All along the Sierra Nevada at Ebbetts Pass, Sonora Pass and Tioga Pass, people and animals are digging out from the winter.
The 2016-17 precipitation season, recorded from Oct. 1 through April 1, brought near-record rainfall to the foothills and frigid, densely snow-packed conditions to the higher elevations.
Along the Sierra ridgeline in Calaveras and Tuolumne counties, a balanced application of force and precision has been required to record season data, clear the passes and prepare for the transition into spring.
Sonora has gotten 50.54 inches of rain since October, said Hannah Chandler, a meteorologist at the National Weather Service. The San Joaquin 5-Station Index, which charts precipitation at locations in Calaveras Big Trees, Hetch Hetchy, Yosemite Headquarters, North Fork Ranger Station and Huntington Lake, has recorded 71 inches of precipitation since October, about 191 percent of average for the current date.
The current precipitation information is just 2 inches short of about 73 inches in 1982-83, the most in the recorded history of the index. At this time two years ago, the yearly precipitation level for the index was just about 15 inches.
Chandler added that, despite this being an “abnormal year for this area,” Sonora and the Sierra Nevada should expect new, small weather systems throughout spring that could bring up to an inch of additional precipitation.
Fluctuating temperatures throughout May, she said, would by extension create fluctuating snow melt.
“What we know is we're not expecting extreme deluges of snowmelt,” she said, noting that the peak of the melt would occur later in May. “Reservoirs are prepared for that snowmelt, and there won't be major flooding like what we experienced in January and February.”
As is typical with snowmelt though, she added, communities should be prepared with the onset of any minor flooding issues.
The final snow survey of 2017 conducted by the California Department of Water Resources found a “water-rich” snow pack at Phillips Station, located at the junction of Highway 50 and Sierra-at-Tahoe Road in the Sierra Nevada, a snow-water equivalent of 27.8 inches or 190 percent of the May 1 long-term average of 14.6 inches, according to a May 1 press release.
The snowpack surveys are conducted on the first of the month January through May.
With April 1 usually when snowpack water content is at its peak, the news release noted, the additional information assists hydrologists in forecasting the spring and summer snowmelt runoff into rivers and reservoirs, which provides one-third of the water used by Californians.
In the Central Sierra region, with 41 stations reporting, the average snow-water equivalent is about 46.1 inches. The percent of the April 1 average was 159 percent and the percent of normal for May 2 was 201 percent.
Bureau of Reclamation Deputy Public Affairs Officer Louis Moore said New Melones Dam was at 2,003,400 acre feet as of midnight Tuesday or about 83 percent of total capacity.
“The storage is absolutely nowhere near what it was last year right now,” he said.
Last year at this time, he said, New Melones was at 622,000 acre-feet, and year before that, he added, was even more “dismal.”
April 1 through Sept. 30, during the snowmelt runoff season, he said, snow accumulated in higher elevations will melt with higher temperatures and flow into the local reservoirs.
Clearing the passes
With sunshine blooming over the Sierras and temperatures on the rise, the operation is now underway to remove the massive drifts of snowpack covering the high-country passes, said Caltrans District 10 Public Information Officer Skip Allum.
Though Sonora Pass on Highway 108, Ebbetts Pass on Highway 4 and Monitor Pass on Highway 89 in Alpine County are in “various stages of the snow removal process,” he said, the annual goal was to have each of those passes open by Memorial Day Weekend, May 29.
For the 2015-16 year, Sonora Pass was opened on May 18, Ebbetts Pass was opened on May 13 and Monitor Pass on April 5, according to a Caltrans press release.
Highway 108 is open as far as Kennedy Meadows Road, with variance of the size of snowdrifts based on the elevation, he said. Ebbetts Pass has the most remaining snowpack with drifts at locations as high as 30 feet, he said, and will likely take the longest to clear.
“We’re getting a little bit of sunlight right now. I think that’s helping,” he said. “I think everyone would agree that this is the longest and most severe winter we've had in many years.”
