In California, the Snow Tells the Future for the Water Supply



Max Whittaker for The New York Times
Frank Gehrke, center, has led snowpack surveys in California for a quarter-century. The state's multibillion-dollar agricultural industry pays close attention.


PHILLIPS, Calif. — Along Highway 50 in the Sierra Nevada, elevation 6,820 feet, a California winter ritual unfolded here on a recent morning. In the snow-blanketed meadow of a local homeowner's backyard, reporters representing news organizations from across the state followed a man on skis who kept plunging an aluminum tube into the snow.
Leading the pack was Frank Gehrke, California's chief snow surveyor, the man responsible for measuring the Sierra Nevada's snowpack, the source of a third of this state's water supply. Part groundhog, whose appearances signal the shift of the seasons, and part Federal Reserve chairman whose utterances on the state of the snowpack can move California's multibillion-dollar agricultural industry, Mr. Gehrke has led the Department of Water Resources' snowpack surveys for a quarter-century.
In the state that is home to Silicon Valley, Mr. Gehrke and his team use the stick-the-tube-into-the-snow method developed by a local classics professor more than a century ago.
"There've been only incremental changes," Mr. Gehrke said, interspersing this winter's second monthly survey with a veteran's calm observations of the snowfall and hints of the possible coming drama that is California's annual snowmelt. "This course is very uniform, which is normal, because the snowpack during accumulation is kind of uniform. But once you start getting into the melt, it starts to go crazy."
His assessment of this month's survey — after a strong start, the snowpack's water content fell to 93 percent of average for this time of the year because of a "midwinter lull" — was carried on television channels throughout the state. Pictures of Mr. Gehrke, grasping the tube with his gray mittens against a backdrop of the Sierra Nevada, appeared on the front page of newspapers in Sacramento and the Bay Area.
In California's water system, one of the world's most sophisticated and complex, the snowpack plays a leading role by supplying water to more than 25 million people and almost one million acres of farmland. Snow that accumulates on the Sierra Nevada's 400-mile range starts to melt in the spring, draining into rivers that feed reservoirs below.
As Mr. Gehrke and his team gauge the depth and water content of the snowpack, other department officials begin forecasting how much water the snowpack will be able to deliver this year.
Those who depend on the snowpack for water adjust their plans accordingly. Water districts may start looking for water elsewhere or carry out conservation measures. Farmers consider the forecasts in deciding what crops to plant or whether to take bank loans to buy more seed and equipment for the year.
Ryan Jacobsen, who is executive director of the Fresno County Farm Bureau and also sits on the board of the Fresno Irrigation District, said that the snow surveys are the "bible for what decisions irrigation districts are going to make for the rest of the year."
"Fresno County is the No. 1 agricultural county in the nation, but we also happen to be situated climatically in the middle of a desert," he said. "It really is the Sierra Nevada snowpack that makes this desert bloom."
It was in 1908 that James E. Church, a classics professor at the University of Nevada, Reno, developed the existing method of forecasting water runoff from the depth and water content of snow. To settle a dispute over water rights in nearby Lake Tahoe, he was able to predict the water from the snowpack on Mount Rose by using a hollow tube that he called the Mount Rose snow sampler. Government agencies adopted his technique and, in 1929, California passed a law mandating that state officials measure the Sierra Nevada snowpack and issue forecasts of the water supply.
"You can almost say it made the development of the West possible," Mr. Gehrke said. "Prior to that, they really didn't even have tools to use to hope to predict how much runoff they would have."

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