A MODFLOW Infiltration Device Package for Simulating Storm Water Infiltration |
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| Authors: | Jan Jeppesen Steen Christensen |
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| Affiliation: | Department of Geoscience, University of Aarhus, DK‐8000 Aarhus C, Aarhus, Denmark |
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| Abstract: | This article describes a MODFLOW Infiltration Device (INFD) Package that can simulate infiltration devices and their two‐way interaction with groundwater. The INFD Package relies on a water balance including inflow of storm water, leakage‐like seepage through the device faces, overflow, and change in storage. The water balance for the device can be simulated in multiple INFD time steps within a single MODFLOW time step, and infiltration from the device can be routed through the unsaturated zone to the groundwater table. A benchmark test shows that the INFD Package's analytical solution for stage computes exact results for transient behavior. To achieve similar accuracy by the numerical solution of the MODFLOW Surface‐Water Routing (SWR1) Process requires many small time steps. Furthermore, the INFD Package includes an improved representation of flow through the INFD sides that results in lower infiltration rates than simulated by SWR1. The INFD Package is also demonstrated in a transient simulation of a hypothetical catchment where two devices interact differently with groundwater. This simulation demonstrates that device and groundwater interaction depends on the thickness of the unsaturated zone because a shallow groundwater table (a likely result from storm water infiltration itself) may occupy retention volume, whereas a thick unsaturated zone may cause a phase shift and a change of amplitude in groundwater table response to a change of infiltration. We thus find that the INFD Package accommodates the simulation of infiltration devices and groundwater in an integrated manner on small as well as large spatial and temporal scales. |
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