‘Disappointing’ snowpack
Still too early to draw conclusions from season’s first measurement
It’s has been a dry fall and winter so it came as no surprise that the snowpack was well below average.
The Department of Water Resources (DWR) manual and electronic snow survey taken Wednesday across the state found little snowpack, which was predictable after a dry December throughout California.
Statewide, the snowpack’s SWE is 2.6 inches, or 24 percent of the Jan. 3 average.
Electronic measurements at Quaking Aspen revealed a snow water equivalent (SWE) of 3.5 inches, 16 percent of average. SWE is the depth of water that theoretically would result if the entire snowpack melted instantaneously.
“As we’re only a third of the way through California’s three wettest months, it’s far too early to draw any conclusions about what kind of season we’ll have this year,” DWR Director Grant Davis said. “California’s great weather variability means we can go straight from a dry year to a wet year and back again to dry. That’s why California is focusing on adopting water conservation as a way of life, investing in above- and below- ground storage, and improving our infrastructure to protect our clean water supplies against disruptions.”
Measurements from the 103 stations scattered throughout the Sierra Nevada indicate the SWE of the northern Sierra snowpack is 2.3 inches, 21 percent of average. The central and southern Sierra readings are 3.3 inches (29 percent of average) and 1.8 inches (20 percent of average), respectively.
“The survey is a disappointing start of the year, but it’s far too early to draw conclusions about what kind of a wet season we’ll have this year,” said Frank Gehrke, chief of the California Cooperative Snow Surveys Program. “There’s plenty of time left in the traditional wet season to reverse the dry trend we’ve been experiencing.”
California traditionally receives about half of its annual precipitation during December, January, and February, with the bulk of this precipitation coming from atmospheric rivers (ARS). So far this winter, an atmospheric high-pressure zone spanning the western United States has persistently blocked ARS from reaching the state. If that zone were to move or break up, storms could deliver considerable rainfall and snow this winter.
Davis noted that forecasting accuracy falls off dramatically after just a week or 10 days into the future.
“Current technology and computer modeling can tell us what our weather might be weeks into the future, but we’re essentially blind to what the weather will be beyond the two-week mark,” he said. “That’s why we are putting in so much effort to improving medium- and longrange modeling.”
California’s exceptionally high precipitation last winter and spring has resulted in aboveaverage storage in 154 reservoirs tracked by the Department. DWR estimates total storage in those reservoirs at the end of December amounted to 24.1 million acre feet (MAF), or 110 percent of the 21.9 MAF average for the end of the year. One year ago, those reservoirs held 21.2 million acre-feet (MAF), 97 percent of average. End-of-year storage is now the highest since December 2012 (24.3 MAF), which was early in the first of five consecutive water years of drought in California.
DWR conducts five media-oriented snow surveys each winter near the first of January, February, March, April, and May. On average, the snowpack supplies about 30 percent of California’s water needs as it melts in the spring and early summer.