Hydraulic and Co-located Pipe Criticalities in the Rehabilitation of Water Distribution Mains

Abstract

[EN] Infrastructures in urban areas can have spatial and also functional correlation. Water distribution networks (WDNs) along with other infrastructures therefore constitute a complex and interlinked multi-utility system in cities. This brings up the risk of cascading failures to the different networks’ elements; for example, a pipe failure could interrupt traffic in a main street, eventually leading to a road network failure. On the other hand, WDNs should be hydraulically robust so that the potable water is supplied to the customers with high reliability. Traditionally, there is a single perspective design approach for WDN rehabilitation and upgrade activities such as pipe replacement, duplicating, and lining, which does not consider the interlinked system in a city. This study aims to assess this issue in terms of an integrated asset management perspective with a multi-utility approach. For this purpose, beyond minimizing costs, two reliability indices will be defined to represent the reliability of a WDN against the hydraulic and multi-utility cascading failures. The hydraulic reliability represents the robustness of the network against the water pressure deficit, and cascading reliability represents the extent to which WDN elements are decoupled from other assets elements. Then, the rehabilitation problem is solved with the contribution of a nature-inspired optimization algorithm, the Non-Dominated Sorting Genetic Algorithm (NSGA-II), through a dynamic approach. In every decision of pipe rehabilitation action, the priority could be given to either the first or second reliability index. These two cases will be assessed and compared to examine the hydraulic and co-location pipe criticality roles in the decision-making for the upgrade of aged water distribution mains on a simplified real network located in the southwest Iran.