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The increases in discharge produced by the bypass flows were not particularly large (only <br />10 to 15% of the discharge in the 15 mile reach), however, two important conclusions can be <br />drawn from these tests: First, the reservoir operators and federal agencies demonstrated that they <br />could coordinate efforts to enhance peak flows to improve habitats used by the endangered fish. <br />They did so voluntarily and without significantly disrupting their ability to supply water for other <br />uses. Some water was "lost" in the process, however, the volumes released were a fraction of the <br />total storage capacity of the upper basin system. Second, the bypass flows were successful in <br />boosting background flow levels within a specific window of time, making it much more likely <br />that the discharges needed to initiate bed load transport were exceeded in a number of places in <br />the 15 mile reach, not just a few isolated spots. Without the bypass flows, transport would have <br />been more limited, and the observed sequence of flows would have fallen well short of the <br />recommendations given in previous reports. Unfortunately, the total storage capacity of the <br />upper basin reservoir system amounts to no more than about half the annual flow of the Colorado <br />River (Pitlick et al., 1999), thus there are clear limits on the potential uses of bypass flows, <br />particularly in a string of dry years such as those experienced from 2002-2004. <br />Changes in Channel Morphology <br />Cross-section Measurements: Survey measurements of 11 main-channel cross sections in <br />the reach near RM 176 show that changes in the overall morphology of the Colorado River were <br />relatively minor during the monitoring period (Fig. 11). Minor amounts of bank erosion (< 2 m) <br />occurred at several cross sections, but the topography of the study reach remained essentially <br />unchanged. Enlarged views of measurements across the secondary channel in this reach (Fig. <br />12) show that minor amounts of sediment were deposited along the right bank, but overall, the <br />topography of the secondary channel at RM 176 changed little during the monitoring period. <br />28