The Ogallala aquifer, the largest unit of the hydrologically connected High Plains aquifer system, is one of the world’s largest fresh groundwater resources. It underlies 175,000 square miles/112 million acres in eight states. The High Plains Aquifer system slowly formed as hundreds of feet of silt, clay, and gravel eroded from the Rocky Mountains and other sources were laid down by braided streams during the Miocene and Pliocene (23 to 2.6 million years ago) and Pleistocene (1.8 million years ago to 11,700 years ago) epochs. The water in the High Plains Aquifer system is relatively old, accumulating over thousands of years primarily through infiltration of precipitation.
This region, mostly characterized as semi-arid grassland and steppe, was labeled the “Great American Desert” on early maps (1820-1850). Early American explorers including Major Steven Long and General Zebulon Pike considered the High Plains region to be both unfit for farming and a natural barrier protecting civilization to the east from the nomadic horse people of the Plains.
Technological advances in the early to mid-20th century led to an explosion of irrigated acres, from 2.1 million irrigated acres in 1949 to more than 15 million acres only half a century later. Today, it’s hard to overstate the importance of water pumped from the High Plains aquifer as a principal driver of the region’s largely agricultural-based economy and way of life. Current annual withdrawals from the aquifer are estimated to be on the order of 19 million acre-feet. Water pumped from the High Plains Aquifer system supports nearly 30% of the U.S. irrigated crop production as well as significant proportion of cattle, dairy and hog production.