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7) Taking the results from the three flow-modeling sites studied here, the seven sites studied by Pitlick et al. (1999), and data from 149 cross sections, we estimate that the framework gravel particles of the Colorado River begin moving at flows ranging from about 35 to 55% of the bank- full discharge (Table 7). Discharges that reach initial-motion and bankfull stages are very similar when the data are grouped with respect to the two major tributaries in the study area, the Gunnison River and the Dolores River. For the reaches above the Gunnison River (strata 9-11), we estimate that discharges of 211 to 278 m3/s (7500-9800 ft3/s) will initiate motion and discharges of 580 to 623 m3/s (20,500-22,000 ft3/s) will reach the bankfull level (see Table 7). For the reaches between the Gunnison River and the Dolores River (strata 6-8), we estimate that discharges of 497 to 548 m3/s (17,500-19,300 ft3/s) will initiate motion, and discharges of 979 to 1320 m3/s (34,600-46,600 ft3/s) will reach the bankfull level. For the reaches below the Dolores River (strata 2-5), we estimate that discharges of 561 to 659 m3/s (19,800-23,300 ft3/s) are required to initiate motion and discharges of 1500 to 2000 m3/s (54,500-71,000 ft3/s) are required to reach the bankfull level. RECOMMENDATIONS 1) The diversion dams in DeBeque Canyon are being modified to allow fish passage, thus we recommend further geomorphic studies to assess patterns of sediment transport and channel change in the reaches above Palisade. More detailed studies are needed to evaluate the mobility of gravel substrates that might serve as spawning habitat for pikeminnow. Additional studies are needed to evaluate the importance of fine sediment deposition and to assess whether normal snowmelt flows and coordinated reservoir releases are effective in flushing fine sediment from the bed. 2) We recommend initiating additional field studies in the Rifle-DeBeque reach to monitor scour and fill in side channels and backwaters. Previous studies have shown that fine sediment is preferentially deposited in these off-channel habitats during periods of low flow (Osmundson et al., 1995; Pitlick et al., 1999); periodic monitoring of scour and fill in side channels provides a useful measure or index of the overall mass balance of sediment moving through the reach. 3) Continued monitoring of suspended sediment at the USGS gauging stations is essential for evaluating short- and long-term trends in the sediment load carried by the Colorado River. Thus we recommend continuation of the existing sediment-sampling programs at the USGS gauges. 4) The data presented in this report indicate that suspended sediment concentrations during the summer months are typically higher at the Cisco gauge than they are at the Cameo gauge. Some of the difference in sediment concentration is due to natural causes, and some of it is due to irrigation return flow. Given that turbidity levels affect primary productivity, we recommend that additional efforts be made to limit sediment input from agricultural areas in the vicinity of Grand Junction. 5) As in the previous study (Pitlick et al., 1999), we emphasize that the single most important thing that can be done to maintain fish habitats in the Colorado River is ensure that the sediment supplied to the critical reaches is carried downstream, otherwise further channel simplification will occur. We have previously shown that flows ranging from 1/2 the bankfull discharge up to the bankfull discharge cant' about 50% of the annual load, thus it is important that flows in this range continue to occur regularly (at least 30 days per year). An additional possibility, that has not been studied in any detail, is to consider implementing better land-use practices to reduce erosion and sediment supply from the Roan Plateau and nearby areas. We recommend initiating a pilot study to examine the relation between climate, vegetation, runoff and sediment yield in this region. 42