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<br />have declined precipitously before Glen Canyon Dam
<br />was built possibly owing to invasion by predatory non-
<br />native species such as catfish, carp, and trout.
<br />Much remains unknown about the pre-dam river
<br />and its environment. Ultimately, we may never
<br />determine whether changes reported in wildlife
<br />populations are in fact significant or merely the result
<br />of limited observation. The observations of the Old
<br />Timers suggest that future monitoring of bighorn sheep
<br />and bat populations may be warranted. Regardless of
<br />whether hard, scientific conclusions can be reached on
<br />all of their observations, one thing is certain: we should
<br />listen to the historical experiences of the Old Timers
<br />and attempt to independently and scientifically test
<br />their ideas about the timing and causes of change along
<br />the Colorado River in Grand Canyon.
<br />
<br />REFERENCES CITED
<br />
<br />Beer, W., 1988, We swam the Grand Canyon: Seattle,
<br />Washington, The Mountaineers, 171 p.
<br />Bowers, I.E., Webb, RH., and Rondeau, R.I., 1995,
<br />Longevity, recruitment, and mortality of desert plants in
<br />Grand Canyon, Arizona, U.S.A.: Journal of Vegetation
<br />Science, v. 6, p. 551-564.
<br />Carothers, S.W., and Brown, B.T., 1991, The Colorado River
<br />through Grand Canyon: Tucson, University of ARizona
<br />Press, 235 p.
<br />Clover, E.U., and Jotter, L., 1944, Floristic studies in the
<br />canyon of the Colorado and tributaries: American
<br />Midland Naturalist, v. 32, p. 591-642.
<br />Cook, W., 1987, The Wen, the Botany, and the Mexican Hat:
<br />Orangevale, California, Callisto Books, 151 p.
<br />Cooley, J., 1988, The great unknown: Flagstaff, Arizona,
<br />Northland Publishing, 207 p.
<br />Dellenbaugh, F.S., 1908, A canyon voyage: New Haven,
<br />Connecticut, Yale University Press, 277 p.
<br />Eddy, c., 1929, Down the worlds most dangerous river: New
<br />York, F.A. Stokes Company, 293 p.
<br />Ferguson, C.W., 1971, Tree-ring dating of Colorado River
<br />driftwood in the Grand Canyon, in Hydrology and
<br />Water Resources in Arizona and the Southwest: Tempe,
<br />Arizona, Proceedings of the 1971 meetings of the
<br />Arizona Section C American Water Resources
<br />Association and the Hydrology Section C Arizona
<br />Academy of Sciences, p. 351-366.
<br />Flavell, G.F., 1987, The log of the Panthon (edited by N.H.
<br />Carmony and D.E. Brown): Boulder, Colorado, Pruett
<br />Publishing, 109 p.
<br />
<br />Fowler, D.D. (editor), 1972, "Photographed all the best
<br />scenery," Jack Hillers's diary of the Powell Expeditions,
<br />1871-1875: Salt Lake City, Utah, University of Utah
<br />Press, 225 p.
<br />Graf, W.L., 1978, Fluvial adjustments to the spread of
<br />tamarisk in the Colorado Plateau region: Geological
<br />Society of America Bulletin, v. 89, p. 1491-1501.
<br />Goldwater, B.M., 1940, A journey down the Green and
<br />Colorado Rivers: Phoenix, Arizona, privately published
<br />by H. Walker Publishing, 80 p.
<br />Griffiths, P.G., Webb, RH., and Melis, TS., 1996, Initiation
<br />and frequency of debris flows in Grand Canyon,
<br />Arizona: U.S. Geological Survey Open-File Report 96-
<br />491,35 p.
<br />Johnson, RR, 1991, Historic changes in vegetation along
<br />the Colorado River in the Grand Canyon, in Marzolf,
<br />G.R (Editor), Colorado River ecology and dam
<br />management: Washington, D.C., National Academy
<br />Press, p. 178-206.
<br />Jones, L., 1962, Colorado River Runner's Scroll Map:
<br />Midway, Utah, Western Whitewater, 1 sheet.
<br />Kolb, E.L., 1914, Through the Grand Canyon from
<br />Wyoming to Mexico: Tucson, Arizona, University of
<br />Arizona Press, 344 p.
<br />Lavender, D., 1985, River runners ofthe Grand Canyon:
<br />Grand Canyon Natural History Association, 147 p.
<br />Leydet, F., 1968, Time and the river flowing, Grand Canyon:
<br />New York, Sierra Club - Ballantine Book, 160 p.
<br />Martin, P.S., 1971, Trees and shrubs of the Grand Canyon,
<br />Lees Ferry to Diamond Creek: Tucson, University of
<br />Arizona, Desert Laboratory, unpublished manuscript,
<br />16 p.
<br />Masland, F.E., Jr., 1948, By the rim of time: Carlisle,
<br />Pennsylvania, c.H. Masland and Sons, 44 p.
<br />Melis, T.S., 1997, Geomorphology of debris flows and
<br />alluvial fans in Grand Canyon National Park and their
<br />influences on the Colorado River below Glen Canyon
<br />Dam, Arizona [Ph.D. Dissertation]: Tucson, University
<br />of Arizona, 490 p.
<br />Melis, TS., Webb, RH., Griffiths, PG, and Wise, T.I.,
<br />1994, Magnitude and frequency data for historic debris
<br />flows in Grand Canyon National Park and vicinity,
<br />Arizona: U.S. Geological Survey Water Resources
<br />Investigations Report 94-4214,285 p.
<br />Melis, T.S., Phillips, WM., Webb, RH., and Bills, D.I.,
<br />1996, When the blue-green waters turn red C Historical
<br />flooding in Havasu Creek, Arizona: U.S. Geological
<br />Survey Water-Resources Investigations Report 96-
<br />4059,136 p.
<br />Melis, TS., Webb, RH., and Griffiths, PG., 1997, Debris
<br />flows in Grand Canyon National Park: Peak discharges,
<br />flow transformations, and hydrographs: Debris-Flow
<br />Hazards Mitigation: Prediction and Assessment: New
<br />York, American Society of Civil Engineers, p. 727-736.
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<br />32 OBSERVATIONS OF ENVIRONMENTAL CHANGE IN GRAND CANYON
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