The Ogallala aquifer, that part of the High Plains aquifer in Oklahoma, is part of a regional aquifer system that underlies parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. In 1978 the US Geological Survey began a 5- year study of the High Plains regional aquifer system to provide hydrologic information for evaluation of the effects of long-term development of the aquifer and to develop a capability for predicting aquifer response to various ground-water-management alternatives (Weeks, 1978). -from Author