>Answering the question, "Is a model calibrated?" is a lot like answering the question, "Did you stop beating your dog?" There is no yes and no, black and white answer. There are just varying shades of gray.

This is a point of agreement.

>I disagree with Ben and Krister's comments that water quality data are needed for model calibration. About 98% of model applications deal with fire flow and pipe sizing and water quality isn't explicitly considered. This points out the fact that different people have different ideas about what a model should do. (Remember the old story about the blind men and the elephant.)

I agree that the data is not necessary for a model designed to substantiate fire flows, however, in analyzing our local water district's use of MODELING, it has become painfully clear that they are ignoring the capability of their MODEL to predict the concentrations of chemical constituents. Normally the effort to model a system is dependent upon who on staff has the time available to pursue the model in a diligent manner. Tests to verify model predictions are based solely on spot checks of the system, with very little attention paid to calibration of test instrumentation. Our local supplier has experienced a number of problems with inadaquate treatment, and in some cases, concentrations of chemicals that have upset the composition of the water to a point that property owners are experiencing failures of piping systems due to corrosion (confirmed by independent labaratory tests).

You pointed out very succinctly that the model should be used as a tool to help control the quality, volume and availability of water. The model requires reasonable attention to detail and frequent input from spot checks on the system to verify predicted results. I see two areas of concern here for a water provider, what do they have to do to meet statutory requirements, i.e. minimums, and what must they do to deliver a quality product. Most of these systems by their very nature provide minimum acceptable STATUTORY quality control. They are in most cases a monopoly. End users seldom get to choose who their provider will be. The result is that not enough attention is paid to modeling even though the quality and ability of modeling software has improved to a point where it could be considered at least as important a tool as the pipe wrench used to assemble the system.

Regards,
M.L. Garrison
Garrison Management Group