HR: 11:50h
AN: H52A-07    [Abstracts]
TI: Influence of Glen Canyon Dam on Fine-Sediment Storage in the Colorado River in Marble Canyon, Arizona
AU: * Hazel, J E
EM: joe.hazel@nau.edu
AF: Northern Arizona University, Department of Geology, Flagstaff, AZ 86011 United States
AU: Topping, D J
H52A-07 AF: U.S.Geological Survey, 4620 Technology Dr., Suite 400, Golden, CO 80403 United States
AU: Schmidt, J C
H52A-07 AF: Utah State University, Department of Aquatic, Watershed, and Earth Resources, Logan, UT 84322 United States
AU: Kaplinski, M
H52A-07 AF: Northern Arizona University, Department of Geology, Flagstaff, AZ 86011 United States
AB: Glen Canyon Dam has caused a fundamental change in the distribution of fine-sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both volume and location of sediment storage. The analysis shows that the bed of the main channel was an important storage environment for fine sediment in the pre-dam era. In years of large seasonal accumulation, ~50% of the fine sediment supplied to the reach from upstream sources was stored on the main-channel bed. In contrast, sediment budgets constructed for two short-duration, experimental releases from Glen Canyon Dam indicate that ~90% of the sediment discharge from the reach during each release was derived from eddy storage, rather than from sandy deposits on the main-channel bed. These results indicate that the majority of the fine sediment in Marble Canyon is now stored in eddies, even though they occupy a small percentage (~17%) of the total river area. Because of a 95% reduction in the supply of fine sediment to Marble Canyon, future high releases not timed with substantial tributary inputs will potentially erode sediment from long-term eddy storage, resulting in continued degradation in Marble Canyon.
DE: 1808 Dams
DE: 1821 Floods
DE: 1825 Geomorphology: fluvial (1625)
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: Fall Meeting 2005