Towards a Shallow Groundwater Routine for Modeling Infiltration BMPs in Urban Stormwater Models
Groundwater flow is an important component of the hydrologic cycle in urban areas. However, few urban runoff models realistically simulate shallow groundwater routing. Most are either too simplistic or too difficult to use. Objectives of this chapter are to examine the utility of shallow groundwater routing routines in SWMM4.3 (and HSPF) and to suggest an approach pertinent to infiltration best management practices (BMPs) for urban areas. A fundamental 4-unit element named JUGRND is tested, which may be suitable for building integrated dendritic surface and subsurface stormwater routing models. Concep-tually, the idea is provide a basis for building a coupled model for those limited situations where groundwater routing directions are predictable and unlikely to change dynamically.
Although water is supplied to the subcatchments by infiltration, the pro-posed element was developed as a stand-alone program. The four fixed units in the array are: two up-gradient, an intermediate and one down-gradient subsurface subcatchment, so that the general planform promises to be useful as a building block for larger models. Current limitations include: only uni-directional down-gradient groundwater flow is allowed, groundwater flow is not allowed between the two up-gradient subcatchments, and unrestrained gravity flow of moisture from the unsaturated zone to the saturated zone is allowed as long as moisture content in the unsaturated zone is greater than field capacity.
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