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<br />.' <br /> <br />Proposed Water Year 2005-2006 Experimental Actions <br /> <br />01815 <br /> <br />5 <br /> <br />Environmental Consequences <br /> <br />Resources considered in the analysis of effects are the same as those considered in the <br />2002 EA. They include sediment, the aquatic and terrestrial food base, reptiles and <br />amphibians, trout and other non-native fish, federally-listed species (Kanab ambersnail, <br />humpback chub, razorback sucker, southwestern wiUow flycatcher, bald eagle, and <br />California condor), recreational activities, cultural resources, and hydropower, The <br />effects of alternating low steady and low fluctuating flows, high experimental flows, and <br />non-native fish suppression flows are described for each of these environmental <br />variables, <br /> <br />Sediment <br /> <br />Alternating Low Steady and Low Fluctuating Flows <br /> <br />Record of Decision daily fluctuating flows, alternating low steady and low fluctuating <br />flows, and the high experimental flow can occur under No Action and the Proposed <br />Action (Figures 1 and 2, Tables 1 and 2), Alternating low steady and low fluctuating <br />flows occur only with a sediment input of 500,000 metric tons after September 1 under <br />No Action, but with or without this sediment input under the Proposed Action, <br />Continuous Record of Decision fluctuating flows under No Action are predicted to <br />export more fine sediment during September and October than the alternating low <br />steady and low fluctuating flows, <br /> <br />High Experimental Flow <br /> <br />Implementation of the high experimental flow in November-December under the <br />Proposed Action, as opposed to January under the No Action, would benefit fine <br />sediment retention because the amount of fine sediment retained would increase with <br />proximity to the events that delivered the sediment to the Colorado River. The Proposed <br />Action also more closely follows the first recommendation of Rubin et al. (2002) to <br />conduct a high experimental flow as soon as possible following tributary sediment <br />inputs in the July-October sediment input season, Fine sediment export from Marble <br />Canyon associated with nonnal December operations under Record of Decision <br />fluctuations following the high experimental flow will be mitigated to some degree, as a <br />percentage of the recent sediment input(s) will be stored along shorelines above the high <br />stage of the December fluctuating flows, <br /> <br />Non-native Fish Suppression Flows <br /> <br />Sand transport rating curves developed from data collected at the Grand Canyon gage <br />in water year 2003 have been evaluated to assess the influence of fluctuating flows in the <br />range of 5,000-20,000 cfs. For a monthly release volume of 500,000 acre-feet following a <br />