One of California's biggest sources of fresh water is in peril. A new study in the journal Nature Climate Change shows the Sierra snowpack shrinking substantially in the years to come.

In some of the most stark projections yet, the study by Stanford climate scientist Noah Diffenbaugh suggests that over the rest of this century, we’ll see a dramatic decline in what’s often called California’s “frozen reservoir.”

"If emissions and population continue to increase as they have, then we see that the Western United States experiences up to 80% of years with snow accumulation below the late-20th-century minimum," he said.

And what is there, he adds, will be melting faster -- and sooner. That would wreak havoc with the state's carefully balanced water supply.

"The reservoir system is built for the current proportion of rain and snow, and if there's increasing rain and also earlier melt of the snow that does fall, then the current reservoir system potentially would be impacted," he said.

If the melt comes too early, there could be flooding, and then not enough water to go around once the dry season hits.

California gets about a third of its water from snow in the Sierra.