HR: 0830h
AN: H41F-1050    [PDF]
TI: Tracing Nitrate Contributions to Streams During Varying Flow Regimes at the Sleepers River Research Watershed, Vermont, USA
AU: * Sebestyen, S D
EM: sdsebest@syr.edu
AF: State University of NY College of Environmental Science and Forestry, 211 Marshall Hall, 1 Forestry Dr, Syracuse, NY 13210 United States
AU: Shanley, J B
EM: jshanley@usgs.gov
AF: US Geological Survey, PO Box 628, Montpelier, VT 05602 United States
AU: Boyer, E W
EM: ewboyer@syr.edu
AF: State University of NY College of Environmental Science and Forestry, 211 Marshall Hall, 1 Forestry Dr, Syracuse, NY 13210 United States
AU: Ohte, N
EM: nobuohte@usgs.gov
AF: Kyoto University, Dept of Environmental Science and Technology, Kyoto, 00000 Japan
AU: Doctor, D H
EM: dhdoctor@usgs.gov
AF: US Geological Survey, Bldg 15, McKelvey Building, Menlo Park, CA 94025 United States
AU: Kendall, C
EM: ckendall@usgs.gov
AF: US Geological Survey, Bldg 15, McKelvey Building, Menlo Park, CA 94025 United States
AB: Quantifying sources and transformations of nitrate in headwater catchments is fundamental to understanding the movement of nitrogen to streams. At the Sleepers River Research Watershed in northeastern Vermont (USA), we are using multiple chemical tracer and mixing model approaches to quantify sources and transport of nitrate to streams under varying flow regimes. We sampled streams, lysimeters, and wells at nested locations from the headwaters to the outlet of the 41 ha W-9 watershed under the entire range of flow regimes observed throughout 2002-2003, including baseflow and multiple events (stormflow and snowmelt). Our results suggest that nitrogen sources, and consequently stream nitrate concentrations, are rapidly regenerated during several weeks of baseflow and nitrogen is flushed from the watershed by stormflow events that follow baseflow periods. Both basic chemistry data (anions, cations, \& dissolved organic carbon) and isotopic data (nitrate, dissolved organic carbon, and dissolved inorganic carbon) indicate that nitrogen source contributions vary depending upon the extent of saturation in the watershed, the initiation of shallow subsurface water inputs, and other hydrological processes. Stream nitrate concentrations typically peak with discharge and are higher on the falling than the rising limb of the hydrograph. Our data also indicate the importance of terrestrial and aquatic biogeochemical processes, in addition to hydrological connectivity in controlling how nitrate moves from the terrestrial landscape to streams. Our detailed sampling data from multiple flow regimes are helping to identify and quantify the "hot spots" and "hot moments" of biogeochemical and hydrological processes that control nitrogen fluxes in streams.
DE: 0400 Biogeosciences
DE: 1806 Chemistry of fresh water
DE: 1832 Groundwater transport
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2003 Fall Meeting