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<br />. <br /> <br />. <br /> <br />003375 <br /> <br />be completed in Phase 1 to determine the feasibility of developing a daily time step model for use <br />during a portion of the year and for analysis of certain alternatives (e,g, eliminating the Shoshone <br />priority call), <br /> <br />Hydrology <br /> <br />(Leo will write) <br /> <br />Baseline Conditions <br /> <br />For purposes of determining the contribution of each alternative toward the 20,000 acre-feet, the <br />baseline condition will be the StateMod Cl scenario with the RIPRAP projects as detailed in <br />Appendix D, Preliminary Draft Programmatic Biological Opinion for Recovery Program Actions <br />and Water Depletions in the Upper Colorado River from Rifle, Colorado to Lake Powell, (U.S. <br />Fish and Wildlife Service, 1999), <br /> <br />Flow Targets <br /> <br />A conference with the U,S, Fish and Wildlife Service (April 1, 1999) indicates that the Service is <br />first and foremost interested in putting additional water on to the peak of the spring runoff <br />hydrograph. Furthermore, the Service is concerned with increasing peak flows when the hydro graph <br />{"-'fl'!?o <br />peak is likely to be in the range of 3,000 -29,000 cfs. The Service is not interested in increasing <br />the peak when the actual peak or augmented peak is likely to be less than 13,000 cfs or greater than <br />29,000 cfs. The Service would like to see as much of the 20,000 acre-feet be made available at the <br />head of the IS-mile reach as possible during the 7-10 day period surrounding the peak spring <br />discharge. <br /> <br />If some portion of the 20,000 acre-feet remains after augmentation of the spring peak discharge and <br />this water can not be carried over for use in the succeeding spring, then this water should be used <br />for augmenting low flows during the August 1- October 31 period. During this August 1- October <br />31 period, the goal would be to maintain minimum flows at the head of the IS-mile reach as <br />specified by the Service (U.S. Fish and Wildlife Service, May 1995): <br /> <br />. During years of above average (50 percent) precipitation, flows would not be less <br />than 1,630 cfs. <br /> <br />. During years of low precipitation, flows would not fall below 1,240 cfs. <br /> <br />. During drought years (the lowest 20 percent), maintain 810 cfs. <br /> <br />Augmentation of low flows in late summer and fall is second priority to augmenting the spring peak <br />discharge during the 7-10 day spring peak period. <br /> <br />P:\I999199-008100 1000wplReport Text. wpd <br /> <br />8 <br /> <br />sA: 7;1 <br />. \, !f <br />Ib1'?0' <br />./ ~ <br />Oel ill f <br />C,f \ <br />'I " <br />o .' ,- <br />'i-I') .,,r <br />~\ )~. <br />JiJ <br />I <br />