Integrated Surface-groundwater Flow Modeling: a Free-surface Overland Flow Boundary Condition in a Parallel Groundwater Flow Model
Interactions between surface and ground water are a key component of the hydrologic budget on the watershed scale. Models that honor these interactions are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. These types of models link the subsurface and surface domains via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in field systems, there is a need for a more general coupled modeling approach. A more general coupled model is presented that incorporates a new two-dimensional overland flow simulator into the parallel three-dimensional variable saturated subsurface flow code ParFlow. In ParFlow, the overland flow simulator takes the form of an upper boundary condition and is, thus, fully integrated without relying on the conductance concept. Another important advantage of this approach is the efficient parallelism incorporated into ParFlow, which is efficiently exploited by the overland flow simulator. Several verification and simulation examples are presented that focus on the two main processes of runoff production: excess infiltration and saturation. The model is shown to reproduce an analytical solution for overland flow and compares favorably to other commonly used hydrologic models. The influence of heterogeneity of the shallow subsurface on overland flow is also examined. The results show the uncertainty in overland flow predictions due to subsurface heterogeneity and demonstrate the usefulness of our approach. Both the overland flow component and the coupled model are evaluated in a parallel scaling study and show to be efficient.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 887270
- Report Number(s):
- UCRL-JRNL-211468; TRN: US200618%%34
- Journal Information:
- Advances in Water Resources, Vol. 29, Issue 7
- Country of Publication:
- United States
- Language:
- English
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