NASA Opens New Era in Measuring Western U.S. Snowpack

[baa...@earthlink.net]

May 02, 2013

Steve Cole
Headquarters, Washington
202-358-0918
stephen...@nasa.gov

Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
alan...@jpl.nasa.gov


RELEASE: 13-131

NASA OPENS NEW ERA IN MEASURING WESTERN U.S. SNOWPACK

WASHINGTON -- A new NASA airborne mission has created the first maps
of the entire snowpack of two major mountain watersheds in California
and Colorado, producing the most accurate measurements to date of how
much water they hold.

The data from NASA's Airborne Snow Observatory mission will be used to
estimate how much water will flow out of the basins when the snow
melts. The data-gathering technology could improve water management
for 1.5 billion people worldwide who rely on snowmelt for their water
supply.

"The Airborne Snow Observatory is on the cutting edge of snow
remote-sensing science," said Jared Entin, a program manager in the
Earth Science Division at NASA Headquarters in Washington. "Decision
makers like power companies and water managers now are receiving
these data, which may have immediate economic benefits."

The mission is a collaboration between NASA's Jet Propulsion
Laboratory (JPL) in Pasadena, Calif., and the California Department
of Water Resources in Sacramento.

A Twin Otter aircraft carrying NASA's Airborne Snow Observatory began
a three-year demonstration mission in April that includes weekly
flights over the Tuolumne River Basin in California's Sierra Nevada
and monthly flights over Colorado's Uncompahgre River Basin. The
flights will run through the end of the snowmelt season, which
typically occurs in July. The Tuolumne watershed and its Hetch Hetchy
Reservoir are the primary water supply for San Francisco. The
Uncompahgre watershed is part of the Upper Colorado River Basin that
supplies water to much of the western United States.

The mission's principal investigator, Tom Painter of JPL, said the
mission fills a critical need in an increasingly thirsty world,
initially focusing on the western United States, where snowmelt
provides more than 75 percent of the total freshwater supply.

"Changes in and pressure on snowmelt-dependent water systems are
motivating water managers, governments and others to improve
understanding of snow and its melt," Painter said. "The western
United States and other regions face significant water resource
challenges because of population growth and faster melt and runoff of
snowpacks caused by climate change. NASA's Airborne Snow Observatory
combines the best available technologies to provide precise, timely
information for assessing snowpack volume and melt."
The observatory's two instruments measure two properties most critical
to understanding snowmelt runoff and timing. Those two properties
have been mostly unmeasured until now.

A scanning lidar system from the Canadian firm Optech Inc. of Vaughan,
Ontario, measures snow depth to determine the first property, snow
water equivalent with lasers. Snow water equivalent represents the
amount of water in the snow on a mountain. It is used to calculate
the amount of water that will run off.

An imaging spectrometer built by another Canadian concern, ITRES of
Calgary, Alberta, measures the second property, snow albedo. Snow
albedo represents the amount of sunlight reflected and absorbed by
snow. Snow albedo controls the speed of snowmelt and timing of its
runoff.

By combining these data, scientists can tell how changes in the
absorption of sunlight cause snowmelt rates to increase.
The Airborne Snow Observatory flies at an altitude of 17,500 feet -
22,000 feet (5,334 to 6,705 meters) to produce frequent maps that
scientists can use to monitor changes over time. It can calculate
snow depth to within about 4 inches (10 centimeters) and snow water
equivalent to within 5 percent. Data are processed on the ground and
made available to participating water managers within 24 hours.
Before now, Sierra Nevada snow water equivalent estimates have been
extrapolated from monthly manual ground snow surveys conducted from
January through April. These survey sites are sparsely located,
primarily in lower to middle elevations that melt free of snow each
spring, while snow remains at higher elevations. Water managers use
these survey data to forecast annual water supplies. The information
affects decisions by local water districts, agricultural interests
and others. The sparse sampling can lead to large errors. In
contrast, the NASA observatory can map all the snow throughout the
entire snowmelt season.

"The Airborne Snow Observatory is providing California water managers
the first near-real-time, comprehensive determination of basin-wide
snow water equivalent," said Frank Gehrke, mission co-investigator
and chief of the California Cooperative Snow Surveys Program for the
California Department of Water Resources. "Integrated into models,
these data will enhance the state's reservoir operations, permitting
more efficient flood control, water supply management and
hydroelectric power generation."

Gehrke said the state will continue to conduct manual surveys while it
incorporates the Airborne Snow Observatory data. "The snow surveys
are relatively inexpensive, help validate observatory data and
provide snow density measurements that are key to reducing errors in
estimating snow water equivalent," he said.

Painter plans to expand the airborne mapping program to the entire
Upper Colorado River Basin and Sierra Nevada.
"We believe this is the future of water management in the western
United States," he said.

For more information about the Airborne Snow Observatory, visit:

http://aso.jpl.nasa.gov/

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