Sonar in the Grand Canyon, 1992

George Tate (right, in light baseball cap) drives a raft on the Colorado River in Grand Canyon, 1992. The crane near the bow was used to deploy a small tripod holding a rotating sidescan sonar, which sat on the riverbed recording the motion of underwater sand dunes. The sonar was connected to a computer (in white box on side of raft) by cable that the researchers ran to the river's edge where they tied off for the night. They collected data for at least 12 hours at each site for a project led by USGS sedimentologist Dave Rubin on the effects of Glen Canyon Dam on sand resources in the Grand Canyon.