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I I I I I I I I I I I I I I I I I I 1 Table 10. Summary of overwinter habitat suitability of 9 backwaters sampled during winter of 1994-95. Site # (River Mile) Backwater Channel Type Suitable Habitat Through Winter (YeslNo) Reason Not Suitable Reach 1 1 (331.6) chute 2 (327.6) chute Yes No Backwater became a flow-through from unknown channel morphology changes Reach 2 3 (318.0) scour 4 (316.2) eddy-return 5 (289.4) scour 6 (288.8) chute Yes No Yes No Ice jams caused darning and flow-through Ice jams caused darning and flow-through Reach 3 7 (260.2) scour 8 (257.1) chute 9 (251.9) scour Yes Yes Yes which enters the Green River about 104 Ian downstream of the dam. In winter, the relatively warmer water, combined with a greater mass from higher than historic releases, have combined to reduce the annual frequency of ice cover on the Green River by 48%. The effects of the dam and its operation on fish during winter remain largely unlrnown. 7.1 Ice Conditions While the frequency of ice cover (i.e., an ice cap) has been reduced by the presence of the dam, shoreline ice, frazil ice, and jam ice continue to be common phenomena in severe and mild winters, and may dominate post-dam ice processes over pre-dam ice cap conditions. We believe that in pre- dam conditions, fish habitat was probably covered most of the winter by a relatively stable ice cap. Relatively warm and high post-dam releases have minimized the formation of an ice cap and fish habitat is probably affected to a greater degree by shoreline ice, frazil ice, and jam ice. This study was conducted during two very mild winters on the Green River, under quite different operational release regimes from Flaming Gorge Dam; high fluctuating releases, and low steady 22