HR: 0800h
AN: H51H-0859    [Abstracts]
TI: Controls on Nitrate Spatial Variability in Paine Run Catchment of Shenandoah National Park
AU: * Ingram, S M
EM: smi3v@virginia.edu
AF: University of Virginia, Todd M. Scanlon Department of Environmental Sciences, University of Virginia Clark Hall, 291 McCormick Road, Charlottesville, VA 22904,
AU: Scanlon, T M
EM: tms2v@virginia.edu
AF: University of Virginia, Todd M. Scanlon Department of Environmental Sciences, University of Virginia Clark Hall, 291 McCormick Road, Charlottesville, VA 22904,
AB: This research examines the catchment-scale controls on in-stream nitrate concentrations by (1) quantifying nitrate spatial variability in a headwater catchment and (2) determining the biophysical processes underlying this variability. The Shenandoah Watershed Study (SWAS) established thirty-eight stream sampling sites in the Paine Run catchment to collect field data on stream chemistry, discharge and transient storage. An evaluation of SWAS data at these sites from the early 1990s to 2007 reveals spatial and temporal variability in nitrate concentrations following the gypsy moth defoliation. We observed high in-stream nitrate concentrations with elevation and an apparent dilution at lower elevations. Main topographic descriptors related to the spatial distribution of nitrate, elevation and contributing area, are associated with differing biophysical factors such as soil residence time, bacterial denitrification, vegetation and mineralization. Previous studies have demonstrated that the physical properties of hyporheic zones can strongly influence denitrification rates. We examined this in the Paine Run catchment with tracer tests to evaluate dilution effects and predict stream outflow and inflow from hyporheic zones responsible for denitrification. We then looked for biophysical processes responsible for higher nitrate levels at higher elevation by using the OTIS model for transient storage to evaluate hyporhiec zones in Paine Run. We also established a method to evaluate soil parameters for depth and permeability. By identifying the controls on nitrate inputs, transport and denitrification, we isolated a set of criteria applied to a quantitative model for nitrate spatial variability. This research has important implications for defining nutrient availability both within the stream network and at the outlet of forested headwater catchments.
DE: 1804 Catchment
DE: 1830 Groundwater/surface water interaction
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting