**5. Conclusions**

Diversifying the water sources is necessary to get the cities ready and more resilient to supplement the water supply system. Adoption of atmospheric water harvesting could be such a solution as they provide another connection point between the natural water cycle and the urban water cycle. A series of systems and off-the-shelf products are available on the market to be installed under various relative humidity environments. Although the higher water generation cost makes atmospheric water harvesting uncompetitive, it can be a reliable and decentralized household water treatment system to meet the water demand particularly by leveraging solar power. In addition, it also provides an alternative water source for regions that have a large bottled water consumer base but have no other favorable water sources. Overall, atmospheric water harvesting shall be taken into consideration to enhance the water supply resilience.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/su14137783/s1, Table S1: Summary of studies or practices of atmospheric water harvesting; Table S2: Summary of desiccants explored and developed in various studies; Table S3: Summary of atmospheric water harvesting machines on the market; Figure S1: Summary of atmospheric water harvesting technologies in practical application. References [129–152] are cited in the supplementary materials.

**Author Contributions:** Conceptualization, R.L. and M.Z.; methodology, R.L.; software, M.Z.; validation, R.L., M.Z. and Y.L.; formal analysis, R.L.; investigation, M.Z.; resources, R.L.; data curation, M.Z.; writing—original draft preparation, M.Z.; writing—review and editing, R.L.; visualization, M.Z.; supervision, R.L.; project administration, R.L.; funding acquisition, R.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The work is funded by the Beijing Municipal Commission of Education (general project, KM202010016013), Beijing Energy Conservation & Sustainable Urban and Rural Development Provincial and Ministry Co-construction Collaboration Innovation Center, and also by the National Natural Science Foundation of China (52000007).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We acknowledge the support from the Key Laboratory of Urban Stormwater System and Water Environment, the Ministry of Education, China, and the Beijing Overseas Talents Association.

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

#### **References**

