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!
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
New plate adds plot twist to ancient tectonic tale
15.08.2017 | Rice University
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Earth Sciences
17.08.2017 | Life Sciences
17.08.2017 | Materials Sciences