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<br />" <br /> <br />0022B4 <br /> <br />Razorback sucker critical habitat in the Yampa River and its 1 DO-year floodplain extends from <br />the mouth of Cross Mountain Canyon downstream to the Green River confluence, Critical <br />habitat for the humpback and bony tail chubs extends throughout the Yampa River in Dinosaur <br />National Monument. <br /> <br />The complete history of the listing of species and designation of critical habitat is available <br />from the USFWS and the Federal Register, Biological support documents as well as economic <br />analyses were included in the designation of critical habitat provided by the USFWS. <br /> <br />2.3 Studies Initiated in 1990 <br /> <br />In 1990, the CRWCD initiated a study to consider the effect of the Juniper water right on <br />instream flows and other water uses, The Yampa Steering Committee was set up to guide the <br />study, The first Phase of this study was to estimate future demands for water in the basin, <br />identify potential storage opportunities, and determine the requirements for stored water in <br />order to satisfy Juniper Project demands. This study treated the demands for the Juniper right <br />as an instream flow. Hydrosphere (1993) summarized the results of this study, <br /> <br />In the second phase of the study, Hydrosphere (1995a) simulated the use of flow targets for <br />the Yampa River, rather than using the Juniper water rights. This study further looked at the <br />feasibility of enlargement of Elkhead reservoir. The flow targets used for this study were <br />preliminary targets that were proposed by the USFWS, <br /> <br />Since that time, there have been several refinements of flow targets as discussed in Chapter 3 <br />of this report. Additional studies have been completed by Hydrosphere and are summarized in <br />the appendix of the report, These studies have iooked at flows recommended by the USFWS, <br />instream flow filings by the Colorado Water Conservation Board (CWCB) and various <br />alternative target flows. <br /> <br />Hydrosphere also completed a Reconnaissance Eva/uation of Yampa River Diversion <br />Structures in 1995. There are hundreds of diversion structures along the Yampa that are <br />used mostly to divert water for irrigation, It was believed at the time of the study that the <br />diversion structures and the maintenance of these structures might inhibit the migration of the <br />Colorado River squawfish and the other endangered fish, The objectives of the study were to <br />develop an inventory of problematic mainstem Yampa Diversion structures in river reaches that <br />are believed to contain endangered fish species: to make a reconnaissance-level evaluation of <br />the potential effects such structures might have on flow conditions, fish passage, an aquatic <br />and riparian habitats; to make preliminary recommendations concerning the structures thought <br />to be most problematic; and to describe, in a preliminary way, the potential alternatives that <br />exist to reduce any adverse effects these structures or the maintenance thereof might have, <br /> <br />The study found that the Maybell Canal and K, Diamond/Patrick Sweeney Ditch diversion <br />structures may represent significant obstacles to fish passage and recommended that a <br />biological study, involving radio telemetry be considered for these two structures (Hydrosphere <br />1995b), <br /> <br />Miller and Rees (1997) and Modde et al. (1999) completed additional studies that indicated <br />that fish were able to pass over the structures during critical periods and the structures did not <br />appear to impede their migration, <br /> <br />Draft 07/28/99 <br /> <br />6 <br /> <br />Ayres Associates <br />