7762

• UCREFRP Catalog Number: 7762
• Author: Valdez, R. A. and B. R. Cowdell.
• Title: Annual Summary Report-1994, Effects of Flow Regulation and Ice Formation on Overwinter Nursery Habitat of Age-0 Colorado Squawfish in the Green River Below Flaming Gorge Dam.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

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3.1 RIVER HYDROLOGY

Flow release data from Flaming Gorge Dam were provided by Bureau of Reclamation, Salt Lake City Office.
Flows and water temperature for the Green River within the study area were measured by the U.S Geological
Survey (USGS) stream gage located near Jensen, UT (station 09261000). Data from this gage for water year
1994 are provisional. Air temperatures were recorded at the National Oceanic and Atmospheric
Administration (NOAA) weather station located in Jensen, UT. Historic flow and temperature data were
summarized from USGS data compiled in the GeoSelect™ Colorado River Database. This database is in CD-
ROM format and is produced by Hydrosphere Data Products, Inc.

3.2 BACKWATER MAPPING

Backwaters were selected in each reach based on size and depth, formation classification (i.e. chute channel,
scour channel, and eddy return channel) and access during winter months. Only backwaters which met the
Interagency Standardized Monitoring Program (ISMP) minimum requirements for a suitable backwater
(surface area of at least 30 m2 and maximum depth of at least 1.0 ft) were selected. Efforts were made to
select backwaters within each reach that represented different depths and formation classifications.
Consideration was also given to accessibility of backwaters during winter months when ice cover prevented
open water boat travel.

For each selected backwater, shoreline was mapped and depth isopleths recorded. The shoreline was mapped
on 17 x 22-in paper using a plane table and an alidade. Prominent features (trees, logs and rocks) and
principal substrate types (as boulder, cobble, gravel, sand and Silt) were included on the map. Contour
isopleths were developed by measuring water depth (in feet) along 5 - 7 transects across the backwater (depths
were recorded in feet because it is consistent with existing ISMP backwater sampling protocol). Each map was
transferred to AutoCAD™, a computer-aided design package. These habitat maps were reduced and printed
on 8 112 x 11-in paper for use as base maps for winter measurements. Surface area of backwaters (in ~ were
calculated from these maps.

3.3 WINTER HABITAT MEASUREMENTS

The amount of winter habitat was determined by measuring and mapping the physical and chemical
characteristics of a backwater. Physical characteristics included changes in shoreline, depth of free water and
thickness of surface and frazil ice. Chemical characteristics included water quality parameters such as
temperature and dissolved oxygen.

3.3.1 Physical Habitat

Physical habitat was quantified (in m2) by recording shoreline configuration, depth of free water, thickness of
ice cover and current velocity on the 8 112 x ll-in base maps. Shoreline configuration and extent of open
water were sketched onto the base maps. Depth of free water, thickness of surface and frazil ice were
measured in feet (:t:0.05 ft) with a staff gage after drilling holes through the ice. Holes were made using an
ice chisel, or a Strikemaster™ 49 cc gas powered ice auger with an 8-in blade Water velocity-as in the case
of a backwater becoming a flow through channel--was measured using a Marsh-McBirney current meter.

3.3.2 Chemical Habitat

Chemical characteristics of backwaters were measured using a Hydrolab Surveyor 2. The Hydrolab measured
water temperature (:t: O.OloC), dissolved oxygen (mg/l), conductivity (pS/cm) and Ph. Measurements were
taken in the mainchannel adjacent to the habitat then along the deepest ponion of the backwater beginning
at the mouth and working toward the back. Typically four to six measurements were taken within a backwater
when free water occurred.