VULNERABILITY ASSESSMENT OF A DRINKING WATER DISTRIBUTION SYSTEM

A water distribution system simulation model, EPANET, is used to predict chlorine residual profiles for a representative water distribution system. The analysis focuses on the identification of vulnerable areas where chlorine residual concentration is low. Alternative vulnerability measures are considered, including the probability that the disinfectant residual will be below the required threshold at any location or time during an EPANET simulation. Sensitivity and uncertainty analyses are conducted to examine the influence of key inputs to the EPANET model, including the bulk flow decay constant, pipe wall decay constant, water demand, and roughness coefficient. The roughness coefficient is indicated to have negligible impact on the predicted results, compared to the other uncertain variables. Methods for computing and mapping the system vulnerability, given the uncertainty in the EPANET model inputs, are demonstrated. The relationship between water age and chlorine residual is investigated as a first step in developing a response surface model for the system that can both simplify future uncertainty analysis and provide insights on vulnerability that are readily applicable to other systems.