HR: 0800h
AN: H41A-0137    [Abstracts]
TI: Influence of Hyporheic Flow and Geomorphology on Temperature in Large, Gravel-bed River, Clackamas River, Northwestern Oregon
AU: * Burkholder, B K
EM: barbara.burkholder@oregonstate.edu
AF: Oregon State University, Department of Geosciences 104 Wilkinson Hall, Corvallis, OR 97331, United States
AU: Grant, G E
EM: gordon.grant@oregonstate.edu
AF: USDA Forest Service, Pacific Northwest Research Station 356W Forest Science Lab, Corvallis, OR 97331, United States
AU: Haggerty, R
EM: haggertr@geo.oregonstate.edu
AF: Oregon State University, Department of Geosciences 104 Wilkinson Hall, Corvallis, OR 97331, United States
AU: Wampler, P
EM: wamplerp@gvsu.edu
AF: Grand Valley State University, Dept of Geology 1 Campus Drive 125 Padnos Hall, Allendale, MI 49401, United States
AU: Khangaonkar, T P
EM: tarang.khangaonkar@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999 BSRC, Richland, WA 99352, United States
AB: The hyporheic zone influences the thermal regime of rivers, acting as a temperature buffer by storing and releasing heat throughout the day. We quantified the amount of hyporheic exchange in a 24-km reach of the lower Clackamas River (median discharge = 115 m³/s; minimum mean monthly discharge = 25 m³/s in August) in northwestern Oregon, and through use of a simple mixing model, estimated how much hyporheic exchange cools the river during hot summer months. Hyporheic exchange was primarily identified by temperature anomalies, which are patches of water that demonstrate at least a 1°C temperature difference from the main channel. Forty hyporheic temperature anomalies were identified through field investigations and TIR (Thermal-Infrared-Radiometry) imagery in Summer 2006. The location of anomalies is associated with gravel bar morphology, specifically features like bar channels and bar heads that act as preferential pathways to hyporheic flow. Further field characterization and groundwater modeling on three Clackamas gravel bars indicate residence times of hyporheic water can vary from hours to weeks and months, largely determined by hydraulic conductivity and how recently the gravel bar formed or was reworked. Upscaling of modeled discharges and hydrologic parameters from these bars to the other anomalies on the Clackamas network shows that hyporheic discharge comprises a small fraction (< 1%) of mainstem discharge, making overall river cooling effects small. However, the presence of cooler patches of water within rivers act as thermal refugia for fish, making the creation or enhancement of hyporheic exchange an attractive method of river restoration.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1813 Eco-hydrology
DE: 1814 Energy budgets
DE: 1830 Groundwater/surface water interaction
SC: Hydrology [H]
MN: 2007 Fall Meeting