How Much Is "Your Un-Calibrated Model" Costing Your Utility? Ten Lessons Learned from Calibrating the CRD Water Model

Measured field data are required to calibrate a hydraulic model. Field data is typically collected through a hydrant testing program — the process of opening a hydrant and measuring the flow from it, while recording residual pressures at other hydrants in the area. This is followed by a desk exercise during which adjustments are made to the parameter values used in modeling the water system until a satisfactory match is obtained between modeled and observed values. The selection of hydrant test locations in a water distribution system is to ensure that effective data for model calibration is collected. For a given number of hydrant tests the objective is to maximize the calibration accuracy, i.e. the model's ability to reproduce the observed data. A total of 35 hydrant tests were completed in August 2009 by CRD staff. 306 hydrant data measurements were analyzed and used to calibrate the water model. Calibration agreements were within 2.5%. The hydraulic modeling predictions agreed with the values observed in the field within the AWWA guidelines on model calibration tolerances. The new calibrated model is being used by CRD as a practical tool for infrastructure planning, operational review, and fire flow and water quality analyses. Ten lessons learned from this project were developed and will be discussed in this paper. These lessons are meant to improve the model development and calibration process by reducing the amount of effort required to develop and calibrate the model, while increasing the accuracy and confidence in the model.