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 Nevada – have lost nearly enough water combined to fill Lake Mead, America’s largest reservoir. The findings, based on satellite data, reflect California’s extended drought and increased pumping of groundwater for human uses such as irrigation.
At the American Geophysical Union meeting this week in San Francisco, UC Irvine and NASA scientists detailed the state’s groundwater changes and outlined research on other global aquifers conducted via twin satellites called the Gravity Recovery and Climate Experiment. GRACE monitors tiny month-to-month differences in Earth’s gravity field primarily caused by the movement of water in the planet’s land, ocean, ice and atmosphere. Its ability to “weigh” changes in water content provides new insights into how climate change is affecting Earth’s water cycle.
Combined, California’s Sacramento and San Joaquin drainage basins have shed more than 30 cubic kilometers of water since late 2003, said Jay Famiglietti, UCI Earth system science professor and director of the UC Center for Hydrologic Modeling. A cubic kilometer is about 264.2 billion gallons, enough to fill 400,000 Olympic-size pools. The bulk of the loss occurred in the state’s agricultural Central Valley. The Central Valley depends on irrigation from both groundwater wells and diverted surface water.
“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 project scientist Michael Watkins of NASA’s Jet Propulsion Laboratory.
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 indicate 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. More than 75 percent of this is due to groundwater pumping in the southern Central Valley, primarily to irrigate crops.
Famiglietti said recent California legislation decreasing the allocation of surface water 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 Matt Rodell of NASA’s Goddard Space Flight Center, Isabella Velicogna of UCI, and Famiglietti found groundwater levels in northwest India declining by 17.7 cubic kilometers per year between October 2002 and August 2008, a loss attributed 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 billion to $8 billion annually,” said Rodell, who was Famiglietti’s doctoral student at the University of Texas at Austin.
Other regions under study include the southeastern U.S., where GRACE clearly captured the evolution of an extended drought that ended this spring; Australia; and the Middle East-North Africa region. There, Rodell is leading an effort to assess regional water resources by using GRACE and other data to systematically map water and weather-related variables. He said 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 ground.
GRACE is a NASA/German Aerospace Center (DLR) partnership. The University of Texas Center for Space Research 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/.
About the University of California, Irvine: Founded in 1965, UCI is a top-ranked university dedicated to research, scholarship and community service. Led by Chancellor Michael Drake since 2005, UCI is among the fastest-growing University of California campuses, with more than 27,000 undergraduate and graduate students, 1,100 faculty and 9,200 staff. The top employer in dynamic Orange County, UCI contributes an annual economic impact of $4.2 billion.
News Radio: UCI maintains on campus an ISDN line for conducting interviews with its faculty and experts. Use of this line is available for a fee to radio news programs/stations that wish to interview UCI faculty and experts. Use of the ISDN line is subject to availability and approval by the university.
Jennifer Fitzenberger | EurekAlert!
Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation
Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences