A REVIEW ON STAGED DESIGN OF WATER DISTRIBUTION NETWORKS

Water distribution networks (WDNs) evolve continuously over time. Changes in water demands and pipe deterioration require construction upgrades to be performed on the network during its entire lifecycle. However, strategically planning WDNs, especially for the long term, is a challenging task. This is because parameters that are essential for the description of WDNs in the future, such as climate, population and demand transitions, are characterized by deep uncertainty. To cope with future uncertainty, and avoid overdesign or costly unplanned and reactive interventions, research is moving away from the static design of WDNs. Dynamic design approaches, aim to make water networks adaptive to changing conditions over long planning horizons. A promising, dynamic design approach is the staged design of WDNs, in which the planning horizon is divided into construction phases. This approach allows short-term interventions to be made, while simultaneously considering the expected long-term network growth outcomes. The aim of this paper is to summarize the current state of the art in staged design of water distribution networks. To achieve that, we critically examined relevant publications and classified them according to their shared key characteristics, such as the nature of the design problem (new or existing network design, expansion, strengthening, and rehabilitation), problem formulation (objective functions, length of planning horizon), optimization method, and uncertainty considerations. In the process, we discuss the latest findings in the literature, highlight the major contributions of staged design on water distribution networks, and suggest future research directions.