Design optimization of water distribution networks: real-world case study with penalty-free multi-objective genetic algorithm using pressure-driven simulation

Abstract

Water distribution systems are an integral part of the economic infrastructure of modern-day societies. However, previous research on the design  optimization of water distribution systems generally involved few decision variables and consequently small solution spaces; piecemeal-solution  methods based on pre-processing and search space reduction; and/or combinations of techniques working in concert. The present investigation was motivated by the desire to address the above-mentioned issues including those associated with the lack of high-performance computing (HPC) expertise and limited access in developing countries. More specifically, the article’s aims are, firstly, to solve a practical water distribution network  design optimization problem and, secondly, to develop and demonstrate a generic multi-objective genetic algorithm capable of achieving optimal and near-optimal solutions on complex real-world design optimization problems reliably and quickly. A multi-objective genetic algorithm was  developed that applies sustained and extensive exploration of the active constraint boundaries. The computational efficiency was demonstrated by  the small fraction of 10-245 function evaluations relative to the size of the solution space. Highly competitive solutions were achieved consistently, including a new best solution. The water utility’s detailed distribution network model in EPANET 2 was used for the hydraulic simulations. Therefore, with some additional improvements, the optimization algorithm developed could assist practitioners in day-to-day planning and design.

Keywords: water distribution system, pressure-driven dynamic simulation, constrained multi-objective genetic algorithm, feasible and infeasible  frontier optimal sets, generational distance, active constraint boundaries