USGS

 

Observations of Environmental Change in Grand Canyon, Arizona

By Robert H. Webb, Theodore S. Melis, and Richard A. Valdez

U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 02-4080

Prepared in cooperation with
GRAND CANYON MONITORING AND RESEARCH CENTER

Report availability: Portable Document Format (PDF).


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.

 

CONTENTS

ABSTRACT

INTRODUCTION

PURPOSE AND SCOPE

Units and Nomenclature

Acknowledgments

SOURCES OF INFORMATION

The Old Timers

Other Pre-Dam or 1960s River Runners

Diaries and Other Accounts

Repeat Photography

Interviews and Interpretation of Observations

SPECIFIC CHANGES OBSERVED IN GRAND CANYON

Aesthetics in Grand Canyon

Water Temperature

Geomorphology

Debris Flows and Floods

Rockfalls

Rapids

Sand Bars

Channel Bars

Driftwood

Riparian and Desert Vegetation

Riparian Vegetation

Marshes

Desert Vegetation

Terrestrial Animals

Birds and Bats

Insects

Beavers

Otters

Large Mammals

Fishes

CONCLUSIONS

REFERENCES CITED

 


For additional information write:

 

Regional Research Hydrologist

U.S. Geological Survey

345 Middlefield Road

Menlo Park, CA 94025

http://water.usgs.gov/nrp

Copies of this report can be purchased from:

 

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286


This pdf is 6.5MB.

 

Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.



[an error occurred while processing this directive]

U.S. Department of the Interior, U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/wri024080
Page Contact Information: GS Pubs Web Contact
Last modified: Thursday, September 01 2005, 02:22:25 PM
FirstGov button  Take Pride in America button