9655

• UCREFRP Catalog Number: 9655
• Author: Guensch, G. R. and J. C. Schmidt.
• Title: 1996 Annual Progress Report - Channel Response to High Discharge in 1996, Green River at Ouray and Mineral Bottom.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

ABSTRACT

The channel response of the Green River to the 1996 flood was measured in areas
considered to contain critical Colorado squawfish nursery habitat These areas
are located at Ouray and Mineral Bottom. Cross-sections at each of these study
reaches were surveyed during various flood stages in 1996. Each reach was also
topographically mapped. Cross-sections surveyed in 1996 were compared with
surveys from 1993 and 1994. At Ouray, the 1996 flood created higher elevation
sand bars than existed after the 1993 or 1994 floods. Bar building occurs during
flood recession. At Mineral Bottom bars do not build nearly as high, relative to
the peak flood stage, as they do at Ouray. As a result, less nursery habitat is
available at Mineral Bottom than at Ouray. Our data illuminate several
characteristics of the Mineral Bottom study reach that may explain its
geomorphic behavior. The channel at Mineral Bottom is generally narrower
than at Ouray, has a slightly higher gradient, and is more isolated from its
historic floodplain due to its high banks. The topographic maps show that bar
complexity at Ouray in 1996 was less than in 1994 or 1995 but greater than that
following the 1993 flood of slightly lesser magnitude..

INTRODUCIlON

Availability of high-quality habitat is one important factor that influences
the survival of the endangered Colorado squawfish (Ptychocheilus luaus) (fyus
and Karp, 1991). The availability of these habitats was partly affected by the
completion of the Flaming Gorge Dam in 1962, and continues to be affected by
the dam's operations. Today, in many locations, the Green River channel is
narrower than it was before closure of the dam (Andrews, 1986; Lyons and
others, 1992; Grams, 1997; Mayers and Schmidt, 1994; Allred and Schmidt, 1996),
and this narrowing has probably decreased the area of available nursery habitat
for the Colorado squawfish.
Schmidt (1996) showed that simplification of the channel in the Uinta
Basin would lead to a more even distribution of nursery habitat in the Green
River and would decrease the relative importance of Ouray as a critical nursery
habitat reach. Schmidt (1996) also showed that the timing of high releases partly
determines the summer distribution of nursery Colorado squawfish in the Uinta
Basin.

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