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GREEN RIVER STUDY PLAN 18 February 2, 2007 Table 1. Anticipated effects and uncertainties (hypotheses) associated with flow and temperature recommendations for the Green River downstream of Flaming Gorge Dam. "Summary" shows the determination on how the studies cumulatively satisfy the hypothesis; Y=hypothesis being addressed by study; P=study partially addresses hypothesis. "Priority" is the prioritization of the importance of evaluating the hypothesis; L=low, M=medium, H=high. Anticipated Effects and Uncertainties (Hypotheses) Summary Priority Reachl--8prinePeak AI. Significant channel maintenance (i.e., rework and rebuild in-channel sediment deposits, increase habitat complexity, and prevent or reverse channel narrowing) in I"odore Canyon in y L wet years or in other years when peak releases are greater than 244 m3/s (8,600 cfs) (Muth et al. 2000). A2. Channel maintenance will improve habitat conditions for endangered fishes and could favor potential spawning of Colorado pikeminnow in this portion of the river (Muth et al. y M 2000). Ul. The increased frequency of bypassing water (spills) would result in increased entrainment of reservoir nonnative species. Reach I monitoring should include specific y M/H efforts to evaluate the potential for establishing undesirable reservoir fishes, such as smallmouth bass in the tailwater (U.S. Fish and Wildlife Service 2005). U2. The response of nonnative fish populations to spring peak flows (U.S. Fish and Wildlife y H Service 2005). Reach 1--8ummer Through Winter Base A3. Target water temperatures in Lodore Canyon are expected to be achieved in 7 of 10 years (average and drier years) and could result in Colorado pikeminnow spawning in this y M portion of the river (Muth et al. 2000). A4. More favorable water temperatures also could result in expansion of humpback chubs y M into this portion of the river (Muth et al. 2000). U3. Ifwarmer water (l60C) could be released at the dam during wetter years, recommended temperature targets could be achieved more frequently (U.S. Fish and Wildlife Service y L 2005). U4. The effect of base flows and release temperatures on nonnative fish populations (U.S. y H Fish and Wildlife Service 2005). Reachl--8prinePeak AS. Wet and Moderately Wet: Significant inundation of floodplain habitat and off-channel habitats (e.g., tributary mouths and side channels) to establish river-floodplain connections and provide warm, food-rich environments for growth and conditioning of razorback suckers (especially young) and Colorado pikeminnow. p H Average: Significant inundation of floodplain habitat and off-channel habitat in at least 1 of 4 average years; some flooding of off-channel habitats in all years. Moderately Dry and Dry: No floodplain inundation, but some flooding of off-channel habitats. May benefit recruitment of Colorado pikeminnow in some years (Muth et aL 2000). A6. Wet and moderately wet years. Significant channel maintenance to rework and rebuild in-channel sediment deposits (including spawning substrates), increase habitat complexity, form in-channel sand bars, and prevent or reverse channel narrowing. p L/M Average years. Significant channel maintenance in at least 1 of2 average years. Moderately dry and dry years. Significant channel maintenance in at least 1 of2 average years (Muth et al. 2000).