Reliability-Focused Design, Management, and Maintenance of Water Distribution Networks

Access to clean water is vital for hygiene and public health and is critical for social and economic activity of urban life. Water distribution networks (WDNs) bring water from sources and treatment facilities to consumers via interconnected systems of pipes and mechanical components. The increasing urbanization and continuous changes in demand patterns and land use result in incremental modifications, expansions, and rehabilitation actions that gradually transform the network. At the same time, the ageing of infrastructures, the practical difficulties of rehabilitating buried assets, and financial constraints often lead to increasing component failure events. When a failure occurs, the damaged component must be disconnected from the source to allow repair or maintenance, which can result in service outages for part of the system. Therefore, a central concept for WDN performance is reliability, defined as the ability of a WDN to maintain adequate service levels when adverse events occur. Two factors are especially critical in determining reliability under component failure scenarios. The first is the hydraulic capacity of the network, which reflects the conveyance capability provided by pipe sizing and the characteristics and operation of other hydraulic components. The second is the Isolation Valve System (IVS), which directly controls the extent of the portion of the network (segments) that must be disconnected to isolate a failed component. This thesis develops advanced methods for the reliability-focussed design, operational management, and maintenance of WDNs. The proposed approaches explicitly account for the actual placement of isolation valves and their impact in each phase. To achieve this, the studies adopt the segment/valve topology of the network, instead of the conventional pipe/node topology. This topology is used as the basis for modelling and evaluating the consequences of component failures, management strategies, and maintenance actions. The research begins with a comprehensive review of state-of-the-art IVS modelling, reliability assessment under segment isolation scenarios, valve placement approaches, and valve maintenance strategies. Through this review, supported by utility survey insights, current gaps and practical limitations in WDN reliability and the role of isolation valves are highlighted. To address the identified gaps, first, a novel coupled method for WDN design is introduced. This method performs pipe sizing and isolation valve placement simultaneously within a multiobjective optimization framework. This approach results in a more comprehensive exploration of the trade-off between reliability and investment cost than the conventional decoupled design approach, in which pipe sizing and valve placement are carried out in separate steps. The thesis then proposes a novel method for partitioning WDNs into District Metered Areas (DMAs). In this method, DMAs are obtained by clustering segments formed by existing isolation valves in the network. Moreover, a novel modularity formulation is introduced that incorporates practical considerations, such as minimizing boundary links between DMAs while supporting a desired partitioning that accounts for the uniformity of selected properties across and within DMAs. Finally, the thesis addresses the identified shortcomings regarding isolation valve maintenance plans, recognizing that the number of valves in real networks is often too high to make comprehensive routine maintenance feasible. To address this, a novel approach is proposed to identify a subset of strategic valves whose guaranteed operability preserves effective segmentation and maintains high reliability even if other valves fail. A clustering-based algorithm is developed to identify these valves, and an assessment framework is introduced to evaluate and compare maintenance strategies while explicitly accounting for uncertainty in the locations of inoperable valves and failure probabilities.