Snowpack: The Canary in a Coal Mine - The Ripple Effect: The Fate of Freshwater in the Twenty-First Century - page 164

Having skied out of the close-wooded trail and onto the white expanse of Gin Flat,
Gehrke took a moment to catch his breath. Then he and a colleague began to check
scientific instruments that had been placed around the meadow to monitor conditions
year-round. The devices, which automatically transmit data to laboratories in Sacra-
mento and Virginia every three hours, measure the depth, temperature, and weight of
the snow, the moisture of the soil under the snow, the humidity and wind speed, and
the intensity of the sun's rays. Gehrke used a long aluminum tube to measure the water
content of the thick drifts of powder and to check the snow-pack's depth.
As California struggled in 2008 with the effects of a second year of drought, Gehrke's
readings from Gin Flat and other sites helped to determine California's water rates, how
much water farmers and industry could use, and whether homeowners' car washing
and garden watering would be restricted.
Though he is a careful scientist, reluctant to make bold statements or far-reaching
predictions, Gehrke noted that in twenty-seven years of taking measurements he'd no-
ticed snowpack levels becoming “erratic”—meaning that California winters had become
“either really dry or really wet.” Sierra-wide, snowpack was only 40 percent of average
in 2007, but in 2008 it would rise to 118 percent.
Gehrke measures snow water equivalent (SWE), which is the amount of water in
snowpack: the depth of water that would result if you melted the entire snowpack.
he average SWE at Gin Flat is thirty-two inches a year. In 1988, during the previous
drought (1987 to 1992), Gin Flat's SWE dropped severely, to only 5.1 inches. Since then
it had risen. In 2007, Gin Flat's SWE was 11.4 inches; in 2008 it was 33.8 inches; and in
2009 it was 30 inches. In 2010, heavy rains seemed to ease the latest drought, and Gin
Flat's average SWE was 43 inches. But Gehrke cautioned that La Niña conditions (low
ocean surface-water temperatures) were expected, and that 2011 would be dry again.
When climatologists talk about a hotter climate, they often depict a world of too much
water, an era in which the coasts of today are submerged by rising oceans. But in recent
years they have begun to focus on a different aspect of climate change, and to imagine
a world in which the snowpack of the Sierra, the Rockies, the Himalayas, and other im-
portant mountain ranges liquefies earlier in the year, faster than ever.
In 2006, Steven Chu —the Nobel-winning physicist whom President Obama named
secretary of energy in 2009—said that decreasing supplies of freshwater from snowmelt
might prove a far more significant problem than slowly rising oceans. “There's a two-
thirds chance there will be a disaster,” Chu told the NewYorkTimesMagazine.“And
that's in the best scenario.” By disaster he meant the possibility of a modern Dust
Bowl in the Southwest, which would cause grave ecological harm and cause millions of
people to evacuate desert cities.