Hoover Dam has helped store Colorado River water since 1935, but reservoir levels are nearing the lowest point since Lake Mead was filled.

Hoover Dam towers more than 700 feet above Black Canyon on the Arizona-Nevada state line, holding back the waters of the Colorado River. On top of the dam, where visitors peer down the graceful white arc of its face, one of its art deco-style towers is adorned with a work of art that memorializes the purposes of the dam.