The Colorado River Compact
In the arid Southwest, water is of vital importance and the Colorado River is the principal carrier of this most precious resource. Seven states-and Mexico-receive water from the Colorado River. The seven states are divided into the Upper and Lower Colorado River Basin with the mid-point at Lees Ferry, Arizona, approximately 15 miles (24km) below Glen Canyon Dam.
Glen Canyon Dam
Glen Canyon Dam was authorized by Congress in 1956 to provide water storage in the Upper Colorado River Basin. The result was Lake Powell, the second largest man-made reservoir in the United States. (Lake Mead is the largest.) It took seventeen years for the lake to reach its full pool level of 3700 feet (1128m) above sea level.
Glen Canyon Dam has created a new Colorado River. Before the dam was built, water temperatures in the river fluctuated seasonally from 80°F (26°C) in the summer to near freezing in the winter. Now, the water temperature below the dam averages 46°F (7°C) year-round. The Colorado River was once filled with silt and sediment. Now, the river deposits its load of silt as it enters Lake Powell near Hite, Utah. Water released from the dam is clear and the Colorado River is muddy only when downstream tributaries contribute sediment.