Rehabilitation, repairing and leakage detection optimization in water distribution systems

Pipe ageing leads to an increment both in breakage frequency and leakages, and to a decrement in the system efficiency. Strategies are then necessary to define when and where to operate in order to improve the water distribution system reliability and to reduce maintenance costs. A decision-making tool based on a multi-objective genetic algorithm technique for optimizing water distribution management strategies is proposed. Funds to be spent over a predefined time interval on pro-active actions (i.e. leakage detections and pipe replacements) are assumed available. The aim is to define how to spend this budget, i.e. where and when to make leakage detections and/or pipe replacements, in order to minimize a) passive costs (repair costs), b) leakages and c) to maximize the water distribution reliability by minimizing the volume of the unserved demands over a long predefined time horizon. The constraint of the funds allocated for pro-active actions to be spent in full within the planning time interval is selected to respect the standard way of operating of a water agency. In fact, once an amount for a given purpose is allocated, i.e. an item is defined, the water agency operates to spend this amount in full for that item within the time interval defined, since residual amounts are not necessarily reallocated to the same item, and return to the global budget of the entire set of activities to be planned for the subsequent period. Results regarding a real water distribution system show that the proposed procedure has the potential to be a useful decision-making tool for scheduling leakage detections and rehabilitation actions.