8253

• UCREFRP Catalog Number: 8253
• Author: Schmidt, J. C.
• Title: Geomorphic Control of the Distribution of Age-0 Colorado Squawfish in the Green River in Colorado and Utah.
• USFW Year: 1996.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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Tyus and Haines (1991) showed that nursery areas for age-0 fish are primarily
backwaters that have no measureable velocity. They summarized sampling data collected
between 1979 and 1988 and showed that two parts of the river have the largest
abundance of age-0 fish in late summer and early fall. These reaches are located about
50 to 150 km and 400 to 475 km upstream from the Colorado River and occur in the
Uinta Basin and in lower Labryinth Canyon, respectively.
The distribution of backwaters is intimately related to the geomorphology and
hydrology of the river. Pucherelli et al. (1990) showed that the number and area of
backwaters in the Uinta Basin are maximized at between 39 and 48 m's'', as measured at
the U.S. Geological Survey gaging station near Jensen (Fig. 1). However, the
distribution of backwaters changes from year to year, because the number, size, and
characteristics of backwaters are intimately related to the topography and distribution
of alluvial bars and the shape and composition of river banks. Andrews and Nelson
(1989) demonstrated that sand bed channels adjust quickly to changing discharge. Tyus
and Haines (1991) observed that there were fewer backwaters in years of high peak
discharge than in years with lower peaks.
METHODS
System-wide geomorphic characteristics of the river corridor
Field surveys measured channel cross-section, bed material size, and topography
of exposed sand bars throughout the study area (Olsson et al., 1992; Grams et al., 1994;
Mayers and Schmidt, 1994; FLO Engineering Inc., 1995; Schmidt, unpubl. data). Valley
widths were determined from 1:24000 scale topographic maps and published geologic
maps. Geomorphic data were aggregated by 8.3-km reach.
Channel planform was classified using the scheme of Ikeda (1989) which is based
on the relative width of the meander-belt and the alluvial valley. Ikeda (1989)