Scientists have found that California is now at its driest in 500 years, following four years of drought.
The Sierra Nevada snowpack that is a vital water source for California fell to a 500-year low last winter and is far worse than scientists had estimated, according to new research.
This recent study reiterates another piece of research by scientists from the University of Minnesota and Woods Hole Oceanographic Institution. They arrived at the same conclusion in December 2014. They used the same methodology,(analysis of blue oak tree rings), however, they estimated that the California drought has been the worst in 1,200 years.
Scientists have compared their measurements of tree-ring data to previous Sierra Nevada snowpack level recordings that have been recorded since the 1930’s and found that oak trees’ growth seem to accurately reflect the lowest snowpack seasons.
“We combined an extensive compilation of blue oak tree-ring series that reflects large-scale California winter precipitation anomalies with a California February-March temperature reconstruction in a reconstruction that explains 63 percent of the Sierra Nevada snow water equivalent variance over the instrumental period,” the scientists wrote.
— NOAA NCEI Climate (@NOAANCEIclimate) September 14, 2015
The answer lies in the rings of Blue oaks that show high winter rain levels with wide bands in the rings, while low levels result in narrow bands.
It became clear after analysis of the new core samples and those taken in previous years that 2015 had the lowest snowpack levels in 500 years.
“The results were astonishing,” Valerie Trouet, an associate professor at the University of Arizona, a senior author for the study, told the Wall Street Journal. “We knew it was an all-time low over a historical period, but to see this as a low for the last 500 years, we didn’t expect that. There’s very little doubt about it.”
The study was prompted by this April’s measurements of snow in the Sierra Nevada Mountains. State officials announced they had found “no snow whatsoever,” for the first time in 75 years. The snow water equivalent (SWE) stayed “at only five percent of its historical average,” the team of researchers said in a statement.
“In the Mediterranean climate of California, with 80 percent of precipitation occurring during winter months, Sierra Nevada snowpack plays a critical role in the state’s water reservoir and provides 30 percent of its water supplies,” the paper’s introduction reads.
This year’s low snowpack has also coincided with “record-high” January-March temperatures in California. This, scientists warned, can impact “human and natural systems,” including urban and agricultural water supplies and increase risk of wildfires.