Novel Comprehensive Approach for Phasing Design and Rehabilitation of Water Distribution Networks

Traditionally, the design and the rehabilitation of water distribution networks (WDNs) have been addressed as separate problems. Here, a comprehensive approach to address both the design and rehabilitation of WDNs is proposed, considering the evolution of urban areas and the aging phenomena that typically involve WDNs. The search for the design and rehabilitation intervention schedule, in terms of installation of new, parallel, and replacement pipes, is addressed as a multiobjective optimization problem in which the solutions represent the trade-off between the system cost and its hydraulic resilience. A modified version of NSGA-II in combination with a pressure driven version of the EPANET 2 software was used to find optimal solutions. Application of the methodology to a literature case study indicates that it leads to a dramatic reduction in the failure costs, through a marginal increase in the investments in the short term, thanks to a farsighted intervention schedule. Also, a sensitivity analysis to the different aging phenomena was performed in order to understand which ones mostly affect the rehabilitation needs and long-term management of WDNs.