May 11, 2021Updated: May 11, 2021 1:59 p.m.
The Sierra Nevada snowpack, a crucial water source for California’s cities and farms, has already dwindled to next to nothing this year, adding to the state’s worsening drought situation.
The latest data from the state Department of Water Resources on Tuesday showed California’s snowpack was just 6% of normal for May 11, and 4% of the normal average for April 1. That date is typically when California’s snowpack is the deepest and has the highest snow water equivalent — the depth of water that would result if the snow melted upon falling,
The data represented a worrisome decline from 15% of normal recorded just a week earlier on May 4, and an even more alarming drop from 59% of normal on April 1.
Snowpack in the Northern Sierra region was 7% of normal for May 11, while the Central Sierra region was 8% and the Southern Sierra region was just 5% of normal.
“We are done with snowmelt runoff for the year,” said Jeffrey Mount, a senior fellow at the Public Policy Institute of California’s Water Policy Center. “There is essentially no chance that things will improve. What we have in our reservoirs now will be augmented by flows out of the mountains, but it is a trickle compared to normal and wet years.”
Mount explained that when the temperature is warm and the sky is clear, thick snowpacks “act like an insulating blanket,” so they melt at a slower pace. Thin snowpacks can melt proportionately faster.
Adding to the problem this year, much of the moisture is being sucked into the dry soil and into the atmosphere instead of turning into runoff that feeds the state’s reservoirs.
“We got unlucky with a very warm, very sunny spring that pretty much wiped out the snowpack rapidly,” Mount said. “This warmth also increased the rate of sublimation, that is, the amount of snow that basically evaporates into the atmosphere without ever making it into runoff.
On Monday, Gov. Gavin Newsom declared a drought emergency in 39 of California’s 58 counties after urging from elected officials in both parties. Last month his declaration included just Sonoma and Mendocino counties. In the Bay Area, Alameda, Contra Costa, Napa and Solano counties are now included in the proclamation.
Mount compared the current situation to the “terrible snowpacks” in 2014 and 2015, which contributed to severe drought conditions in those years.
During the drought period from 2012 to 2016, conditions were much worse in Southern California than Northern California from 2012-14. But now things have reversed, and Northern California is suffering the brunt of the most recent drought, according to the PPIC.
The snowpack provides as much as a third of California’s agricultural and residential water supply. Most of the Bay Area gets its water from Sierra Nevada snowmelt stored in the Hetch Hetchy Reservoir in Yosemite National Park, as well as the Sacramento-San Joaquin Delta and Russian and Mokelumne river systems.
Mount said the state’s most important reservoirs, which are north of Sacramento, are “alarmingly low” this year and the effects will “reverberate around the state.” He said south of Sacramento, “things are bad, but not dire.”California Drought
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Those conditions add to wildfire risk, and the state is already seeing unusual wildfire activity for this time of year. Cal Fire has reported more than 1,800 fires burning nearly 9,400 acres so far in 2021, more than twice the five-year average. A red flag warning was issued last weekend through Tuesday for parts of the Bay Area, with two fires sparking over the weekend in Contra Costa County.
Mount said the potential is there for a repeat of last year’s record-breaking wildfire season, depending on the weather this summer and fall.
“We could get lucky, but given our luck so far, I surely wouldn’t count on it,” he said. “Plan for a very bad fire season.”
This will also have a significant impact on Central Valley farmers, who on top of the stresses of the drought were told last week by the U.S. Bureau of Reclamation they will not receive any of their expected federal agricultural water allocation this year — which already was only 5% of what is normally expected.Kellie Hwang is a San Francisco Chronicle staff writer. Email: email@example.com Twitter: @kelliehwang