Computational methods for simulating interaction between surface & subsurface hydrologic systems

Water supply, water quality, and environmental remediation studies increasingly demand that interactions between surface and subsurface hydrologic systems be considered and simulated in order to provide decision-makers with accurate and defensible alternatives. Interactions between surface and subsurface hydrologic systems are currently modeled with a variety of approaches. Computations of system interactions can be decoupled, sequentially coupled, or fully coupled. In practice, emphasis is sometimes focused on surface or subsurface processes depending on project needs, available resources, and professional experience of those performing the study. However, simulators for interactions between surface and subsurface hydrologic systems should be chosen based on the strength of each process within the context of the study needs. In a test of currently available methodologies, four different approaches to simulating interactions between surface and subsurface hydrologic systems are applied to the same hydrologic system. The approaches consist of various combinations of finite difference, finite volume, finite element and adaptive finite element models. Decoupled, sequentially coupled and fully coupled interactions between the surface and subsurface systems are represented. Comparisons of the three simulation methods are presented, revealing relative strengths and weaknesses of each approach. Simulation of interactions between surface and subsurface hydrologic systems often requires the exchange of data and results between models of disparate data types, resolutions, and dimensions. Modeling system tools that seamlessly perform these exchanges play an important role in producing meaningful simulation results.