Published: Jan. 27, 2017

Sierra Nevada SWE maps

A map showing snow-water equivalent totals in California's Sierra Nevada range as of Jan. 24, 2017. Credit: Leanne Lestak / University of Colorado Boulder.

The recent “atmospheric river” weather pattern that pummeled California with storms from late December to late-January may have recouped 37 percent of the state’s five-year snow-water deficit, according to new CU Boulder led research.

Using NASA satellite data, computer models, and ground-based snow sensors, researchers at CWEST estimate that the recent storms deposited roughly 17.5 million acre feet of water during the month of January. Compared to averages from the pre-drought satellite record, that amount represents over 120 percent of the typical annual snow accumulation for the Sierra Nevada range.

Snow-water deficit represents the cumulative annual deficit below the average annual snowpack water storage. On average, California has experienced a snow-water deficit of approximately 10.8 million acre feet per year from 2012 to 2016. The total five-year snow-water deficit over that period is roughly 54 million acre feet, but two powerful recent storms appear to have recouped roughly 37 percent of that total in less than one month.

“When the snow stopped falling five years ago, the state had to tap into its groundwater reserves to keep up,” said Noah Molotch, director of CWEST and a research associate at INSTAAR. “One snowy winter won’t be able to entirely reverse that, but there is, at least, some cautious optimism.”

Molotch indicated that the recent storms brought much needed snow but have also brought some flood risk.

“The concern moving forward relates to what happens with the weather for the rest of the winter,” said Molotch. “Reservoirs across the Sierra foothills are now relatively full and if we get another intense atmospheric river with warmer air temperatures, the risk for rain-induced flooding is considerable.”

Read more at CU Boulder Today,the LA Times, NASA, NASA's Jet Propulsion Laboratory, the San Francisco Chronicle, the Sacramento Bee and the Washington Post.  Listen to the below radio interview with KCBS San Francisco on the Sierra snowpack.