The rapid march of climate change across Australia's main food-growing region has caught the country by surprise and will reshape farming across an area bigger than France and Germany, says the top water official. "I think we've been caught unawares," Murray-Darling Basin Commission Chief Executive Wendy Craik told Reuters, glancing out at the unusually hot spring weather baking much of the continent's southeast, where many Australians live. "It's happened very suddenly. It's right outside any of our experience over 117 years of records, and this year is proving to be not so good either," said Craik, who faces a Herculean task of allocating dam water levels now at historic lows. Craik manages river flows and dam storages across a vast plain that is home to 2 million people and half the nation's farms, watered by the Murray and Darling rivers and producing $17 billion (US$13.2 billion) worth of food exports for Asia and the Middle East. But a decade of drought increasingly blamed on climate change is shrinking rivers and threatening fruit and vegetable production on sprawling semi-arid fields, which Craik says have relied on half-a-century of irrigation to thrive. Water in the past came from the massive Snowy Mountains Scheme, a chain of alpine dams and underground pipes built after World War Two to hold and divert snow-melt from east to the western Murray-Darling. But irrigation is now threatened by what scientists say is the "accelerated climate change" already occurring in Australia and bringing more frequent storms, droughts and estimated average temperature rises of between 1.4 to 5.8 degrees Celsius by 2100. KEEPING THE WATER FLOWING Wheat growers hope recent rains will still bring them through this year with a bumper crop. But fruit, rice, cotton and dairy farmers face savage cuts to irrigation licence entitlements by authorities across four basin states, advised by Craik. "We do actually have a step-change in inflows into the system," says the former biology and fisheries scientist, now one of Australia's most influential bureaucrats. "Most of the dams and weirs were built during the second half of the last century. Most of the irrigation entitlements were handed out then, when it was relatively wetter. We've set our system up for times when it was more benign," Craik says. Even in good times, only 12 percent of rainfall runs into rivers or soaks into the ground in the world's driest populated continent, with the rest lost to evaporation. That leaves Australia with just 1 percent of water carried by the world's rivers, despite having 5 percent of total land area and only 21 million people. Modelling released by Treasurer Wayne Swan on Friday forecast the nation's population would more than double to about 45 million by the end of the century. The centre-left government has allocated A$10 billion (US$7.8 billion) to improve water infrastructure, buy back water licences handed out too freely to farmers over many years and begin a bruising arm-wrestle with states over control of scarce water resources. Basin farmers, Craik says, will have to cope using water-saving drip irrigation and drought-resistant crops, pointing to grape growers who produced a near-record 1.83 million tonne-crop this year despite the current drought. "I think the halcyon days are over. But improved efficiencies and improved technologies will go a long way," she says. But growers have also begun to move beyond the basin, which has traditionally grown 70 percent of irrigated crops. Parts of northern Australia, for example, receive large amounts of monsoon rain, some of which is captured in large dams, such as the Ord River Irrigation Scheme in northern Western Australia state. "I suspect we will increasingly see more grown in parts of northern Australia, and other areas. The basin now accounts for only 45 percent of irrigated cropping by value, down from 70. It's already starting to reduce," Craik says. (US$1 = A$1.27) (Editing by David Fogarty)