Phased Methodology for the Optimal Rehabilitation of a Network with an Intermittent Water Supply Based on Hydraulic Criteria

Abstract

The intermittent supply of drinking water represents a major technical and social challenge, affecting more than 1 billion people worldwide. This paper proposes a methodology with three stages to rehabilitate a deteriorated system with intermittent service in a time horizon of five years as part of the Battle of Intermittent Water Supply problem. First, the initial assessment stage identifies vulnerable areas and critical supply hours. The network is analyzed to establish whether it is possible to deliver the desired demand in a scenario without any leaks. The latter is to set a baseline scenario for the upcoming stages. The sectorization stage defines the optimal district metered areas to reduce water losses and increase supplied water through the improved control of flows and pressure. This stage is divided into clustering, by means of the Girvan–Newman algorithm, and partitioning by defining the location of valves. Finally, the third stage determines the optimum investments for asset rehabilitation. The optimization process is performed individually and sequentially for valve settings, pump replacements, storage tanks upgrade, pipe rehabilitation, leakage repair, frequency inverter installation and pumping operation modification, and simple controls. The final solution validates how hydraulic criteria, in combination with optimization techniques and engineering judgment, can significantly improve the operation of an intermittent water distribution system. It is very common that the normal dynamics and performance of drinking water distribution systems are affected by the availability of water resources, either for lack of large enough sources or for low maintenance and operation, which result in high losses or very low pressures in some part of the network. In such cases the operation could become intermittent, a common problem in some cities. Therefore, an adequate rehabilitation of the existing infrastructure is essential to mitigate the socioeconomic impact generated by the lack of opportune maintenance. This study proposes a methodology for the rehabilitation of systems through three stages: (1) identification of the most vulnerable areas according to hourly consumption peaks; (2) sectorization of the network with the aim of having a better control of flows and pressures to reduce leaks; and (3) optimal investment for rehabilitation. During this work, technical knowledge and engineering criteria are integrated to provide integral solutions. These include favorable operating conditions, such as simple controls, valve status, and operation of pumping systems with frequency variators. Finally, a series of indicators is established to measure the progress of the improvement of the network over a chosen period.