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Good to the Last Drop

On the southern High Plains of Texas, amid swaths of cotton fields, groundwater in the region’s major aquifer has been vanishing at an alarming rate—up to five acre-feet a year in the late 1950s and more than two acre-feet a year as recently as 1998. (An acre-foot is 325,851 gallons of water.) But in the past six years the annual rate of decline has dropped to half a foot. One reason: Growers have introduced drip irrigation and more efficient sprinkler systems to offset higher pumping costs.

Popularized in Israel more than 40 years ago, drip irrigation can be installed above or below ground and delivers water directly to a plant’s roots. Besides using 25 to 50 percent less water than conventional irrigation practices, it also increases crop yields and reduces the risk of disease. Its use is limited, however, partly because it’s expensive to install and partly because water is cheaper in the United States than in most countries. “In Texas, on the High Plains, there is no cost to get water if you own the land,” says Eduardo Segarra, an agricultural economist at Texas Tech University. “You can pump literally as much as you want.”

In places like California’s San Diego County, however, where water can cost more than $500 an acre-foot (compared with $36 an acre-foot in parts of Arizona), farmers are more apt to rely on—and pay for—the most efficient irrigation systems available. “If water costs increased two or three times, it would make sense in almost every case to convert to subsurface drip,” says Thomas Thompson, a professor of plant and soil science at Texas Tech, who has run showcases for growers thinking of switching to drip irrigation.

Still, as aquifers continue to be pumped dry and water grows ever scarcer throughout the West, drip is becoming increasingly popular. In 1998 about 2.3 million acres of farmland nationwide had drip or low-flow irrigation. That number rose to nearly 3 million acres in 2003—an increase of more than 30 percent. Of course, some farmers simply use the water they save with drip to irrigate more land. But with a third of pre-development groundwater in some parts of the High Plains already mined, it’s only a matter of time before more people start making a bigger effort to conserve. “We’ve got a finite resource and we’ve got increased demand,” says Jim Bordovsky, a research scientist at the Texas Agricultural Experiment Station, in Lubbock. “It doesn’t take a genius to figure out something has to be done.”—Jesse Greenspan

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