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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 sucb 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 facl 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 cer1ain: 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 />Buwers, J.E., Webb. R.H., and Rondeau. R.J., 1995.
<br />Longevity. recruitment. and mortality of desen 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 JOtlN. L., 1944. Floristic studies in the
<br />canyon of the Colorudo and tributaries: American
<br />Midland Naturalist. \'. 32. p. 591-642.
<br />Cook, w., 1987, The Wen. the Botany, and the Mexican Hat:
<br />Orangevale, Cali!i)rnia. Callisto Books, 151 p.
<br />Cooley, J., 1988, The great unknown: Flagstaff, Arizona.
<br />Northland Publishing. 207 p.
<br />Dellenbaugh. FS., 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. FA. 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
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<br />Flavell. G.F. 1987. The log of the Panthon (edited by N.B.
<br />Carmony and D.E. Brown): Boulder. Colorado. Pruett
<br />Puhlishing. 109 p.
<br />
<br />Fowler. D.o. (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 />Grar. W.L 1978, Fluvial adjustments to the spread of
<br />tamarisk in the Colorado Plateau region: Geolugical
<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, privutely published
<br />by H. Walker Publishing, 80 p.
<br />Griffiths, P.G., Webb, R.H., and Melis, T.S.. 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. R.R., 1991, Historic changes in vegetation along
<br />the Colorado River in the Grand Canyon. ill Mnrzolf.
<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. I 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 of the Grand Canyon:
<br />Grand Canyon Natural History Association. 147 p.
<br />Leydet. E. 1968, Time and the river flowing, Grand Canyon:
<br />New York, Sierra Club - Bnllantine Book. 160 p.
<br />Martin, P.S., 1971. Trees and shrubs of the Grand Canyon.
<br />Lees Ferry to Diamond Creek: Tucsun. University of
<br />Arizona, Desert Laboratory. unpublisheLl manuscript.
<br />16 p.
<br />Masland, FE.. 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 />alluvinl fans in GranLl Canyon Nationnl Park find 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. T.S.. Webb, R.H., Griffiths, P.G. and Wise, T.J..
<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, W.M., Webb, R.H.. and Bills. D.J..
<br />1996, When the blue-green waters turn red C Historical
<br />flooding in HavaslI Creek. Arizona: U.S. Geological
<br />Survey Water-Resources In\'estigations Report 96-
<br />4059, 136 p.
<br />Melis, T.S.. Webb. R.H., and Griffiths. P.G.. 1997. Debris
<br />flows in Grand Canyon National Park: Peak dischiJrges.
<br />flow transformutions. and hydrographs: Debris-Flow
<br />Hazards Mitigation: Prediction and Assessment: New
<br />York. American Society of Civil Engineers. p. 727-736.
<br />
<br />32 OBSERVATIONS OF ENVtRONMENTAL CHANGE tN GRAND CANYON
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