Rehabilitation scheduling of water distribution systems based on multi-objective genetic algorithms

Pipe ageing leads to increasing breakage frequency and decreasing system efficiency, thus rehabilitation strategies are necessary to define when, where and how to operate. These strategies are constrained by the amount of funds available not in a single instalment but yearly and spread over a time period of several years. A procedure based on a multi-objective genetic algorithm to search for a near optimal rehabilitation scheduling is proposed. With reference to a fixed time horizon, the goal is the minimisation of the overall costs of repairing and/or replacing pipes, and the maximization of the hydraulic performances of the water network; the constraints are represented by the available funds which are quantified yearly in pre-selected instalments. A head-driven hydraulic simulator is linked to the optimizer to represent the different hydraulic and breakage scenarios which become possible in consequence of the rehabilitation plans generated by the genetic algorithm. Preliminary results regarding a simple case study show that the proposed procedure has the potential to be a useful tool for rehabilitation scheduling.