A new report by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) examined the headwater regions of California’s ten major reservoirs, representing half of the state’s surface storage, discovered each could experience a 79% decline in peak snowpack water volume by 2100.

Berkeley Lab used supercomputers to investigate current warming trends and carbon emissions.

Scientists analyzed how a future warmer world would affect “snowpack upstream of 10 major reservoirs — three in Northern California, three in Central California, and four in Southern California. The reservoirs are Shasta, Oroville, Folsom, New Melones, Don Pedro, Exchequer, Pine Flat, Terminus, Success, and Isabella,” said The Mercury News.

By 2039 to 2059, the snowpack runoff could drop by 54%, the study determined, and then 79% from 2079 to 2099. The study noted that three northernmost reservoirs, Shasta, Oroville and Folsom, could see an 83% reduction, by 2100.

Alan Rhoades, a postdoctoral fellow at Berkeley Lab and lead author of the study, said his team of researchers found that peak runoff could come four weeks earlier by 2100, at the beginning of March rather than April 01.

Mountain snowpack is a significant source of water for California: “Our precipitation is really intermittent and extremes-driven,” Rhoades said. “We get 50% of our annual precipitation in five to 15 days, or one to two weeks. Our water demand is highest during the summer months when we don’t get a lot of precipitation, so we really rely on mountain snowpack as a stopgap for our water supply.”

“So as the world continues to warm, these storms will get even warmer and won’t readily get to freezing, whereby you could have snowfall or snow accumulation and the persistence of snow on the surface,” he said.

As a result of warmer weather, the amount of snow is projected to decrease while rain could increase. The study noted that it did not look at rainfall, only mountain snowpack.