ABSTRACT
The Ogallala aquifer underlies about 174,000 mi2 of land in the U.S. Great Plains. States with the largest land areas above the aquifer are Nebraska, Texas, Kansas and Colorado with smaller amounts in New Mexico, Oklahoma, South Dakota, and Wyoming (Fig. 1). The aquifer extends approximately 800 mi north to south and 400 mi east to west. The aquifer consists of sand and gravel beds that generally lie from 50 to 300 ft beneath the surface and are 150-300 ft thick. In some areas, however, the saturated thickness of the aquifer exceeds 1000 ft.[1]
The water contained in the Ogallala aquifer is essentially fossil water taken 10,000-25,000 yr ago from the glacier-laden Rocky Mountains before it was geologically cut off by the Pecos River and the Rio Grande.[2]
More than 3 billion acre-feet (an acre-foot is a foot of water on 1 acre, or 325,851 gal) are stored in the aquifer.
