HR: 0800h
AN: H51D-1172    [Abstracts]
TI: Separation in storm-event trajectories of DOC and nitrate concentrations with seasons
AU: Graham, J
EM: jmgraham888@yahoo.com
AF: SUNY College at Buffalo, 1300 Elmwood Avenue Great Lakes Center HC 215, Buffalo, NY 14222 United States
AU: * Inamdar, S
EM: inamdasp@buffalostate.edu
AF: SUNY College at Buffalo, 1300 Elmwood Avenue Great Lakes Center HC 215, Buffalo, NY 14222 United States
AU: Mitchell, M
EM: mitchell@mailbox.syr.edu
AF: SUNY-ESF, 1 Forestry Drive, Syracuse, NY 14210 United States
AU: Tuk, J
EM: jmtuk27@yahoo.com
AF: SUNY College at Buffalo, 1300 Elmwood Avenue Great Lakes Center HC 215, Buffalo, NY 14222 United States
AB: The temporal evolution of DOC and nitrate concentrations during storm events and the flow paths responsible for their release have received considerable attention. Some researchers observed DOC and nitrate peaks on the hydrograph rising limb and attributed it to "flushing". Flushing was defined as the release of solutes from near-surface soil layers associated with a rising water table. In contrast, others found a nitrate peak on the rising limb and a delayed DOC peak at or after discharge peak. In this case, the early nitrate peak was attributed to "displacement" of groundwater into the stream and the DOC peak was attributed to flushing. We studied the temporal patterns of storm-event DOC and nitrate for more than 20 storm events over a year in a watershed in Western New York, USA. Storm event sampling was conducted across four partly nested catchments - 696 (s1), 3.4 (s2), 1.6 (s3) and 1.9 (s5) ha. The four watersheds contained varying proportions of hillslope and valley-bottom saturated areas. Early spring rainfall events showed very similar nitrate and DOC trajectories with a peak in concentration at or after the discharge peak. Riparian groundwater elevations showed peak water tables coinciding with solute peaks suggesting flushing of both DOC and nitrate from the catchment. For summer and fall events however, there was a clear separation between the DOC and nitrate trajectories. Nitrate was at its highest early on in the storm event and then followed a dilution trajectory as the event proceeded. DOC concentrations increased through the event (as nitrate dropped) with a peak in concentration just after discharge peak. This seasonal shift in DOC and nitrate trajectories was observed across catchment scales. These observations show that both flushing and displacement mechanisms could occur in a watershed and their expression is regulated by the availability of the solutes in the soil profile. DOC concentrations were found to be high in upper soil layers across all seasons, but nitrate build-up in the upper soil layers was limited to the dormant period before spring onset. We hypothesize that the temporal expression of solutes (especially DOC) is regulated by the total extent of the saturation in the watershed, the areal distribution of the saturated areas and their connectedness, and the seasonally regulated availability of the solutes. These hypotheses are currently being evaluated by comparing the temporal expressions across catchment scales.
UR: http://www.buffalostate.edu/orgs/glc/gowanda/overview.htm
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting