Groundwater depletion in semiarid regions of Texas and California threatens US food security

Groundwater depletion in semiarid regions of Texas and California threatens US food security
Groundwater depletion has been most severe in the purple areas indicated on these maps of (A) the High Plains and (B) California's Central Valley. These heavily affected areas are concentrated in parts of the Texas Panhandle, western Kansas, and the Tulare Basin in California's Central Valley. Changes in groundwater levels in (A) are adapted from a 2009 report by the US Geological Survey and in (B) from a 1989 report by the USGS. Credit: US Geological Survey

The nation's food supply may be vulnerable to rapid groundwater depletion from irrigated agriculture, according to a new study by researchers at The University of Texas at Austin and elsewhere.

The study, which appears in the journal , paints the highest resolution picture yet of how depletion varies across in California's and the High Plains of the central U.S. Researchers hope this information will enable more sustainable use of water in these areas, although they think irrigated agriculture may be unsustainable in some parts.

"We're already seeing changes in both areas," said Bridget Scanlon, senior research scientist at The University of Texas at Austin's Bureau of Economic Geology and lead author of the study. "We're seeing decreases in rural populations in the High Plains. Increasing urbanization is replacing farms in the Central Valley. And during some farmers are forced to fallow their land. These trends will only accelerate as issues become more severe."

Three results of the new study are particularly striking: First, during the most recent drought in California's Central Valley, from 2006 to 2009, farmers in the south depleted enough groundwater to fill the nation's largest man-made reservoir, near Las Vegas—a level of groundwater depletion that is unsustainable at current recharge rates. Second, a third of the groundwater depletion in the High Plains occurs in just 4% of the land area. And third, the researchers project that if current trends continue some parts of the southern High Plains that currently support irrigated agriculture, mostly in the Texas Panhandle and western Kansas, will be unable to do so within a few decades.

California's Central Valley is sometimes called the nation's "fruit and vegetable basket." The High Plains, which run from northwest Texas to southern Wyoming and South Dakota, are sometimes called the country's "grain basket." Combined, these two regions produced agricultural products worth $56 billion in 2007, accounting for much of the nation's food production. They also account for half of all groundwater depletion in the U.S., mainly as a result of irrigating crops.

In the early 20th century, farmers in California's Central Valley began pumping groundwater to irrigate their crops. Over time, groundwater levels dropped as much as 400 feet in some places. From the 1930s to '70s, state and federal agencies built a system of dams, reservoirs and canals to transfer water from the relatively water-rich north to the very dry south. Since then, groundwater levels in some areas have risen as much as 300 feet. In the High Plains, farmers first began large-scale pumping of groundwater for crop irrigation in the 1930s and '40s; but irrigation greatly expanded in response to the 1950s drought. Since then, groundwater levels there have steadily declined, in some places more than 150 feet.

Scanlon and her colleagues at the U.S. Geological Survey and the Université de Rennes in France used water level records from thousands of wells, data from NASA's GRACE satellites, and computer models to study groundwater depletion in the two regions.

GRACE satellites monitor changes in Earth's gravity field which are controlled primarily by variations in water storage. Byron Tapley, director of the university's Center for Space Research, led the development of the GRACE satellites, which recently celebrated their 10th anniversary.

Scanlon and her colleagues suggested several ways to make irrigated agriculture in the Central Valley more sustainable: Replace flood irrigation systems (used on about half of crops) with more efficient sprinkle and drip systems and expand the practice of groundwater banking—storing excess surface water in times of plenty in the same natural aquifers that supply groundwater for irrigation. Groundwater banks currently store 2 to 3 cubic kilometers of water in California, similar to or greater than storage capacities of many of the large surface water reservoirs in the state. Groundwater banks provide a valuable approach for evening out water supplies during climate extremes ranging from droughts to floods.

For various reasons, Scanlon and other experts don't think these or other engineering approaches will solve the problem in the High Plains. When groundwater levels drop too low to support irrigated farming in some areas, farmers there will be forced to switch from irrigated crops such as corn to non-irrigated crops such as sorghum, or to rangeland. The transition could be economically challenging because non-irrigated crops generate about half the yield of irrigated crops and are far more vulnerable to droughts.

