AnAqSim Example Application Series
Public water supply wellfields provide water for a variety of beneficial uses in homes, businesses and industries, and for farmland irrigation in many communities. Water districts often perform analyses of the area over which water enters and flows though the aquifer supplying a well or wellfield, so that groundwater protection measures can be implemented. In certain states, Massachusetts for example, the delineation of a groundwater protection area (referred to as a Zone II Area in Massachusetts) is required to be performed under relatively severe (no recharge to the aquifer while pumping at the maximum permitted rate) hydrologic conditions. In this example, we demonstrate how AnAqSim can be used to delineate a Zone II groundwater protection area. AnAqSim is particularly well-suited for this type of analysis because it has a number of special features and tools that make it easy to delineate pumping well Zones of Contribution (ZOC) in general, and Zone II Areas in particular, including:
- ability to specify an area of the model over which AnAqSim automatically calculates recharge or leakage (useful in confirming that the model area determined from pathline tracing to be contributing recharge to the well matches the specified withdrawal rate at the well).
- ability to capture a snapshot of heads for a selected time step in a transient aquifer simulation (e.g. “freeze” calculated heads on the 180th day following termination of recharge as is required for a Zone II analysis), and then perform pathline tracing;
- easy setup of an array of pathline starting locations over some area of the aquifer surface for forward tracing toward the pumping well; and,
- constraining the display of pathlines, so that only those pathlines captured by selected model features (e.g. wells for which Zone II protection areas are to be delineated) are shown on the plot.
The example comes with a detailed guide on model set up and Zone II delineation with AnAqSim, and all associated modeling files.
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