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ANN THOMPSON: With its rugged, snowcapped mountains, clear
freshwater lakes, and massive sequoia trees, the Sierra Nevada
mountain range in California is one of the most visually
stunning landscapes in the United States.
In addition to its beauty, snow pack and snow melt from this
400-mile stretch of mountains serves a purpose: providing
drinking water to about thirty percent of the residents in
California, irrigation water to the more than $35 billion a year
agricultural industry in the San Joaquin valley, and water to run
the hydroelectric power industry that supplies at least 15% of
the state's electricity.
MARTHA CONKLIN: In California, we wait with bated breath to
hear about the size of the snowpack. In recent years, our
precipitation patterns have been changing with maybe less
precipitation during the wintertime and a little more
precipitation in the springtime. It's so nice to see this put
together. How's it going to help solve the water balance
for the meta?
THOMPSON: Martha Conklin is a hydrologist at the University of
California-Merced and is supported in part by the
National Science Foundation. She belongs to a team of
scientists that study the Sierra Nevada snowpack to make more
precise measurements and predictions of snowmelt and
runoff, so the water can be better managed.
CONKLIN: We'll come up with information systems that are
going to be useful for better water resources decisions. We
actually provide knowledge to the state of California on how
it's going to meet the changing snowpack and how to adapt our
water management systems to do that.
THOMPSON: Following the Earth's water cycle, water precipitates
as snow over the higher elevations of the Sierra
Nevada from November to April, accumulating
into a thick snowpack.
CONKLIN: That basically provides free water storage for
us for six months of the year because that water that falls as
solid precipitation just sits up there.
THOMPSON: The snowpack remains intact until the weather warms
during the spring and summer months and generates snowmelt.
The water then moves slowly downhill before it ends up in
streams and rivers as runoff, or percolates into the soil as
groundwater. But warming temperatures in a changing
climate cause more water to precipitate as
rain rather than snow. This rain never accumulates as snowpack.
Instead, runoff occurs earlier, potentially leading to water
shortages later in the year. Tom Harmon is an environmental
engineer and lead scientist for the water sustainability project
at UC Merced.
TOM HARMON: We've relied a lot on past history to try to judge
how much water we'll have and statistically that used to work
out. But now the climate change is changing those statistics and
we can't use the past as a very good predictor anymore.
THOMPSON: Harmon, Conklin and other scientists are conducting
research at the Southern Sierra Critical Zone Observatory, or
CZO, located near Shaver Lake, California. The data from this
observatory is used to understand snowpack
accumulation, its water content, and melt rate. The information
is then used by many water management groups
throughout California to help better manage dams
and water release schedules.
HARMON: I think now the next challenge is how to put together
that data carefully, accurately and connect it with a theory
that makes sense and covers all the processes in sufficient
detail; that we gain predictive capabilities.
THOMPSON: To more accurately measure snowpack, the Southern
Sierra CZO has developed a system of wireless sensors
strategically clustered around several watershed locations that
collect data in real time.
MATT MEADOWS: We're measuring precipitation, distribution of
precipitation in the snow pack, and how that snow melts and goes
into the soil, what our soil water content is, and how the
water actually moves from the soil into the stream.
THOMPSON: In addition, a network of flux towers that soar
to more than 150 feet high, measure fluctuations in the
atmosphere that quantify the net rate of water exchange during
evapotranspiration, or the water from snowpack, vegetation, and
the soil, that moves into the air thus removing water from the
critical zone. By collecting this data, scientists can
provide information that can help determine not
only how much water will be available, but when and where
it will be available.
CONKLIN: We look at what we can do with developing better
information about the snowpack is to provide information to
decision-makers that they can make better decisions and they
know how much water is available in the system.
THOMPSON: Knowing where the snow is and how much runoff and
river flow to expect in a given season can provide the
information necessary to help water managers allocate water
resources for people, agricultural, environmental,
and industrial needs.
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