Inverse wave reflectometry method for hydraulic transient-based pipeline condition assessment

Established water distribution systems (WDSs) typically consist of pipelines buried underground that are aging and deteriorating, and as such, it is difficult to assess their condition for maintenance and replacement. This paper proposes a novel hydraulic transient-based inverse wave reflectometry method (IWRM) for condition assessment of water pipelines in WDSs. Instead of using the method of characteristics (MOC) for the transient modeling, a computationally high-efficiency wave reflectometry method (WRM) has been developed to simulate the transient response of a pipe system. Further efficiency improvement has been made by simplifying the friction term in the WRM. An IWRM has then been developed by combining the WRM with a differential evolution algorithm to calibrate the locations and magnitudes of the pipeline impedance changes (wall thickness changes and wave speed changes) caused by deterioration. The IWRM is able to concentrate on the major wave reflections caused by pipe impedance changes and minimize the effects from background noise and other interferences, such as background pressure fluctuations (i.e., those caused by pump operations, tank level fluctuations, and household water usage) and wave reflections by pipe fittings. The proposed method has a high efficiency due to its fast WRM simulation and its small number of optimization variables. Extensive numerical verifications have been conducted on reservoir-pipeline-valve systems with a uniform deteriorated pipe section, a nonuniform deteriorated section, and multiple deteriorated sections. The deteriorated sections in these case studies were all well detected even though the pressure signals were contaminated with strong noise. Experimental verification has also been conducted on a laboratory copper pipeline with one thinner-walled pipe section successfully identified.