Eyes wide open - Managing the resolution of field anomalies during calibration of water supply models

In 2009 Metrowater accelerated its programme of Model Update and Master Planning for its water supply network. Previous master plans were up to 12 years old and considerable changes had occurred that required the development of new tools, strategies and solutions. Metrowater had completed a number of studies in prior years, but has recently updated five models (out of a possible 11 models) that will be used to assess network performance & develop solutions for meeting growth and level of service standards.

This paper examines the issues involved in achieving a robust calibration of the hydraulic models to be used for master planning. Despite a comprehensive field test plan being executed prior to calibration of three zone models, significant anomalies were identified, that required further investigation to meet the model calibration criteria set by Metrowater.

This demonstrates Metrowater’s and the consultants approach and commitment to calibration, an eyes wide open approach that actively seeks to uncover and resolve anomalies. With a full complement of pressure and flow loggers in the initial calibration, it was possible to be confident of the model calibration parameters (pipe connectivity, diameter, minor losses and friction etc). The model parameters can be altered to match the calibration data, however this may require parameters outside the range of industry standards. In these cases the calibration data is indicating areas where the system is not behaving as it should, i.e. as an open water reticulation. The calibration effort then switched from tuning the model to further system investigations, as it was clear there were anomalies in the system.

These anomalies are typically part or fully closed valves or system restrictions (poor condition pipe). This paper will detail the system investigation process and show the findings of this investigation. Narrowing down the cause of the anomaly required in some cases system reconfiguration to isolate parts of the network and a systematic approach to obtain useable results. In some cases the anomaly was not resolved, but in most situations it was. This “eyes wide open” approach required a considerable investment of time and money to ensure that the final model was fit for the purpose of providing operational and planning outputs.

Ultimately the master plan projects have benefitted from the extra scrutiny with 14% lower cost solutions being developed. A register of outstanding issues has been created to ensure the field anomalies are flagged & prioritised for removal once they impact on customer service. The resulting solution set will ensure that Metrowater and its successor will continue to provide quality water services into the future.