Shrinking Sierra Snowpack Heightens Drought Worries

Manual surveys on Thursday confirmed concerns over the withering mountain snowpack — a critical source of water for millions of Californians. Statewide, water content in the Sierra’s accumulated snows is an anemic 25 percent of the average for this time of year.

That’s despite a really soggy December in which some California cities got nearly three times their normal rainfall — and rainfall is the operative word. But those storms weren’t cold enough to deliver much snow to the middle elevations. 2014 went down as California’s warmest year on record.

“The temperature side of things should not be neglected here, says climatologist Kelly Redmond, who has been tracking patterns in the Sierra for 25 years at the Western Regional Climate Center in Reno. “It has its own consequences that sort of stack on top of the precipitation deficits.”

In the Lake Tahoe region, Redmond says the “freezing level” — the elevation at which temperatures dip to freezing — has hovered at around 10,200 feet, or about 3,000 feet higher than the long-term average. That means less snow stored in the high peaks for use this summer.

Follow that with what is now looking like a record-dry January for most of the state — and you’re left with a snowpack that is little more than a quarter of what’s normal for this date.

The good news: we’re in better shape than we were last year at this time but still far, far behind the kind of winter that all the experts said we would need to even begin to reverse the drought. While, thanks to December’s deluge, many cities in the Central Valley remain slightly ahead of normal for the season so far a closely-watched index of eight gauges in the northern Sierra — a key indicator for some of the state’s biggest reservoirs — has slipped below its average for late January, with little indication of major storms on the horizon.

So while might be tempting to say, “Hey, what’s the problem — we’re running just about average,” state water managers have said California would likely need upward of 150 percent of its average precipitation to start turning things around. And time is running out. The occasional “March miracle” notwithstanding, the rhythms of California’s Mediterranean climate are such that precipitation typically starts tapering off after February.

This video from the state Department of Water Resources shows how patchy the snow cover is, even around 7,000 feet of elevation. The “12 percent of average” that surveyor Frank Gehrke mentions is the reading from the single snow course where the video was shot, not the statewide number.