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<br />curves used by IFIM, and also improve biological resolution of the method. Presently, 2-D <br />modeling is not widely used for fishery applications and is still an unlmown commodity as far as <br />its practicality for instream flow assessment. <br />The intent of this study is to develop and validate a methodology for determining instream <br />flow recommendations for warm water fish communities in Colorado (Anderson and Stewart <br />1999). This is to be accomplished by determining relationships between habitat availability and <br />flow using a 2-D flow model to simulate meso-habitat diversity and abundance over a range of low <br />flows on several sections of three different rivers. Also fish population and species' life history <br />data will be collected within each of the study sites to provide habitat use and preference data to <br />determine relationships between base flows and habitat availability for native fish species of warm <br />water riverine fish communities. <br /> <br />The study goal was amended in 1999 to submit instream flow recommendations to the <br />Colorado Water Conservation Board (CWCB) for the Yampa River ami Colorado River in the 15- <br />Mile Reach. This assignment was made following a decision by the CWCB to withdraw the 1995 <br />water rights filings for the two rivers instead of defending the filings in water court. . The 1995 <br />filings were based on recommendations made by the U. S. Fish and Wildlife Service (USFWS)in <br />regard to recovery of endangered fish species [Modde and Smith (1995) and Osmundson et al. . <br />(1995)]. The CWCB at that time felt the 1995 recommendations had become too controversial due <br />to lack of support from the Service. A tentative date for instream flow recommendations was set, <br />but that date has been moved back a year due to difficulties with contract administration and flow <br />recommendations are expected to be submitted in August 2003. <br />The CWCB also expressed a desire to have a more standardized approach for instrean1 flow <br />filings for rivers having endangered fish concerns. Up to now, all flow study concerning <br />endangered fish have used different methodologies. The lack of consistency was viewed by the <br />CWCB as troublesome. By using the same methodology for both the Yampa and the Colorado <br />River, it was thought that some of the scientific and social difficulties could be avoided. Also, this <br />study will provide guidance and recommendations for the design and evaluation of future flow <br />studies. <br /> <br />Study Objectives: <br /> <br />1). Model fish habitat availability on wann water sections of three rivers (Yampa, <br />Colorado and Dolores) using the established methods (I-D models) and evaluate <br />the practicality of using 2-D flow models to quantify fish habitat. <br /> <br />70 - 6 <br />