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7 RESULTS AND DISCUSSION Physical and Chemical Descriptions The Gunnison and Dolores rivers differed in several physical and chemical characteristics. Generally, the Gunnison River had greater channel width, higher flow rates, fewer rapids and more floodplain area than the Dolores River. Gunnison River flows ranged from 850 to 13,200 cfs at Whitewater from 1979 through 1980 (Figure 2 and 3). Flows on the Dolores River varied from 50 to 1890 cfs at the San Miguel confluence in 1981 (Figure 4). The 1981 flows were quite different from those of the previous 2 years (Figures 5 and 6). Large silt deposits were observed in both rivers, in backwaters and other habitats characterized by low velocities. Conductivity and salinity values were generally lower in the Gun- nison River than in the Dolores River. Several salt mining operations and salt settling ponds are located on the Dolores River, which probably contributed to higher conductivity and salinity. Conductivity and salinity values dropped during the runoff period in both rivers, presum- ably due to the diluting effect of snowmelt. Dissolved oxygen concen- tration and turbidity was nearly the same in both rivers during respec- tive flow periods. River temperatures were also similar for the Gunnison and Dolores rivers~ The river temperatures ranged from l3.SoC (5 May 1981) to 280C (17 June 1981) in the Gunnison River and 13.40C (12 May 1981) to 260C (10 June 1981) ~n the Dolores River. Gunnison River Stratum Q: Colorado-Gunnison River confluence to Whitewater. The lower 3 miles of this stratum is drastically altered due to the effects of the Redlands Diversion. A large deep pool is located below the spillway (RM 3.0) before the river becomes shallower downstream. Little or no flow was observed below the structure in late summer because nearly all water is diverted through Redlands Canal, and irrigation returns bypass this lower Gunnison reach and flow directly into the Colo- rado River. The upper section of stratum Q has wide floodplains, few riffles and rapids, and several gravel pits and quarries along the river corridor. A long deep pool is formed directly above Redlands Diversion where water is impounded by the structure. Maximum depths reach approxi- mately 30 ft (near the dam) with a mean stratum depth of approximately 6.6 ft. The width of the river varied from 260 to 525 ft in this stratum. Conductivity ranged from 1000 to 1600 values were 0-1 parts per thousand (ppth). trations were generally 9 to 10 mg/l. The stratum during the study. umhos cm-l while salinity Dissolved oxygen concen- river was turbid in this Stratum R: Whitewater to Bridgeport. In the upper portion of stratum R, the river flows through canyon topography, and the lower 2.2 miles has larger floodplain areas with gradually ~loping banks. This