6006

• UCREFRP Catalog Number: 6006
• Author: Holden, P. B. and L. W. Crist.
• Title: Documentation of Changes in the Macroinvertebrate and Fish Populations in the Green River Due to Inlet Modification of Flaming Gorge Dam
• USFW Year: 1981.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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INTRODUCTION

Flaming Gorge Dam on the Green River of northeastern Utah became
operational in November of 1962. A rainbow trout fishery was
established in the first 26 miles of the dam's cold tailwaters in Utah.
From 1963 until 1967 this section of river was considered one of the
best cold water fisheries in the U.S. This fishery declined signifi-
cantly in the late 1960's and 1970's and overly~cold water temperatures
were hypothesized to be the reason (Mullan et ale 1976). The dam, with
its reservoir and cold tailwaters, along with a pre-impoundment fish
eradication program, has been implicated as a major decimating factor of
native Green River fish populations, especially those of the Colorado
squawfish (Ptychocheilus lucius) and humpback chub (Gila cypha), pre-
sently considered "endangered" (Miller 1963, Seethaler 1978).
Modifications of the penstock inlets of Flaming Gorge Dam were installed
in early 1978 for the purpose of warming the tail waters so the trout
fishery could be improved. It was also anticipated that the warmer
flows would enhance the conditions necessary for successful reproduction
of the rare fish populations in Dinosaur National Monument, especially
Colorado squawfish. These modifications became operational on June 30,
1978. The Water and Power Resources Service funded two studies to moni-
tor the effects of the inlet modification. The Utah Division of
Wildlife Resources (DWR) studied the trout fishery from the dam to the
Utah border (29 miles below the dam, hereafter MBD); BID/WEST, Inc.,
studied macroinvertebrates for 85 miles below the dam and the fishes for
75 mi 1 es be 1 ow the Utah DWR trout fi shery study area for three years.