Mass imbalances in EPANET water-quality simulations

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. Overly long time steps can yie...

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Bibliographic Details
Published in:Drinking water engineering and science 2018-04, Vol.11 (1), p.25-47
Main Authors: Davis, Michael J, Janke, Robert, Taxon, Thomas N
Format: Article
Language:English
Subjects:
Algorithms
Analysis
Computer simulation
Conservation of mass
Constituents
Convergence
ENVIRONMENTAL SCIENCES
Errors
Mass
Modelling
Quality
Routing
Simulation
Water conservation
Water distribution
Water distribution systems
Water engineering
Water pollution testing equipment
Water quality
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Summary: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. Overly long time steps can yield errors in concentration estimates and can result in situations in which constituent mass is not conserved. The use of a time step that is sufficiently short to avoid these problems may not always be feasible. 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 because of fundamental limitations in the water-quality routing algorithm used in EPANET. In general, these limitations cannot be overcome by the use of improved water-quality modeling practices. This paper 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, toward 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.
ISSN:1996-9465
1996-9457
1996-9465
DOI:10.5194/dwes-11-25-2018