The clearing of the passes is a multifaceted process, he said. Snow is first cleared from the roads using a variety of machines and equipment including cylindrical, thrashing snow blowers, street sweepers, tractors, trucks and plows. Allum said there were up to seven individuals at Sonora Pass, made up of both long-term crewmembers as well as seasonal employees.
And once the snow is clear, then the road surface has to be evaluated for fissures and damage and set up for repair. The surrounding environment has to be analyzed for evidence of rockslides, mudslides and fallen trees, and roadside culverts need to be unclogged and functioning correctly, he said.
Once debris, rocks and fallen trees are removed, repairs can begin.
It requires warm temperatures and dry conditions to maintain to fresh painting of road stripes or setting concrete.
Statewide, he said, Caltrans estimated winter storm damage to the state highway system at $974 million.
Yosemite National Park spokesman Scott Gediman said there is not prospective opening date for the opening of Tioga Pass on Highway 120 in Yosemite.
“Basically we have been plowing the road for a couple of weeks now and as folks know there is near record pack,” he said. “We have made progress but it's not just a question of plowing the road we need to mitigate avalanche concerns.”
Tioga Pass in Yosemite National Park opened during the 2015-16 year on May 18, according to the Caltrans news release.
There were more than 50 miles east to west of ground to cover, Gediman said, with over 100 inches of snow in locations along Highway 120.
But the opening of Big Oak Flat Road, an extension of Highway 120 in Yosemite National Park, has “streamlined operations” for plowing Tioga Pass, he added.
Adaptive animals and sensitive species
Unlike with human populations, the unusually cold and wet winter did not wreak havoc on Sierra-bound species such as the black bear, deer, and the California scrub jay, said California Fish and Wildlife Senior Wildlife Biologist Greg Gerstenberg.
“Wildlife is adaptive and can handle wet periods and dry periods,” he said. “There was some impact, but very insignificant. We have not had any reports of issues at this time.”
Gerstenberg said there has already been reports of bears foraging in vegetation as low as 4,000 feet, and that the cold, snow packed winter probably would not significantly impact the bear population or extend their hibernation period.
Resident birds such as the scrub jay would have generally persisted in the conditions, he added, and will likely be met by steller's jays, migratory birds who travel north, up in elevation in the springtime and summer, to the conifers and pines of the forest.
But there are some sensitive species that may have experienced some level of depopulation during the unusual cold of the 2016-17 winter, added Sonora Unit California Fish and Wildlife biologist Nathan Graveline, but that was pending additional information once the snow actually cleared.
The Sierra Nevada red fox, he said, exists on both the west and east side of the area surrounding Sonora Pass, and may have been safely isolated from competitors such as the gray fox and coyote. With such low temperatures and extensive snowpack though, he added, real results from this winter were pending. His “hunch” though, he said, erred on the adaptive ability of the creatures.
“We've been in such a dry, warm cycle for the past couple years. We tend to have a harder time adapting, but I think with a lot of the wildlife, it’s built into their DNA to be able to adapt. But maybe the temperature changes and precipitation changes are more extreme than they are used to.”
Another notably sensitive species to the area was the bighorn sheep, he said, which had been repopulated into its historical range in the Tuolumne Meadows area of Yosemite National Park from the east side of the Sierras.
“They need time to adapt to a new area,” he said, adding that, though bears and deer can “cover a lot of ground,” bighorn sheep don’t have established migratory corridors that would give them familiarity with their surroundings.
Gediman added that many of the bighorns were outfitted with collars that could be monitored, but the winter’s effect on the the larger population was unclear with much of the snowpack still intact near Tioga Pass.
“We don't have definite numbers on mortalities and how much and why,” he said. “With so much snow, it certainly makes just surviving and living and gathering food more challenging.”
Helicopter-monitored aerial surveys only provided studies with a certain amount of information he said, and acknowledged that different herds were scattered throughout the area.
Once Tioga is cleared, he added, Yosemite workers will have more access to the herds to learn how the season has affected their populations.