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14 I I I I I I I I I I I I I I I I I I I Site 8: Site 8 was a downstream oriented chute channel located below the Jensen Bridge (RM 298.2). This backwater had an area of 620 m2 with a maximum depth of 3.6 ft. Average surface ice thickness was 1.0 ft on February 1, decreasing to 0.7 ft by February 22. This backwater was suitable habitat though the entire winter. Site 9: Site 9 was a long downstream chute channel located against the shore below the Jensen Bridge (RM 297.2). This backwater had an area of 1220 m2 and a maximum depth of 4.0 ft. By February 1, much of the shallow regions (< 0.5 ft) had frozen solid, reducing the area of suitable habitat to 610 m2. On February 22 similar ice conditions existed, however dissolved oxygen concentrations in the back third of the backwater were below 3.0 mg/l (range 1.4 to 2.9 mg/l). The combination of free water loss due to ice formation and habitat exclusion from low D.O. levels reduced useable habitat to approximately 500 m2. Even with wintertime reduction in habitat of more than 50% this area was still sufficiently large to shelter fish during the winter. Site 10: Site 10 was a downstream chute-channel located above the Bonanza Bridge (RM 295.5). This backwater had an area of 520 m2 and a maximum depth of 4.0 ft. By February 1 this habitat had been replaced by a deep, swift side channel. No evidence of the original backwater remained. Site 11: Site 11 was a large, shallow scour-channellocated above the Bonanza Bridge at (RM 292.5). This backwater had an area of 3400 m2 with a maximum depth of 1.8 ft. By February 1, this area had a thin ice cover (average 0.3 ft) which did not significantly reduce habitat. On February 22 this habitat had changed to a shallow side channel, with current velocities of = 1.0 ft/sec. This area was considered unsuitable winter habitaL Site 12: Site 12 was a narrow chute channel located above the Bonanza Bridge at RM 293.0. This backwater had an area of 360 m2 with a maximum depth of 2.2 ft. On February 1, surface ice was an average 0.6 ft thick with and average 1.7 ft of free water. By February 22, warming temperatures had reduced average ice cover to 0.3 ft. This backwater was suitable habitat though the entire winter. 6.2.3 Reach 3 Reach 3 extended from the Bonanza Bridge (RM 290) to Ouray, UT (RM 248). Two backwaters were sampled in Reach 3. River ice conditions included large areas of broken surface and jam ice. Mats of jumbled, irregular surface ice, composed of compacted frazil and dislodged shoreline ice moved into Reach 3 from Reach 2. This ice began jamming in constricted portions of the channel the first week of February. Several jams dammed water, diverting flow into dry, high water channels. Two large ice jams, one near the Ouray Refuge Headquaners (RM 255.5 to 254.0) and another at Old Charlie Wash (RM 251.3 to 249.0), persisted throughout February breaking up by the first week of March. Site 13: Site 13 was a deep downstream chute channel located in the Ouray Wildlife Refuge (RM 255.8). This backwater had an area of 1650 m2 and a maximum depth of 5.0 ft. By February 4 an ice jam had diverted water into the dry, high water channel that formed this backwater. This diverted water created a deep (=-6.0 ft), swift (>2.0 ft/sec), side channel in place of this backwater. On February 25 the jam had cleared leaving a backwater in the dry, high water channel, with little change to the habitaL Due to the severely changing conditions in this habitat in February, is was not considered suitable habitat throughout the winter.