8119

• UCREFRP Catalog Number: 8119
• Author: Valdez, R. A. and B. R. Cowdell.
• Title: Effects of Flow Regulation and Ice Formation on Overwinter Nursery Habitat and Survival of Age-0 Colorado Squawfish in the Green River Below Flaming Gorge Dam - Draft.
• USFW Year: 1996.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

Fall Mapping and Reconnaissance
Winter Ice Measurements I
Ground Reconnaissance of Study Area (UDWR)
Aerial Reconnaissance of Study.Area
Winter Ice Measurements II

September 28 - October 1, 1993
January 31 - February 4,1994
February 10,1994
February 16,1994
Februarv 21-24. 1994

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3. Reach 3 began 119 miles downstream of the dam and extended from Bonanza Bridge (RM
290) to Ouray, UT (RM 248). This lower reach was hardly affected by fluctuating releases
and had a low-gradient with primarily a sand substrate.

3.0 METHODOLOGY

Three scheduled 5-day field trips, including one in the fall and two in winter, were conducted during
each of the winters of 1993-94 and 1994-95 (Table 1). The fall trip (i.e., October), was conducted
to reconnaissance and map backwaters after initiation of winter dam releases and prior to ice
formation. The two subsequent winter trips (i.e., January, March), were conducted to relocate and
remap study backwaters and to evaluate ice conditions. This study consisted entirely of habitat
assessment and did not involve fish sampling. Overwinter survival was based on fall and spring
densities of fish from sampling under the Interagency Standardized Monitoring Program (ISMP,
McAda et al. 1994, Valdez and CowdellI995). The third scheduled year offield sampling was
canceled because of warm weather in winter of 1995-96.

Table 1. Purpose and dates of fields trips on the Green River for the winter ice study.
PURPOSE DATES
YEAR 1: 1993-94

YEAR 2: 1994-95
Fall Mapping and Reconnaissance
Winter Ice Measurements I
Winter Ice Measurements II

October 20-23, 1994
January 6-8, 1995
Februarv6-8.1995

In addition to the scheduled field trips, short-tenn ground and aerial reconnaissance trips were
conducted to evaluate the progress of ice formation and to determine the most appropriate time for
field measurements of backwaters. Additional monitoring of ice conditions was perfonned by
employees ofUDWR, Northeast Regional Office in Vernal.

3.1 River Hydrology and Chemistry

Special releases were made from Flaming Gorge Dam during this study to test the effect of flow .
volume, flow magnitude, and range of flow fluctuation on ice fonnation processes. In the first year

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