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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Table 12. Instream Flow Regimens for Fish. Wildlife. Recreation. and Related
Environmental Resources

Most requests for streamflows are for maintaining or preserv~ng a

stream fishery. a waterfowl habitat. or a particular species (Enviro Con-

trol. Inc.. 1976; table 13). In the survey conducted by Enviro Control.

Narrative description
of flows

Fishery
classification

Recommended base flow regimens
a
(percentaRe of averaRe flows)
Oct.-Mar. Apr,-Sept.

lne. of the actual effects of various recommended flows on fish and wild-

life in the Rocky Mountain region. only about 20 percent resulted in im-

Flushing or maxtmum
b
Optimum range

Outstanding

Excellent

Good

Fair or degrading

Poor or minimum

Severe degradation

200

60-100

I

II

III

IV

40
30
20
10
10

60

50
40

30
10

provement for fish and wildlife; 60 percent were judged to be maintenance.
and thus had no effect; and about 20 percent were detrimental (table 14).

In general. the effects of different streamflows were based on the judg-

ment of biologists who were familiar with the streams. although some ef-

fects were determined from rigorous follow-up studies.

The responses of fish and macroinvertebrates to streamflow in the

mainstem Upper Colorado River are little known. Although the past and

probable future variations in streamflow of the Upper Colorado River have

Source: From D. L. Tennant. "Instream Flow Regimens for Fish. Wildlife.
Recreation. and Related Environmental Resources." Fisheries, Bulletin of the
American Fisheries Society vol. 1. no. 4 (1976) pp. 6-10,

a
Average flow usually fills the active stream channel approximately 1/3
full or to the line of permanent terrestrial vegetation. and 3 times the average
flow often fills the active channel nearly to the point of spilling out on the
first bench of the flood plain.

b
Optimum is a nebulous term; however. this flow range best covers that defi-
nition for all the factors considered by Tennant.

been assessed (Brittan and coauthors. 1961). this assessment did not in-

.
-

.
-

clude fish and wildlife. Research must be directed at understanding the

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effects of changes in streamflow on the ecosystem, For prediction. the

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use of mathematical models implemented with computers will aid the under-

p
~

standing of the complexity of stream ecosystems. Although ecosystem
modeling is considered to be in its infancy. a literature review by Kadlec
(1971) contains over 600 references. However. none of the models discussed

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were capable of simulating a general stream dynamic ecosystem. Sensitivity

analysis must be made to determine the factors that are most responsive to

change in any model. This kind of analysis is especially important in the

formation of models with different resolution that can be used by manage-

ment agencies. Time and budget constraints (for manpower and equipment)

will dictate what data a management agency is able to collect. Finally.
mathematical models must be calibrated and then validated with empirical