7378

• UCREFRP Catalog Number: 7378
• Author: Wydoski, R. S.
• Title: Potential Impacts of Alterations in Streamflow and Water Quality on Fish and Macroinvertebrates in the Upper Colorado River Basin.
• USFW Year: 1980.
• USFW - Doc Type: 77-147
• Copyright Material: YES

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Ecology of Fish and Instream Flows

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Flows of streams in the Colorado River Basin are being rapidly al-

tered as a result of domestic. industrial. and irrigation uses. and fur-

ther alterations may develop in relation to proposed energy development

schemes. All water in this basin is considered to be in use at the pres-

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ent t~e. but reallocations still take place regularly with the result

that water flows in natural streams are continually being reduced (Neuhold.

Herrick. and Patten. 1975). State agencies have been asked to provide

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gies for determining streamflow needs (Stalnaker and Arnette. 1976). and

information on an acceptable range of water flows to sustain a viable

fishery. However. this range is difficult to determine because a stream

is a complex ecosystem and the only proven way of predicting how fish

will respond to changes in streamflow is to measure their microhabitat

requirements by life stage. Although much published material is avail~

able on stream ecology (e.g.. Hynes (1970) cited over 1.200 references).

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information on the response of fish to changes in flow has been scattered

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throughout the published literature. A number of reviews have been com-

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pleted on streamflow requirements of fish. particularly saLmonids (Fraser.

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1972b; Giger. 1973; Hooper. 1973; Pacific Northwest River Basins Commis-

sion. 1972; Wesche. 1973). In addition. workshops are being held to fur-

ther define this problem. For example. a workshop was held in September

1975 to review. synthesize. and prepare a working document on methodolo-

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another was held on instream flow needs in May 1976 that considered this

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subject in greater scope and depth (Orsborn and Allman. 1976).

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Because recent activity in the evaluation of streamflow requirements

of fish has been extensive. 1 cannot synthesize the existing knowledge in

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