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0 November 6, 2007 <br />Summary of Phase I Whooping Crane Data Analysis <br />Prepared for: <br />Technical Advisory Committee of the Platte River Program and <br />Western EcoSystems Technology, Inc. <br />Prepared by: <br />Bureau of Reclamation <br />Conclusion and Recommendation <br />Of the three methods considered: gage data; Manning's equation combined with a ratio; <br />and HECRAS, the HECRAS method using the existing Platte River model is <br />recommended because it provides the most reliable results on water surface change at <br />the greatest number of locations. The HECRAS method uses an explicit computation of <br />physical processes with fewer assumptions in comparison to the Manning's equation/ratio <br />method that is an approximate or empirical computation relying on multiple assumptions. <br />There was also no time savings with the less reliable Manning's equation/ratio method <br />• since it took as much computation time as the HECRAS method. <br />The HECRAS method and gage data method use a cross section instead of a flow ratio <br />and the success of these methods is dependent on the similarity of the computational <br />cross section' to the actual cross section at the Whooping Crane (WC) site. The HECRAS <br />model currently has 58 cross sections providing better opportunity for a match then the <br />single cross sections associated with the 4 gage sites. Because the gage method is simple <br />and fast however, it is recommended as a secondary method or check for purposes of <br />quality control. <br />Two other benefits of the HECRAS method are: <br />• the model provides data in addition to the water surface information, which can be <br />used for the Whooping Crane analysis (velocity, flow area, channel width, water <br />surface depths at alternate locations, etc.); and <br />• although average daily flow data was used for this analysis, water surface <br />variations resulting from large changes in daily flow data and flow travel time can <br />be studied with the HECRAS model if a question at specific sites comes up in the <br />future. <br />1 A cross section traverses the full width of the flood plain, while a transect may traverse less than this <br />distance, i.e. a single channel at locations with multiple channels. <br />Summary of Phase I Whooping Crane Data Analysis November 6, 2007 <br />1 <br />