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

54

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

effects on common native fishes and trout. Floods do
temporarily eliminate low-velocity, nearshore habitat
for juvenile trout and common native fish, increasing
mortality and energy expended on survival. However,
floods do not appear to have long-term effects on the
aquatic system. (See Appendix B, section v.)

IMPACT OF FLOOD RELEASES ON RESOURCES

CRITICAL RESOURCES
NaTive Trou t Trout WW Ter res.
Chub Fish Repro/Grow Fishirg Boating Beaches Habitat
+ 0 lX - - - -

Figure VI-5. Flood releases have adverse impacts (-)
primarily on terrestrial resources and recreation.
They have no significant impact (0) on trout and common
native fish, and appear to benefit (+) humpback chub.

Fluctuating Releases Have Negative Impacts On
Recreation, Little Effect On Terrestrial Resources,
And Mixed Effects On Aquatic Resources

The direct and indirect adverse impacts of fluctuating
releases on the critical resources are shown in Figure
VI-6. Fluctuations, which can cause the river level to
rise and fall by more than 13 feet each day, have the
strongest negative effect on white-water boating.

White-water boatina. The quality of white-water
boating is reduced by fluctuations. Boaters place a
high value on the naturalness of the setting for their
trip, and the daily rise and fall of the river is seen
by boaters as unnatural. Fluctuations also make it