Fuzzy hierarchical decision support system for water distribution network optimization

In this article, fuzzy hierarchical multi-objective optimization has been applied for the design of water distribution networks, using genetic algorithms (GAs). The problem has been formally structured as a multi-level multi-criteria decision making (MCDM) process with two objectives: cost minimization and benefits maximization, resulting in a Pareto trade-off curve of non-dominated solutions. A number of criteria are introduced and individually assessed by fuzzy reasoning. The overall benefits function is a combination (aggregation) of criteria, according to their relative importance and their individual fuzzy assessment. It is obtained through an analytic hierarchy process, applied directly within the GA, using an original mathematical approach. The decision maker enters data and preferences using exclusively linguistic ‘engineer friendly’ definitions and parameters. In this way, the whole design algorithm moves away from strict numerical functions and acts as a decision support system for the water network design optimization. The model has been applied to ‘Anytown’, a well-known benchmark network.