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The invasion and proliferation of saltcedar and other woody plants is of considerable concern because of the danger of extreme bank stabilization and resultant loss of ephemeral shoreline habitats. We recommend that a period of high flows be evaluated as a means to control this vegetative overgrowth. The efficacy of specific flows and the duration required to reach a certain amount of vegetative scouring is presently unknown. However, we recommend that flows approximating average annual historic flows of the Green River, or higher, be provided for a period of at least 3 to 5 days. Summer (June 22-September 22) Green River flows should decrease gradually in concert with the emergence of larval Colorado squawfish on spawning grounds in Yampa and Desolation-Gray canyons. The flow regimen of the Green River should resemble (in timing, duration) the hydrologic conditions of the Yampa River with respect to low, moderate, and high wat~r flows. Gradual decreases in spring flows (e.g., not more than about 14.2 m /s per day) should be in~tiated with larval drift, attaining a target flow of not more than 51.0 m /s (about 1800 cfs) at Jensen, Utah during the summer. Flows at Jensen should not fluctuate more than about 25% below the target flow on a weekly or greater basis. River flows should remain at that level or attain a lower flow target for the remainder of the summer. Water temperatures in the upper Green River should not differ more than 5°C from the temperature of the Yampa River at Echo Park, and should average 22-25°C in Gray Canyon from July 1 - August 15. Autumn (September 23-December 21) Green River flows of about 51 m3/s (25% fluctuation below target or lower and more .natural regimens) should be sustained until November of each year, or until most age-0 Colorado squawfish emigrate from backwaters. Winter (December 22-March 20) Colorado squawfish, razorback sucker, and other native fishes are relatively cold-adapted and are active in winter. Current winter flows in the mainstream Green River reduce the availability of preferred fish habitats and promote ice breakup that jams and scours these habitats. Thus the existing flows are considered undesirable. It is recommended to stabilize winter flows at lower levels and to maintain ice cover, once formed, until normal spring breakup. Water elevations may be lower than, but not exceed ice level. Further study of winter conditions and relative effects on endangered fishes and their habitats remain a high priority. Low winter flow levels of natural streams are well tolerated by native Colorado River fishes, but are generally considered detrimental to less cold- adapted non-native forms. Lower winter flows that better approximate natural conditions should be provided and also evaluated for their potential detrimental effects on introduced fishes such as channel catfish and carp. 32