Scientific research has extended Utah's climate record back to 1429 using tree rings. Revealing extreme droughts, including one that lasted 16 years.

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Tree rings reveal nightmare droughts in Western U.S.

May 1, 2014

Source:

Brigham Young University

Summary:

Scientists extended Utah's climate record back to 1429 using tree rings. They found Utah's climate has seen extreme droughts, including one that lasted 16 years. If history is repeated in the rapidly growing Western states, the water supply would run out based on current consumption.

Scientists extended Utah's climate record back to 1429 using tree rings. They found Utah's climate has seen extreme droughts, including one that lasted 16 years. Credit: Image courtesy of Brigham Young University
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If you think the 1930s drought that caused The Dust Bowl was rough, new research looking at tree rings in the Rocky Mountains has news for you: Things can get much worse in the West.

In fact the worst drought of this century barely makes the top 10 of a study that extended Utah's climate record back to the year 1429.
With sandpaper and microscopes, Brigham Young University professor Matthew Bekker analyzed rings from drought-sensitive tree species. He found several types of scenarios that could make life uncomfortable in what is now the nation's third-fastest-growing state:

• Long droughts: The year 1703 kicked off 16 years in a row with below average stream flow.
• Intense droughts: The Weber River flowed at just 13 percent of normal in 1580 and dropped below 20 percent in three other periods.
• Consecutive worst-case scenarios: The most severe drought in the record began in 1492, and four of the five worst droughts all happened during Christopher Columbus' lifetime.

"We're conservatively estimating the severity of these droughts that hit before the modern record, and we still see some that are kind of scary if they were to happen again," said Bekker, a geography professor at BYU. "We would really have to change the way we do things here."
Modern climate and stream flow records only go back about 100 years in this part of the country, so scientists like Bekker turn to Mother Nature's own record-keeping to see the bigger picture. For this study, the BYU geographer took sample cores from Douglas fir and pinyon pine trees. The thickness of annual growth rings for these species is especially sensitive to water supply.


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Scientists: Past California droughts have lasted 200 years

MSNBC news

MCT: Aric Crabb, Bay Area News Group

Police officers Eric Baade, left, and Daren Prociw ride across the bed of Folsom Lake.

5 hr ago By Paul Rogers of San Jose Mercury News

Researchers have documented multiple droughts in California that lasted 10 or 20 years in a row during the past 1,000 years.

SAN JOSE, Calif. — California's current 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 historical period began.
And they worry that the "megadroughts" typical of California's earlier history could come again.
Related: California says it won't be able to fill water demand
Through studies of tree rings, sediment and other natural evidence, researchers have documented multiple droughts in California that lasted 10 or 20 years in a row during the past 1,000 years — compared to the mere three-year duration of the current 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 stretched 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 Cal State East Bay. "We're living in a dream world."
California in 2013 received less rain than in any year since it became a state in 1850. And at least one Bay Area scientist says that based on tree ring data, the current 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 massive economy, Silicon Valley, Hollywood and millions of acres of farmland, all in a semiarid 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.
Related: Water war fought underground
Stine, who has spent decades studying tree stumps in Mono Lake, Tenaya Lake, the Walker River and other parts of the Sierra Nevada, said that the past century has been among the wettest of the last 7,000 years.
Looking back, the long-term record also shows some staggeringly wet periods. 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.
What would happen if the current drought continued for another 10 years or more?
Without question, longtime water experts say, farmers would bear the brunt. Cities would suffer but adapt.
The reason: Although many Californians think that population growth is the main driver of water demand statewide, it actually is agriculture. In an average year, farmers use 80 percent of the water consumed by people and businesses — 34 million of 43 million acre-feet diverted from rivers, lakes and groundwater, according to the state Department of Water Resources.
"Cities would be inconvenienced greatly and suffer some. Smaller cities would get it worse, but farmers would take the biggest hit," said Maurice Roos, the department's chief hydrologist. "Cities can always afford to spend a lot of money to buy what water is left."
Roos, who has worked at the department since 1957, said the prospect of megadroughts is another reason to build more storage — both underground and in reservoirs — to catch rain in wet years.
In a megadrought, there would be much less water in the Delta to pump. Farmers' allotments would shrink to nothing. Large reservoirs like Shasta, Oroville and San Luis would eventually go dry after five or more years of little or no rain.
Farmers would fallow millions of acres, letting row crops die first. They'd pump massive amounts of groundwater to keep orchards alive, but eventually those wells would go dry. And although deeper wells could be dug, the costs could exceed the value of their crops. Banks would refuse to loan the farmers money.

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