From NASA:
Abundant Snowpack Blankets the Sierra Nevada
March 3, 2017
Snowpack on the Sierra Nevada provides one-third of the water consumed by California citizens, farmers, and businesses each year. For the first time in at least five years, there should be more than enough of it.
According to the California Department of Water Resources (DWR), the water stored as snow in the Sierra Nevada range was 185 percent of the long-term average for the beginning of March. One year ago, it was 83 percent of the norm. According to the latest measurements from 98 ground-based stations, the average snow-water equivalent in the mountains was 45.5 inches as of March 1, 2017. Snow-water equivalent is an estimate of how much water you would get if all of the snow melted at once.
The abundance of snow is spread out across the mountain range. California DWR reported snowpack at 159 percent of normal in the Northern Sierra/Trinity region, 191 percent in the Central Sierra, and 201 percent in the Southern Sierra. State water scientists noted that the snowpack is the highest it has been since 1983 (the end of a major El Niño event).
At Phillips Station near Lake Tahoe—one of the oldest reporting stations in the region and a site of frequent media interest—the snow depth is 43.4 inches this week. One year ago, it was 24.3 inches, and two years ago it was 6.5 inches.
To derive the snow-water estimate, the researchers combined data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Aqua and Terrasatellites; from ground-based snow sensors from California DWR; and from a computer model. The imagery and data were calibrated against past measurements made in the region by NASA's Airborne Snow Observatory, which uses lidar to measure the snowpack in yearly spring flights.
The natural-color images were acquired by Aqua MODIS on December 28, 2016, and February 6, 2017, the most cloud-free days around the time of the snow surveys.
According to California DWR, the current water year (which began on October 1, 2016) is on pace to be the wettest on record. In a March 2 report from the U.S. Drought Monitor, just 25.5 percent of California has any measurable level of dryness or drought, and just 4 percent of the state remains in severe drought. At the beginning of January 2017, about 83 percent of California qualified as dry or in a drought; that number was 100 percent at the start of the water year, with 43 percent in extreme or exceptional drought.
News outlets reported that 43 feet of snow have fallen on the Mammoth Mountain ski resort in Southern California this winter. The venue hopes to stay open for skiing until July.
From the CA DWR:
Snowpack's Water Content Remains Far above Average
Sacramento - The Sierra Nevada snowpack continues to build during one of the wettest winters in California's recorded history. Today's manual snow survey by the Department of Water Resources (DWR) at Phillips Station in the Sierra Nevada found a snow water equivalent (SWE) of 43.4 inches. February's Phillips survey found 28.0 inches of SWE, and January's reading was 6.0 inches. The March 1 average at Phillips is 24.3 inches.
SWE is the depth of water that theoretically would result if the entire snowpack melted instantaneously. That measurement is more important than depth in evaluating the status of the snowpack. On average, the snowpack supplies about 30 percent of California's water needs as it melts in the spring and early summer.
More telling than a survey at a single location are DWR's electronic readings from 98 stations scattered throughout the Sierra Nevada. Statewide, the snowpack today holds 45.5 inches of SWE, or 185 percent of the March 1 average (24.6 inches). On January 1 before a series of January storms, the SWE of the statewide snowpack was 6.5 inches, just 64 percent of the New Year's Day average. On February 1, the statewide SWE was 30.5 inches, 174 percent of average for that date.
Measurements indicate the water content of the northern Sierra snowpack is 39.2 inches, 159 percent of the multi-decade March 1 average. The central and southern Sierra readings are 49.0 inches (191 percent of average) and 46.4 inches (201 percent of average) respectively.
State Climatologist Michael Anderson said the winter season has been "historic," especially in the central and southern Sierra where elevations are higher and where snowfall has been near the 1983 record amount.
The Phillips snow course, near the intersection of Highway 50 and Sierra-at-Tahoe Road, is one of hundreds surveyed manually throughout the winter. Manual measurements augment the electronic readings from about 100 sensors in the state's mountains that provide a current snapshot of the water content in the snowpack.
Frank Gehrke, chief of the California Cooperative Snow Surveys Program, conducted today's survey at Phillips and said of his findings, "It's not the record, the record being 56.4 (inches), but still a pretty phenomenal snowpack.... January and February came in with some really quite phenomenal atmospheric river storms, many of which were cold enough to really boost the snowpack."
Gehrke said the central and southern regions in the Sierra Nevada are tracking close to 1983, which had the maximum recorded snowpack statewide. "Most of the snow courses are well over their April 1 accumulations, which at (Phillips) is 25 inches," Gehrke said, "so we've busted through April 1 values pretty much at all snow courses throughout the state."
Water Year 2017's heavy precipitation is particularly remarkable because of the five dry years that preceded it. Since October 1, the Northern California, San Joaquin and Tulare Basin indices' rainfall totals are, respectively, 76.5 inches (average is 34.7), 60.7 inches (average is 27.4) and 41.0 inches (average is 19.4). Collectively, the three regions had a total of 178.2 inches of rainfall, or 218 percent of the five-month average (81.5 inches).
Many Californians continue to experience the effects of drought, and some Central Valley communities still depend on water tanks and bottled water. Groundwater - the source of at least a third of the supplies Californians use - will take much more than even an historically wet water year to be replenished in many areas.
California's climate is the most variable of any state. Historically, it swings from drought to flood and back to drought. In addition, as global warming drives up average temperatures in California, more precipitation will fall as rain, not as snow stored in the Sierra Nevada and other mountains. To help prepare for these ever-wider extremes, Californians can learn ways to save water every day by visiting SaveOurWater.com.
Electronic snowpack readings are available at the California Data Exchange Center's (CDEC) Snow Water Equivalents webpage, For earlier readings, click the calendar icon below the map, select a date, then Refresh Data.
Water Year 2017's precipitation can be found at CDEC's Precipitation page. Look in the right- hand column for the Northern Sierra 8-station index for updated rainfall readings in the critical northern portion of the state, as well as the San Joaquin 5-station and Tulare Basin 6-station links.
For a broader snapshot of current and historical weather conditions, see DWR's Water Conditions and Drought pages.
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