7245

• UCREFRP Catalog Number: 7245
• Author: Rose, K. L. and D. R. Hann.
• Title: Consolidated Instream Flow Report, Habitat Modeling on the Green River Using the Physical Habitat Simulation System.
• USFW Year: 1989.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: NO

channel and that fish species respond directly to available hydrologic and
physical habitat conditions.

Application of the methodology is comprised of several steps: 1) determining
the species distribution within the stream using literature reviews, field
observation, and consultation, 2) selecting a study reach using either a
critical reach or representative reach approach, 3) measuring physical
habitat and hydrologic characteristics in the reach using a multiple transect
approach, 4) determining species preference or use of streamflow variables
(depth, velocity and substrate), 5) using hydraulic simulation to determine
depth and velocity combinations at unobserved streamflows with respect to
substrate conditions, and 6) calculating weighted-useable-area (WUA) based on
the results from steps 4 and 5. _

1. Soecies Distribution

The four rare fishes, historically located throughout much of the upper and
lower basins, have become restricted in distribution and abundance because of
obstructions to migration, changes in flow regime, and other physical and
biological factors (Miller et al. 1982; Jones and Tyus 1985; Tyus et al.
1987). To protect the remaining riverine habitat, the FWS Biological
Subcommittee completed a report to the UCRB Coordinating Committee identifying
"sensitive areas" of rare and endangered fish habitats in the Green, Colorado,
White and Yampa Rivers (Biological Subcommittee 1984). Rivers were segmented
and defined as "sensitive" by any of these four criteria: 1) endangered
species were identified or collected in the reach, 2) the reach was used as a
~pawning migration route, 3) the reach was confirmed or suspected as a
spawning area, or 4) the reach was considered a high density nursery area
(Biological Sub-Committee 1984).

Segment 3 within the Green River (FWS Segmentation Workshop, 8-12 December
1986) was identified as a sensitive reach because it is a high concentration
area and a suspected spawning area for adult Colorado squawfish, as well as a
nursery and distribution area for young-of-year and juvenile squawfish
(Biological Subcommittee 1984; FWS 1987; Tables 1 and 2). In addition it is a
concentration area and suspected spawning area for adult razorback suckers,
as well as a low concentration area for adult humpback chub. The biological
concerns within Segment 3 are as follows: 1) for Colorado sQuawfish: adult and
juvenile habitat year round, young-of-year nursery habitat from mid-July to
November 1, spawning habitat from mid-June to September, and migration routes
from mid-May to October (one month before and after spawning), 2) Razorback
sucker: adult habitat year round and spawning habitat from April to July, 3)
Humoback chub: adult habitat year round (FWS 1987; Table 2).

This segment, from river mile 248.1 to 345.0 (the Ouray Bridge upstream to the
confluence with the Yampa river), has six sub-segments within it based on
physical changes within the river channel. Sub-segment E from RM 326.8 to

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