Marble Canyon Dam States Geological Survey, which designated sites for "an unbroken string of [hydroelectric] dams from the mountains of Colorado and Wyoming to the last canyons of the Colorado River along the California/Arizona border". Although the Bureau of Reclamation expressed interest at this time in developing hydroelectric generation at the Marble site, these plans were postponed in favor of building the Hoover Dam, which would provide a much greater storage capacity for irrigation and flood control. However, once Hoover was completed the Bureau once again set its sights on the Grand Canyon, which has the greatest hydroelectric potential of any canyon in
Course of the Colorado River the vertical-walled Marble Canyon which is crossed by the twin Navajo Bridges as it enters Grand Canyon National Park. At the southern end of Marble Canyon, the river is joined by another tributary, the capricious Little Colorado River, which drains the Painted Desert region of northeast Arizona and western New Mexico. Although normally a calm and clear spring-fed stream, it can rise dramatically following monsoon storms over the Colorado Plateau. Then the river then turns abruptly west directly across the folds and fault line of the plateau, through the Upper and Lower Granite Gorges of Grand Canyon, which is long