INTEGRATED SURFACE- AND GROUND-WATER MODEL DEVELOPMENT

Due to the increasing complexity of environmental and water-resource problems, modeling techniques are required that simulate, on a basin scale, both the surface and subsurface hydrology. In previous studies, precipitation-runoff models have been used to generate groundwater-recharge information for subsurface models; however, incompatibilities in the spatial and temporal resolutions have been a significant impediment to a robust coupling of these models. Surface water models and groundwater models need to be integrated to provide the feedback between the models to allow a water balance to be achieved. The U.S. Geological Survey's (USGS) Modular Modeling System (MMS) provides a common framework where the most appropriate algorithms can be combined in ways that address a specific user's needs and constraints.

In this study, several hybrid MMS model applications with varying levels of representation (spatial and vertical) of subsurface hydrologic processes are constructed using algorithms from the Precipitation-Runoff Modeling System (PRMS) surface-water model and the MODFLOW groundwater model. The coupled models are applied and tested on watersheds in the USGS and U.S. Bureau of Reclamation's Watershed and River System Management Program (WaRSMP).