Woe, California: Sierra Nevada Snowpack Hits a 500-Year Low

The epic drought reaches a low-water mark (literally) for the snows that provide much of the state’s water in the spring and summer.

The Sierra Nevada snowpack—the source of more than one-third of California's water supply—is the lowest it has been in 500 years.

The finding comes from a new historical analysis of tree rings published Monday in the peer-reviewed journal Nature Climate Change.  It demonstrates how severe California's four-year-old drought has become.  The state began rationing water for the first time in its 165-year history earlier this year.

The Sierra Nevada snowpack is a critical source of water for California during the spring and summer months, when rain is rare.  As the snow melts, the water replenishes soil moisture and reservoirs below.  With less snow this year, the region's already strained agriculture sector, drinking water supplies and hydroelectric power face serious challenges.  It also means California's forests will remain dry, fueling already rampant wildfires.

But the research also gives a clue as to how global warming could change the nature and severity of the region's droughts in the decades to come.

"We know that the drought in California is a hot drought, its high temperatures differentiate it from droughts in the past," said Soumaya Belmecheri, a geochemist who works on climate reconstructions at the Laboratory of Tree-Ring Research at the University of Arizona and lead author of the study.  "As temperatures continue to rise from global warming, this research shows the snowpack may no longer be a reliable source of water.  That has huge implications on everything from wildfires to biodiversity to human civilization."

Scientists had previously put the current California drought into historical context, looking back thousands of years.  But they hadn't yet done the same for the Sierra Nevada snowpack levels.

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