Snowpack to Snowmelt

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The transformation of water in California's played out like high drama over the past few months. National forest lands provide 60% of the state's water supply, and some of that water is stored temporarily in snowpack. When that snow melts, it recharges drinking water, agricultural lands, and even hydropower. But heavy snowpack has a flip side too, most noticeably the power to damage forest infrastructure and amplify the strength of our streams.

Act I – Snowfall in California

This year, the snowpack was deeper and at lower elevations compared to average years thanks to winter’s atmospheric storms. At the time of the early April measurements — understood to be the peak of the snowpack — the statewide average snow water equivalent was over 61 inches. That’s 241% of average for that time of year. The snowpack in the Southern Sierra surged further to over 63 inches, or 300% of average for that time of year. Heavy snow brings a mixed bag of benefits and complications.

“It’s really good that we’ve gotten a lot of snow,” said Lisa Fong, Assistant Regional Hydrologist, Pacific Southwest Region, USDA Forest Service. “The U.S. Drought Monitor is showing that California moved out of severe drought and extreme drought. However, with warming temperatures, snowpack in the mountains can melt faster than we’d like and cause flooding.”

Act II – Rising Action with Heavy Snowpack 

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So, why is it important to know how much water is in the snowpack? To prepare for potential flooding is one key reason. To gather that data requires a hybrid of high-tech and old school. Aerial surveys and electronic snow sensors are important, but so are boots-on-the-ground snow surveys. These are conducted on snow courses – predetermined locations where snow measurements are taken annually for decades, sometimes a century. 

Throughout the state, there are over 265 snow courses that are part of the statewide California Cooperative Snow Surveys program. National forests are responsible for taking monthly snowpack measurements at 82 of those during the winter and early spring.

Collecting snow cores at the sample sites requires precision and a mathematical state of mind. Following a snow course map, teams of surveyors drive samplers – tubes with cutting teeth at the bottom – all the way to the ground to extract snow cores at five to 10 different points. Calibrations on the side of a sampler measure the height of the snow core that surveyors will also weigh on the spot with a scale that cradles the tube for a reading. 

“During mellower years, it can take as little as 20 minutes to sample 10 holes. But with deep snow years, 10 holes can take up to three hours. And we have 100 holes to sample, each of them four times in a season,” said Ryan Kalinowski, a Wildlife Biologist with the Groveland Ranger District on the Stanislaus National Forest, who has been surveying for eight years. 

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While a science, conducting these surveys is also a backcountry quest for those up for the challenge. Remote locations, cold temperatures, fierce winds, and steep terrain are typical plot thickeners for these data-collection expeditions. Depending on the location of the snow course and its distance from a drivable road, snow surveyors may require snowshoes, skis, over-snow vehicles, or even helicopters to access the sampling points. 

“There are cold feet and hands, cross-country travel, and difficult sampling. But those of us who choose to deal with those things absolutely love surveying. And we feel the data we are collecting is really important information, so we take it seriously,” said Kalinowski.

Act III – The Snow Melt Finale

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Snowpack data is especially important in California — a state that frequently faces years of extreme drought conditions, followed by extreme precipitation events like this winter’s atmospheric storms. Snow surveys help us forecast the flooding, high stream flows, and other forest changes as the recreation season and warming temperatures arrive. 

And this high snowpack year, which will lead to heavy snow melt, means delayed access and swift cold water.

First, delayed access. The storm damage and incredible amount of snow from this winter’s atmospheric rivers left many roads and trailheads inaccessible. Even campgrounds did not evade extensive damage. This means while staff are working as quickly as possible, visitors may not be able to get to favorite spots until much later this season, or perhaps until a future year. 

Second, changes in stream flow and temperature that make water safety especially important this year for vehicles, hikers, equestrians, mountain bikers, swimmers and anglers alike. With snowmelt, river flows can change throughout the day — what is crossable in the morning, may become too deep and swift by afternoon. Snow melt will also make the water much colder than recent years, which can cause faster onset of hypothermia and muscle cramping. 

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“We really encourage people to pause and assess before fording a stream or river because we are seeing conditions not seen in a long, long time,” said Garrett Villanueva, Regional Trail and Travel Management Program Manager. “Being prepared for changing conditions is one of the most important things this year. We should all bring extra water, a sleeping bag, warm clothes, and good shoes in case we can't get out for a day or few days beyond what we intended. Having a full tank of gas and letting someone know where we are with a check-in, check-out plan are important too.”

While we anticipate that melting snowpack and previous damage from the atmospheric storms will delay or prohibit access to some of our favorite areas on national forests this year, there is a silver lining. Lakes, reservoirs, waterfalls and rivers are all getting a refill, which is a boon for forest habitats and future recreation opportunities. 

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“It is amazing to see Shasta Lake — one of the largest lakes in the state — change from a dry lakebed, 180 feet below the dam’s crest, to a magnificently full, 450-million-acre-foot lake!” said Christine Mai, Hydrologist and Snow Survey Program Lead on the Shasta-Trinity National Forest. “From a hydrologist perspective, I feel excited to see water flowing in places where it hasn't been for a long time, knowing that habitats are going to be rejuvenated. It’s a beautiful thing.”

Additional Weather and Planning Resources
California National Forests | Contact Directory
Caltrans QuickMap — Current information on road closures
Weather Watches, Warnings and Advisories | National Weather Service
Turn Around, Don’t Drown | Ready.gov
California Office of Emergency Services | Cal OES
#RecreateResponsibly | Water Safety