The Ogallala Aquifer, also known as the High Plains Aquifer, underlies portions of eight states in the United States:

* Colorado

* Kansas

* Nebraska

* New Mexico

* Oklahoma

* South Dakota

* Texas

* Wyoming

It's important to note that not all of these states rely on the Ogallala Aquifer to the same extent. The aquifer is a major source of water for agriculture in the region, and its depletion has become a significant environmental concern.