Geoscience Reference
In-Depth Information
the importance of snow
In the higher mountain elevations of the West, precipitation ot en falls as
snow. h is snow provides a crucial amount of water, i lling streams, lakes,
and reservoirs to be tapped during the long, dry summer. Across the West,
the melting of the winter snowpack provides a signii cant proportion—50
to 80 percent—of the annual water supply for ecosystems as well as human
consumption.
Water managers throughout the West rely on early forecasts of snowpack
to plan for each water year. h ese forecasts are based on measurements of
the mountain snowpack, obtained by hardy snow surveyors who head out
on skis into the mountains to determine how much meltwater will be avail-
able in the coming year. Each year in California, over 300 snow courses are
checked, each 1,000 or more feet long with measurements made every 100
feet on average. h e practice has been a part of the state's water management
program since the early 1900s, and the data collected provide valuable plan-
ning information for farmers, utility companies, municipal water managers,
and l ood control managers.
During the 1950s, 1960s, and early 1970s, another researcher in the UC
Berkeley Department of Geography, Douglas Powell, spent his winters on
skis taking part in the annual state snow surveys. Clear, sunny fall days may
be welcome to most Californians, but Powell was always happier when the
storm clouds arrived early, heralding a wet year that would replenish the
state's water supplies. He would ot en remind his summer-session students,
with a hint of wistful optimism, that storms—even thunderstorms—could
arrive as early as September. Moreover, autumn blizzards in the Sierra
Nevada range are not unheard of: in 1846, a series of October blizzards
dropped ten feet of snow, trapping the Donner Party during their ill-fated
trek across the Sierra.
Few of Powell's colleagues or students (this topic's authors among them)
have experienced the linkages between landscape and climate as intimately
as he did. For several weeks each year, he and his team strapped on cross-
country skis and backpacks loaded with log and i eld notebooks, pens, and
special snow collection tubes to determine the depth, water content, and
density of the snow he would trek across each day. h ey would measure the
water content of the snow by i lling a special tube with snow, weighing it,
and weighing the empty tube. One ounce of snow translates into one inch of
water content of the snow, so the snowpack can be converted into the amount
