On-line Abstracts

Fedra, K., Diersch, H.J. and Härig, F. (1994)

Interactive Modeling of Groundwater Contamination: Visualization and Intelligent User Interfaces. In D.C. Adriano, A.K. Iskandar and I.P. Murarka [Eds.] Contamination of Groundwaters. Advances in Environmental Science. Science Reviews. Northwood, UK. pp. 189-220.

Abstract

The management and remediation of groundwater contamination problems is among the more complex tasks in environmental management and technology. Not only is the available information usually sparse and the physical processes very complex, i.e., dynamic and spatially distributed, they are also difficult to analyze, understand, and communicate. At the same time, problems are often of considerable urgency and the economic and political stakes are usually high.

Numerical simulation models are certainly powerful tools with enormous potential, but they are difficult to use and difficult to validate. Their results are difficult to communicate and thus not easily understandable by a non-technical audience.

Putting groundwater models into an interactive framework, with a user-friendly interface, employing computer graphics for problem visualization can help to improve this situation. This makes available numerous support functions, such as transparent data base handling that allows the efficient use of models and at the same time the effective communication of model results. The discussion centers on three basic concepts, i.e.,

• integration of various sources of information and tools that go beyond the immediate groundwater model, but are important components in a problem-oriented application; examples include coupling to geographical information systems or image processing of remote sensing data, various data base management systems, models for related systems such as surface water or land fills, or multi-criteria decision support tools;
• interaction , i.e., the ability to run the models interactively, produce dynamic animated output, define scenarios interactively, run, modify, and re-run a problem or set of problems, tune output and display options in real time, etc., to get immediate answers in an exploratory and experimental man--machine dialogue; and
• visualization, i.e., the graphical and symbolic representation of the system and its behavior in time and space, but also including the entire problem that goes beyond the basic physical system and includes economic and socio-political dimensions and attributes.

This chapter introduces an interactive approach to groundwater contamination modeling, and discusses the approach, its philosophy, and concrete implementation examples based on two 2D finite-element and finite difference simulators respectively.

Combining groundwater flow and transport models with an AI-based and symbolic, graphics user interface, selected functions of geographical information systems (GIS), and transparent data and file handling, the systems are designed to allow the easy and efficient use of complex groundwater modeling technology in a problem- rather than model-oriented style.

Using color-graphics super-microcomputer workstations, the approach provides a problem manager with numerous built-in support functions such as the selection of site-specific, as well as generic, groundwater problems from problem libraries and GIS functions for the comparative analysis of model runs, the preparation of topical background maps, the interactive modification of a problem for extensive scenario analysis, or the complete interactive design of a new problem. Using either satellite imagery (such as LANDSAT or SPOT) or Digital Line Graph (DLG) standard vector maps as a background, problems can be edited and modified and then simulated under interactive user control. The results are presented as dynamic graphical output, that can be interactively controlled and configured. Repeated simulations, comparing alternative assumptions on parameter values or management options can be compared in a variety of analysis functions such as GIS -based overlay techniques.

The systems also feature extensive problem-editing capabilities, ranging from the interactive location of wells or sources of pollution to a Computer Aided Design (CAD) component for the interactive design of a complete problem geometry. This allows the user to design very efficiently, and parametrize, a new problem from the very beginning, using a map or an auxiliary grid as a background for the definition of problem geometry and hydrogeological parameters.

Building some of the knowledge of an experienced groundwater modeler into the software system and its interface through the rule bases driving, e.g., numerous transparent, error-correction functions and an automatic mesh generator, allows for a very fast and efficient formulation of a new problem, even by an inexperienced user. Freed from the task of very detailed and demanding formalization of the computer representation of the problem, the user can thus concentrate on, e.g., the management, regulatory, economic, or technological aspects of his problem. Designed for complex applications such as hazardous waste management, site evaluation, and groundwater contamination problems, ease of interactive use, responsiveness, and efficiency in problem definition and comparative analysis are the most important characteristics of this interactive approach to groundwater simulation.