GROUND-WATER MODELING – GETTING READY FOR PRIME TIME

In 35 years of numerical ground-water modeling, much has been accomplished. Yet this is no time to be complacent. From the perspective of resource managers, the utility of models is far from satisfactory. Indeed, model results often are largely incomprehensible or at best questionable because of (1) simplifications that allow solution of difficult numerical problems obscure the relation between models and actual systems, (2) a lack of basic commonly accepted methods and guidelines for modeling natural systems, including how to use data to support models and use models to communicate system characteristics and dynamics important to resource-management and data-collection decisions, and (3) limits in graphical interfaces, visualization software, and 3D analysis. These deficiencies pose many interesting and challenging scientific problems, such as: - Should alternative system representations be designed using stochastic or deterministic methods, or a combination? What methods are best suited to ground-water systems considering the water-supply and water-quality problems involved? How should geologic theory and measurements be included? - How relevant are measured values of hydraulic conductivity to model values? - How do the different methods developed for sensitivity analysis, data needs assessment, calibration, uncertainty evaluation, and resource management compare? - Can integrated models of surface and subsurface process models be useful for ground-water systems of typical size? - Does the infrastructure exist to take advantage of the high-tech data explosion? Faster computers, better graphical interfaces and visualization technology, new agreements between US federal agencies, within programs of the European Union, and a new level of collaboration between US university scientists through CUAHSI make answers to these questions attainable. Selected efforts are described. Ground-water modeling will, hopefully, proceed from being useful but confusing to being a prime-time tool for water-resource managers.