HR: 10:40h
AN: H31G-02    [PDF]
TI: Inferring residence time distributions from hillslope tracer experiments
AU: * McGuire, K J
EM: kevin.mcguire@orst.edu
AF: Department of Forest Engineering, Oregon State University, 215 Peavy Hall, Corvallis, OR 97331 United States
AU: Weiler, M
EM: markus@2hydros.de
AF: Department of Forest Engineering, Oregon State University, 215 Peavy Hall, Corvallis, OR 97331 United States
AU: McDonnell, J J
EM: jeff.mcdonnell@orst.edu
AF: Department of Forest Engineering, Oregon State University, 215 Peavy Hall, Corvallis, OR 97331 United States
AB: Water residence time in catchments is typically determined by black-box modeling of environmental tracers (e.g., $^{18}$O and $^{2}$H), in which input (rainfall) and output (discharge) tracer concentrations are used to estimate parameters of an assumed distribution that represents the residence time. In this study, a different approach was taken, where the residence time distribution (RTD) was determined directly from an artificial tracer experiment. Two tracers (Amino G acid and bromide) were applied as line sources (20 and 40 m from the stream, respectively) to the soil surface of a steep forested hillslope in the H.J. Andrews Experimental Forest. Tracer concentrations and seepage flow were monitored for approximately 100 days. The resulting breakthrough curves were modeled using a simple, process-based hillslope model conditional on spatially varying soil depth and depth-varying drainable porosity and hydraulic conductivity. The model preserved internal hydrological behavior such as water table dynamics and satisfactorily reproduced seepage discharge and tracer concentrations. Using the model and assuming the same parameterization, we infer the RTD of conservative tracers applied to the entire hillslope. The derived RTDs were then compared to functions that represent RTDs used in black-box models.
DE: 1832 Groundwater transport
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting