Survival analysis of water distribution network under intermittent water supply conditions

Intermittent water supply (IWS) is established temporarily or continuously in many water distribution networks (WDNs) worldwide due to prolonged drought, low rainfall periods, water scarcity and high level of leakage. IWS causes several adverse consequences on the network operation, resulting in ineffective supply and demand management. This paper presents a survival analysis of the network elements, including water mains, service connections, and valves using the Kaplan-Meier approach to determine the survival probability and the probability of failure rates of events of interest. The objective is to explore the changes in failure rates of network elements after implementing an IWS scheme. The non-parametric survival method is applied to the large zone (Zone-5) of the WDN in Tehran (Iran) based on the frequency of failures before, during, and after the implementation of an IWS regime. The results show that the probability of failure rates significantly increase after implementing the IWS scheme, and can remain for several years after, even when the network returns to continuous water supply (CWS). The results of this study can assist utility managers to understand the detrimental effects of IWS systems on increasing failure rates.