The Ogallala Aquifer

Beneath much of Nebraska lies one of the largest bodies of freshwater in the world. The Ogallala Aquifer, which geologists also call the High Plains Aquifer, extends under roughly one hundred seventy-four thousand square miles of the Great Plains, reaching into eight states from South Dakota to Texas. In Nebraska it is thickest, sometimes running more than a thousand feet deep beneath the Sandhills. Farmers have been drawing it up for nearly a century.

The aquifer accumulated over millions of years as water filtered down through sediment eroded from the Rocky Mountains. It is an ancient reserve. Most of the water being pumped today fell as rain or snow during the last ice age or earlier. The aquifer recharges slowly, at rates that geologists measure in fractions of an inch per year across most of the High Plains.

Nebraska is one of the heaviest users of Ogallala water. The irrigated agriculture that center-pivot systems made possible depends on this ancient water. In Kansas and Texas, water table levels have dropped by more than a hundred feet in some areas since widespread pumping began after World War Two. Nebraska's decline has been slower, partly because the Sandhills act as an unusually effective natural recharge zone. But the trend is downward, and it continues.

The arithmetic is not comfortable. The crops grown here feed tens of millions of people. The water that makes those crops possible accumulated over timescales that no human institution was built to think about. What happens when the wells begin to come up short is a question that Nebraska, and the whole High Plains, has not yet fully answered.