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<br />EXECUTIVE SUMMARY <br />Nursery habitat availability is considered a bottleneck to successful recruitment of <br />Colorado pikeminnow (Ptychocheilus Lucius). Detailed geomorphic studies were conducted in a <br />1.5-km reach to examine channel response to flows and the geomorphic setting of nursery <br />habitats during a 2-year period. Videography was used to extend relationships in the 1.5-km <br />reach to a longer 10-km reach. <br />Nursery habitat availability vazied yeazly with little persistence in location or geomorphic <br />setting of individual habitats for the 2 years of this study. A small number of habitats provided <br />most of the area ofhigh-quality (i.e., deep) habitat, and most of the total azea of habitat was <br />formed by three geomorphic classes. Although the 1993 flood reduced the azea of available <br />habitat, azea of deep habitat increased. The 19941ow-peak flood increased the area of habitat, <br />but most habitats were shallow. <br />The 1993 and 1994 multi-peaked habitat availability curves for the 1.5-km-reach bank- <br />attached baz were the result of the superposition of curves from habitats in each geomorphic <br />classification, and showed that the discharge that maximized habitat availability changed yearly. <br />A complexity index was evaluated for the 10-km reach as surrogate for habitat availability. Total <br />base-flow habitat availability was significantly correlated to the complexity index, but deep <br />habitat availability was not. <br />Measured channel topography was used as input to a flow and sediment transport model. <br />Simulated hydrograph runs produced greater bank-attached bar aggradation and thalweg scour <br />than steady flows, although some unrealistic patterns of scour occurred. <br />New flow recommendations must include occasional high flows sufficient to rebuild <br />channel topography. Flaming Gorge Dam releases should be used to augment the Yampa River <br />flood peak, but not increase low flood-peak duration. The conceptual model for habitat <br />availability developed here maybe used to tazget the formation and availability of habitats. Base <br />flow recommendations designed to maximize habitat availability should be evaluated annually. <br />Winter flows should be reevaluated for their negative effects on habitat. <br />LIST OF KEY WORDS <br />Green River, geomorphology, flow, nursery habitat, Colorado pikeminnow <br />A-xi <br /> <br /> <br /> <br />~~ <br /> <br />n <br />'L ~ <br />1 <br />t <br /> <br /> <br /> <br /> <br /> <br />I <br /> <br />1 <br />1 <br /> <br />