The High Plains of North America are officially classed as semi-arid, not arid, but the distinction does not matter very much. Little rain falls on the wide earth of this immense, dun-colored region once roamed by the buffalo peoples, the Cheyenne and the Pawnee and the Ogallala and the Comanche. The Rockies wring moisture from the western sky; winds blowing north from the Gulf of Mexico swing to the right, dropping their wet gifts well to the east of the hundredth meridian. Thunderstorms and tornados wreak brief havoc, and the southward swing of the jet stream in winter brings cold storms down from Canada; but for most of the year, over most of the Plains, the sky is Ogallala blue.

The explorers and surveyors who followed Coronado into this land called it the Great American Desert. They thought it worthless for farming; today, it is one of the prime agricultural areas of the world. The magic that has made this possible is another sort of blue - a wide, dark blue that hides beneath the soil. Groundwater is the glass slipper that has transformed this Cinderella landscape into a princess. Under the sand hills, under the shortgrass prairie, under the rich harvest of corn and wheat and cotton, lurks an ocean: the Ogallala Aquifer. It sprawls from central Texas to southern South Dakota and from eastern Colorado almost into Iowa, and there is enough water in it to refill Lake Erie. Nine times.

It is hard to overestimate the impact that this bounty of buried water has had on American life. If you snack on popcorn or peanuts, you are probably eating Ogallala water; if you dress in cotton clothing, you are probably wearing it. The Ogallala grows wheat, and milo, and sunflowers, and sorghum. It grows alfalfa, for cattle, and it grows the cattle as well. It provides drinking water for large parts of eight states. The fourteen million acres of crops spread across its flat surface account for at least one-fifth of the total annual U. S. agricultural harvest. Five trillion gallons of water are drawn from the Ogallala annually - about thirty per cent of all groundwater used for irrigation in the United States. If the aquifer went dry, more than $20 billion worth of food and fiber would disappear immediately from the world's markets.

Or perhaps we should say when the aquifer goes dry. That is not hypothetical doomspeak, it is happening: not overnight, not next week, but steadily, stealthily, and for the most part irreversibly. The bulk of the water here is what geologists call "fossil water" - dampness from a distant era, preserved in earth and stone like the bones of dinosaurs. Most of it arrived during the aquifer's formation; much of the rest trickled in as groundwater flow while the aquifer was still connected to its sources in the snow-covered Rocky Mountains. Now that connection has been severed - save in one small place - and except for the inconsequential rains, inflow has ceased. Water is being pulled out much faster than it can be put back in. Since widespread irrigation began in the 1950s, the Ogallala has sustained a net loss of as much as 120 trillion gallons - eleven per cent of its original volume. One entire Lake Erie, plus a little. Gone. Most of it gone with full knowledge that it was going. Groundwater overdraft is not an accident here, it is a way of life. But because it means that the water will someday disappear, it is also a way of death.

- from Chapter I: The Phantom Reservoir