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Observations of environmental change in Grand Canyon, Arizona

Water-Resources Investigations Report 2002-4080

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Abstract

Few scientific data have been collected on pre-dam conditions of the Colorado River corridor through Grand Canyon National Park. Using historical diaries, interviews with pre-dam river runners (referred to as the ?Old Timers?), and historical scientific data and observations, we compiled anecdotal information on environmental change in Grand Canyon. The most significant changes are the: lowering of water temperature in the river, near-elimination of heavily sediment-laden flows, erosion of sand bars, invasion of non-native tamarisk trees, reduction in driftwood, development of marshes, increase in non-native fish at the expense of native fishes, and increase in water bird populations. In addition, few debris flows were observed before closure of Glen Canyon Dam, which might suggests that the frequency of debris flows in Grand Canyon has increased. Other possible changes include decreases in bat populations and increases in swallow and bighorn sheep populations, although the evidence is anecdotal and inconclusive. These results provide a perspective on managing the Colorado River that may allow differentiation of the effects of Glen Canyon Dam from other processes of change.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Observations of environmental change in Grand Canyon, Arizona
Series title:
Water-Resources Investigations Report
Series number:
2002-4080
Edition:
-
Year Published:
2002
Language:
ENGLISH
Description:
41 p.