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<br />000912 <br /> <br />events may need to be tempered to reduce damages to personal <br />property. <br /> <br />LEAST TERN AND PIPING PLOVER NESTING <br /> <br />Hydrologic characteristics needed to provide secure habitat are <br />generally high flows in early summer with steadily declining <br />flows through mid and late summer. Recent investigations <br />(Ziewitz et al. 1992, Sidle et al. 1992) suggest recurring, <br />stochastic flow pulses contribute to renewal of sandbars that are <br />used for nesting. Base flow levels are needed to improve <br />security from terrestrial predators and disturbances. <br /> <br />The analytical information available that is most pertinent to <br />the needs stated above (i.e., inundation of low sandbars and <br />provision of a water barrier) are represented by the <br />wetted area versus discharge curve. Figure D1 represents wetted <br />area versus discharge relationship for segments of the river <br />frequently occupied by nesting terns and plovers. The curve was <br />developed by the u.s. Bureau of Reclamation (unpublished data) <br />from data collected for the Instream Flow Incremental Methodology <br />hydraulics programs. The shape of this wetted area curve, in <br />combination with field observations, suggests that most of the <br />lowest lying, barren sandbars that could potentially be occupied <br />by nesting birds are inundated at flows near 1300 cfs. <br />Constructed nesting islands and more suitable sandbars that <br />survive small spates in river discharge are located at higher <br />elevations. <br /> <br />Recommended Targets: <br /> <br />Improve the frequency of high flows (1300 cfs or higher) early in <br />the nesting season (May 15 to June 20) to deter nesting on low <br />sandbars. Maintain average flows of 800 to 1000 that are steady <br />or slowly declining through the remaining nesting period. This <br />level is somewhat lower than 1300 and would provide a buffer to <br />small, frequent spate flows that frequently occur. It is also <br />high enough to provide some protection as a deterrent to <br />terrestrial predators. <br /> <br />OTHER MANAGEMENT CONSIDERATIONS <br /> <br />Some aspects of a prescribed flow regime were identified but not <br />addressed in this report. These are an evaluation of potential <br />effects of other man-induced impacts on endangered species <br />management (e.g., recreation, water quality, contaminants, exotic <br />invading organisms) that might require flow management <br />consideration. Another is to monitor the biological, economic, <br />and physical effectiveness of channel/habitat reconstruction as <br />they occur; reformulate hydraulics and habitat simulation models, <br />as needed, as change occurs. <br /> <br />15 <br />