The Great Plains corn industry owes much of its business to the Great Plains cattle feeding industry. Conversely, the Great Plains cattle feeding industry depends in large part on Great Plains corn. But both industries rest much of their survival on a less-than-certain foundation - the Ogallala Aquifer.

The aquifer, which serves parts of eight states, will be there only until it's used up, and that's the problem.

The Ogallala isn't like a reservoir that refills with spring rains. It recharges slowly - very slowly - as snowmelt and rain seep into the ground. But to supply the needs of the grain and cattle feeding industries, 20th century agriculture has used the aquifer's water much faster than it refills.

Yet as groundwater supplies have fallen, a remarkable transformation has taken place. Grain farmers, cattle feeders and non-residents have turned into avid water conservationists to make their aquifer last. Some areas served by the Ogallala now consume only a third of the water they did just a few decades ago.

To glimpse what has happened, look at southwestern Kansas, where new wells are banned in areas where the aquifer is overtaxed. Or travel to the Texas Panhandle, where aircraft seed clouds each year, hoping to increase rainfall and ease demands on the Ogallala.

Throughout the region, efforts are under way to find more efficient irrigation methods or develop new irrigation equipment that uses less water. These efforts have met with much success.

One example is the development of irrigation equipment that delivers water closer to the ground, minimizing losses to wind and evaporation, says Leon New, an extension irrigation engineer at Texas A&M University. He and others jointly developed the equipment.

And in laboratories around the country, scientists are seeking to create the water-miser crops of the future. But that's a tall order. Scientists have found water and plant growth are closely intertwined.

"In other words, it's sort of a law of nature that if you want a lot of grain, you've got to use a lot of water," explains Jay Ham, a Kansas State University agronomist. "It's hard to alter that relationship."

Still, plant breeding and genetic engineering programs by seed producers may bring small but important gains.

"We hope to develop hybrids that will allow the same yields on less water," says Joe Keaschall, plant scientist at Pioneer Hi-Bred International.

Pioneer researchers are trying to boost water-use efficiency through traditional crossbreeding programs and through biotechnology that seeks to identify genes for water efficiency and heat tolerance.

The goal of such efforts is to maintain the economic vitality of the Great Plains by making the water last. After all, water, not oil, may be the region's most valued asset.

"The oil isn't going to do us any good if we don't have water," says Texas A&M's New.

And if the water goes, the corn industry suffers two ways. First, water restrictions could force irrigated operations to switch to more risky and less productive dryland farming. Second, restrictions could force cattle feeders to curtail or close operations. That would cost corn farmers business.

The Ogallala owes its existence to the Rocky Mountains. As erosion wore down the Rockies millions of years ago, rain washed bits of sand and gravel eastward across the Great Plains. Over time, the sediments grew thicker, forming something like an immense sandbox with a clay liner at the bottom that prevents water from escaping.

Gradually, water filled the gaps between the sand, creating a very large, high-quality supply. For most of the Ogallala's history, the aquifer remained largely untapped.

Although permanent settlement began in the late 19th century, early arrivals thought the region unsuitable for agriculture or grazing. The Great Plains were marked by drought, insect infestations, fires and a scarcity of surface water. It didn't rain enough to make dryland farming worthwhile for many.

From the late 1950s on, a series of innovations in irrigation technology opened the Great Plains to high-yield farming. These innovations made irrigation easier, more efficient and more effective. As growers seized the new technology, they sucked huge volumes of water from the ground each year, turning the one-time dust bowl region into the nation's grain belt.

Cattle feeders followed the grain boom, building giant feedyards up and down the 174,000 square miles served by the Ogallala - a region that starts in South Dakota. It then runs south through Nebraska, Colorado, Kansas and Oklahoma, and winds up in the Texas Panhandle.

"There was this huge abundance of corn and alfalfa," says Hank Hansen, who advises farmers and cattle feeders on water rights in the Southwest Kansas Ground Water Management District. "The feeders saw that potential and said, rather than shipping the grain, why not feed the cattle here?"

But there was a price for this new prosperity. The aquifer was emptying at an alarming rate.

As time passed, conservation fever caught hold. While no single water-saving measure did the trick, small improvements added up and water use fell dramatically. For example, in the 1960s and 70s, the High Plains Underground Water District in Lubbock, TX, depleted the aquifer by roughly 1.4 million acre-feet of water a year.

With conservation measures, "we've cut it to about a third of what it was," says Wayne Wyatt, the district's general manager. "There's a whole lot of difference between what's happening now and what happened in the early days of irrigation."

Back then, water was funneled down an irrigation ditch, then poured down furrows in the fields.

"The effective use of water was probably no more than 50% of what was pumped," says Wyatt. "The losses where the best technology is used now are probably about 5% of what's pumped."

Cattle feeders took similar measures to cut water consumption. The end result has been sharply lower water consumption throughout the Great Plains and a longer life for the aquifer on which these two interlinked industries depend.

Despite these efforts, the water is still being used faster than Nature can replenish it and agribusiness continues to search for more ways to use less. But nobody knows whether the Ogallala can be made to last indefinitely.

"How long will it last?" asks Ginny McGuire, a hydrologist with the U.S. Geological Survey. "That's hard to say because, as the water level goes down, you get more regulation and more conservation technology, so you use less. Also, as the water level goes down, people's behavior changes."