The proper estimation and regular update of model parameters is crucial for the actuality of a mathematical simulation model representing the hydraulics and water quality of a real physical water distribution system. Especially, when the model is running online, uncertainties in model parameters can result in large discrepancies between model predictions and behavior of the real system. Therefore, adequate techniques for data acquisition, maintenance and update of model parameters have to be developed. In what follows the “parameterization” of a hydraulic online simulation model is described including the classification of parameters regarding data source, update cycles and function in the model. The parameterization framework was developed to benefit the modeling of water critical infrastructure systems.