HR: 0800h
AN: H31G-0740    [Abstracts]
TI: Influence of Morphology and Permafrost Dynamics on Surface Water - Groundwater Exchange in Arctic Headwater Streams under Present and Enhanced Thaw Conditions
AU: * Zarnetske, J P
EM: zarnetsj@geo.oregonstate.edu
AF: Department of Geosciences, Oregon State University, 104 Wilkinson Hall, Corvallis, OR 97331",
AU: Gooseff, M N
EM: mgooseff@engr.psu.edu
AF: Department of Civil & Environmental Engineering, Pennsylvania State University, 212 Sackett Bldg, University Park, PA 16802,
AU: Bowden, W
EM: breck.bowden@uvm.edu
AF: Rubenstein School of the Environment and Natural Resources, University of Vermont, Aiken Center, Burlington, VT 05401,
AU: Greenwald, M J
EM: Morgan.Johnston@uvm.edu
AF: Rubenstein School of the Environment and Natural Resources, University of Vermont, Aiken Center, Burlington, VT 05401,
AU: Brosten, T R
EM: TroyBrosten@mail.boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725,
AU: Bradford, J H
EM: johnb@cgiss.boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725,
AU: McNamara, J P
EM: jmcnamar@boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725,
AB: We investigated surface water - groundwater (hyporheic) exchange in two morphologically distinct arctic headwater streams with expanding (thawing) sub-channel permafrost active-layers using solute injection experiments (SIEs) coupled with groundwater flow and particle tracking model simulations. Results of SIEs were used to characterize surface-subsurface water exchange under varying active-layer conditions throughout the 2005 thaw season (May - September). Ground penetrating radar, stream water surface and channel topographic surveys characterized sub-stream active-layer, vertical head, and morphologic conditions. These data were used to parameterize and calibrate the models. Within the context of predicted arctic warming, the models were used to assess the current and potential future ranges of sub-channel permafrost and the influence of those ranges on hyporheic flow paths, residence time distributions, and exchange area of the thawed active-layer (i.e., potential hyporheic zone). Average active-layer thicknesses were consistently at least two-fold greater in the higher-energy, alluvial stream than in the low-energy, peat-lined stream. Alluvial hyporheic exchange was characterized by shorter residence times and longer flow paths that occurred across greater portions of the active-layer. For both reaches, results indicate that morphologic (longitudinal bed topography) and hydraulic conditions (surface and groundwater flow properties) set the potential for hyporheic flow. Forward simulations of deepening sub-channel active-layers, as predicted under a warming arctic climate, only influence hyporheic exchange until a threshold depth is achieved. This depth is primarily determined by the hydraulic head gradients imposed by the dominant morphology of the stream. Therefore, hyporheic exchange extent in arctic streams is likely to be independent of greater active-layer depths.
DE: 0706 Active layer
DE: 0744 Rivers (0483, 1856)
DE: 1830 Groundwater/surface water interaction
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: 2007 Fall Meeting