The objective of work package 4.3 is the development of a concept for estimation of the parameter uncertainty impacts on the reliability of the simulation results. The major steps of work package 4.3 are: • Survey and classification of parameter/measurement uncertainties (sources, range, importance); • Development of a concept for estimation of the parameter uncertainty impacts on the reliability of the simulation results; • Estimation of confidence intervals for hydraulic and water quality model results. This deliverable describes the treatment and modelling of parameter uncertainties based on the available information, the propagation of these uncertainties using the mathematical model of water distribution networks and the evaluation with respect to the confidence intervals. After that the effectiveness will be illustrated in a number of example applications. The deliverable is structured as follows: First a review on uncertainty quantification applications to water distribution networks is given, then the modelling of parameter uncertainties will be described, followed by an overview of the different options for propagation. The application is demonstrated using two example networks and the results are evaluated. The deliverable closes with the conclusions that could be drawn and the next steps in the development.