Tree Ring Data Show|500-Year Calif. Drought

SACRAMENTO (CN) - Tree ring data show that snow pack, a vital source of California's overdrawn water supply, has sunk to its lowest level in more than 500 years, scientists said Monday.

Measurements in April found the Sierra Nevada snowpack at just 5 percent of its average, the lowest in 120 years of record-keeping, prompting California to issue its first mandatory water restrictions. Scientists who examined more than 1,500 trees determined that snowpack levels during the 2014-15 winter were not just the lowest on record, but the lowest in five centuries.

The study in the peer-reviewed British journal Nature Climate Change analyzed the state's persistent drought and warned of the possibility of more to come due to the state's warming climate. California's winter was the warmest on record and coincided with the lack of precipitation to keep the Sierra Nevada unseasonably barren.

California's maze of reservoirs and aqueducts are fed by spring snowmelt from the Sierra Nevada and the lack of snow in recent years has strained the state's usually reliable water savings account.

While snowpack levels have been taken in California for more than 100 years, the latest study examined the state's blue oak trees to compare today's drought with past ones. The study warned that manmade global warming is contributing to the state's warming climate and that winters to come could feature a lack of snow as well.

Paltry snow levels have left the state's foothills and valleys bone dry and kept firefighting crews working throughout the summer.

Dry conditions fueled a pair of wildfires raging through Northern California, combining to char more than 130,000 acres. The Valley fire in Lake County has destroyed hundreds of homes and killed an elderly woman Sunday, while the Butte fire has burned more than 70,000 acres in Amador and Calaveras counties.

In Central California, the state's largest blaze, the Rough Fire, has blackened more than 138,000 acres.

The devastating wildfires prompted Gov. Jerry Brown to declare a state of emergency in four counties over the weekend and Monday he told reporters global warming is increasing the intensity of California wildfires.

"This is not just this year," Brown said Monday. "This is the future, from now on. It's going to get worse, just by the nature of how the climate's changing."

Brown, who recently vowed to advance California's climate change policy despite opposition from the oil industry, also warned of migration caused by drastic climate change.

"What we've seen in Europe now with mass migrations - that will happen in California," Brown said.

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