Reviewing the Long-Term Sustainability of Urban Water System Rehabilitation Strategies with an Alternative Approach

It is generally difficult to assess the performance of an infrastructure with a substantially longer life span than economic models can handle, and the life cycle concepts in urban water systems are normally limited to single-asset projects. In order to explore the long-term impact of urban water infrastructure rehabilitation strategies, a life cycle approach for survival functions is suggested. A life cycle factor based on survival functions is introduced, which is a measuring value of the total expected service life of all pipes within a group of pipes. Another factor, termed the sustainability factor, is based on the relationship between the life cycle factor and a rehabilitation reference method, which makes it possible to correct the long-term performance of rehabilitation methods based on their expected service life provision. A case study presents the implications for investments in infrastructure rehabilitation when applying the sustainability factor in long-term planning, and shows the importance of considering the service life of rehabilitation methods when planning renewal interventions that minimize costs over their life cycles.