Determining In-Channel Transient Storage by Comparing Solute Transport in a Bedrock Channel - Alluvial Channel Sequence, Lookout Creek Basin, Oregon, USA
Abstract
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.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFM.H41A0290L
- Keywords:
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- 1824 Geomorphology (1625);
- 1832 Groundwater transport