Taming the Colorado River in the 20th century

Before the advent of Bureau of Reclamation dams - Hoover and Glen Canyon - the Colorado River flowed freely to the Gulf of California (Sea of Cortez). In 1920, a stream gage near Yuma, Arizona recorded ~129,000 cubic feet per second (~3,600 cubic meters per second (cms)). After Hoover Dam was constructed, flow near Yuma fell below ~ 500 cms. Maximum flow declined further after Glen Canyon Dam came on line, to below ~ 100 cms. The units of this historical hydrograph are cubic meters per second on the y-axis and years on the x-axis. These data show that annual floods on the Colorado River are a pale shadow of the pre-dam period.