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Study says Sierra Nevada snowpack lowest in 500 years

Mt. Whitney, as seen from HWY 395 on the eastern side of the Sierra Nevada mountain range in California.
Florence Low / California Department of Water Resources
Mt. Whitney, as seen from HWY 395 on the eastern side of the Sierra Nevada mountain range in California.

The snowpack in the Sierra Nevada mountain range is the lowest it's been in 500 years, according to a report from researchers at the University of Arizona.

"We should be prepared for this type of snow drought to occur much more frequently because of rising temperatures," said Valerie Trouet, an associate professor of dendrochronology at the school's Laboratory of Tree-Ring Research, in a statement from the university. "Anthropogenic warming is making the drought more severe."

Trouet points to a combination of record-high temperatures and unusually low winter precipitation in January, February and March as factors leading to the low snowpack, adding that the state witnesses roughly 80 percent of its precipitation in the winter months. 

Snowpack levels are typically tallied at the beginning of April, when the snowpack is supposed be highest. April 1, however, is when Gov. Jerry Brown declared mandatory water restrictions for the state while he was in the Sierra Nevada standing on dry ground -- the historical average snowpack there at that time is usually five feet.

Winters that yield less snow means there's even less water for the state to use during summer, as melting snow is supposed to restock the state's reservoirs and aqueducts. With the low snowpack researchers are examining long-term consequences.

"This has implications not only for urban water use, but also for wildfires," said Soumaya Belmecheri, one of the report's authors.

The university says its research is the first of its kind to compare the 2015 snowpack with levels across five centuries. This was accomplished by examining tree-ring data that showed annual winter precipitation in central California from 1405 to 2005 along with yearly snowpack measurements dating back to the 1930s, the university says.

Next up for the researchers is looking into and even recreating the atmospheric circulation patterns that impact to the California drought and the Sierra Nevada snowpack, Trouet says in the release.