Proceedings and Articles: ModelCARE99 Mary C. Hill Predictive Modeling of Flow in a Two-Dimensional Intermediate-Scale, Heterogeneous Porous Media MARY C. HILL, FRANK A. D'AGNESE & CLAUDIA C. FAUNT US Geological Survey 3215 Marine St., Boulder, Colorado 80303, USA, email: mchill@usgs.gov 1999, IAHS Publication no. 265 ABSTRACT Fourteen guidelines are described which are intended to produce calibrated groundwater models likely to represent the associated real systems more accurately than typically used methods. The fourteen guidelines are discussed in the context of the calibration of a regional groundwater flow model of the Death Valley region in the southwestern United States. This groundwater flow system contains two sites of national significance from which the subsurface transport of contaminants could be or is of concern: Yucca Mountain, which is the potential site of the United States high-level nuclear-waste disposal, and the Nevada Test Site, which contains a number of underground nuclear-testing locations. This application of the guidelines demonstrates how they may be used for model calibration and evaluation, and to direct further model development and data collection. Fig. 5 Using composite and prediction scaled sensitivities to identify critical parameters. SUMMARY AND CONCLUSIONS The primary advantages of the model calibration approach presented in this paper are (1) it is more objective and tests the model against measured data more rigorously than most alternatives, and (2) the statistics are designed to communicate the strengths and weaknesses of the simulations clearly to non-modelers such as resource managers, funding agencies, and interested citizens. The analysis of the Death Valley regional flow system presented indicates that the available hydraulic-head and spring-flow data used in the regression provide substantial information relevant to the advective-transport predictions. There appears to be sufficient information in the existing regression data to estimate many aspects of the hydraulic-conductivity field and areal recharge distribution with additional defined parameters, and the achievable detail will be greatly enhanced if additional and more precise measurements of flows into, out of, and through the system can be attained to reduce parameter correlation. mchill@usgs.gov Last Modified: August 15, 2000