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thresholds for mobilizing the bed material were exceeded very infrequently. Over the 7-year period of the study, the discharge required to produce initial motion (-1/2 the bankfull discharge) was exceeded for a total of 78 days, which is only about 1 /3 the frequency recommended in previous reports. The discharge required to completely mobilize the bed (bankfull discharge) did not occur at all. Geomorphic changes in the 15- and 18-mile reaches were monitored using periodic surveys of main-channel cross sections and backwaters, and comparative analysis of aerial photographs taken in 1993 and 2000. These measurements indicate that, overall, the large-scale morphology of the Colorado River has changed little in the last decade. Vertical and lateral deposition of fine sediment occurred in all of the side channels monitored, however, the changes detected in these features were again relatively minor. Additional analyses of suspended sediment records from gauging stations in the study area reconfirm the importance of late-spring flows for carrying sediment. The analysis indicates that roughly 80% of the sediment carried in suspension consists of silt- and clay-sized particles. Concentrations of suspended sediment at all gauging stations are consistently higher on the rising limb of the hydrograph than they are on the falling limb, thus the total annual sediment load is dominated by late-spring flows. Both sediment concentration and water discharge are high in the spring, thus the total annual sediment load is dominated by flow conditions during this period of time. About 20% of the total suspended sediment load consists of sand. This sediment reaches a peak 2-3 weeks after the peak in water discharge, and not far in advance of the typical period of time when Colorado pikeminnow are preparing to spawn. It is not clear that the sand moving at this time of the year represents a problem in an ecological sense; however, it is evident that the 11