9520

• UCREFRP Catalog Number: 9520
• Author: Haines, G. B., D. Irving and T. Modde.
• Title: White River Base Flow Study for Endangered Fishes, Colorado and Utah, 1995-1996.
• USFW Year: 2004.
• USFW - Doc Type: 5D,
• Copyright Material: NO

pikeminnow population. The foundation of our analysis was predicting how these habitats change

with changing flow. The original scope of work called for measuring meso- and microhabitats at

three experimental flows and using the empirical relations as a basis for determining this change.

The realized flows during the study, however, did not cover a wide enough range for this analysis.

As a result, we modeled the meso- and microhabitats-discharge relations over a broader range of

flows to determine the appropriate relations.

Model Critique

The reliability of the physical habitat simulation results (WUA, riflle surface area, wetted

perimeter) depends on the hydraulic model and the species habitat suitability criteria. We used the

hydraulic model to predict depth and velocity for each cell at differing discharges. Its accuracy

depends primarily on how far from the calibration flows those predictions are extrapolated.

Bovee and Milhous (1978) recommended the useful range of extrapolation is 0.4 to 2.5 times the

calibration flow. In our study, the calibration flows ranged from about 339 to 551 cfs, and we

made 14 simulations between 1 and 600 cfs. Thus, simulated flows < 134 cfs are suspect and may

result in 50 to 60 percent error.

The hydraulic parameters, e.g., wetted perimeter, width, depth, and velocity, are more

precisely estimated than the habitat areas. The hydraulic parameter estimates were determined for

each cross section independently, whereas the habitat areas were determined by tying 2 cross

sections together per habitat cluster, resulting in large cell surface areas and imprecise estimates.

The recommended number of cross sections in a stream reach the size of the habitat clusters is 6

to 8 cross sections (Bovee et al. 1998).

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