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30 BIOLOGICAL REPORT 24 Flow Regimes Recommended to Protect and Enhance Endangered Fishes in the Upper Colorado River Basin In this section I present flow recommendations made by the U.S. Fish and Wildlife Service, and in the following section I discuss the problems with these recommendations. Flow recommenda- tions have not been made for the Gunnison, White, and Dolores rivers, major tributaries that have considerable potential as habitat for endan- gered fishes, as well as for augmenting flows in important segments of the Colorado and Green rivers. Yampa River (U.S. Fish and Wildlife Service 1990): • The "historical" flow pattern ("percentile flows that occur naturally"), based on a de- rived monthly regime that included 68,800 acre-feet depletion of historical flow, will be maintained. Green River (U.S. Fish and Wildlife Service 1992): Between 1 April and 15 May releases from Flaming Gorge will ramp upward (< 400 cfs/day), corresponding to the trend measured in the Yampa. Releases from Flam- ing Gorge will correspond to the peak flow in the Yampa to yield flow between 13,000 and 18,000 cfs for 1 (dry year) to 4 (wet year) weeks between 15 May and 1 June. This may require release of 4,000-4,700 cfs from Flam- ing Gorge for the duration of the peak; if peak flow in the Yampa is < 9,000 cfs (very dry year), release from Flaming Gorge will be 4,000-4,700 cfs for 1 week, corresponding to the Yampa peak flow. Releases from Flaming Gorge will ramp down (< 400 cfs/day) to 2,000 cfs for at least 1 week and then to 1,100-1,800 cfs at Jensen (first gauge below the Yampa-Green conflu- ence) by 20 June in dry years, 10 July in normal years, and 20 July in wet years (tar- get dates can be adjusted as new information on larval drift and entrainment in nursery areas becomes available). Hourly flows at Jensen will be maintained at 1,100-1,800 cfs (±12.5%) until about 15 September; compen- sation for freshets from the Yampa (natural events) is not required. Water released from Flaming Gorge during this period will be from the warmest strata possible to produce temperatures in the Green River at Jensen that are no more than 50 C colder than tem- peratures in the Yampa at its confluence with the Green. From 15 September to 1 November flows will be as above, except during wet years, when a range of 1,100-2,400 cfs (±12.5%) will be allowed. From 1 November flows will remain stable through the ice formation and spring breakup period, except as necessary to pro- duce storage in Flaming Gorge that will en- sure spring through autumn flows given above. If ice is not present, flows may vary within constraints of the U.S. Bureau of Rec- lamation agreement with Utah (i.e., 800- 4,700 cfs). Section 7 consultation will occur if emergency events impact Reclamations ability to comply with the above for more than 20 h during any month. Beginning in spring 1992 "research flows" will be allowed. These experimental flows will be used to refine the current recommended flows as per priorities annually agreed upon by the U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, and Western Area Power Administration. The effects of winter base- flow on full peaking power fluctuations will be evaluated, along with 1 year of stable winter releases at or below 2,000 cfs and 1 year of spring flows utilizing jet tube bypass at the dam. Other research concerns listed were temperature control by selective withdrawal, feasibility of retrofitting bypass tubes for gen- eration to allow bigger spring peaks, and mechanisms of legal protection of instream flows, presumably through appropriation of conditional instream flow rights. Various studies underway in FY 93 are summarized in Bureau of Reclamation (1992) and include studies of larval drift of squawfish, razorback sucker, and humpback chub; overwinter sur- vival of YOY squawfish; geomorphic classifi- cation and ecology of backwaters; nonnative fish management; and wetlands rehabilita- tion (Old Charley Wash). Colorado River Above Confluence With the Green River (Kaeding and Osmundson 1989; Osmundson and Kaeding 1991): • At the state line gauge: (1) maintain or increase the current 25% peak flows (high day of the year) at 30,000- 40,000 cfs (squawfish recruitment peaks);