Conceptual Framework for Leak Development in Water Distribution Systems

Water distribution systems, like all infrastructure, are subject to deterioration and failure, but their buried nature makes continuous condition monitoring impractical. This means that the pipe failure rate is often the only measure of pipe condition. However, most failures occur at the end of a long deterioration process that is driven by a range of factors. The aim of this paper is to propose a conceptual framework that describes the development of different failure types from weak point initiation to the point where the leak flow rate is large enough to be discovered. The paper discusses factors and mechanisms that influence the strength of and loads on pipes, and how these evolve over time. This is combined with a description of the factors affecting the leakage flow rate. The concept of a strength index is defined as the pressure at which a leak will become discoverable and is used to present the development of weak points and leaks on the same scale as the system pressure load. Finally, it is demonstrated how the development of leaks in a typical district metered area (DMA) can be presented using the conceptual framework. The paper provides a framework for the analysis of water distribution system condition over time that can be combined with local knowledge of a system (pipe materials, age, operational practices, and so on), information about failures (causes, types, and dimensions) and specific investigations to better understand the current state of the network.