Integrated Surface-Groundwater Modeling of Shallow Water-Table Systems Incorporating Discrete Landforms as Computational Elements

A new integrated surface-groundwater model, the integrated hydrologic model or IHM, is currently being developed which significantly advances the technology from its predecessor models FHM and ISGW. IHM combines the EPA surface water model HSPF and the USGS groundwater model MODFLOW with near simultaneous integration and physical interpretations of HSPF vadose zone process dynamics. The two model components are linked through an interface that provides a surface-water-to-groundwater transition that maintains strict water balance and smoothness in physical processes. Water table transitions from seasonal deep to at or above land are simulated. The interface can accommodate a specific yield that varies as the capillary fringe approaches land surface, which is an important phenomenon in shallow water-table environments.