Observations of environmental change in Grand Canyon, Arizona
By: by Robert H. Webb, Theodore S. Melis, and Richard A. Valdez ; prepared in cooperation with Grand Canyon Monitoring and Research Center.
Series: Water-resources investigations report ;; 02-4080
Publisher: U.S. Geological Survey
Published: 2002
Place of publication: Tucson, Aziz
Language: eng
Number of pages: 33
Subjects: Grand Canyon (Ariz.) -- Environmental conditions -- History.