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GREEN RIVER STUDY PLAN 19 February 2, 2007 Table 1. Continued. Anticipated Effects and Uncertainties (Hypotheses) Summary Priority A 7. Provide conditions for gonadal maturation and cues for spawning migrations and y L reproduction by the endangered fishes (Muth et al. 2000). U5. The area of terrace and depression floodplains inundated at different flows (U.S. y H Department of the Interior 2006). U6. Flow and stage at which floodplains with levee breaches become sufficiently inundated (area, depth, volume) to provide nursery habitat for razorback suckers (U.S. Fish and P H Wildlife Service 2005). U7. Area, depth, volume, and persistence of floodplain depression habitat after peak flows recede and the relationship, if any, between these and the magnitude of the peak flow (U.S. P H Fish and Wildlife Service 2005). U8. Abundance and entrainment of drifting razorback sucker larvae as a function of distance from the razorback sucker spawning bar (U.S. Department of the Interior and Western Area y L/M Power Administration 2005). U9. Entrainment and retention of larvae in floodplain nursery habitats as a function of the physical characteristics of the habitat including size, volume, local hydraulic conditions, y H inlet(s), and outlet(s) (U.S. Fish and Wildlife Service 2005). UIO. Temporal relationships between drifting larvae and hydrology during the runoff period with a focus on the peak flow characteristics (magnitude, duration, ramp rate) needed to y H entrain most drifting larvae (U.S. Department of the Interior and Western Area Power Administration 2005). Ull. The frequency of connection needed to successfully recruit razorback sucker larvae into the adult population, including the frequency needed to sustain adequate water quantity and P H quality and allow escapement of subadults and adults to the main channel (U.s. Department of the Interior and Western Area Power Administration 2005). U12. Nonnative fish colonization of inundated floodplain depressions may interfere with y L recovery of endangered fish in those habitats (U.S. Fish and Wildlife Service 2005). UB. The frequency of total drying (reset) needed to control nonnative fish populations (U.S. P M Department of the Interior and Western Area Power Administration 2005). U14. For a given volume, what is the optimum combination of flow magnitude and duration to maximize larval fish entrainment (e.g., lower peak flows for a longer duration could maintain connection to floodplain nursery habitats for a longer period of time and entrain as many or more razorback sucker larvae as higher peak flows for shorter duration. With recent y H modifications of levees andintake structures, flows less than the recommended 18,600 cfs may provide significant connection and inundation to floodplain nursery habitats, and subsequent entrainment of razorback sucker larvae; U.S. Department of the Interior and Western Area Power Administration 2005). U15. Rates of sediment deposition and erosion in breaches and floodplain depressions as a function of breach configuration, peak flow, and connecting flow magnitude and duration P H (Muth et al. 2000). U16. The response of nonnative fish populations to spring peak flows (U.S. Fish and y M Wildlife Service 2005). Reach 2-Summer Throue:h Winter Base A8. Base flows in summer and autumn scaled to the hydrologic condition favor the P H formation of backwaters and other low-velocity shoreline nursery habitats (Muth et al. 2000). A9. Maintenance of the mean base flow within recommended levels of seasonal and within- day flow variability throughout summer, autumn, and winter will promote favorable P H conditions for all life stages of endangered fishes that use low-velocity habitats (Muth et al. 2000).