Reliability-Based Assessment of Lifecycle Cost of Urban Water Distribution Infrastructures

Abstract

Water distribution systems, as an urban infrastructure, have an indisputable role in the productivity of a society and the quality of life of its residents. It is necessary to develop policies for evaluation of the urban infrastructure performance and determining the proper time of maintenance and rehabilitation activities to increase system productivity and expand the system’s efficient performance time. In this paper, an algorithm is developed to evaluate the efficiency of urban water infrastructure performance, broken down into costs and benefits, and to determine the optimal time of water distribution network (WDN) rehabilitation using a probabilistic approach. The proposed algorithm is examined in a real water distribution network in Iran. Considering different break scenarios, the WDN’s performance within the projected performance period is simulated. The efficiency of the WDN is quantified using a reliability-based indicator, and costs and benefits of its performance are also evaluated. Based on the estimated reliability of the WDN and its calculated revenue, the actual remaining operation period of infrastructure is determined. A threshold of system revenue to costs ratio can be considered for determining the end of system life span; here 0.5 is considered. Based on the results in the case study, it can be concluded that the efficient lifetime of a WDN can be much less than its designed life span (here the efficient lifetime is 14–16 years, while the design life span is 20 years). The results of this study could be used efficiently in large water distribution networks to determine the rehabilitation time and avoiding the high costs of WDN failure.