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<br />Instream flow techniques require integration of two processes that combine detailed <br /> <br />knowledge of habitat requirements (by species and life stage), and the availability of <br /> <br />necessary habitats. Both the collection and analysis of these data bases have been very labor <br /> <br />intensive. Recent advances in surveying technique (e.g. G.P. S.) and computer capabilities <br /> <br />(G.I.S.) allow for collection and processing of much larger databases. Also, two-dimensional <br /> <br />(2-D) flow models may have potential for application in instream flow studies (Leclerc el aI., <br /> <br />1995; Bovee, 1996). In theory, 2-D models offer a significant improvement over one- <br /> <br />dimensional (I-D) modeling by increasing spatial resolution, allowing for highly accurate <br /> <br /> <br />quantification of physical habitat availability. A spatially explicit flow model may eliminate <br /> <br /> <br />the need for microhabitat suitability curves used by IFIM, and also improve biological <br /> <br /> <br />resolution of the method. Presently, however 2d modeling is not widely used for fishery <br /> <br />applications and is still an unknown commodity as far as it practicality for instream flow <br /> <br />assessment. <br /> <br />The original intent of this study was to develop and validate a methodology for <br /> <br />determining instream flow recommendations for warm water fish communities in Colorado <br /> <br /> <br />(Anderson 1999). This is to be accomplished by determining relationships between habitat <br /> <br /> <br />availability and flow using a 2-D flow model to simulate meso-habitat diversity and <br /> <br /> <br />abundance over a range of low flows on several sections of three different rivers. Also fish <br /> <br /> <br />population and species' life history data will be collected within each of the study sites to <br /> <br /> <br />provide habitat use and preference data to determine relationships between base flows and <br /> <br /> <br />habitat availability for native fish species of warm water riverine fish communities. <br /> <br />A new study goal was added in 1999 to submit instream flow recommendations for the <br /> <br />Yampa River and Colorado River in the IS-Mile Reach to the Colorado Water Conservation <br /> <br />Board (CWCB), with biological justifications for a water right filings in those rivers, by <br /> <br />August 2002. The CWCB withdrew water rights filings made in 1995 for these rivers. The <br /> <br />2 <br /> <br />I <br />'I <br />I <br />'. <br />I <br />I <br />I <br />:. <br />,J <br />I <br />" <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />,I <br />