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inundated. This discharge is consistent with flow-modeling results indicating that the threshold <br />for initial motion of the bed material in this reach is exceeded at a discharge of 286 mN. That <br />value is within 3% of the value recommended in previous reports. Adjusting the model results to <br />account for spatial variations in grain size increases the threshold slightly, indicating there is <br />very little bed load transport within the reach at flows less than 300 m3/s (10,600 ft3/s). <br />The results discussed in this report are broadly consistent with the results presented in <br />previous reports, therefore, all of the previous recommendations are retained. It is assumed that <br />periodic movement of the gravel bed material of the Colorado River is important for maintaining <br />habitats used by native fishes and other aquatic organisms. It also assumed that periodic <br />movement of the bed material is important for maintaining a channel with some morphologic <br />complexity or heterogeneity. Finally, it is assumed that the mass balance of sediment carried by <br />the Colorado River must be maintained over the long run, otherwise there will be continued <br />narrowing and simplification of the channel, and a loss of associated habitats. Specific <br />recommendations for discharges that will achieve these purposes are discussed below. <br />59