These Landsat images feature the significant growth in the use of center-pivot irrigation—essentially enormous sprinkler systems—in Kansas between 1972 and 2011. The Arkansas River flows east just south of Garden City in southwestern Kansas. From 1972 to 1990, Garden City's population grew from about 15,000 to about 24,000. The town's population as recorded by the 2010 Census stood at 26,658.
Much of the former shortgrass prairie of western Kansas is now irrigated cropland. Common crops in this area are corn, wheat, and sorghum. Red areas in the images are healthy vegetation. Light-colored cultivated fields in the images are fallow or recently harvested wheat fields.
These images show center-pivot irrigation systems (the small circles) multiplying between 1972 and 1988. From 1969 to 1987, irrigated acreage in Kansas increased by 62%, from 1.5 million acres to 2.4 million acres. In the five years from 1984 to 1988, Kansas farms with center-pivot irrigation systems increased 19%, from 2,630 farms to 3,122 farms.
This area uses irrigation water from the Ogallala Aquifer, one of the world's largest aquifers, which underlies an area from Wyoming to Texas. Landsat images are useful for measuring irrigated crop acreage, a key component of modeling aquifer response to changes in water use. Landsat is also used to monitor the depletion of the aquifer, which is affected by not only the irrigation but also drought.
These 2011 images show the seasonal progression of the irrigated crops in this area, from around the peak of the growing season to harvest. The August image is at the height of the growing season, and the November image is after many fields have been harvested. The harvested fields are a conspicuous white and not red because the vegetation has been removed.
Taking a closer look at Garden City shows the expansion in area the city experienced since 1972. They also show the proximity of the city to those center-pivot irrigation circles. Four of these circles take up almost 1 square mile, or one section, of land.
Southwest of Garden City is an area absent of irrigated crops. This marks the location of the Finney County Game Refuge, a reserve for many Plains natives, including an American bison herd.
Another gap in irrigated cropland is a bit to the west of the game refuge. Marked by light spots is Holcomb Station, a coal-fired power plant operated by the Sunflower Electric Power Corporation. The plant opened in 1983, so it does not appear in the 1972 Landsat image. The 362-megawatt station uses coal mined in Wyoming's Powder River Basin.