Snowpack needs years to recover
Study: Despite El Niño rains, pre-drought levels won’t be reached until at least 2019
Despite the state’s wettest winter in five years, the Sierra Nevada snowpack will not return to pre-drought levels until at least 2019, according to a new analysis.
“The deficit we have is so large, it is very, very unlikely to recover in one year,” said Steven Margulis, professor of civil and environmental engineering at UCLA, who led the team of hydrology researchers who produced the study using highresolution satellite images.
California’s snowpack is vital to the state’s water supply.
This winter’s El Niño storms provided significant rain and snow, considerably softening California’s drought emergency as it entered its fifth year, particularly in Northern California. But the cumulative effects of the drought mean that the recovery period will be longer than for previous dry spells, according to the UCLA team’s analysis published Tuesday in American Geophysical Union’s online journal.
“With the consecutive years of ongoing drought, the Sierra Nevada snowpack’s total water volume is in deficit, and our analysis shows it will to take a few years for a complete recovery, even if there are above-average precipitation years,” said Margulis, who led the team of researchers from UCLA, NASA, the University of Ohio, and the Universities Space Research Association in Columbia, Maryland.
California’s snowpack is vital to the state’s water supply, providing nearly a third of the state’s needs in a typical year. Using the detailed data set, the researchers predicted that it will take until 2019 for the Sierras to regain the amount of snowpack they had before the record-setting drought began in 2012.
“It’s a cautionary tale,” Margulis said. “If you start having multiyear droughts, you get much longer time periods for recovery.” But the analysis should not be taken as a weather forecast, cautioned Jan Null, a consulting meteorologist at Golden Gate Weather Services. “Climatology and statistics are not forecasting tools,” said Null. “They only tell us what happened in the past.”
While the analysis can be helpful, Null cautioned that it does not amount to a fouryear weather forecast. “I’m always leery of simple solutions, because California weather is really complex even in the best of times.”
The analysis comes as California begins to recover from what researchers have called the state’s worst drought in its history. The state experienced heavy El Niño storms this winter that led Gov. Jerry Brown to relax statewide mandatory water restrictions in May. This winter was the wettest in the past five years, and some of California’s largest reservoirs are now 90 percent full.
The study, released in the journal Geophysical Research Letters, included findings from a new data set that uses NASA satellite images with resolution about 10 times sharper than previously available maps.
The researchers combined their new high-resolution data set with snow survey data from the California Department of Water Resources to examine snowpacks as far back as 1951. Since then, before the current drought, 1977 was the only time it took longer than one year for the snowpack to recover, researchers found.
The researchers hope that the new method of data collection will be useful in monitoring snowpack in more regions and informing policies surrounding climate change.
“This unprecedented information can help policy-makers make more informed decisions with regard to this critical resource,” Margulis said, “especially as climate change affects it.”