The Ogallala is a very extensive geological formation. It is a vitally important aquifer mainly in the western parts of Kansas. Five million years ago, Ogallala sediments were up to 800 feet thick. The modern Ogallala formation in Scott County varies from 0 to 215 feet in thickness. The sands of this formation provide a filter system for the groundwater, making its quality generally high, suitable for domestic, livestock and irrigation uses.