9569

• UCREFRP Catalog Number: 9569
• Author: Valdez, R. A.
• Title: Synthesis of Winter Investigations of Endangered Fish in the Green River Below Flaming Gorge Dam.
• USFW Year: 1994.
• USFW - Doc Type: 18-11,
• Copyright Material: NO

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Winter 2 (1987-88). Lower air temperatures and releases from Flaming Gorge Dam

in Winter 2 produced lower water temperatures and more extensive ice formation than in

Winter 1. Monthly maximum air temperatures for January and February were 4.2 to 2.10C

below normal, while minimum temperatures were 3.9 to 2.0oC below normal. Water

temperatures averaged 0.0 to 1.~C from December through February (Figure 7), which

caused supercooling of the river to -1.50C.

River ice formation was extensive in Winter 2. An aerial raptor survey in late

January by UDWR (personal communication with Miles Moretti, UDWR, Apri120, 1988)

revealed that the Green River and Colorado River were ice covered to Lake Powell, except

for ice-free areas in large rapids in Desolation and Cataract canyons.

Diverse ice conditions and formations in the study area appeared to affect local river

hydrology by blocking or diverting normal flow patterns. These ice conditions were formed

by relatively warm dam releases, distance downstream from the dam, and channel gradient.

A longitudinal view of the Green River represents gradient and obseIVed ice formation in

January and February, 1988 (Figure 8). The river from Flaming Gorge Dam to the Ouray

Bridge is about 162 miles (260 km) long, with an elevational change of 905 feet (5,605 to

4,700 feet). In Winter 2, water from Flaming Gorge Dam first became supercooled in

Ladore Canyon, about 50 miles (80 km) below the dam. Short sections of solid surface ice

were present for brief periods at Echo, Island, and Rainbow parks. Surface ice in these areas

was frequently broken, dislodged and transported downstream by fluctuating dam releases,

leaving ice only along shorelines. The central third of the channel was often free-flowing

and filled with frazil ice during cold periods, and with large masses of jam ice during large