Optimal water distribution network design accounting for valve shutdowns

The hydraulic system functioning is determined by the boundary conditions (e.g. network topology, pipe resistances/diameters, tank levels, status of control devices, status of pumps, etc.). Shutdown of isolation valves, in order to detach a portion of the hydraulic network for planned or unplanned works, generates abnormal working conditions due to the induced topological modification of the network, which may reduce the hydraulic capacity of the water system with respect to the portions still connected. Thus, a challenge for network design is to optimize diameters versus system management under abnormal working conditions, i.e. accounting for the isolation valve system. To this purpose, a methodology for optimal system design accounting for valve shutdowns is herein presented. As the optimization asks for the evaluation of network configurations that can be generated by the isolation valve system, a strategy to reduce the computational burden is required. In fact, the analysis of a large number of network configurations could be required in real-world applications. A strategy to evaluate only the critical configurations, i.e. those ones for which the hydraulic capacity becomes insufficient to satisfy water requests in the still connected network, and dominating configurations, i.e. those ones which are the most critical, is presented. The optimization procedure is explained and discussed using a small size network and the computational efficiency is demonstrated using a large size network.