Imprecision in Groundwater Modelling and Management

Abstract

The response of groundwater systems to pumping and/or contamination depends primarily upon the aquifer parameters (transmissivity and storage coefficient), hydrologie and geologic conditions at its boundaries (boundary conditions), as well as upon the location and intensity of pumping and/or contamination sources within the system. Although a combination of geological studies, pumping tests, and core analysis give valuable insight into the nature of an aquifer, measurements are generally scarce and the numerical values of aquifer and flow parameters are never known with the desired precision and accuracy. In fact, most water resources planning and management takes place in an environment in which the basic input information, the goals, the constraints, and the consequences of possible actions are not known precisely. In other words, water resources planners and managers are bound to deal with imprecision — mostly due to insufficient data and imperfect knowledge — which should not be equated with randomness and the consequent uncertainty (Bellman and Zadeh, 1980). The existence of management problems with some imprecision-related aspects was early recognized by many, but for a long time there was no appropriate apparatus for handling imprecision. The breakthrough occurred in 1965, when L.A. Zadeh introduced the concept of a fuzzy set and originated the fuzzy sets theory.