Deficiency of Reliability Indicators in Water Distribution Networks

Abstract

In recent studies about reliability analysis of water distribution systems (WDSs), different reliability indicators have been used to measure and compare the reliability of water networks. These indicators have been used as objective functions in WDS optimization design problems alongside network construction cost. In this research, it is shown that these prevalent indicators cannot completely model the ability of networks in the face of abnormal operational conditions such as nodal demand changes or pipe burst. Six well-known indicators were considered in reliability assessment of 20 different structures of five WDSs under a large number of abnormal operating conditions. Results show that some WDS structures, in spite of having higher reliability indicator values, are unable to adequately tolerate abnormal conditions. This deficiency may also result in removing some desirable water network structures in optimization procedures due to low values for reliability indicators. The research suggests a stochastic method, based on the correlation between the value of reliability indexes and the ability of WDS to operate in abnormal conditions, to find the best reliability indicator before the reliability analysis of each WDS.