AWWA ACE63259

The concept for this paper originated with the question of how to define acceptable calibration criteria for water distribution models. A 2001 report by the AWWA Engineering and Computer Applications Committee (ECAC) titled "Hydraulic and Water Quality Modeling of Distribution Systems: What Are the Trends in the US and Canada" reported that only 48% of the 174 survey respondents considered their hydraulic model to be calibrated. Respondents had various definitions of calibration, used various methods to achieve calibration, and accepted varying accuracies of calibration. The definition of calibration criteria will become increasingly important as a result of increasing regulatory focus on water quality in the distribution system. The recently promulgated Stage 2 Disinfection Byproducts Rule (Stage 2 DBP Rule) is the first U.S. Environmental Protection Agency (USEPA) regulation that specifically identifies computer modelling as a method for evaluating monitoring locations. It allows water age and source trace results from calibrated distribution system models to be used as an alternative to extensive field measurements in initial studies required by the rule. Prior to promulgation of the Stage 2 DBP Rule, a 1999 report by the ECAC titled Calibration Guidelines for Distribution System Modeling suggested that additional meaningful discussion is needed among the United States (US) modeling community regarding the need and validity of calibration standards. To further that effort, this paper presents extended period simulation (EPS) model calibration results for several medium and large utilities across the US. The results of the calibrations are evaluated relative to the guidelines in the ECAC report. In consideration of different practices and their impact on calibration accuracies, information on the development and calibration of a model in the United Kingdom (UK) is also presented. Includes 9 references, tables, figures.