Sierra "phenomenal" snowpack not a record, but water content at 179% of average

The Sierra Nevada snowpack continues to build during one of the wettest winters in California’s recorded history and this was evident as the monthly snow survey was conducted by the Department of Water Resources at Phillips Station near Sierra-at-Tahoe.

The snow water equivalent (SWE) measured was 179 percent of average, or 43.4 inches.

The 113 inches of snow at Phillips Station contains the fifth-highest March 1 reading of the SWE. In 1969, the record reading was 57.4 inches of snow-water content in 160.9 inches of water.

“It’s not the record but still a pretty phenomenal snowpack," said Frank Gehrke, chief of the California Cooperative Snow Surveys Program. "January and February came in with some really quite phenomenal atmospheric river storms, many of which were cold enough to really boost the snowpack.”

This year's February 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.

The top six water-content years measured at Philips on March 1 (recorded since 1946):

1969 - 160.9 inches of snow with a water content of 57.4 inches
1986 - 142 inches of snow with a water content of 56.4 inches
1952 - 138 inches of snow with a water content of 55.7 inches
1956 - 118 inches of snow with a water content of 44.1 inches
2017 - 112.5 inches of snow with a water content of 43.5 inches
1993 - 126 inches of snow with a water content of 42.1 inches

The SWE, or water contect, is how much water would come out of the snow should it happen to melt all at once. This is more important that how deep snow is as it provides water to the state this spring and summer.

On average, the snowpack supplies about 30 percent of California’s water needs as it melts in the spring and early summer.

There are 98 stations in the Sierra Nevada that measure the SWE, and as a state the snowpack is now at 185 percent of the March 1 average as it now holds 45.5 inches of water.

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.

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.