Australian authorities declared a natural disaster over flood-stricken areas on Monday, but rains submerging large swathes of New South Wales state could be a boon for crop exports after a crippling drought, farmers said.

Days of heavy rains in outback New South Wales state over New Year have swollen rivers and left hundreds of rural properties cut off by floodwaters, with more than 1,200 people evacuated.

But farmers said the big wet would mean they were able to plant summer and winter crops in the months ahead, refilling reservoirs and easing a long-running dry that has wiped billions of dollars from agricultural exports.

"If you look at the total...agricultural export income earnings of around A$30 billion ($27 billion), and you think that quite easily this rain could increase that by 10 percent and could in fact increase it by quite a lot more than that, 10 percent would be A$3.2 billion," New South Wales Farmers' Association President Charles Armstrong told state radio.

The damage bill from the flooding is expected to run into millions of dollars in Australia's most powerful state, home to a third of the 21 million population and a A$320 billion economy accounting for a third of national GDP.

State Premier Kristina Keneally toured flood-affected areas of the state's west on Monday and made the natural disaster declaration.

"It will give primary producers, it will give local business and other organisations the opportunity to access longer term funding and support for repair and rebuilding," she said.

An evacuation center has been set up in Coonamble, about 500 kilometers northwest of Sydney, where the Castlereagh River peaked at 5.14 meters, just below the level of flood levees protecting the town.

A rain depression, which started as a powerful cyclone off the west Australia coast and travelled across the outback over Christmas, has flooded dry rivers and turned dust bowl paddocks to mud in the New South Wales state wheat belt.

Farmers say it is the best rain in 10 years in some areas, although not enough to fully replenish irrigation dams.

"There will be an opportunity to perhaps have more irrigated crops and a greater food supply as a result of that than we've had in the last few years," Armstrong said.

The rains have eased concern of a late winter crop planting season in March and April, although meteorologists are still expecting a drier than normal summer in crop growing regions.

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