7144

• UCREFRP Catalog Number: 7144
• Author: Inslee, T. D.
• Title: Spawning and Hatching of the Razorback Sucker
• USFW Year: 1982
• USFW - Doc Type: Western Association of Fish & Game Agencies
• Copyright Material: NO

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DESCRIPTION OF THE EXISTING ENVIRONMENT

Physical Characteristics

The Green River in the Moon Lake study area is a slow-moving,
meandering stream with a shifting sand substrate. This differs from
river reaches above and below the study area where canyons and steep
gradient turn ;the river into a swift, rapid-filled stream with inter-
mixed cobble and sand substrates. The river is generally 200-300
meters wide and relatively shallow. Although holes in eddies may reach
depths of 3-5 meters, most of the river is under 2 meters except during
spring runoff in May and June when it may rise 2 meters. Summer tem-
peratures usually reach about 230 C, although much warmer temperatures
are found in backwaters. During winter, most of the study area may be
frozen over. The river is generally turbid, but during long dry spells,
such as occurred during the summer of 1979, it becomes relatively clear
and has a greenish cast rather than the normal brown appearance.
Flows in the Green River peak in June at near 15,000 cfs, and then
recede to normal low flows of 3,000 cfs during fall and winter. Flows
vary on a daily as well as a seasonal basis due to the requlation im-
posed by Flaming Gorge Dam, over 160 km upstream from the study area.
During natural low flow periods, daily fluctuations created by power
generation at the dam may approach 0.5 meter in depth in the study area.
Instream habitat in the study area varies with flow, and therefore
with season. During high flows, the river is full bank to bank and
only a few islands dissect the main channel. Many small eddies are