The Sierra Nevada snowpack, an important source of water for California, has reached its lowest level in 500 years, according to a new study. The finding accentuates the severe drought being experienced in the state, which began in 2012, The Guardian reports.
The Sierra Nevada snowpack provides 30 percent of the water in California. As the snow that formed in the winter melts, it replenishes the water reservoirs in the region and provides water supply for the summer months.
However, on April 1, its snow water equivalent was recorded at only 5 percent. One snow survey site showed bare ground instead of the usual five-feet-thick snow, according to USA Today.
"Our study really points to the extreme character of the 2014-15 winter," lead author Valerie Trouet of the Laboratory of Tree Ring Research at the Univeristy of Arizona told USA Today.
To determine precipitation patterns for the past five centuries, the researchers examined the rings of about 1,500 blue oak trees in California. They bore holes in the trees and extracted a piece of the trunk that showed the rings. Wide rings indicated a wet winter while narrow rings indicated a dry winter.
The researchers also determined temperature patterns using tree rings from other species. With data on precipitation and temperature patterns, they were able to identify the amount of snowfall.
"It was definitely a 500-year low. In the 500-year reconstruction, it was unprecedented," Trouet said. "When you are a climate scientist, first you get excited by the result. Then you realize the extreme level of the snowpack is not something to get excited about."
Scientists point to two things that caused the snowpack's low level. First, the winter temperatures were too warm for snow formation. Second, the "Ridiculously Resilient Ridge" phenomenon that formed over the north Pacific caused storm tracks to divert from their usual path kept the rains away from California.
Snow droughts are likely to occur in the future because of rising temperatures due to global warming.
"We should be prepared for this type of snow drought to occur much more frequently because of rising temperatures," Trouet said.
The study was published in the Sept. 14 online issue of the journal Nature Climate Change.
