Development and Application of Geographic Information System Based Utilities for a Fully Coupled Surface-Subsurface Distributed Parameters Hydrologic Model

Managing the environment and the water resources in hydrologic systems characterized by strong surface-subsurface interaction is challenging. A number of fully coupled surface-subsurface models have been developed in the last few years to elucidate the processes controlling such interaction for both water movement and water quality. One such model is the MODFLOW Hydrologic Modeling System (MODFLOW-HMS), which is a physically based model capable of simulating the land phase of the hydrologic cycle including overland and channel flow on the surface, variably saturated flow in the subsurface, as well as transport during flow in both system. Such a model requires a considerable amount of data to describe the tempo-spatial variation in model parameters and environmental conditions. A number of Geographic Information System (GIS) utilities were developed to estimate model parameters as well as environmental conditions that drive the computational engine of the model. The utilities were collected in one system named the ArcView GIS Interface (AGI). AGI utilizes readily available data including Digital Elevation Models, soil maps and databases, land use and land cover, rain gages and NEXRAD data, and Reach Files. The presented paper discusses the algorithms used to process these data and estimate the spatial and temporal variation in parameters over the MODFLOW-HMS finite-difference mesh. Examples from the Mad River, Ohio study showing the use of AGI in estimating MODFLOW-HMS model parameters are presented.