Integrated surface–groundwater flow modeling: A free-surface overland flow boundary condition in a parallel groundwater flow model

Abstract

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.

Groundwater and Surface Water Interaction at the Regional-scale – A Review with Focus on Regional Integrated Models

“…While being apparently straightforward, the concept has been criticised, as the streambed leakage coefficient, which is typically not measurable in the field, can change drastically over time and a clear interface does not necessarily always exist (e.g. Kollet and Maxwell 2006). Therefore it is usually determined by inverse modelling together with other parameters, e.g.…”

“…Overviews describing different coupling strategies are provided by Barthel et al (2008a), Ebel et al (2009), Furman (2008, Kollet and Maxwell (2006), Markstrom et al (2008), Levy and Xu (2012), Rossman and Zlotnik (2013), Sebben et al (2013), and Spanoudaki et al (2009).…”

“…Loague et al 2006), have received wide attention and significant progress has been made with their development in recent years (Gaukroger and Werner 2011;Maxwell et al 2014). The software packages mentioned most often in the literature include ParFlow (Kollet and Maxwell 2006), HydroGeoSphere (Therrien et al 2009), InHM (VanderKwaak 1999, and OpenGeoSys ). More examples are described in Sebben et al (2013), Shi et al (2013), Partington et al (2013), Maxwell et al (2014) and Bronstert et al (2005).…”

Enhanced fixed-size parallel speedup with the Muskingum method using a trans-boundary approach and a large subbasins approximation

“…When modeling horizontal water dynamics on parallel computers, decomposition generally focuses on the study domain (i.e., domain decomposition) and involves classifying the subbasins of a large river basin (or the reaches of a large river network); and orchestration consists of instructing a given computing core to address a subset of all subbasins (or all river reaches) [e.g., Kollet and Maxwell, 2006;Neal et al, 2009;Li et al, 2010;David et al, 2011bDavid et al, , 2013aVivoni et al, 2011;Hwang et al, 2014]. Interestingly, decomposition methods that are suitable for parallel computing of the horizontal movements of water differ from the traditional hydrological approaches to codifying subbasins [e.g., Seaber et al, 1987;Verdin and Verdin, 1999] or classifying river reaches [e.g., Horton, 1945;Strahler, 1952] as further developed in this study.…”

Best practice regarding the three P's: profiling, portability and provenance when running HPC geoscientific applications

“…Saturated and variably saturated subsurface flow in heterogeneous porous media are simulated in three spatial dimensions using a Newton-Krylov nonlinear solver (Ashby and Falgout, 1996;Jones and Woodward, 2001;Maxwell, 2013) and multigrid preconditioners, where the three-dimensional Richards equation is discretized based on cell centered finite differences. ParFlow also features coupled surface-subsurface flow 20 which allows for hillslope runoff and channel routing (Kollet and Maxwell, 2006). Because it is fully coupled to the Common Land Model (CLM), a land surface model, ParFlow can incorporate exchange processes at the land surface including the effects of vegetation (Maxwell and Miller, 2005;Kollet and Maxwell, 2008).…”