A summer’s flight from Chicago to Denver can give one a new perspective on water use. Before the plane climbs above the clouds, one can see vast stretches of prairie land, cut into rectangles of dark green crops. From the sky, the crops seem to go on and on, delineated only by roads, trees and winding rivers. According to the National Corn Growers Association, more than 85 percent of all corn produced in the United States is nonirrigated, and much of it is raised on this fertile land that’s been under agricultural production since white men settled the region in the 1800s.

As the flight continues over Illinois, Iowa, Nebraska and eastern Colorado, one might notice that the farmscape begins to change. Circles, one-half mile in diameter, start to be dispersed amongst the rectangles. Further on, the land looks like a pale green and yellow checkerboard with dark green checkers placed atop of the squares. As the plane descends over eastern Colorado, the prevailing color of the land is brownish yellow, a striking contrast to the circles full of dark green crops.

The land west of the Missouri River is fertile, but crops must be coaxed out of the ground with irrigation. The dark green circles are a result of center-pivot irrigation, which enables the arid prairie states to be as fruitful as the Midwestern states. Colorado, for example, with its mountains and high prairies, is the 13th largest corn-producing state in the United States, according to Dave Kramer, general manager of Sterling Ethanol LLC and Yuma Ethanol LLC in northeastern Colorado. What’s more, Yuma County is one of the top three largest corn-producing counties in the country, producing 42 million bushels per year.

Irrigation has also enabled Nebraska to be an integral part of the Corn Belt. About 60 percent of corn acres in the state are irrigated, according to the Nebraska Corn Board. The state’s corn supply and ambitious development recently bumped its ranking to the second largest ethanol-producing state, after Iowa. Nebraska has more than 1,565,000 gallons of annual capacity built or under construction.

Water Source
Yes, the land is fertile, thanks to a generous supply of groundwater. The High Plains aquifer, also known as the Ogallala aquifer, lies under portions of eight states: South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico and Texas. It is one of the largest aquifers in the world, spanning about 175,000 square miles. According to the U.S. Geological Survey, approximately 27 percent of the irrigated land in the United States is in this region, and about 30 percent of the groundwater used for irrigation in the United States is pumped from the Ogallala aquifer. In 2000, irrigation withdrawals were 17 billion gallons per day and 1.9 million people were supplied by groundwater from the Ogallala aquifer with total public supply withdrawals of 315 million gallons per day, according to the USGS. The aquifer is not only large, but it’s also accessible. “It’s relatively shallow, the quality is relatively good, so it’s very user friendly,” says David Hume, a hydrogeologist and senior associate at Leggette, Brashears & Graham Inc.

The aquifer was formed over millions of years, but has since been cut off from its original natural sources and is being depleted faster than it can be recharged. The water table in the Ogallala Formation is separated from overlying land-use practices by as much as 400 feet of unsaturated sediments, and recharge has been estimated to take at least 50 years. Over extraction has led to substantial declines in the water table in many places, complete exhaustion of extractable groundwater in others, and debate and legislation about the aquifer’s future, according to a report by Environmental Defense, a nonprofit environmental advocacy group formerly known as the Environmental Defense Fund. The report, “Potential Impact of Biofuels Expansion on Natural Resources; a case study of the Ogallala aquifer region,” was released in September. Large portions of the aquifer show declines in the water table of more than 100 feet. Some reports have found that the water level is dropping by 3 to 5 feet a year in some areas. Estimates for its lifespan range from 60 to 250 years, depending on the area.

In the arid Plains, states have developed complicated legal arrangements for issuing water rights and developing water diversions. Water is appropriated by the government and the rights to it are traded and sold to the highest bidder. Lately, expanding cities have bought water rights from irrigation districts—essentially putting irrigated agriculture out of business. “Some areas in the Ogallala aquifer region, particularly in parts of Colorado and Nebraska, have existing groundwater protections that will reduce opportunities to convert new land to irrigated production,” the Environmental Defense report states. “Strengthening and expanding any existing local and regional groundwater conservation efforts may be one of the most effective ways to minimize groundwater depletion and the destruction of significant remaining blocks of wildlife habitat.”

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