Center pivot irrigation (CPI) is responsible for two things: creating those beautiful-though-at-time perplexing crop circles one sees out the window of planes, and for largely transforming the American High Plains from a dust bowl-prone, erratic cropland into a breadbasket the envy of the world. Invented in 1940, CPI allows farmers—those in more arid climates—to water crops in a more efficient, effective manner than traditional surface irrigation techniques. Various technologies exist today, from CPI systems that rain on top of crops to those that have hoses that deliver water directly on to the soil, but they have proven so transformational that they have changed the way crops are grown and harvested. The benefit of a central pivot means not only that irrigation systems can move on their own, without the need for guidance systems or frequent human adjustment, but also that the system itself can be relocated from field to field as needed. Farmers thus plant in circles, resulting in the green polka dot plantings across much of the central United States.
But though the technology has been transformational, it has come with a price. Its widespread adoption and use over several decades has depleted ground water levels from Wyoming to Brazil to Saudi Arabia.
