WSP01163

• File Number: 8220.101.09
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 10/16/1972
• Author: Jacobson/Cecil Baltz
• Title: Abstract - Benefits to Environment - Glen Canyon to Hoover Dam
• Water Supply Pro - Doc Type: Report/Study

A NEW SPORT FISHERY

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The cool, clear releases from Glen Canyon Dam have provided a
habitat for a new sport fishery. Where only trash fish once survived, Rain-
bow trout are now found. Particularily enticing to the trout fisherman is
the 15 mile reach of still water between Lees Ferry and Glen Canyon Dam.
Table 4 is based on a 5-year study - 1965 through 1969. Since then the
fishermen have continued to enjoy the same success.

TABLE 4

10.9
12.0
12.2
12.2

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River Fishery Between Lees Ferry and Glen Canyon Dam

1965
1966
1967
1968
1969

4,161
2,681
4,430
4,161
4,180

15,723
11 ,424
18,952
22,829
22,830

Harvested Fish
(Rainbow Trout)

14,500
7,895
8,594
9,430
9.440

Average Size
(inches)

Year

Fishing Trips

Fishing Hours

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The river runner is generally occupied with sight seeing and adventure
forms of camp life other than fishing, although trout now exist throughout
Grand Canyon. Trout also have recently been introduced in Lake Mead and
are known to migrate upstream. The introduction of trqut in Lake Mead, how-
ever, was not necessarily related to the cooler inflow incident to Glen Canyon
Dam operations, but essentially came about through a new food implant, the
thread-fin shad.

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Prior to the construction of Glen Canyon pam, the fluctuation pattern
of Lake Mead was at the mercy of the snow pack and res\llting spring runoff.
Now, by manip\llating Glen Canyon releases, Lake Mead water levels can be
steadied during the April through June bass spawning season and then raised
in July through September to aid the young-of-the-year bass in escaping the
larger fish by hiding in submerged vegetative cover.

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These are real fishery benefits seldom extolled in connection with
dam and reservoir developments.

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LAKE MEAD EVAPORATION

Most spectacular of the environmental changes, incident to the oper-
ation of Glen Canyon Dam, is the reduction in evaporation loss at Lake Mead.
Cold water releases from the depths of Lake Powell, constituting essentially
the total inflow to Lake Mead, now arrive about 5 1/2 degrees (Fahrenheit)
cooler than the former unregulated inflow as shown in Table 5; whereas, the

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