Here’s something to add to your doomsday list of natural resources that people need to survive but are threatened by climate change: snow.
It’s a key source of freshwater for more than 1 billion people across the globe, slaking thirst, irrigating croplands, and driving turbines that generate electricity. Conveniently, in much of the world, snow also acts as a natural reservoir, storing water during wet seasons, then rationing it out slowly during drier summer months. But today, growing populations, warming temperatures, and changing weather patterns are straining that supply like never before. “June is the new July,” says Auden Schendler, vice president of sustainability at Aspen Skiing Company in Colorado. “Snowmelt comes earlier than it used to, and it all happens in one big flood.”
Which means that knowing exactly how much snow is in the highlands—and when it’s coming down to lower elevations to feed rivers, aqueducts, and irrigation channels—is ever more important. But how do you measure something that’s spread over thousands of miles of steep, rugged, alpine terrain?
Tom Painter, a research scientist at NASA’s Jet Propulsion Laboratory, has an answer: by measuring snow from thousands of feet in the air. Using sophisticated, aircraft-borne sensors that gauge snow’s depth and the amount of light it reflects, Painter and his team are assembling the most accurate measurement ever made of just how much water the mountains hold.
This is welcome news in California, where the water content of accumulated snow is at historically low levels. Runoff from the Sierra Nevada mountains provides about a third of the entire state’s water, and up to 80 percent in some areas, supplying tens of millions of people and almost 1 million acres of farmland.
Painter can’t make it snow, but he can provide more and better data to water managers, who need to plan how to most efficiently fill their reservoirs; farmers deciding which crops to plant and when; and cities trying to figure out if they’ll have enough water to supply their residents—or will need to start rationing. “The demand for knowledge about water resources is at an all-time high,” says Painter, a gregarious, athletically built 46-year-old.
For decades, state water officials have estimated the snowpack’s water content by a straightforward method that will appeal to steampunk aficionados: They clamber into the mountains on snowshoes and stick aluminum tubes into the snow. The tubes indicate depth while collecting a sample revealing water volume. More recently, California has added a network of tabletop-size scales scattered through the mountains that electronically transmit the weight of snow that has fallen on them.
Both systems yield reliable measurements but only of the snow where the measurement is taken; extrapolating out from that to a whole basin, or a whole mountain range, is better than guesswork but less than precise. What’s more, both the scales and the human surveyors are concentrated at lower elevations, leaving scientists to wonder what lies farther uphill. “The old system worked OK historically because there was always enough water,” says Painter. “But now it’s all been allocated out, and demand is starting to exceed supply.” More