HR: 1340h
AN: H33D-1623    [Abstracts]
TI: Residence Times and Pathway Analysis Using a Coupled Three-Dimensional Variably Saturated Groundwater Flow and Land Surface Model
AU: * Kollet, S J
EM: stefan.kollet@uni-bonn.de
AF: Meteorological Institute Bonn University, Auf dem Huegel 20, Bonn, 53121, Germany
AU: Maxwell, R M
EM: maxwell5@llnl.gov
AF: Atmospheric, Earth, and Energy Sciences Department Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94500, United States
AB: The analysis of residence times and pathways of solutes in the subsurface is important in the characterization of biogeochemical processes and contaminant transport. Recent theoretical and experimental studies have shown power law (fractal) residence time distributions because of the fractal character of the topography. The theoretical studies focused on a steady-state analysis of the flow field utilizing an undulating water table boundary condition that follows the topography. However, processes of the vadose zone including root water uptake and evaporation have been neglected until this work. In this study, the three-dimensional variably saturated groundwater flow model ParFlow, coupled to a land surface model, is used to study the influence of processes of the vadose zone on pathways and residence time distributions. A small catchment is simulated incorporating topography; land and soil cover information; and one year of realistic atmospheric forcing. Transient Lagrangian transport simulations of a conservative tracer are performed, also including dispersion (i.e. heterogeneity), to develop spectral transforms of the arrival time distributions. The resulting power spectra show power law behavior over a wide range of scales. While the spectral scaling exponent (SSP) decreases with increasing heterogeneity, the influence of the vadose zone appears to cause an increase in the SSP. Additionally, the effect of explicit representation of subsurface heterogeneity and spatial model resolution on the scaling behavior is studied. This work was conducted under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory (LLNL) under contract W-7405-Eng-48. This project was funded by the Laboratory Directed Research and Development Program at LLNL.
DE: 1805 Computational hydrology
DE: 1828 Groundwater hydraulics
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: 2007 Fall Meeting