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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flow of 8,000 cfs would protect trout spawning areas
from dewatering. Fluctuations which strand adults and
eggs would be eliminated, providing increased
protection for natural reproduction. Once fry have
emerged from spawning areas in March, a minimum flow
would not be needed. Trout fry would benefit from
keeping flows under 25,000 cfs to maintain nearshore,
low-velocity rearing habitat.

Three two-week periods of fluctuations were added to
this otherwise steady flow scenario to benefit trout
growth by increasing the available food supply. It is
not known whether these three two-week periods of fluc-
tuations are adequate to increase trout growth, or, if
so, would be as beneficial to trout growth as the
year-round fluctuations of current operations. (See
Appendix B, Section v.)

The impact of the trout scenario on other critical re-
sources would be mostly beneficial. The reduction in
fluctuations and elimination of flood releases would
improve conditions for trout fishing and white-water
boating, and reduce loss of beach area, terrestrial
habitat, and wildlife. The impact of the trout
scenario on humpback chub is unknown because it is not
known whether the high flows in May and June are high
enough to back up the Little Colorado River and
increase nursery habitat for larval chub. Backwaters
would remain more stable under this plan compared to
current operations, thereby benefiting common native
fish.

Releases For BEACHES, TERRESTRIAL VEGETATION, AND
WILDLIFE Are Mostly Favorable To Other Resources

Protection of terrestrial habitat and beaches requires
a scenario (Figure VII-4) that eliminates both frequent
flooding and extreme fluctuations. The elimination of
floods would protect camping beaches from loss. Steady
flows would be lower than the peaks of current fluc-
tuations, even in high-water years. stabilization of
camping beaches and substrate to this lower peak flow
level would result in more area of beaches and
vegetation than under current operations (Appendix A,
Section v.)