February 04, 2014 |
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Scientists Fear Long California Drought

Being billed as the driest period in the state's recorded rainfall history

California's drought is being billed as the driest period in the state's recorded rainfall history. But scientists who study the West's long-term climate patterns say the state has been parched for much longer stretches before that 163-year period began.

And they worry that the "megadroughts" typical of California's early history could return.

Through studies of tree rings, sediment and other natural evidence, researchers have documented multiple droughts in California that lasted 10 or 20 years during the past 1,000 years "” compared to the mere three-year duration of this dry spell. The two most severe megadroughts make the Dust Bowl of the 1930s look tame: a 240-year-long drought that started in 850 and, 50 years after the conclusion of that one, another that lasted at least 180 years.

"We continue to run California as if the longest drought we are ever going to encounter is about seven years," said Scott Stine, a professor of geography and environmental studies at California State University. "We're living in a dream world."

California in 2013 received less rain than in any year since it became a state in 1850. At least one Bay Area scientist says that based on tree-ring data, this rainfall season is on pace to be the driest since 1580 "” more than 150 years before George Washington was born. The question is: How much longer will it last?

A megadrought today would have catastrophic effects.

California, the nation's most populous state with 38 million residents, has built a nation-sized economy: Silicon Valley, Hollywood and millions of acres of farmland, all in a semi-arid area. The state's dams, canals and reservoirs have never been tested by the kind of prolonged drought that experts say will almost certainly occur again.

Stine, who has spent decades studying tree stumps in Mono Lake, Tenaya Lake, the Walker River and other parts of the Sierra Nevada, said the past century has been among the wettest of the last 7,000 years.

Looking back, the long-term record shows some staggeringly wet periods, too. The decades between the two medieval megadroughts, for example, delivered years of above-normal rainfall "” the kind that would cause devastating floods today.

The longest droughts of the 20th century, what Californians think of as severe, occurred from 1987 to 1992 and from 1928 to 1934. Both, Stine said, are minor compared to the ancient droughts of 850 to 1090 and 1140 to 1320.

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