Distances across this grandest of gorges range from four to more than 15 miles. During the past three and a half decades, operators of the Glen Canyon Dam have managed the Colorado River's flow in order to provide hydroelectric power to humans living in Arizona and Utah. Since 1963, the dam has subdued the river's entrance into the Grand Canyon. In addition, abrupt releases of water from massive Lake Powell, ponded behind the dam, have eroded beaches, destroyed vegetation, and killed fish downriver throughout the Grand Canyon. Consider that the Glen Canyon Dam is only one of 431 dams built on rivers and streams throughout Arizona.
Water is a precious commodity in the arid Southwest.
As a result, people stockpile it for crop irrigation, electric power, and even recreation. There also is demand for water downstream from the dams. Plants and animals depend on the rivers for survival. If they don't get enough water, they will die. It does not have to be this way.