Colorado River Flooding
Western floods of 1983
A big snowmelt in the Rocky Mountains led to record flooding on the Colorado River in 1983 (and again in 1984). Heavy and unseasonably late snows in May were followed rapidly by warm temperatures and record rainfall in early June. The resulting huge surge of water was not forecasted and not enough water was dumped from Colorado River reservoirs in time to compensate. High inflows forced opening of the emergency spillways at Glen Canyon and Hoover Dams for the first time since their construction except for brief tests. Releases from Hoover Dam reached a record high of 48,000 cubic feet per second (1,400 m3/s) (much higher than the maximum allowed flood release of 28,000 cubic feet per second (790 m3/s)), which damaged levees and riverside property along the Lower Colorado River Valley, resulting in seven deaths. However, this was still much lower than the peak inflow above Lake Powell, which was recorded at 122,700 cubic feet per second (3,470 m3/s) on July 1.
The Colorado, which is usually dry at the mouth due to extensive diversions, reached the Gulf of California for the first time since the 1960s. Due to a spillway design error at Glen Canyon coupled with the relentless flooding, the dam at Glen Canyon very nearly failed, which would have emptied Lake Powell (the second-largest man-made lake in the US) and flooded out the entire lower valley of the Colorado River, cutting off water supplies to millions of people. By August as the water finally began to recede, the dam held, though only barely. Damages along the Colorado River amounted to about $80 million ($182 million in 2012 dollars).