Abstract:A novel water distribution network (WDN) analysis model, segmentvalve diagram with flow directions (SVFD), is proposed to elaborate the reliability of WDNs in case of accident. By transforming a WDN valve topology model into a directed graph and marking directions of water flowing through valves with directed edges, this model can more accurately determine the valves to be closed when a pipe burst occurs, and is conducive to obtaining the really complete outage area. This paper takes advantage of SVFD to evaluate topological reliability of WDNs, and designs 5 new evaluation indicators oriented to accident impact, isolation difficulty and emergency disposal time. Reliability analysis of WDNs in 3 Chinese cities is conducted with these indicators, which shows that compared with the traditional classic indicators based on the segmentvalve diagram, the improved indicators can reflect the actual impact and disposing difficulty of pipe network accidents more accurately and clearly.