**6. Conclusions**

This paper has conducted a critical review of studies that deal with smart water techniques applied in water systems, with a particular focus on the understanding of how to address the key components for the framework of the smart water system (SWS). Four critical components composed of the SWS (instrument layer, property layer, function layer, benefit layer, and application layer) and two metrics (smartness and cyber wellness) are proposed to characterize SWS. In this review, a total

number of 32 literature including 1 international forum, 17 peer-reviewed papers, 10 reports, and 4 presentations, explicitly supporting the smart water system's definition, architecture, and metrics, are analyzed. The main conclusions drawn from this study can be summarized as follows:


Overall, this review has defined what SWS is and established a systematic framework for SWS, including architecture and metrics of SWS, which also shows that SWS has great potential to maximize the benefits in water sectors over the coming decades. This study is useful for designing assessing, and rehabilitating SWS when different goals are required in practical applicability in the field or lab. Future research directions are also clarified for this cross-disciplinary work, to assist the water areas to move towards a smarter future. As smart water technologies are under development, more real-world tests will be needed to realize the full benefits of smart water system.

**Author Contributions:** Conceptualization, J.L.; methodology, J.L.; formal analysis, J.L. and X.Y.; investigation, J.L. and R.S.; resources, J.L.; data curation, J.L.; writing—original draft preparation, J.L.; writing—review and editing, J.L. X.Y. and R.S.; visualization, J.L.; financial support, R.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work is mainly supported by the Teaching Assistance Scholarship of the Civil and Environmental Engineering Department at the University of Utah. The publication fee is financially covered by the Climate and Energy Fund of the University of Innsbruck.

**Acknowledgments:** We would like to show our great thanks to the financial support Climate and Energy Fund and also the assistance from the program "Smart Cities Demo-Living Urban Innovation 2018" (project 872123) of the University of Innsbruck.

**Conflicts of Interest:** The authors declare no conflict of interest.
