Simulating MODFLOW-Based Reactive Transport Under Radially Symmetric Flow Conditions

Authors

  • Ilka Wallis,

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  • Henning Prommer,

    1. CSIRO Land and Water, Private Bag No. 5, Wembley WA 6913, Australia.
    2. School of Earth and Environment, The University of Western Australia, Crawley, 6009.
    3. National Centre for Groundwater Research and Training, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
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  • Vincent Post,

    1. National Centre for Groundwater Research and Training, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
    2. School of the Environment, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
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  • Alexander Vandenbohede,

    1. Department of Geology and Soil Science, Ghent University, Krijgslaan 281 (S8), B-9000 Gent, Belgium.
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  • Craig T. Simmons

    1. National Centre for Groundwater Research and Training, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
    2. School of the Environment, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
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Corresponding author: School of the Environment, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia; +61-8-82012724; fax: +61-8-82015635, ilka.wallis@flinders.edu.au

Abstract

Radially symmetric flow and solute transport around point sources and sinks is an important specialized topic of groundwater hydraulics. Analysis of radial flow fields is routinely used to determine heads and flows in the vicinity of point sources or sinks. Increasingly, studies also consider solute transport, biogeochemical processes, and thermal changes that occur in the vicinity of point sources/sinks. Commonly, the analysis of hydraulic processes involves numerical or (semi-) analytical modeling methods. For the description of solute transport, analytical solutions are only available for the most basic transport phenomena. Solving advanced transport problems numerically is often associated with a significant computational burden. However, where axis-symmetry applies, computational cost can be decreased substantially in comparison with full three-dimensional (3D) solutions. In this study, we explore several techniques of simulating conservative and reactive transport within radial flow fields using MODFLOW as the flow simulator, based on its widespread use and ability to be coupled with multiple solute and reactive transport codes of different complexity. The selected transport simulators are MT3DMS and PHT3D. Computational efficiency and accuracy of the approaches are evaluated through comparisons with full 2D/3D model simulations, analytical solutions, and benchmark problems. We demonstrate that radial transport models are capable of accurately reproducing a wide variety of conservative and reactive transport problems provided that an adequate spatial discretization and advection scheme is selected. For the investigated test problems, the computational load was substantially reduced, with the improvement varying, depending on the complexity of the considered reaction network.

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