HR: 1330h
AN: NB33F-04    [Abstracts]
TI: Surface-Subsurface Hydrologic Exchange and the Supply of Nitrogen to the Hyporheic Zone of the Tanana River in Interior Alaska
AU: * Clilverd, H M
EM: fthmc1@uaf.edu
AF: University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775 United States
AU: Jones, J B
EM: ffjbj@uaf.edu
AF: University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775 United States
AU: Kielland, K
EM: ffkk@uaf.edu
AF: University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775 United States
AU: Lisuzzo, N J
EM: fsnjl@uaf.edu
AF: University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK 99775 United States
AB: Vegetation in the taiga forest is commonly limited by nitrogen, with limitation especially acute in early successional floodplain stands. Hyporheic flow has been hypothesized as an important source of nitrogen to developing floodplain vegetation. A series of hyporheic well transects were sampled over the growing season to examine how hyporheic flow of the Tanana River in interior Alaska influences the flux and transformation of nitrogen in ground water of the floodplain. A two-end member mixing model was then used to estimate mixing of river and ground water in the hyporheic zone. During peak river flow (mid-July to early-August), the ground water rose on average 1 m from base flow conditions (May to June). With this increase in water table height, nitrate concentration in hyporheic water increased from 1.40 μM during low flow to 4.38 μM during high flow. In general, subsurface nitrate concentration changed with river concentration. Hyporheic nitrate concentration tended to decline with distance from the river, dissolved organic nitrogen and dissolved organic carbon concentrations tended to increase with distance from the river, and ammonium concentration exhibited little change. This study suggests river-floodplain connectivity as an important regulator of hyporheic nitrogen concentration.
DE: 0400 Biogeosciences
DE: 1831 Groundwater quality
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly