerate, is primarily used for cotton crowing, although Clyde also grows wheat, barley, chickpeas, canola, cottonseed, beef, lamb and mutton in the Bourke area. Clyde is the Australian holding company for the UK based Swire Group. Conservative pro-farm lawmakers said the farm's purchase would be a huge blow to small farming towns that relied on income from big stations to ride out the economic impact of the drought.

"The Bourke community has been gutted by the news one of the nation's major food-producing properties, Toorale Station, will be turned into a national park," said John Cobb, the conservative opposition water security spokesman. The national government has targeted irrigation farmland in northern Queensland state to obtain their water entitlements.

Australia, the world's driest inhabited continent, is feeling an accelerated version of global warming, climate scientists say, leading to extreme droughts and sudden severe storms. Average yearly temperatures are projected to increase by as much as 6 degrees Celsius by 2070.