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Tree rings tell history of extreme droughts in Western U.S.

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While U.S. authorities are concerned about the severity of recent drought afflicting the western part of the country, researchers have found evidence that the worst is yet to come. Analysis of tree rings in the Rocky Mountains shows that the region suffered from "nightmare droughts" sometime in the past.

The tree ring study was conducted by researchers from the Brigham Young University (BYU) and according to their findings, the U.S. may experience even worse droughts in the coming years. The study shows that even the worst drought that occurred in the last one hundred years has barely made it to the list of the worst droughts that have ever occurred in the Western U.S. The researchers published their findings in the Journal of the American Water Resources Association.

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 Matthew Bekker, BYU professor of geography. "We would really have to change the way we do things here."

The analysis of the tree rings helped the researchers create a climate record for the state of Utah that dates back to 1429. To conduct the study, the research team went around the Rocky Mountains gathering samples from the older trees in the area. In particular, the team focused on a specific type of tree that is known to be sensitive to droughts. Based on their findings, the team was able to construct three worst case scenarios that have occurred in the past and may occur again in the future.

The first scenario involves a type of drought that lasts over an extended period of time. The team found evidence that such a scenario happened in the year 1703 where a 16-year drought was thought to have occurred. The second scenario involves droughts that are uncommonly intense or severe. A drought that occurred back in the year 1580 was said to have depleted the Weber River reducing its flow to a mere 13 percent compared to normal.

The last scenario also happens to be the worst of the three: severe droughts occurring consecutively. Evidence of such as scenario occurring clearly indicated in the tree rings in the Rocky Mountains. The team found that four out of the five worst droughts to ever have occurred in the region happened over the course of a single lifetime. The consecutive droughts started in the year 1492 and all four happened during the lifetime of famed explored Christopher Columbus.

"We're trying to work with water managers to show the different flavors of droughts this region has had," Bekker said. "These are scenarios you need to build into your models to know how to plan for the future."

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