Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2017-168
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
30 Mar 2017
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
A consistent implementation of the dual node approach for coupling surface-subsurface flow and its comparison to the common node approach
Rob de Rooij Water Institute, University of Florida, 570 Weil Hall, P.O. Box 116601, Gainesville, FL-32611-6601, USA
Abstract. Commonly, the dual node approach for coupling surface-subsurface flow is conceptualized as a hydraulic separation of the surface and the subsurface by a distinct interface with a given thickness. Since such an interface is not supported by field observations, it has been argued that the dual node depends on a non-physical parameter in the form an ill-defined interface thickness. As such, the alternative common node approach is considered to be a more general and a more elegant approach since it is based on the physical principle of head continuity along the surface-subsurface interface. In this study, however, it is argued that if properly implemented, then the dual node approach is actually the more general, the more elegant as well as the more accurate approach. This insight is obtained by considering that the topmost subsurface nodal values represent the mean values within discrete control volumes and by deriving the dual node approach from equations that govern infiltration and infiltrability. It is shown that the dual node approach should be conceptualized as a simple one-sided first-order finite-difference to approximate the vertical subsurface hydraulic gradient at the land surface and that there is no need to assume a hydraulic separation between the two flow domains by a distinct interface. Whereas a consistent properly implemented dual node approach is in agreement with the physical principle of head continuity at the land surface, it is shown that the common node approach is not. Studies that have compared the two coupling approaches have been based on improperly implemented dual node approaches. As such, this study presents a re-evaluation of how the common node compares to the dual node approach. Cell-centered as well as vertex-centered schemes are considered.

Citation: de Rooij, R.: A consistent implementation of the dual node approach for coupling surface-subsurface flow and its comparison to the common node approach, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2017-168, in review, 2017.
Rob de Rooij
Rob de Rooij
Rob de Rooij

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Short summary
The dual node and common node approach are widely used to simulate coupled surface-subsurface flows. In this study it is shown that the dual node when properly implemented is more general, more elegant as well as more accurate. This is a significant finding because it contradicts the findings of other studies. Numerical simulations also show that the dual node approach is often also more computationally efficient in comparison to the common node approach.
The dual node and common node approach are widely used to simulate coupled surface-subsurface...
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