HR: 14:10h
AN: H53F-03    [Abstracts]
TI: A two-layer model to simulate seasonal variations in surface water chemistry draining a northern forest watershed
AU: * Chen, L
EM: lchen05@syr.edu
AF: Syracuse University, 151 Link Hall, Syracuse, NY 13244
AU: Driscoll, C
EM: ctdrisco@mailbox.syr.edu
AF: Syracuse University, 151 Link Hall, Syracuse, NY 13244
AB: For many forested headwaters in the northeastern U.S., stream flow is a mixture of water derived from different soil layers. Therefore as a result of the seasonal fluctuations in hydrologic flow paths, considerable seasonal variation in surface water chemistry is evident in these headwaters. Especially during high flow season, flow tends to be routed through the upper soil layers, which are usually characterized by higher concentrations of NO3-, DOC, naturally occurring organic anions and Al. High streamflow coupled with shallow flow path results in dilution in base cations, increased leaching of organic acids, NO3- and Al to stream water, and depression in pH and ANC. While during base flow season, stream discharge is primarily generated from lower soil layers with higher base cation concentrations and lower concentrations of organic anions and NO3-. Previously, an integrated biogeochemical model (PnET-BGC) based on single soil-layer formulation was found to be inadequate to simulate these seasonal variations. In order to better simulate the seasonal variations in stream water chemistry draining acid-sensitive forest watersheds, a two soil-layer version of the model (PnET-BGC2) was formulated and applied to a northern forest ecosystem, the Hubbard Brook Experimental Forest (HBEF). End member mixing analysis was used to better understand hydrologic flowpaths contributing to temporal patterns in stream chemistry and to parameterize the model. The resulting two-layer model is generally able to reproduce the seasonal variations in surface water runoff, concentrations of base cations, SO42-, NO3-, pH and ANC.
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting