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- Creators: Department of Physics
- Creators: Koch, Carolyn
- Member of: Programs and Communities
Vegetation changes in the canyon of the Colorado River between Glen Canyon Dam and Lake Mead were studied by comparing photo graphs taken prior to the completion of the Glen Canyon Dam in 1963 with those taken afterwards at the same sites. The old photo graphs, taken by J. K. Millers, T. H. O'Sullivan, William Bell, F. A. Nims, R. B. Stanton, N. W. Carkhuff, N. H. Darton, L. R. Freeman, E. C. LaRue, and others, document conditions as they were between 1872 and 1963. In general, the older pictures show an absence of riparian plants along the banks of the river. The new photographs of each pair were taken in 1972 through 1976. The most obvious vegetation change revealed by the photograph comparison is the in creased density of many species. Exotic species, such as saltcedar and camelthorn, and native riparian plants, such as sandbar willow, arrowweed, desert broom, and cattail, now form a new riparian community along much of the channel of the Colorado River between Glen Canyon Dam and the Grand Wash Cliffs.
The matched photographs also reveal that changes have occurred in the amount of sand and silt deposited along the banks. The photo graphs show that in some areas erosion has been significant since the time of the earlier photograph while at other locations sediment has accumulated on river bars and terraces. Detailed maps are presented showing distribution of 25 plant species. Some of these, such as Russian olive and elm, were unknown along the Grand Canyon reach of the Colorado River before 1976.
Relevant data are presented to show changes in the hydrologic regime since completion of Glen Canyon Dam. Flooding, as expressed by annual maximum stage, has decreased in amplitude, and its sea son of occurrence has changed from spring (May-June) to a longer period from April through October. Dam construction has had a moderating influence on several other hydrologic variables. Compared to the predam era, discharge through the year now varies within narrow limits, changing little from month to month or season to season; annual maximum discharges are now strikingly uniform, and sediment load has materially decreased. Increases have occurred in some characteristics, however, such as daily variation in river stage and median discharge.
The interaction of decreased flooding, decreased sediment load, and increased riparian plant coverage makes the future of existing river fans, bars, and terraces uncertain. The establishment of a new ecological equilibrium at the bottom of the Grand Canyon may re quire many decades.
The ASU School of Dance presents Undergraduate Projects Showing, October 25-26, with works by undergraduate dance students, performed at Margaret Gisolo Dance Studio.
The ASU School of Dance presents School of Dance LIVE!, September 7-9, with works by dance faculty, performed at Galvin Playhouse.
The ASU School of Dance presents Rhythms of Life, November 3-5, with works by guest artists performed at Dance Studio Theatre, PEBE 132.
The ASU School of Dance presents New Danceworks II, January 26-29, with works by dance faculty, graduate students, and visiting artists, performed at the Dance Studio Theatre, PEBE 132.
The ASU School of Dance presents Sharing Unimaginable Worlds: Spring Concert 2006, April 27-30, with works by dance faculty, alumni, graduate, undergraduate, and visiting artists, performed at Galvin Playhouse.
The ASU School of Dance presents Poetry Both Fierce and Fragile: Spring Concert, April 19-22, with works by guest artists, dance faculty, graduate, and undergraduate students, performed at Galvin Playhouse.
The ASU School of Dance presents Emerging Artists I, February 15-18, with works by guest artists, dance faculty, and undergrad students, performed at Dance Studio Theatre, PEBE 132.
The ASU School of Dance presents Moving Ground, November 16-19, with works by dance faculty, graduate, and visiting artists, performed at the Dance Studio Theatre, PEBE 132.