Snowpack: The Canary in a Coal Mine - The Ripple Effect: The Fate of Freshwater in the Twenty-First Century - page 163

CHAPTER 17
Snowpack: The Canary in a Coal Mine
GEHRKE AT THE ROSETTA STONE
Gin Flat is a small meadow surrounded by pine and cedar trees that sits in the thin air at
seventy-two hundred feet above sea level in Yosemite National Park, in California's Sierra
Nevada. In winter it is covered with layer upon layer of deep snowpack, the snow that ac-
cumulates at high altitude in regions that are cold for most of the year. Snowpack “stores”
water like a giant reservoir, which it then slowly releases during the spring and summer
snowmelt. Snowmelt from the Sierra flows into streams and rivers that empty into the
Sacramento and San Joaquin Rivers, which flow through the Sacramento-San Joaquin
Delta, a vast estuary near the state capital. The Delta supplies freshwater to millions of
Californians and thousands of acres of farmland around San Francisco, Los Angeles, and
as far south as San Diego. The Sierra snowpack is California's most important source of
freshwater.
Gin Flat has been called the Rosetta Stone of the California water supply because it has
just the right conditions—a balance of snow, sun, and air temperature—to help scientists
predict snowmelt, water flows, and potential floods and droughts in coming seasons. Be-
cause it is just above the altitude where snow turns to rain, Gin Flat is an ideal spot to
test the theory that global warming will lead to more rain and less snow at higher eleva-
tions. Such a shift, climatologists hypothesize, will result in major hydrological changes:
less water stored as snowpack, and more runoff, flooding, and evaporation, which could
in turn lead to less freshwater flowing to arid Southern California in the spring and early
summer, when it is needed most.
Every winter Frank Gehrke clips into his cross-country skis, harnesses himself to a
sled loaded with equipment, and slips and slides his way up a three-mile-long trail to
Gin Flat. Gehrke is chief of California's Department of Water Resources' (DWR) Co-
operative Snow Surveys Program. He is considered the dean of the state's snow studies
experts, and thus an expert on the future of California's water supply. Gin Flat (named
after a former speakeasy) is a “snow course” that has been providing DWR with valuable
snowpack data since 1930. California has two hundred and eighty similar sites, eighteen
of them in Yosemite. Because of its location and long data record, Gin Flat is always the
first and most important site for testing.