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2006 Darcy Lecture

All Models Are Wrong: How Do We Know Which Are Useful?

by Eileen Poeter


Abstract: Hydrology is modeling, starting from the moment a hydrologist stands on a hill and develops a concept of the system; continuing with application of an analytical model such as Darcy's law, the Theis equation, or chemical equilibria; and sometimes extending to elaborate numerical models. Darcy created the first quantitative ground-water model in 1856, driven by the practical goal of providing clean water supply to Dijon, France. It was clearly useful because it not only served his immediate purpose, but hydrologists still call on it daily. Today we strive to solve complex ground-water flow and transport problems and we are asked to use model results to make decisions without the luxury of a long assessment period. Consequently, the ground-water profession is searching for appropriate approaches for developing conceptual models, evaluating which models are useful, and describing the uncertainty associated with their predictions. Formulation of a reasonable set of alternative conceptual models, coupled with quantitative representation (which may range from simple to complex), is critical to the process. In spite of its apparent simplicity, this task is more difficult than numerical modeling because it reaches beyond consideration of scientific principles and quantitative algorithms into the realm of human nature and judgment. The problem is exacerbated by the dense, opaque character of the subsurface that makes data acquisition expensive, causing us to accomplish the work with sparse, uncertain information. Nevertheless, movements to meet this challenge are gaining momentum in the ground-water profession. Currently available practical approaches to the problem are presented in down-to-earth terms and future challenges are considered.


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Link to the card distributed at the lecture


Speaker Bio: Eileen P. Poeter is currently a Professor of Geological Engineering at Colorado School of Mines and Director of the International Ground Water Modeling Center (IGWMC, Dept. GE, CSM, 1500 Illinois St., Golden CO, 80401; 303-273-3829, fax 303-384-2037;; She obtained her Ph.D. in Engineering Science in 1980 and an M.S. in Engineering in 1978, both from Washington State University, and a BS in Geology from Lehigh University in 1975. She worked for Golder Associates in the early 80's before moving to academia and continues to work as an independent consultant to stay in touch with the needs of industry. Her research focuses on groundwater modeling and parameter estimation (she is first author of UCODE_2005, a universal inversion code, and associated codes for evaluating the results of the parameter estimation; and of MMRI, a multi-model ranking and inference code) water resource evaluation, and evaluation of heterogeneous and fractured aquifers. She is, a part of the JUPITER (Joint Parameter IdenTification and Evaluation of Reliability) development team. JUPITER is an application-programming interface for evaluating sensitivity, assessing data needs, estimating parameters, selecting/ranking models, and evaluating uncertainty currently under development by the USGS, in coordination with EPA to interface with their contemporary software modeling frameworks.

2006 Darcy Lecture Schedule: click here for a pdf of the schedule


JUPITER Web pages mentioned in the Presentation


References Mentioned in the Presentation click here for related references


Thanks to:

National Ground Water Association, for organizing and providing financing for this lecture tour
CSM Hydrologic Science and Engineering Program, Students and Professors for inspiration throughout the years and making my time available for the lecture tour

Colorado School of Mines, for making my time available for the lecture tour
Department of Geology and Geological Engineering, for making my time available for the lecture tour

International Ground Water Modeling Center, for making my time available for the lecture tour