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analysis of flow alternatives and to better address micro-habitat relationships <br />of the forage fish community, the Service groups species having similar <br />habitat versus flow relationships into five habitat guilds. To evaluate <br />hydrology scenarios, the habitat versus flow curves are combined with a <br />hydrology time series (e.g., OPSTUDY output) to generate a habitat time <br />series; habitat time series produced for differing hydrology alternatives are <br />then compared. Factors other than physical microhabitat variables contribute <br />to the flow requirements of forage fish; therefore, the 5ervice has considered <br />the relationship between flows and specialized habitats, and water quality <br />(temperature) in its determinations of flows necessary to maintain fishery <br />habitat. <br />2. Tern and Plover Nesting Model - The U.S. Fish and Wildlife Service developed a <br />Tern and Plover Nesting Model for use in the analysis of the Program for the BO. <br />The purpose of the model is to predict the relative impacts of the annual and <br />seasonal hydrology cycle on the formation of suitable nesting sandbars, and on <br />nesting opportunity. Note that this is not a computer simulation model but a set of <br />analytic tools and procedures. Model inputs include daily flow values and <br />elevations at SEDVEG model transects for a given hydrology scenario. The <br />functional relationships in the model include duration of nesting and fledging <br />periods and potential elevation of sandbar habitat based upon recent flood peaks. <br />The model characterizes the elevation difference between high, vegetation <br />scouring and sandbar forming flows, to the flows throughout the summer nesting- <br />season. The model also includes an estimate of the likelihood and timing of <br />inundation of various elevations during the nesting season. Model output includes <br />indices for comparing relative improvement ar impairment of available sandbar <br />nesting habitat available and likelihood of nest inundation or disruption of nesting <br />for differing hydrology scenarios. <br />PRIORITY HYPOTHESES <br />Priority Physical Hypotheses <br />e??S <br />Management Hypotheses YG ? <br />?p ? <br />1. The U.S. Fish and Wildlife Instream Flow Recommendations in combination ? <br />with clear/level/pulse management practices will result in the o-? <br />creation/maintenance of habitat for terns and plovers including reduction in <br />predation and inundation of nests and the abundance and composition of prey'- <br />base. <br />2. The ability to deliver 5000 cfs of Program water for three (3) days to the <br />upper end of the associated habitat (at Overton gage) for pulse flows when <br />other demands on water are low and quantities of Program water that are <br />likely to yield 800 cfs at the habitat during the irrigation season are necessary <br />to maintain in-channel habitat for the three target bird species. <br />3. Peak flows will remove through scouring in-channel vegetation, and in <br />combination with increased sediment, will create and/or maintaining wide