Optimization of water distribution systems

A Tabu Search optimisation technique is proposed for designing, planning and maintaining water distribution systems. As design and maintenance of pipe networks for water supply distribution require high costs, achieving the highest level of performance of existing networks at minimum costs is mandatory. The problem involves setting a lot of variables, as location and diameters of new pipes, operations on existing pipes, and so on. The domain of variables is discrete in nature, due to the fact that pipes are available with unified dimensions. Furthermore, the objective function to be minimised, i.e., the total cost of the plant, is non linear, non differentiable, highly illconditioned, and presents a huge amount of local minima. Recently, increasing attention has been paid to heuristic optimisation techniques, such as genetic algorithms (GA), simulated annealing (SA), and tabu-search (TS) for large combinatorial optimisation problems. In particular, GA has been applied to the problem of designing and maintaining water distribution networks. Results show good performance of the GA in terms of objective function values, but high computation time. One of the most promising approaches to combinatorial optimisation problems is the TS metaheuristic, that showed flexibility and effectiveness in a lot of applications. The aim of this paper is to present a TS based algorithm to the design of water distribution systems, and to demonstrate its validity in this field.