The Ogallala Aquifer

Beneath your feet, if you are somewhere in the western half of Nebraska, lies one of the largest bodies of freshwater in the world. The Ogallala Aquifer, also called the High Plains Aquifer, extends under roughly one hundred seventy-four thousand square miles of the Great Plains. It reaches into eight states. In Nebraska it is thickest and most expansive, sometimes running more than a thousand feet deep beneath the Sandhills. Farmers have been drawing it up for nearly a century.

The aquifer formed over millions of years as water percolated down through sediment washed off the Rocky Mountains. It is not a fast system. It recharges slowly, at rates that geologists measure in fractions of an inch per year in most areas. In the Sandhills region of Nebraska, recharge is somewhat faster because the sandy soils allow surface water to move downward quickly. But across most of the High Plains, the water being pumped out today accumulated during the last ice age or earlier.

Nebraska is among the states that draw the most water from the Ogallala. The irrigation economy that the center pivot made possible is running on that ancient reserve. In parts of the High Plains, including Texas, water levels have already dropped by more than a hundred feet since widespread pumping began in the nineteen forties. In Nebraska, the decline has been slower, but it is measurable and it continues.

Water managers, farm bureaus, and researchers at the University of Nebraska have spent decades studying the problem without arriving at a simple solution. Conservation programs have slowed the rate of depletion in some areas. The prairie grasslands of the Sandhills, which are not farmed and which act as a natural recharge zone, protect a significant portion of the aquifer's Nebraska core. But the arithmetic does not close. The plains grow a large share of the nation's food. The water that makes that possible is finite.

What happens when the wells begin to come up short is a question that western Nebraska, and the whole High Plains, is not yet ready to answer.