Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model
1
Energy Geosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
2
Center for Water and the Environment, The University of Texas at Austin, Austin, TX 78712, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Micòl Mastrocicco
Water 2021, 13(7), 902; https://doi.org/10.3390/w13070902
Received: 20 February 2021
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Revised: 22 March 2021
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Accepted: 25 March 2021
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Published: 26 March 2021
(This article belongs to the Section Hydraulics and Hydrodynamics)
A new high-performance numerical model (Frehg) is developed to simulate water flow in shallow coastal wetlands. Frehg solves the 2D depth-integrated, hydrostatic, Navier–Stokes equations (i.e., shallow-water equations) in the surface domain and the 3D variably-saturated Richards equation in the subsurface domain. The two domains are asynchronously coupled to model surface-subsurface exchange. The Frehg model is applied to evaluate model sensitivity to a variety of simplifications that are commonly adopted for shallow wetland models, especially the use of the diffusive wave approximation in place of the traditional Saint-Venant equations for surface flow. The results suggest that a dynamic model for momentum is preferred over diffusive wave model for shallow coastal wetlands and marshes because the latter fails to capture flow unsteadiness. Under the combined effects of evaporation and wetting/drying, using diffusive wave model leads to discrepancies in modeled surface-subsurface exchange flux in the intertidal zone where strong exchange processes occur. It indicates shallow wetland models should be built with (i) dynamic surface flow equations that capture the timing of inundation, (ii) complex topographic features that render accurate spatial extent of inundation, and (iii) variably-saturated subsurface flow solver that is capable of modeling moisture change in the subsurface due to evaporation and infiltration.
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Keywords:
coupled surface-subsurface model; shallow coastal wetland; wetting/drying; diffusive wave approximation; evaporation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
MDPI and ACS Style
Li, Z.; Hodges, B.R. Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model. Water 2021, 13, 902. https://doi.org/10.3390/w13070902
AMA Style
Li Z, Hodges BR. Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model. Water. 2021; 13(7):902. https://doi.org/10.3390/w13070902
Chicago/Turabian StyleLi, Zhi, and Ben R. Hodges. 2021. "Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model" Water 13, no. 7: 902. https://doi.org/10.3390/w13070902
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