Kansas lies in the heart of the American “breadbasket,” where farmers grow corn, wheat, and sorghum and raise cattle. Over the past 60 years, two irrigation technologies have transformed agriculture in the area. Instead of waiting for rain, farmers in Garden City, Kansas, now use groundwater pumps and a technique called “center-pivot irrigation” to extract water from deep underground and distribute it over their fields.
Garden City’s bounty is possible because beneath these fields lies the great Ogallala Aquifer. This vast reservoir of groundwater stretches across eight states, from South Dakota and Wyoming to New Mexico and Texas. Because the semi-arid climate of America’s High Plains does not receive enough rainfall to support intensive agriculture, farmers pump this stored water to irrigate their fields.
The growth and change in irrigation practices is visible in these Landsat images from August 16, 1972 (left), and August 14, 2011 (right). The 1972 image was taken by Landsat 1, which had only been launched three weeks prior; the 2011 image was captured by Landsat 5. Both use false-color such that healthy vegetation appears bright red, while sparse grasslands and fallow fields appear in shades of green.
Over time, Garden City's rectangular fields of rain-fed farms and traditional irrigation methods gave way to the large circles made by center-pivot irrigation. Farmers pump water directly from groundwater wells in the center of a field, up to a long pipe studded with low-hanging sprinklers. The pipe rotates around the center well like the hands of a clock. It is a labor- and water-saving method that has revolutionized agriculture worldwide, increasing yields and allowing food production in areas where plants would otherwise wither from drought.
Because the Ogallala Aquifer recharges slowly as rainwater seeps down through the ground, some of the water used to irrigate these fields has been trapped underground since the last Ice Age. But it also means this aquifer is slowly going dry. Even with the rise of water-conserving measures, more water has come out of the ground that is going back in. According to the U.S. Geological Survey data from 1980–1995, water levels in southern sections of the Ogallala Aquifer dropped 20 to 40 feet (6 to 12 meters).