Executive Summary for December 30th

Annual snow surveys resume today and are likely to show conditions are spot-on average for this time of year. But the measurements that matter will come later in the winter. Also today, an update from NASA shows the El Niño weather phenomenon is on pace to match the record year of 1997

Published on Dec. 30, 2015 Read time Approx. 3 minutes

Editor’s note: Water Deeply is taking Thursday and Friday off for the New Year’s holiday. This will be our last executive summary for the week. We will return on Monday, January 4.

Today: First Snow Survey of the Season

Officials from the California Department of Water Resources today plan to conduct the first mountain snow survey of the season. Thanks to automated snowpack sensors, we already know the results: the state’s crucial Sierra Nevada snowpack is essentially on pace with the historical average for this date.

That’s great news after four years of drought. But it only matters in terms of easing the drought if the remaining months of winter are well above average. Therein lies the coin toss. It’s too soon to gamble on the promise of more water availability in 2016. Only time will tell.

The mountain snowpack is crucial to statewide water supplies for a number of reasons. The simple one is that it delivers, in an average year, about one-third of California’s total freshwater supplies. Perhaps as importantly, gradual snowmelt naturally rations that supply throughout the spring months, allowing reservoirs to be gradually refilled as they are depleted by urban and agricultural water demand.

By the start of summer, in an ideal year, the reservoirs are all brim-full of snowmelt, allowing Californians to survive their rainless hot months until storms resume in November.

The snow survey is set for 11 a.m. PST today at the usual spot: a patch of land along Highway 50 near Echo Summit, on the way to Lake Tahoe.

The automated sensors already tell us the statewide snowpack is at 107 percent of normal as of December 29 – essentially dead-on average for that date. While officials rely a great deal today on the automated sensors, they still get out in the field with manual measuring tools, which they plunge into the snow to gauge depth and water content.

In truth, this event is less a snow survey than a media stunt. It’s a chance for the cameras to capture images and tell a story about California water supply. And it will be played out monthly until April.

It’s that April number that really matters, because it marks the end of winter. If the snowpack is still average in April, that’s a lot better than the last four years, which were well below average, but not enough to break the drought.

For instance, a year ago the snowpack measured 45 percent of average. On April 1, 2015, it was a dismal 5 percent.

Remember that the snowpack is not a permanent thing. Without new storms, the snowpack will shrink. Even if mountain temperatures remain below freezing (which, of course, can’t be guaranteed), the forces of wind and sunlight will erode a little of that snowpack every day. And they already have: On Friday, the statewide snowpack peaked at 115 percent of average, then shrank to 107 percent as of Tuesday.

If the April measurement this year is well above average, we can begin to speculate about whether the drought is over or merely less intense. Officials say the magic number in their heads is 150 percent of average.

The last time the snowpack entered that range was April 1, 2011, when it stood at 166 percent of normal, on the eve of the current four-year drought.

El Niño On Track to Match Record Year of 1997

An update on the El Niño weather phenomenon from NASA gives us hope those snow surveys in the months ahead will continue the positive trend.

Satellite images that decipher Pacific Ocean temperatures tell us, NASA says, that the current El Niño is looking a lot like 1997, the strongest El Niño recorded in 50 years of monitoring. That’s good news for more storms making their way into California in the months ahead.

While no one can predict the exact timing or intensity of U.S. El Niño impacts, NASA tells us, it is expected to bring some relief to drought-stricken California and the U.S. West

“The water story for much of the American West over most of the past decade has been dominated by punishing drought,” said Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory. “Now we’re preparing to see the flip side of nature’s water cycle – the arrival of steady, heavy rains and snowfall.”

Much will depend upon how cold those storms are. El Niño also tends to bring warmer conditions, which could mean a smaller snowpack but more rain – potentially bringing flood risk along with it.

Top image: Frank Gehrke, chief of the California Cooperative Snow Surveys at the Department of Water Resources, checks the depth of the snow pack at Leavitt Lake, California, in April 2015. (Rich Pedroncelli, Associated Press)

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