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PRRIP — ED OFFICE FINAL 6 05/27/2010 <br />110 Platte flows or on the type or availability of pallid sturgeon habitat (as defined only by the <br />111 study's habitat classifications). <br />112 <br />113 Analysis and conclusions <br />114 Percentage of Program water reaching Louisville: Analysis of historic reach gains and losses <br />115 showed not all flow reaching Grand Island is translated downstream to Louisville and that <br />116 predicted changes in discharge due to Program water management activities is likely within the <br />117 range of gage uncertainty. <br />118 <br />119 Changes in habitat classifications: 2 -D modeling accurately predicted changes in the six <br />120 habitat classifications over the range of modeled discharges. <br />121 <br />122 Dry Conditions Analysis: The period of record was analyzed for one period in the spring and <br />123 one in the fall when flows were above target at Grand Island, the Program could divert some <br />124 portion of that excess, and flows were simultaneously in the 4,000 -6,000 cfs range at Louisville. <br />125 Assuming habitat connectivity is important for pallid sturgeon and that connectivity declines <br />126 below 4,000 cfs, this analysis showed that short-term connectivity could be problematic, but only <br />127 for one or a few days. <br />128 <br />129 Conclusion: Generally, Program water management will not result in measurable changes on <br />130 flow in the lower Platte River. However, given that short-term connectivity could be problematic <br />131 under certain but infrequent hydrological conditions and assuming the biological significance of <br />132 habitat connection for pallid sturgeon above 4,000 cfs, the study tool could be used by the <br />133 Program to implement proactive measures (e.g. altering excess -to- target -flow diversion timing or <br />134 duration) to prevent potential negative impacts on habitat connectivity. Use of the tool for this <br />135 purpose would be greatly enhanced if additional data were collected and analyzed regarding <br />136 what defines pallid sturgeon habitat in the lower Platte and how that habitat is being utilized (see <br />137 discussion regarding Priority Hypothesis PS -4). <br />138 <br />139 Outstanding Issues <br />140 With respect to PS -2, several issues have been identified and are expanded upon in the <br />141 concluding Technical and Policy Issues to Address section of this assessment. In brief form, the <br />142 issues are as follows: <br />143 <br />144 1) Peer review of the Lower Platte River Stage Change Study <br />145 2) Assessment of the representativeness of the stage change study's 2 -D modeling section <br />146 3) Definition of pallid sturgeon habitat and use <br />147 <br />148 PS -4: Flows in the lower Platte will affect pallid sturgeon habitat suitability. <br />149 <br />150 Proposed assessment strategy and rationale <br />151 Before testing additional pallid sturgeon hypotheses, more progress is required on better defining <br />152 pallid sturgeon habitat in the lower Platte River, how that habitat is being utilized, and whether <br />153 this habitat selection is resulting in pallid sturgeon reproduction and recruitment (IMRP pallid <br />PRRIP Pallid Sturgeon Assessment Page 4 of 8 <br />