Fast network multi-objective design algorithm combined with an a posteriori procedure for reliability evaluation under various operational scenarios

This paper presents a methodology for the optimal design of water supply networks. It features a multi-objective optimisation (aimed at minimising costs and maximising resilience) and a subsequent 'retrospective' evaluation of network reliability under various operational scenarios. The multi-objective optimisation is based on an algorithm specifically developed for the design of real networks which feature a very high number of nodes and pipes. The 'retrospective' evaluation of network reliability is assessed considering resilience contrasted with several other indexes adopted to describe the operational performance of the network under critical scenarios such as segment isolation or hydrant activation, and different water demand conditions. In the applications two case studies, made up of a simple benchmark network and a real network respectively, are considered for the multi-objective optimisation; the 'retrospective' evaluation of reliability is performed only on the real network. The latter example clearly highlights that the procedure proposed allows reliability and performance to be offset against cost, consenting informed choice of the optimal network configuration.