NASA Data Reveal Major Groundwater Loss in California's Heartland

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

News release: 2009-194 Dec. 14, 2009

NASA Data Reveal Major Groundwater Loss in California's Heartland

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-194&cid=kintera_release_2009-194

PASADENA, Calif. - New space observations reveal that since October 2003, the aquifers for
California's primary agricultural region -- the Central Valley -- and its major mountain water source --
the Sierra Nevadas -- have lost nearly enough water combined to fill Lake Mead, America's largest
reservoir. The findings, based on data from the NASA/German Aerospace Center Gravity Recovery
and Climate Experiment (Grace), reflect California's extended drought and increased rates of
groundwater being pumped for human uses, such as irrigation.

In research being presented this week at the American Geophysical Union meeting in San Francisco,
scientists from NASA and the University of California, Irvine, detailed California's groundwater
changes and outlined Grace-based research on other global aquifers. The twin Grace satellites monitor
tiny month-to-month changes in Earth's gravity field primarily caused by the movement of water in
Earth's land, ocean, ice and atmosphere reservoirs. Grace's ability to directly 'weigh' changes in water
content provides new insights into how Earth's water cycle may be changing.

Combined, California's Sacramento and San Joaquin drainage basins have shed more than 30 cubic
kilometers of water since late 2003, said professor Jay Famiglietti of the University of California,
Irvine. A cubic kilometer is about 264.2 billion gallons, enough to fill 400,000 Olympic-size pools.
The bulk of the loss occurred in California's agricultural Central Valley. The Central Valley receives
its irrigation from a combination of groundwater pumped from wells and surface water diverted from
elsewhere.

"Grace data reveal groundwater in these basins is being pumped for irrigation at rates that are not
sustainable if current trends continue," Famiglietti said. "This is leading to declining water tables,
water shortages, decreasing crop sizes and continued land subsidence. The findings have major
implications for the U.S. economy, as California's Central Valley is home to one sixth of all U.S.
irrigated land, and the state leads the nation in agricultural production and exports."

"By providing data on large-scale groundwater depletion rates, Grace can help California water
managers make informed decisions about allocating water resources," said Grace Project Scientist
Michael Watkins of NASA's Jet Propulsion Laboratory, Pasadena, Calif., which manages the mission
for NASA's Science Mission Directorate, Washington.

Preliminary studies show most of the water loss is coming from the more southerly located San
Joaquin basin, which gets less precipitation than the Sacramento River basin farther north. Initial
results suggest the Sacramento River basin is losing about 2 cubic kilometers of water a year. Surface
water losses account for half of this, while groundwater losses in the northern Central Valley add
another 0.6 cubic kilometers annually. The San Joaquin Basin is losing 3.5 cubic kilometers a year. Of
this, more than 75 percent is the result of groundwater pumping in the southern Central Valley,
primarily to irrigate crops.

Famiglietti said recent California legislation decreasing the allocation of surface waters to the San
Joaquin Basin is likely to further increase the region's reliance on groundwater for irrigation. "This
suggests the decreasing groundwater storage trends seen by Grace will continue for the foreseeable
future," he said.

The California results come just months after a team of hydrologists led by Matt Rodell of NASA's
Goddard Space Flight Center, Greenbelt, Md., found groundwater levels in northwest India have
declined by 17.7 cubic kilometers per year over the past decade, a loss due almost entirely to pumping
and consumption of groundwater by humans.

"California and India are just two of many regions around the world where Grace data are being used
to study droughts, which can have devastating impacts on societies and cost the U.S. economy $6 to
$8 billion annually," said Rodell. Other regions under study include Australia, the Middle East -
North Africa region and the southeastern United States, where Grace clearly captured the evolution
of an extended drought that ended this spring. In the Middle East - North Africa region, Rodell is
leading an effort to use Grace and other data to systematically map water- and weather-related
variables to help assess regional water resources. Rodell added Grace may also help predict droughts,
since it can identify pre-existing conditions favorable to the start of a drought, such as a deficit of
water deep below the ground.

NASA is working with the National Oceanic and Atmospheric Administration and the University of
Nebraska-Lincoln to incorporate Grace data into NOAA's U.S. and North American Drought
Monitors, premier tools used to minimize drought impacts. The tools rely heavily on precipitation
observations, but are limited by inadequate large-scale observations of soil moisture and groundwater
levels. "Grace is the only satellite system that provides information on these deeper stores of water
that are key indicators of long-term drought," Rodell said.

Grace is a partnership of NASA and the German Aerospace Center (DLR). The University of Texas
Center for Space Research, Austin, has overall mission responsibility. JPL developed the satellites.
DLR provided the launch, and GeoForschungsZentrum Potsdam, Germany, operates the mission. For
more on Grace, see http://www.csr.utexas.edu/grace/ and http://grace.jpl.nasa.gov/ . Other media
contacts: Margaret Baguio, University of Texas Center for Space Research, 512-471-6922; Jennifer
Fitzenberger, University of California, Irvine, 949-824-3969.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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