Revisiting Optimal Water-Distribution System Design: Issues and a Heuristic Hierarchical Approach

For the past three decades, a number of studies have been dedicated to water-distribution system (WDS) optimal design using alternative optimization algorithms. Many of those, however, focused on the introduction and application of new optimization techniques. Application systems optimized in previous studies are generally limited to simple transmission networks, so-called benchmark systems, in which local distribution lines were mostly excluded. Efforts seeking logical approaches to solve complex problems with large number of decisions are lacking. In this paper, logical and efficient approaches that could be utilized to optimize real-life scale WDS by the aid of existing optimization techniques are presented. This study aimed two main objectives: first, the effect of local distribution lines in final system design is investigated, and second, a heuristic to improve the efficiency of meta-heuristic search methods is proposed. Applications to real WDS demonstrate that (1) by integrating the transmission and distribution scales in optimization model, oversizing the transmission system could be avoided and the capacity of local distribution pipes could be appropriately evaluated, and (2) a proposed heuristic is logical and improves optimization performances, and is easily transferrable to any type of random search algorithms. Other issues related to solving the design problem facing engineers are raised and research directions are proposed.