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PRRIP — ED OFFICE FINAL 6 05/27/2010 <br />67 • PS -2: Program water management will result in measurable changes on flow in the lower <br />68 Platte River. <br />69 • PS -4: Flows in the lower Platte will affect pallid sturgeon habitat suitability. <br />70 <br />71 Assessment of Pallid Sturgeon Priority Hypotheses <br />72 <br />73 PS -2: Program water management will result in measureable changes on flow in the lower <br />74 Platte River. <br />75 <br />76 Assessment strategy and rationale <br />77 To test this hypothesis, the Program initiated the Lower Platte River Stage Change Study (IMRP <br />78 pallid sturgeon activity #3) in 2008 to develop a tool to evaluate the potential effects of Program <br />79 water management activities (storage projects, re- timing, water conservation, depletions covered <br />80 by state and federal depletions plans) on stage and how stage changes might affect the physical <br />81 characteristics of the lower Platte River. Field sampling, 1 -D and 2 -D modeling, and analysis <br />82 were completed in 2009 and the study is now final. <br />83 <br />84 Space and time frames <br />85 Study scale <br />86 The full study scale was the lower Platte River from the Elkhorn River confluence to the <br />87 Missouri River confluence, as defined in the Program document. Intensive fieldwork and <br />88 modeling were conducted on a smaller study reach from the Highway 50 bridge to the reclaimed <br />89 Pedestrian Bridge near Louisville, Nebraska. <br />90 <br />91 Time scale <br />92 Data collection and modeling began in September 2008 and concluded in October 2009. A final <br />93 report was delivered to the ED Office in December 2009 and the study team made a presentation <br />94 to the GC in March 2010. <br />95 <br />96 Performance measures, expected response, analysis, and conclusions <br />97 Performance measures <br />98 • Water depth and velocity between 3,700 cfs and 40,000 cfs <br />99 • Percentage of Program water reaching Louisville <br />100 • Changes in habitat classifications (slackwater, flat, riffle, run, isolated pool, plunge) <br />101 between 3,700 and 40,000 cfs <br />102 • Number of days below 4,000 cfs @ Louisville (Dry Conditions Analysis) <br />103 • Range of flows below 4,000 cfs @ Louisville (Dry Conditions Analysis) <br />104 • Number of consecutive days below 4,000 cfs @ Louisville (Dry Conditions Analysis) <br />105 <br />106 Expected response <br />107 We predicted that given the influence of the Loup and Elkhorn Rivers on lower Platte flows, <br />108 water management activities in the lower Platte, flow attenuation, and their size and timing, <br />109 Program water management activities would not have a statistically significant impact on lower <br />PRRIP Pallid Sturgeon Assessment Page 3 of 8 <br />