Vulnerability Assessment of a Drinking Water Distribution System: Implications for Public Water Utilities

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. Vulnerability is defined as the probability that the disinfectant residual will be below the required threshold at any location or time during an EPANET simulation. Uncertainty analysis is 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 results suggest that public utilities can use this method to determine highly vulnerable system locations and locations with low vulnerability (i.e. high chlorine residual), which may be ideal for sensor placement.