7926

• UCREFRP Catalog Number: 7926
• Author: Annear, T. C. and A. L. Conder.
• Title: Relative Bias of Several Fisheries Instream Flow Methods.
• USFW Year: n.d.
• USFW - Doc Type: Cheyenne, Wyoming.
• Copyright Material: NO

Description of Methods and Their Applications

In this paper, the term maintenance flow eMF) refers to an instream flow

necessary for maintaining a viable sport fishery during late summer (July ...

October).

I t should not be construed as a minimum flow.

The term "Method"

relates to the manner in which a generated data set was used to determine an MF.

Several methods may be derived from a single data set (Table 1). A critical

riffle was defined as the single riffle at a study site which required the

highest discharge to meet established hydraulic criteria.

Thirteen streams in Wyoming, ranging in average flow (AF) from 3.5 cfs to

1400 cfs and representing a variety of stream types (Table 2), were studied from

April to November, 1981. All of the study sites were on unregulated streamS

except the Big Horn River where the study site was located 30 miles downstream

from Boysen Reservoir. Most of the streams were dewatered somewhat fo~~~~riga-

tion. Pat O'Hara Creek was almost totally dewatered at the study site. Speci-

fic locations and morphological data are listed in Annear and Conder (1983).

All of the methods were used for each stream.

Tennant Method

Fixed percentage methods define an instream flow (minimum, optimum, etc.) as

a predetermined percentage of the historic AF at a particular site on a stream.

The Tennant method (Tennant 1976) lists eight categories of stream flow for

various instream flow needs. These range from "flushing or maximum" to "severe

degradationll. Recommendations can?e dfveloped entirely in the office'!!.3bthough

it may be helpful to visit the stream at least once to assess the adequacy of

the recommendation.

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