Abstract
Due to rapid deterioration of water pipes and decreasing financial resources for pipe replacement, several theories of asset management are being widely used to minimize waterworks life cycle cost (LCC). The concept of pipe replacement methods such as downsizing in pumped water distribution systems in the context of depopulation have not been established sufficiently even though a large amount of research has been done by using pipe replacement planning models to minimize LCC. This study, therefore, first proposes a pipe replacement planning model using a genetic algorithm that codes replacement timing and diameter as integer, and then applies a proposed model for pumped water distribution system in a depopulation scenario. The results show that the proposed model can reasonably plan pipe diameter, accounting for pump operational cost, and plan diameter downsizing for pipes that have surplus pressure. Prescriptively, it is rational to determine pipe diameter according to peak water demand over the planning period; thus, it is also rational to determine pipe diameter according to water demand at the time of replacement in situation of steady depopulation.