"Basically irrigated agriculture in much of the southern High Plains is unsustainable," said Scanlon.

Explore further

California's troubled waters: Satellite-based findings reveal major groundwater loss in Central Valley (w/ Video)

More information: “Groundwater depletion and sustainability of irrigation in the United States high plains and central valley,” by Bridget R. Scanlon et al. PNAS, 2012.
Citation: Groundwater depletion in semiarid regions of Texas and California threatens US food security (2012, May 28) retrieved 22 September 2019 from
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May 28, 2012
"From the 1930s to '70s, state and federal agencies built a system of dams, reservoirs and canals to transfer water from the relatively water-rich north to the very dry south."

And thanks to whakko environmentalists they have hardly built any dams since the 1970s.

If your population grows and you live in a semi-arid or arid climate, you need dams for the drought/rain cycles.

May 28, 2012
The Ogallala Aquifer (pictured in the left image) was huge, but it was never able to supply the demands that it has had on it. As large as it is, it is also very slow to be replenished. Even if we quit drawing water now, it could take a hundred years to restore.

Our midwest breadbasket is going to be crumbs soon.

May 28, 2012
"Researchers successfully test solar desalination system for arid land agriculture"

Most of the western states are owned by the federal govt. Is it any wonder the govt has poorly managed the land?

Free trade is the most effective security for food. If the rest of the world's agriculture was motivated by the market instead of socialism, even more, less expensive food would be on the market.

May 28, 2012
NotrealityParker: Take a look at the current water level in the dams that are already in place, esp. California. Pretty low, huh? That and the fact that rivers can only support a limited number of dams may be why more dams aren't built.

If it were that easy to build more dams, we could solve our energy needs in a decade of frenzied dam building, and pipe the water across the land to make the deserts burst forth with proper capitalist cheap foodstuffs.

May 28, 2012
Impossible. Denialist Tards have repeatedly told us that they will grow vast quantities of corn and wheat on the barren rock of the Canadian and Russian shields.

Just look at the vast vista of potential crop land.

Moss and fungus will grow anywhere. We just have to engineer it so we can eat it.

May 28, 2012
Putting in more dams and reservoirs in the upper areas of the aquifers will help maintain their levels. The excess water runoff during the wet periods will replenish them.. rather than simply waste it downstream.

May 29, 2012
ParkerTard thinks that dams magically create water and cause it to grow in the ground like the oil he claims grows in the ground.

Dams accumulate water when it rains and saves it for dry seasons. If you don't build dams, the water runs into the ocean. You have to be pretty deranged to not know that.

May 29, 2012
We humans can't live in a place that is too dry, no matter how we beat and punish the land to wring precious water from it. How is that so hard to understand?

May 29, 2012
Since water is not actually consumed (i.e. H2O is not broken down into component elements when drank or when used to wash or water), the solution is to find out where it is all going, then retrieve it. If it is evaporating and raining down elsewhere, then it will have to be piped back in. If it is ending up in the ocean, then we have to develop an economical, massive desalination capability to make fresh water out of the salt water. In a dire scenario, we may have to mine the ice of Greenland for fresh water and/or relocate people from places that are too dry to places that are more hospitable. Population reduction will end up figuring in there somewhere, too.

May 29, 2012
Parker Tard seems to have forgotten the purpose and conclusion of the research. The study of ground water and it's loss in the U.S. west coast.

Parker Tard seems to think that a dam is an aquifer.

"Dams accumulate water when it rains and saves it for dry seasons." - ParkerTard

The article is about food security being threatened.

It wouldn't be threatened if more dams had been built.

Eco-loons stopped the dams from being built and forced Californians to squandered hundreds of billions on wind mills just to kill eagles and triple the price of electricity.

Now they will starve and will die from the heat because they can't afford to run the A/C units.

The dams would have provided cheap electricity and water for agriculture.

Jun 02, 2012
giant pipelines of water will be proposposed as a works project to bring water from canada and alaska to the west coast.

it's a dumber idea than effective conservation but it won't end the world. and it will make plenty of 'jobs' and 'water security' while inevitably creating regressive problems.

an inelegant solution, but maybe not such a bad idea. ---

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