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Southern Great Plains could run out of groundwater in 30 years, study finds

A new study looking at key aquifers beneath the Great Plains and California's Central Valley suggests that areas of Texas and Kansas are drawing groundwater at an unsustainable rate.

By / May 30, 2012

Wheat harvesters work on Tuesday near Clearwater, Kan. The Ogallala aquifer runs beneath much of western Kansas.

Fernando Salazar/The Wichita Eagle/AP

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Key farming regions in the US are drawing water from underground sources at unsustainable rates, with slightly more than one-third of the southern Great Plains at risk of tapping out its sources within the next 30 years.

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Those are among the conclusions of a study of the nation's two major aquifers – one underlying the high plains, the other beneath California's Central Valley – published this week in the Proceedings of the National Academy of Sciences.

Concerns over the loss of groundwater in these areas aren't new. But the researchers say the tools they've used build a detailed picture of these critical water sources – how the amount of water they contain varies with time, location, and regional climate patterns – could allow for more nuanced approached to local water management.

Other water specialists suggest that the ability to combine detailed well measurements with satellite data could open the door to developing regionwide, even multistate planning for groundwater use – an approach that currently is applied to surface water.

Moreover, careful tracking of aquifers is likely to become more critical as global warming's effects become more pronounced, particularly during the second half of this century, the team suggests.

A number of recent studies have highlighted the problem of groundwater depletion globally for irrigation, notes Bridget Scanlon, who heads the Sustainable Water Resources Program at the University of Texas at Austin and was the study's lead author.

“We wanted to look in more detail at the two areas where there has been the most groundwater depletion in the US and try to better understand what is going on so that we could see if its possible to manage them more sustainably or reduce the depletion,” she says.

Ogallala aquifer

Some of the biggest surprises involved the Ogallala aquifer, a resource that stretches north along the Texas-New Mexico border through the Oklahoma panhandle and western Kansas to extend through virtually all of Nebraska and into eastern Wyoming.

Farming in the high plains contributes about $35 billion a year to the economy. Conventional wisdom has held that from north to south, the aquifer represents “fossil” water from the melting of the continent's glaciers at the end of the last Ice Age. And in the central and southern high plains, that remains true. This is where groundwater losses have been most pronounced.

About 4 percent of the land area above the aquifer, which falls in parts of Kansas and Texas, is responsible for about a third of its water losses, the team estimated.

But the researchers found that in the northern high plains, groundwater levels either have been holding relatively steady or have increased between 1950 and 2007 – fed by rain and seepage from lakes that come and go with the rainy season and snow melt. Some water also finds its way underground from the Platte, Republican, and Arkansas Rivers. The water percolates through soils that are coarser than soils in the central and southern high plains.

Overall, however, the Ogallala Aquifer has lost an average of 5.3 cubic kilometers of water a year between the 1950s and 2007 – a rate that increased to an average of 7 cubic kilometers of water between 1987 and 2007.

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