Quasi 3D modeling of water flow in vadose zone and groundwater

Kuznetsov, M.; Yakirevich, A.; Pachepsky, Yakov; Sorek, S.; Weisbrod, Noam

doi:10.1016/j.jhydrol.2012.05.025

Cited by 39 publications

(34 citation statements)

References 24 publications

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“…Owing to high non-linearity in the soil-water sub-models, the assembled matrices can only be solved with unified small time-steps, which adds to the computational expense. The one-way coupling scheme, as adopted by the MODFLOW-UZF1 package (Grygoruk et al, 2014; Niswonger et al, 2006), as well as the free drainage mode of MODFLOW-SWAP model (Xu et al, 2012), assumes that the water table depth is of minor influence on 60 flow interactions at the phreatic interface, and is thus problem specific.The feedback coupling method, in contrast, is widely used (Kuznetsov et al, 2012;Seo et al, 2007;Shen and Phanikumar, 2010;Stoppelenbrug et al, 2005;Xie et al, 2012;Xu et al, 2012) as a compromise between numerical accuracy and computational cost. In a feedback coupling scheme, the soil-water and groundwater sub-models can be built with different governing equations, numerical schemes, and scales of discretization.…”

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confidence: 99%

Capturing soil-water and groundwater interactions with an iterative feedback coupling scheme: New HYDRYS package for MODFLOW

Zeng¹,

Yang²,

Shi³

2018

Preprint

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Accurately capturing complex soil-water and groundwater interactions is vital for describing the coupling between subsurface/surface/atmospheric systems in regional-scale models. The non-linearity of the Richards' equation for water flow, however, introduces numerical complexity to large unsaturated-saturated modeling systems. An alternative is to use quasi-3D methods with a feedback coupling scheme to join practically sub-models with different properties, such as governing equations, numerical scales, and dimensionalities. In this work, to reduce the non-linearity in the coupling system, two different forms of 10 the Richards' equation are switched according to the soil-water content at each numerical node. A rigorous multi-scale water balance analysis is carried out at the phreatic interface to link the soil water and groundwater models at separated spatial and temporal scales. With a moving-boundary approach at the coupling interface, the non-trivial coupling errors introduced by the saturated lateral fluxes are minimized for problems with dynamic groundwater flow. It is shown that the developed iterative feedback coupling scheme results in significant error reduction, and is numerically efficient for capturing drastic flow 15 interactions at the water table, especially with dynamic local groundwater flow. The coupling scheme is developed into a new HYDRUS package for MODFLOW, which is applicable for regional-scale problems.quasi-3D methods are categorized into (1) the fully coupling scheme, which simultaneously builds the nodal hydraulic 50 connections of models at both sides and implicitly solves the assembled matrices;(2) the one-way coupling scheme, which delivers the soil-water model solutions onto the upper boundary of the groundwater model without feedback mechanism; and (3) the feedback (or two-way) coupling scheme, which explicitly exchanges the head/flux solutions in vicinity of the interface nodes.The fully coupling scheme (Gunduz and Aral, 2005; Zhu et al., 2012) is numerically rigorous but tends to increase the 55 computational burden for practical conditions. For example, the potential conditional diagonal dominance causes nonconvergence for the iterative solvers (Edwards, 1996). Owing to high non-linearity in the soil-water sub-models, the assembled matrices can only be solved with unified small time-steps, which adds to the computational expense. The one-way coupling scheme, as adopted by the MODFLOW-UZF1 package (Grygoruk et al., 2014; Niswonger et al., 2006), as well as the free drainage mode of MODFLOW-SWAP model (Xu et al., 2012), assumes that the water table depth is of minor influence on 60 flow interactions at the phreatic interface, and is thus problem specific.The feedback coupling method, in contrast, is widely used (Kuznetsov et al., 2012;Seo et al., 2007;Shen and Phanikumar, 2010;Stoppelenbrug et al., 2005;Xie et al., 2012;Xu et al., 2012) as a compromise between numerical accuracy and computational cost. In a feedback coupling scheme, the soil-water and groundwater sub-models can ...

