7618

• UCREFRP Catalog Number: 7618
• Author: Rose, K. L. and D. R. Hann.
• Title: Summary of Historic Habitat Modeling on the Yampa River Using the Physical Habitat Simulation System
• USFW Year: 1989.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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Calibration

The Maybell study site was modeled with a single IFG4 data deck with three
sets of velocity and WSL measurements from all six transects (Figure 3). The
results of the calibration are presented in Table 9. All of the transects
have been assigned a "good" rating with 90 percent calibration.

WUA Predictions

The calibrated data deck was run through the HABTAT4 program for adult
Colorado squawfish (size 5; 400+mm). The results presented in Table 10
suggest that Colorado squawfish habitat is maximized at 300 cfs. Results are
consistent with trends at the Spawning Bar and Replicate study site.

When compared to the historic mean monthly flows of record for the Yampa
River, from 1922 to 1986 (Attachment 3), 300 cfs is exceeded 100.0, 93.8, 61.5
and 24.6 percent of the time in June, July, August, and September
respectively.

The model predicts that a flow of 300 cfs optimizes WUA for adult Colorado
squawfish at 25,4059.74 sq. feet/l000 feet of linear stream, thus,
theoretically, a 90 percent habitat retention level could be attained at a
range of flows between 200 and 500 cfs. As with the previous two study sites,
the model's predictive optima represents a rare historic event in June, July
and August and likely would not create optimal biological conditions for
Colorado squawfish.

4. GOVERNMENT BRIDGE

The Government Bridge study site, located at RM 97.1 (Figure 4), was surveyed
and described by Rose and Brewer in 1985, and 1986. The geomorphic stability
of this area has not been considered; however, the stability in the Yampa
River between RM's 58 and 88 was evaluated using aerial photographs taken in
1954 and 1981. Comparison of these photographs indicate that channel
morphology is very stable throughout the Maybell area. Thus= channel
stability was assumed (Wahle and Johnson 1984). Andrews (1980) and O'Brien
(1987) also concluded that the Yampa River is in long term equilibrium.

Calibration

The water surface profile (WSP) and IFG4 programs were used to model physical
habitat at the Government Bridge site (Figure 4). WSP with 3 sets of stage
discharge measurements was used to simulate water surface elevations (WSE) for
streamflow and survey data collected at eight transects. Initial roughness
coefficients at each transect were selected and adjusted so that simulated WSE
closely approximated the WSE observations at 1275 cfs (Table 11). Refer to
Milhous et al. (1984) and Bovee (1982) for a description of WSP and IFG4.

After the WSE's at each transect were calibrated, WSP was used to simulate
WSE's at each transect for a series of flows. The simulated WSE's were
transferred to the IFG4 program using WSEI4 so that mean column velocities
across each transect could be predicted for each flow. Because only one set
of velocity measurements were made at each transect, Manning's equation was
used in IFG4 to supply velocities at all verticals for simulated flows.

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