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-2- INTRODUCTION In the fall of 1962 the Ashley Dam of the Flaming Garde Prey,ect will be. completed. This dam will impound waters of t:~e Green River. cahic?~~ enclose approximately 14,300 square miles of drainage area. Ashley Dam is being constructed on the Green River pzoper in Norrheastern Utah. Thi dam, 495 feet high, will impound approximately 3,930,000 acre feet of water and form a reservoir some 43,000 surface acres in size when full. The upper Green River has long been regarded as one of the finest fishing streams in the State of Wyoming. LTnfort?inately, this situation doea not prevail thoughout the entire length of the stream The lower section of the Green River courses through 100 miles of the Green River, Bridger and Wasatch formations. These formations are composed of gravel, sandstone and shale, and are ovexlain with sandy soils which are highly erosive. Corsse~uently, the lower section of the giver suffers annually from silt laden run-off waters in the spring. The ..:3infall in this area varies from 13 inches in the headwaters to 8 i~ic?~es along the lower section. Fluctuation varies from a high of approximately 12,000 cfs duri~:g spring run-off to a low of about 350 cfs in .the late fall, Tile lower section is also subject to high temperatures during the summer and tell which approach the tolerance limit of trout. The yearly temperature rangy is from freezing point to abo;~t 7g~ F. in July. Attempts to establish game fish populations in the lower section of the Green River have ~Ret with little success. Shifting beds of silt and sand cover large expanses of the river's bed, limiting development of fish food organisms. Habitat areas for sa2monia species are practically non-existent. Large populatf.ons of borytail, suckers, squawfish and carp represent the majority of rich present. Advent of the Seedskadee project will further limit development of game fish from the backwaters of the Flaming Gorge Reservoir to the Fontenelle Darr of the Seedskadee project. Present plans call for diversion and storage of surplus spring flows in the Green River to irrigate 59,620 acres of pre- seatly undeveloped lands. Anticipated effects of this project range from increased t~srbidities, increased dissolved solids *_o increased water tem- peratures and complete dewatering of the river bed for~some ten miles below Fontenelle Dart in the fall of the year. This study e:~titled "Pre-Impoundment Study of the Flaming Gorge Reservoir" was initiated as a part of an inter-state cooperative fisheries management program with the State of Utah. An attempt was made to evaluate the present status of the Green River and anticipated changes in habitat, from a sport fisheries standpoint, resulting from the previously mentioned installations. Financing for this study was obtained, in part, from Dingell-Johnson funds-. The project number assigned to the study was F-25-R-1, and the period of time covered during the study was from July 1, 1955 to April 30, 1960.