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

Two of the eight categories listed by Tennant have been commonly used

making MF-type recommendations and both were included in this study.

categories are "fair or degrading" 00% AF) and "minimum or poor" 00% AF) fOt

the period of April through September.

Average flow was obtained from

appropriate U. S. Geological Survey (USGS) gaging records wherever possible. On

ungaged streams, AF was obtained using a hydrograph simulation model developed

by ~.Jahl (unpublished 1970 report on a proposed stream flow data program for

Wyoming, available at th~ USGS Office in Cheyenne).

Wetted Perimeter

This method assumes that a direct relationship between wetted perimeter and

fish habitat exists in streams. By plotting the response of wetted perimeter to

inc remen tal changes in dischar~e, the inves tigator usually can identify an

in flee tion in the resulting curve where small decreases in flow result in

increasingly greater decreases in wetted perimeter.

This point on the curve

represents a flew at which the water surface recedes from stream banks and fish

habitat is lost at an accelerated rate.

This flow is the instream flow esti-

.
mate. Rose and Johnson (1976) present one application of this method.

Data for generation of this curve are obtained by using one of several com-

puter models.

The IFG-I model (Mllhous 1978) was used in this study.

Users

have the option with this model of either (1) basing simulations on data from a

single visit to the site and using the Manning equation for discharge balancing

or (2) developing a stage-discharge relationship by collecting field measure-

. ments on several occasions. The latter alternative provides more accurn~ simu-

'':~.'~

lations (Bovee and Milhous 1978) and was used in this study.

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