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Drinking Water Engineering and Science An interactive open-access journal

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https://doi.org/10.5194/dwes-2017-28
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
26 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Drinking Water Engineering and Science (DWES).
Mass imbalances in EPANET water-quality simulations
Michael J. Davis1, Robert Janke2, and Thomas N. Taxon3 1Argonne Associate of Seville, Environmental Science Division, Argonne National Laboratory, Argonne, Illinois, USA
2National Homeland Security Research Center, U.S. Environmental Protection Agency, Cincinnati, Ohio, USA
3Global Security Sciences Division, Argonne National Laboratory, Argonne, Illinois, USA
Abstract. EPANET is widely employed to simulate water quality in water distribution systems. However, in general, the time-driven simulation approach used to determine concentrations of water-quality constituents provides accurate results only for short water-quality time steps. The use of an adequately short time step may not always be feasible. Overly long time steps can yield errors in concentration estimates and can result in situations in which constituent mass is not conserved. The absence of EPANET errors or warnings does not ensure conservation of mass. This paper provides examples illustrating mass imbalances and explains how such imbalances can occur. It also presents a preliminary event-driven approach that conserves mass with a water-quality time step that is as long as the hydraulic time step. Results obtained using the current approach converge, or tend to converge, to those obtained using the preliminary event-driven approach as the water-quality time step decreases. Improving the water-quality routing algorithm used in EPANET could eliminate mass imbalances and related errors in estimated concentrations. The results presented in this paper should be of value to those who perform water-quality simulations using EPANET or use the results of such simulations, including utility managers and engineers.

Citation: Davis, M. J., Janke, R., and Taxon, T. N.: Mass imbalances in EPANET water-quality simulations, Drink. Water Eng. Sci. Discuss., https://doi.org/10.5194/dwes-2017-28, in review, 2017.
Michael J. Davis et al.
Michael J. Davis et al.
Michael J. Davis et al.

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Short summary
EPANET does not always conserve constituent mass during water-quality simulations. The failure to conserve mass can result in significant errors in constituent concentrations. We document the occurrence of mass imbalances, explain why they occur, provide recommendations for minimizing mass imbalances, and present a preliminary water quality algorithm for use in EPANET that always conserves mass. Our paper should be of interest to anyone who performs water-quality simulations using EPANET.
EPANET does not always conserve constituent mass during water-quality simulations. The failure...
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