Why was Glen Canyon Dam built?

Glen Canyon Dam.

The construction of Glen Canyon Dam was authorized by the Colorado River Storage Project (CRSP), which was passed by a slim Congressional majority on March 1, 1956. Construction of the Dam began a year later, with no environmental review of impacts conducted whatsoever. (The National Environmental Policy Act, which requires Environmental Impact Statements to be conducted, was not yet in existence.)

The political motivation for the construction of the dam came from the Upper Basin states (Colorado, Wyoming, Utah, and New Mexico), who wanted to preserve their claims to shares of the river's water, as apportioned to them in the 1922 Colorado River Compact. By the 1940's, it was realized that the Compact had grossly overestimated the annual flow of the river; only through impoundment could the Upper Basin states ensure that their claims would remain valid.

The dam became politically feasible, in the eyes of fiscal conservatives, when the Bureau of Reclamation adopted an accounting system called "river basin accounting." Under this system, the electricity generated by Glen Canyon Dam (currently less than 3% of the Southwest's needs) would pay for the construction of other, smaller irrigation dams authorized by the CRSP. In short, Glen Canyon Dam was designed to be a "cash cow" for the Bureau of Reclamation; even today, not a single drop of Lake Powell water is used for commercial irrigation purposes.

Five million yards of concrete were poured nonstop at the dam site between June 1960 and September 1962; upon completion, the total height of the dam stood at 710 feet. When full, the water in Glen Canyon averages 560 feet in depth, flooding 180 miles up Glen Canyon, making "Lake" Powell the second largest man-made reservoir in the Western Hemisphere.