The High Plains aquifer underlies 111.8 million acres (about 175,000 square miles) in parts of eight States—Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. Water-level declines began in parts of the High Plains
McGuire, Virginia L. vlmcguir@usgs.gov. Water-level changes and change in water in storage in the High Plains aquifer, predevelopment to 2013 and 2011-13. 2014-01-01.