With the enormous snow melt from the Rocky Mountains, you would think large lakes would abound in Colorado. Oddly enough, the largest natural lake is less than a mile across. Over the past 100 years, of course, Colorado has thrown dams across many of the rivers to form reservoirs, but the state has very few large natural lakes. So where does all that water go?
A great deal of water from the Rocky Mountains is, of course, channeled into the Colorado and several other large rivers and flows out of the state, but that doesn’t account for all of the water. In fact, a large percentage disappears into one of the largest underground aquifers in the world. Called the Ogallala Aquifer or the High Plains Aquifer, this vast body of water extends northward from Western Texas into South Dakota and underlies about 174,000 square miles of eight states (about the size of Lake Huron). It is this system that supports the vast breadbaskets of America. About 27% of the irrigated land in the United States sits above the aquifer and groundwater drawn from it provides 82% of the drinking water for the people who live above it.
The aquifer was created during the late Miocene and early Pliocene ages when the Rockies where geologically active. Huge rivers and streams ran from the mountains to the plains and erosion eventually filled these ancient channels with loose rock and sediment. These loose rocks trap and hold water extremely well, forming the Ogallala formation that makes up the aquifer. Melt water and rain water from the Rockies, particularly from Colorado, recharges the aquifer, although modern day usage is stressing the water levels to a great degree. Better irrigation techniques and water management have slowed the usage, but approximately 2.7 feet per year is lost from the aquifer despite these conservation techniques. In a few decades, this amazing underground source could be depleted.