Robust Design of Water Distribution Networks for a Proactive Risk Management

In the last three decades the optimal design of water distribution systems problem has been studied by a great many researchers, and this has resulted in the development of a large number of models and the application of optimization techniques. The design of these infrastructures is based on future predefined and perfectly known working conditions for the water distribution networks, a premise that may direct the optimization process to solutions which, although optimal for the imposed scenario, may perform badly if reality turns out to be significantly different. In fact the working conditions can be disrupted by accidents such as broken pipes or reservoirs, technical failures, change in demand, etc. In the context of a proactive attitude toward risk, it is important to consider these aspects at the design phase. This paper presents a robust optimization-based approach for designing a water distribution network aimed at obtaining solutions that can cope with the uncertainty of the network's working conditions. Robust optimization is a scenario based technique, and in the present case its goal is to provide significant savings in comparison with the worst case scenario solution, while incurring only minor suboptimality for the rest of the scenarios, and being almost feasible for all the scenarios. The solution of the robust optimization problem is obtained with a methodology that uses the link between a simulated annealing algorithm, the optimizer, and a hydraulic simulator, here used to solve the problem's hydraulic constraints. The application of the proposed methodology is illustrated with an example of a water distribution network.