Interactive modeling of ground-water vulnerability within a geographic information system environment

During the last several years, the geographic information system (GIS) technology has emerged as an extremely effective tool for analyzing and prioritizing natural resource management alternatives. Because natural resource management problems are spatial in nature, the GIS technology provides a tool for defining the extent of the problem, and facilitates the design and implementation of alternative management strategies. The flexible design of a GIS coupled with the ability to integrate models with spatial data gives resource managers and planners the tools to effectively manage natural resources and to assess the implementation of regulatory policies before they are implemented. This paper describes an interactive modeling system developed within a GIS environment to facilitate rapid appraisal of the susceptibility of ground water to contamination by pesticides. The interactive system combines three widely used screening models with the ARC/INFO GIS software and a graphical user interface. Implemented on a color-graphic engineering workstation, the interactive modeling system can be used to visualize the spatial distribution of model inputs and outputs. The advantage of this system is that instead of ad-hoc linkage between GIS software and a simulation model, a fully integrated and interactive system in which the model equations are programmed within the GIS was developed. The impetus for developing the interactive ground-water modeling system was the relative lack of tools that fully integrate models with GIS and the potential benefits to the resource manager in developing such integrated environmental modeling systems. There is an increasing demand, from the GIS perspective, for tools that perform functions other than organization and display of spatial data. From the ground-water modeling perspective, several advantages can be derived from fully integrating process-based models with the data management, analysis, and display capabilities of the GIS.