Australia will need several years of heavy rainfall to reverse the devastating effects of a drought that has battered farm production, the Bureau of Meteorology said in a report received Monday.

The report came despite months of drenching rains spawned by the La Nina weather phenomenon in the agricultural east of the country that sparked optimism that the worst drought in 100 years might at last be over.

But the Bureau's latest findings show that the "big dry," nearly a decade of below-average rainfall and high temperatures, is stubbornly lingering across much of the continent and the rain needed to end it is not in sight.

"Several years of above average rainfall are required to remove the very long-term deficits," the May report said, adding that long-term rainfall deficiencies have increased in most areas over the past two years.

"The combination of record heat and widespread drought during the past five to 10 years over large parts of southern and eastern Australia is without historical precedent and is, at least partly, a result of climate change," it added.

Drought slashed 10 percent from the value of Australia's agricultural production in 2006-07, according to official figures, and has devastated many rural communities as farmers and local businesses were starved of rain.

The latest La Nina -- in which the eastern Pacific Ocean cooled, bringing rainfall to the driest continent on earth -- was heralded by some experts last year as a drought-breaker.

But the heavy rains only benefited parts of the country and now appear to have run their course, according to Lynette Bettio, a climatologist with the bureau's National Climate Centre.

"It does seem to be over ... it's winding down," she said, adding that La Nina had only helped end the drought in some areas of the vast nation, leaving southern agricultural lands largely dry.

"We really didn't receive that above average rainfall needed," Bettio said.

The Bureau of Meteorology said long-term rainfall deficiencies persisted from the coast of South Australia across much of the southern states of Victoria and into New South Wales, and also covered parts of northeastern Queensland state and northern South Australia.