California consumes water fast
Steve Gorman
California's two main river basins and the aquifers beneath its
agricultural heartland have lost nearly enough water since 2003 to fill
Lake Mead, America's largest reservoir, new satellite data showed on
Monday.
Depleted aquifers account for two-thirds of the loss measured, most
of it attributed to increased groundwater pumping for irrigation of
drought-parched farmland in California's fertile but arid Central
Valley, scientists said.
A sign on a farm trailer reading “Food grows where water flows,”
hangs over dry, cracked mud at the edge of a farm April 16, 2009
near Buttonwillow, California. David McNew/Getty Images |
The findings have major implications for the economy as the Central
Valley is home to one-sixth of all irrigated US cropland, a hydrologist
at the University of California, Irvine, and member of the research team
Jay Famiglietti said.
The Central Valley, stretching 805 km from Bakersfield to Redding,
has traditionally produced over half the US harvest of fruits and
vegetables. California as a whole ranks as the nation's No. 1 farm state
in terms of crop value, more than US$36-billion a year.
Central Valley farms have increasingly tapped into aquifers during
the past few years to help offset drastic cuts in their regular
allocations of irrigation water pumped in by the state and federal
government from farther north.
How much water remains in California's aquifers is unknown, but
satellite studies show that groundwater is being used up faster than
nature can restore it.
"I don't think people realize how quickly groundwater is being
depleted", Famiglietti said. "It does point to the fact that the pumping
is occurring at an unsustainable rate".
Results of the satellite-imaging study, conducted by NASA and the
German space agency, were presented by researchers at the American
Geophysical Union meeting in San Francisco.
The data are based on subtle month-to-month fluctuations in the
Earth's gravitational field used to gauge changes in the presence of
groundwater, surface water, ice and precipitation.
The amount of water available in the state's two biggest river
basins, the Sacramento and the San Joaquin, both of which drain
California's Sierra Nevada mountain range, has diminished by more than
30 cubic kilometers since late 2003, the study found.
That's nearly enough to fill Lake Mead on the Colorado River in
Nevada, a major water source for Nevada and southern California.
Two-thirds of that loss, the rough equivalent of 8 million Olympic-sized
pools, was groundwater.
The San Joaquin basin accounts for the bulk of the overall loss,
about 3.5 cubic kilometers of water a year, with more than 75 percent of
that total the result of groundwater pumping in the southern end of the
Central Valley, researchers said.
The California findings come months after another team of U.S.
hydrologists found groundwater levels in northwest India have declined
by nearly 18 cubic kilometers a year over the past decade, a loss due
almost entirely to pumping and the consumption of groundwater by humans.
Reuters |