Green crop circles cover what was once shortgrass prairie in southwestern Kansas. Like crops throughout large sections of the U.S. Midwest, these crops are partly fed by water from the Ogallala Aquifer, a giant layer of underground water. 

"We are basically drying out the Great Plains," according to Kurt Fausch, professor emeritus at Colorado State University. Fausch has studied the depletion of the Ogallala Aquifer, which supports about a sixth of the world's grain crops. Fausch tells Colorado Matters that streams and rivers that depend on the Ogallala are drying out, too, due to half a century of over-pumping from the aquifer.

In research published recently in the Proceedings of the National Academy of Sciences, Fausch, who's a stream ecologist, and his colleagues write that the depletions are leading to fish extinctions and threatening agriculture in Eastern Colorado and other states from South Dakota to northern Texas.