Sierra Nevada’s 500-year snowpack low deepens California drought

On April 1 of this year, California Gov. Jerry Brown declared the first-ever mandatory water restrictions throughout the state while standing on dry ground at 6,800-foot elevation in the Sierra Nevada.

California mountain snowpack is declining at a tremendous rate, said researchers.

Snowpack in the Sierras has been measured approximately since the 1930s, so the researchers checked their snowpack estimates from tree rings and the temperature reconstruction against actual snowpack measurements for 1930 to 1980.

The report is just the latest in a number of studies seeking to characterize the drought of four-years in California and put it into a broader context historically. Until the past year or so, researchers have been reluctant to blame the drought on man-made global warming and climate change, driven by the release of carbon dioxide into the atmosphere as a outcome of the combustion of fossil fuels.

An expert in hydrology said that the current climate change studies show that the state will see much more rain than snow. The historical average snowpack on the site for that date is more than five feet, according to the California Department of Water Resources.

We all know snowfall in the Sierras has been light in recent years, but new research reveals that 2015 marked a 500-year-low for snowpack in the region. Another third is pumped from underground aquifers. “The Sierra Nevada snowpack supplies about 30 percent of water in California-it’s a storage system and a water bank”. Therefore, less snow fell, while more rain drenched the area of which the state is very ill equipped in collecting and storing the run off. High temperatures also accelerate the snowmelt in the spring, leaving little water to flow into reservoirs during the summer when it’s needed most.

“With anthropogenic warming, those high temperatures are going to be rising”, Trouet said.

From that and other data, they have reconstructed a timeline and a record of the annual winter precipitation in California from 1405 to 2005. “We can assume that the return interval is going to get shorter”.

Lucas Silva, a soil and biogeochemistry researcher at UC Davis who was not involved in the study, said he was glad the topic was getting attention in a major journal, even though he expressed doubt that tree-ring data could accurately pinpoint past drought conditions. “This is not just unprecedented over 80 years – it’s unprecedented over 500 years”, Trouet, said. “I’m curious and interested, but sceptical that they can really tell that this is about water only”, Silva said.