Application of segment based robustness assessment for water distribution networks

In recent years, water utilities have placed a greater emphasis on the reliability and resilience of their water distribution networks. This focus has increased due to the continuing aging of such infrastructure and the potential threat of natural or man-made disruptions. As a result, water utilities continue to look for ways to evaluate the resiliency of their systems with a goal of identifying critical elements that need to be reinforced or replaced. In the process developing practices for improving system reliability, some type of quantifiable metric is necessary. This document presents a simple graphical method for use in evaluating the performance of a system in response to a pipe failure. The proposed methodology takes into account that multiple pipes may be impacted during a single failure as a result of the necessity to close multiple isolation valves in order to isolate the "segment" (group of pipes) required to contain the leak. In the proposed assessment, the segments are identified and used to delineate the pipe section taken out of service. The impact of each segment failure event on the performance of the network is then simulated using EPANET2. The assessment methodology is applied to the several water distribution network models that have been developed based on the available geographical information from a sample of real systems that contain the locations of the actual isolation valves. Using networks that accurately reflect the distribution of isolation valves in small water distribution systems provides an opportunity to represent their performance under a failure more accurately, and provide insights on how network type and valve distribution affect their built-in reliability level. The long-Term objective of the proposed methodology is to provide a simple approach that can be used by small water distribution systems operators to perform reliability assessments of their systems which can then be used to prioritize maintenance and expansion efforts.