Track climate change with tennis balls

U. WASHINGTON—Measuring snowmelt is as easy—and economical—as launching a tennis ball into a tree.

Because changes in snowfall and melt brought on by climate change will affect communities and environments at lower elevations, water managers want to know exactly where snow is accumulating and on what date it starts to melt.

Jessica Lundquist, assistant professor of civil and environmental engineering at the University of Washington, attaches dime-sized temperature sensors, first developed for the refrigerated food industry, to tennis balls weighted with gravel.

In the summer months, she uses a dog-ball launcher to propel the devices high into alpine trees where they will record winter temperatures.

“It’s fun, like backyard science,” Lundquist says.

She began adapting the devices for environmental science while a postdoctoral researcher in Colorado and has refined them over the years. “It turns out they work phenomenally well.”

Scientific weather stations typically cost about $10,000.

Lundquist’s system measures and records the temperature every hour for up to 11 months in remote locations for just $30 apiece. Another advantage is that they are easily deployed in rough terrain.

One quarter of the Earth’s continents have mountainous terrain, Lundquist says, and mountain rivers, largely fed by snowmelt, provide water for 40 percent of the world’s population.

If winters become warmer due to climate change, the snow line is expected to inch up the mountainside, and snow is expected to melt earlier in the springtime.

“Mountains are the water towers of the world,” Lundquist explains. “We essentially use the snow as an extra reservoir. And you want that reservoir to hold the snow for as long as possible.”

“People typically assume that temperature decreases with elevation,” Lundquist says. But actual mountain temperatures depend on the vegetation, slope and variable weather. “If you have a management decision, there’s a specific place you have to make a decision for.”

If more rain falls instead of snow, it will increase the risk of flooding during storms.

Lundquist’s sensors are currently being used by the California-Nevada River Forecasting Center as part of a project pinpointing at what elevation snow turns to rain, to improve storm flooding forecasts. As part of that project, UW graduate students are placing her sensors in river canyons that are too steep for traditional weather stations.

She is also deploying sensors in Yosemite National Park to see if earlier snowmelt may cause earlier drying of streambeds and affect vegetation growth in the Tuolumne Meadows. Her sensors there provide ground verification of satellite measurements.

The City of Seattle is also using Lundquist’s sensors to study how different restoration approaches for trees in the Cedar River watershed, which supplies water to the city, affect snow retention.

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