Vulnerability Assessment to Support Integrated Water Resources Management of Metropolitan Water Supply Systems

: The combined actions of natural and human factors change the timing and availability of water resources and, correspondingly, water demand in metropolitan areas. This leads to an imbalance between supply and demand and, thus, an increase in the vulnerability of water supply systems. Accordingly, methods for systematic analysis and multifactor assessment are needed to estimate the vulnerability of individual components in an integrated water supply system. This paper introduces a new approach to comprehensively assess vulnerability by integrating water resource system characteristics with factors representing exposure, sensitivity, severity, potential severity, social vulnerability, and adaptive capacity. These factors provide a way to consider broader system elements beyond the traditional vulnerability evaluation methods solely on the basis of the magnitude of failure (i.e., severity). In this way, the new vulnerability index gives a more detailed assessment with the potential to recognize critical conditions and components in an integrated system. The effectiveness and advantages of the proposed approach are checked using an investigation of the water supply system of Salt Lake City (SLC), Utah. First, an integrated water resource model was developed using a system simulation software to allocate water from different sources in SLC among designated demand points. The model contains individual simulation modules with representative interconnections among the natural hydroclimate system, built water infrastructure, and institutional decision making. The results of the analysis illustrate that basing vulnerability on a sole factor may lead to insufficient understanding and, hence, inefficient management of the system. For example, ranking of different water sources on the basis of the traditional vulnerability index (i.e., severity) in SLC is not consistent with the ranking on the basis of the proposed integrated vulnerability index. Therefore, during a failure event in the system, such as a water shortage, incomplete understanding of the system’s performance may lead to incorrect decisions by managers. The new vulnerability index and assessment approach was able to identify the most vulnerable water sources in the SLC integrated water supply system. In conclusion, use of a more comprehensive approach to simulate the system behavior and estimate vulnerability provides more guidance for decision makers to detect vulnerable components of the system and ameliorate decision making. DOI: 10.1061/(ASCE)WR.1943-5452.0000738. © 2016 American Society of Civil Engineers