HR: 1340h
AN: H13D-1538    [Abstracts]
TI: Effects of In-Stream Geomorphic Structures on Stream Temperatures and Streambed Heat Flux Through Induced Hyporheic Exchange
AU: * Hester, E T
EM: ethester@email.unc.edu
AF: Ecology Curriculum University of North Carolina, 1412 Crestview Drive, Blacksburg, VA 24060, United States
AU: Poole, G C
EM: gpoole@eco-metrics.com
AF: Institute of Ecology University of Georgia, Ecology Building, Athens, GA 30602, United States
AU: Doyle, M W
EM: mwdoyle@email.unc.edu
AF: Dept of Geography University of North Carolina, CB 3220, Saunders Hall, Chapel Hill, NC 27599, United States
AB: In-stream geomorphic structures such as debris dams and log dams are common in undisturbed streams, are often installed as part of stream restoration projects, and can significantly enhance hyporheic exchange. While this exchange is important ecologically for many reasons, including affecting summer temperatures in streams that are impacted by loss of riparian shade and climate change, the thermal impact of these structures is relatively unknown. We conducted field experiments with a variable-height weir-type structure in a stream monitored with a three-dimensional temperature and water level sensor network. Results indicate that structures induce a coherent hyporheic flow cell that varies predictably with structure height. Data from the sensor network were analyzed to estimate the impact of structure presence and size on advective and conductive heat transfer processes between the stream and the hyporheic zone. These thermal process data were used to estimate the net thermal impact of structure-induced hyporheic exchange on stream temperatures. Results indicate that 1) both advection and conduction have a net cooling effect on the stream in summer, 2) advection tends to increase with structure size, and 3) streambed hydraulic conductivity determines the relative importance of advection and conduction. However, the net cooling effect of these structures via induced hyporheic exchange can be outweighed by warming effects due to exchange of heat with the atmosphere.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1807 Climate impacts
DE: 1814 Energy budgets
DE: 1828 Groundwater hydraulics
DE: 1830 Groundwater/surface water interaction
SC: Hydrology [H]
MN: 2007 Fall Meeting