Snow depth in the Cascades as measured by the Snohomish County Public Utility District last week didn’t set a record, but it came close.
The snow depth and water content at two locations were the second highest in the PUD’s 28 years of taking measurements.
Every March, two or three PUD staff members take a helicopter into the Cascades to measure snow and water content at three spots in the Sultan River basin. The highest is Stickney Ridge at 3,600 feet; next is Olney Pass at 3,300 feet, and the lowest is Kromona Mine at 2,400 feet.
On March 25 at Kromona Mine the snow was 117 inches deep and at Olney Pass, 123.5 — roughly 10 feet. Each measurement is the second highest recorded at those spots by the PUD. The depth at Stickney Ridge this year was measured at 159.3 inches, the fourth highest on record.
The utility uses the snowpack information to determine how much water to let through its three dams for hydropower and still have enough for the summer, said Bruce Meaker, a principal engineer for the PUD.
“The target is to get back up to a relatively high position by the end of June,” he said.
The PUD generates about 5 percent of its power by running water from Spada Lake through a pipeline to turbines in a pumphouse four miles downstream on the Sultan River. The PUD also operates small dams at Youngs Creek near Sultan and Woods Creek near Monroe.
About 80 percent of the drinking water for Snohomish County comes from Spada Lake, via Lake Chaplain, to the city of Everett.
A rainy autumn can be thanked for the deep snowpack, according to the National Weather Service in Seattle.
Rain in the lowlands usually translates to snow in the Cascades. Seattle averages 27 inches (three-quarters of its annual average) for the rainy season each year, from Oct. 1 to April 1, said Art Gabel, a meteorologist with the weather service.
Seattle was about 6 inches ahead of average for that period by the end of December but now, thanks to a relatively dry spell s far in 2013, has fallen back to about 3 inches ahead for the six-month period, Gabel said.
A deep snowpack with lots of water usually means plenty of drinking water for the summer and more hydropower for the county, Meaker said.
“But it’s not a slam dunk,” he said.
A sunny spring could evaporate some of that snow before it can melt and run down the mountain into the Spada Lake reservoir.
“It can go directly from solid to vapor,” he said. “The conditions have to be just right. … We won’t know until we see it in the reservoir.”
According to the Climate Prediction Center — the long-range forecasting arm of the National Weather Service — the snowpack should be safe. The center predicts above-average rainfall and roughly average temperatures for the Northwest from April through June.
The PUD takes its measurements in March because that’s when the snow usually hits its peak, PUD spokesman Neil Neroutsos said. Technicians have been making the trip into the mountains since 1986. They collect and measure the snow with a long tube marked in inches and feet. The tube is weighed with a hand-held scale to determine the water content. The snow is collected at 10 different spots at each of the three locations and the numbers are added and averaged.
The snowpack tends to run in five- to seven-year cycles between spikes, Meaker said. The recent low point was three years ago, in March 2010. This year is likely the peak of this cycle, he said. If history holds, there will be less snow next year.
“The cycles aren’t perfect but they’re pretty consistent,” Meaker said.
The record high for each of the three locations is 197.8 inches at Stickney Ridge, 137 inches at Olney Pass and 125.6 inches at Kromona Mine — all in 2008.
Bill Sheets: 425-339-3439; sheets@heraldnet.com.
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