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mentioning

confidence: 99%

Capturing soil-water and groundwater interactions with an iterative feedback coupling scheme: New HYDRYS package for MODFLOW

Zeng¹,

Yang²,

Shi³

2018

Preprint

View full text Add to dashboard Cite

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“…Additionally, the current numerical coupling of HYDRUS‐1D and MODFLOW produces unrealistic sudden inflow and outflow fluxes at the interface when the groundwater table depth is updated in HYDRUS‐1D as a result of its change in MODFLOW (Twarakavi et al ; Kuznetsov et al ). These numerical instabilities need to be resolved before the solute transport component can be incorporated into the HPM.…”

Section: Introductionmentioning

confidence: 99%

Implementation of Solute Transport in the Vadose Zone into the “HYDRUS Package for MODFLOW”

et al. 2018

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The "HYDRUS package for MODFLOW" is an existing MODFLOW package that allows MODFLOW to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package is based on incorporating parts of the HYDRUS-1D model (to simulate unsaturated water flow in the vadose zone) into MODFLOW (to simulate saturated groundwater flow). The coupled model is effective in addressing spatially variable saturated-unsaturated hydrological processes at the regional scale. However, one of the major limitations of this coupled model is that it does not have the capability to simulate solute transport along with water flow and therefore, the model cannot be employed for evaluating groundwater contamination. In this work, a modified unsaturated flow and transport package (modified HYDRUS package for MODFLOW and MT3DMS) has been developed and linked to the three-dimensional (3D) groundwater flow model MODFLOW and the 3D groundwater solute transport model MT3DMS. The new package can simulate, in addition to water flow in the vadose zone, also solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption. Due to complex interactions at the groundwater table, certain modifications of the pressure head (compared to the original coupling) and solute concentration profiles were incorporated into the modified HYDRUS package. The performance of the newly developed model is evaluated using HYDRUS (2D/3D), and the results indicate that the new model is effective in simulating the movement of water and contaminants in the saturated-unsaturated flow domains.

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“…The accurate simulation of variably saturated flow in porous media is a valuable component to understanding physical processes occurring in many water resource problems. Examples range from coupled hydrologic-atmospheric models to irrigation problems; see for example [39,6,23]. Computer simulations of subsurface flow generally proceed by computing a numerical solution of the three dimensional Richards' equation [33].…”

Section: Introductionmentioning

confidence: 99%

Enhancing speed and scalability of the ParFlow simulation code

2017

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Regional hydrology studies are often supported by high resolution simulations of subsurface flow that require expensive and extensive computations. Efficient usage of the latest high performance parallel computing systems becomes a necessity. The simulation software ParFlow has been demonstrated to meet this requirement and shown to have excellent solver scalability for up to 16,384 processes. In the present work we show that the code requires further enhancements in order to fully take advantage of current petascale machines. We identify ParFlow's way of parallelization of the computational mesh as a central bottleneck. We propose to reorganize this subsystem using fast mesh partition algorithms provided by the parallel adaptive mesh refinement library p4est. We realize this in a minimally invasive manner by modifying selected parts of the code to reinterpret the existing mesh data structures. We evaluate the scaling performance of the modified version of ParFlow, demonstrating good weak and strong scaling up to 458k cores of the Juqueen supercomputer, and test an example application at large scale.Comment: The final publication is available at link.springer.co

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Quasi 3D modeling of water flow in vadose zone and groundwater

Cited by 39 publications

References 24 publications

Capturing soil-water and groundwater interactions with an iterative feedback coupling scheme: New HYDRYS package for MODFLOW

Capturing soil-water and groundwater interactions with an iterative feedback coupling scheme: New HYDRYS package for MODFLOW

Implementation of Solute Transport in the Vadose Zone into the “HYDRUS Package for MODFLOW”

Enhancing speed and scalability of the ParFlow simulation code

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