HR: 0800h
AN: H41A-0290    [Abstracts]
TI: Determining In-Channel Transient Storage by Comparing Solute Transport in a Bedrock Channel - Alluvial Channel Sequence, Lookout Creek Basin, Oregon, USA
AU: LaNier, J
EM: lanierju@geo.oregonstate.edu
AF: Oregon State University, Department of Civil, Construction, and Environmental Engineering, 202 Apperson Hall Oregon State University, Corvallis, OR 97331 United States
AU: Gooseff, M N
EM: gooseff@cc.usu.edu
AF: Colorado School of Mines, Dept. of Geology and Geologic Engineering, 1516 Illinois Street, Golden, CO 80401 United States
AU: * Haggerty, R
EM: haggertr@geo.oregonstate.edu
AF: Department of Geosciences, Oregon State University, 104 Wilkinson Hall Oregon State University, Corvallis, OR 97331 United States
AB: Current stream tracer techniques do not allow separation of in-channel (e.g., eddies) and out-of-channel (hyporheic) transient storage, yet this separation is important to understanding stream biogeochemical processes. We characterize in-channel transient storage with a rhodamine WT solute tracer experiment in a 304-m cascade-pool type bedrock reach with no hyporheic zone. We compare the solute breakthrough curve (BTC) from this reach to that of an adjacent 367 m alluvial reach with significant hyporheic exchange. In the bedrock reach, transient storage has an exponential residence time distribution with a mean residence time of 3.0 hr and a ratio of transient storage to stream volume of 0.14, demonstrating that at moderate discharge, bedrock in-channel storage zones provide a small volume of transient storage with substantial residence time. In the alluvial reach, though pools are similar in size, transient storage has a power-law residence time distribution with a mean residence time of $>$ 100 hr (estimated at nearly 1200 hr) and a ratio of storage to stream volume of 105. Because the in-channel hydraulics of bedrock reaches are simpler than alluvial step-pool reaches, the bedrock results are probably a lower end-member on volume and residence time, and demonstrate that in-channel storage may be appreciable in some reaches.
DE: 1824 Geomorphology (1625)
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting