7423

• UCREFRP Catalog Number: 7423
• Author: U.S. Bureau of Reclamation.
• Title: Glen Canyon Environmental Studies Draft Report, September 1987.
• USFW Year: 1987.
• USFW - Doc Type: Washington, D.C.
• Copyright Material: NO

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In addition, increasing dam releases from 30,000 t~
45,000 cfs causes a reduction in recreation benefits
of 17 percent for a commercial and 45 percent for a
private white-water trip (See Appendix C, Section III.)

If flood flows lead to substantial loss of beach area
in the long-term, recreation benefits (not commercial
revenue) for white-water boating will be reduced by
approximately 50 percent. In an average year, this
reduction could represent a loss in recreation benefits
of approximately $5.2 million dollars (See Appendix C,
Section III.)

Trout fishina. Flood releases have negative impacts
on trout fishing. At Glen Canyon, fishing boats are
required to have a minimum of 25 horsepower motors when
flows rise above 40,000 cfs in order to handle the
strong currents. Accidents, such as swamping of boats,
occur more frequently at flood flows than at flows
between 10,000 and 16,000 cfs, the safest flow range
for fishing from boats. High water also disperses the
fish populations and reduces the probability of a
catch. Compared to optimum conditions, which occur at
approximately 10,000 cfs, flood flows of 45,000 cfs
reduce recreation benefits from a fishing trip by 60
percent. (See Appendix C, section III.)

Aauatic resources. No direct adverse impacts on adult
fishes have been shown to result from spring flood
releases. In fact, floods appear to benefit humpback
chub. Younger age classes were well represented in
humpback chub populations following the recent
high-water years of 1984 and 1985, indicating good
reproduction in those years. Flood releases from the
dam back up flow in t~e Little Colorado River and form
a large lake-like area at its confluence with the
Colorado River. This increases the size of the
quiet-water habitat required for rearing of larval
chub. Once chub reach a size that allows them to sur-
vive in the mainstem river, dam operations have few
direct impacts on them. Floods also have few direct

* Recreation benefits were assessed by measuring the
"consumer surplus" associated with recreation under
different flow levels. Consumer surplus is the amount
that recreationists would be willing to pay, beyond
their actual expenses, to participate in the activity.
This is a standard method of measuring recreation
benefits for federal water resources development
projects (See Appendix C, section II.)

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