The Ogallala Aquifer that lies deep beneath the Great Plains from Texas to Colorado contains enough water to fill Lake Erie nine times! Every year five trillion gallons are pumped out for irrigation, and if (or when) the aquifer goes dry, $20 billion worth of food and fiber grown with that irrigation will disappear. William Ashforth tells the fascinating history of the Ogallala from its formation millions of years ago to glimpses of the future when the Great Plains could return to their Sahara Desert-like past.