AWWA WQTC59015

The Greater Cincinnati Water Works (GCWW) is in the process of developing a dynamic water quality model for its distribution system based on an existing detailed skeletonized hydraulic model. To calibrate the water quality model for free chlorine, two hundred locations were selected system wide, divided into routes based on service areas, and monitored by collecting grab samples over a 24 hour period. To verify the accuracy of the initial calibration, GCWW utilized its existing extensive distribution system free chlorine residual database for comparison to the model predicted chlorine residuals. This paper describes what GCWW found about the effects of local system conditions on calibration performance. This study suggests that a calibrated model loses its accuracy as a predicted location gets further away from the calibration points. It also suggests that local system conditions such as warm temperature, low velocity and old pipe have a strong influence on modeling performance. The results from performing this evaluation will assist GCWW in improving the calibration accuracy of future hydraulic and water quality models by identifying vulnerable areas of distribution systems which need more calibration points based on local system conditions. Includes tables, figures.