During the past 500 years, nine droughts in the American West dwarfed the Dust Bowl of the 1930s, reports a new study, while extremely wet years flooded much of the Wasach Front, the region where 80 percent of Utah's population now lives.
The longest of the nine droughts spanned 16 years from 1703 to 1718. The most severe drought struck in 1492, the same year the Christopher Columbus invaded Hispaniola, and lasted until 1500. Seven of the 10 worst droughts occurred in the late 15th and 16th centuries, just as the Spanish conquistadors arrived.
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During the most intense drought, in 1580, the Weber River in Utah dropped to only 13 percent of its normal flow. The Journal of the American Water Resources Association published the study.
The Dust Bowl forced millions of Americans to migrate from failed farms. And yet the West in the 20th century actually enjoyed the most stable climate of the past five centuries.
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"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 lead author environmental geographer Matthew Bekker, of Brigham Young University. "We would really have to change the way we do things here."
Bekker and his team used tree-ring analysis, or dendrochronology, to create a climate report for for the past 576 years in Utah. Thick tree ring bands in cores drilled from Douglas firs and pinyon pines represented wet years. Thin bands resulted from droughts. The dendrochronologists used modern weather, tree ring and river-level records to calibrate their estimates of the past conditions.
Photo: Bekker and his students hike to collect tree ring samples in Utah. Credit: Brigham Young University