Great Miami Buried Valley Aquifer

Not well known is that Dayton, Ohio sits on top of 1.5 trillion gallons of water, used to provide water for about 400,000 residents in the surrounding communities to drink, businesses such as Cargill and Miller-Coors to make their products, and for the geyser fountain at the junction of the Great Miami and Mad Rivers to spray its jets. Known as the Great Miami Buried Valley Aquifer (GMBVA), it's comprised of sand and gravel deposits that are completely saturated with water, and is quickly replenished by water that seeps down from the overlying rivers, streams, and lakes.

http://www.daytonohio.gov/701/Great-Miami-Buried-Valley-Aquifer