Simulation models have been used successfully in many engineering applications, and their use has expanded and matured in recent years in concert with the evolution of new, more powerful computers. Among the more promising enhancements of simulation methods has been the incorporation of artificial intelligence, or expert systems technology. This integration is particularly beneficial when focused on simulation models that are complex and difficult to use or calibrate due to special expertise required of the user, and/or the large investment of time and money involved. The purpose of the paper is to demonstrate the use of expert system technology in this context. The focus of the paper is on the development of an expert system to aid in the calibration process and subsequent use of a stream‐quality simulation model. An expert system shell (in this case, KES) is used to facilitate the fast and efficient development and testing of the expert system. A biochemical oxygen demand‐dissolved‐oxygen model, graphic...