Evaluating Segment and Valve Importance and Vulnerability

Abstract

Because consideration of segments and valves is essential for evaluating the reliability and resilience of water distribution networks (WDNs) when shutdowns are required, a quick method of identifying critical and vulnerable segments and valves would benefit utilities. While the importance and vulnerability of segments can best be evaluated by extensive hydraulic analysis, hydraulic analyses can be time consuming. It can also be challenging to visualize the segments of a water distribution network and their associated valves. To address these limitations, this study develops a method based on graph theory to identify important and vulnerable segments without hydraulic calculations. The method generates a matrix that represents how reachable water sources are from segments when a given segment must be isolated while distinguishing between continuous water sources and ephemeral storage. This study also applies measures from graph theory to determine the number of valves to operate to isolate a segment and provides a rigorous proof to support the intuitive equation. A method to visualize the connectivity of segments with the graph-theory measures is demonstrated. The developed methods are applied to multiple valving scenarios of a case study and two real WDNs. Correlations between graph-theory based measures derived from the segment-valve topology and hydraulic simulation-based criticality are higher than in previous studies that apply graph theory to the pipe-junction topology of WDNs (r≥0.6). Results indicate that the developed methods can be used by utilities as a preliminary screening to eliminate the need for some hydraulic simulations. These findings are expected to provide decision support for utilities.