**5. Conclusions**

The purpose of this investigation was to analyze a regional water supply system that possessed a high degree of complexity. Tianjin was selected for the analysis. The major research design of the paper is using the concept of independent events in probability theory, the investigation combines the encounter probability of different frequencies of multiple water sources with a refined water resources allocation model, it is the major innovation point of the paper. Multiple water sources with different design frequency combinations were set for simulation, and the analysis results can draw the following conclusions.


**Author Contributions:** Conceptualization, S.Z. and J.Y.; Investigation, C.Z.; Methodology, S.Z., J.Y., Z.X. and C.Z.; Supervision, S.Z. and C.Z.; Validation, S.Z., J.Y. and Z.X.; Writing—original draft, J.Y.

**Funding:** This study was supported by the 13th Five-Year National Key Research and Development Program of China (2016YFC0401406, 2016YFC0401407) and the Fundamental Research Funds for the Central Universities (2019MS030).

**Acknowledgments:** The authors thank the Haihe River Water Conservancy Commission for providing the data of water plant and pipeline network, Tianjin Water Bureau for providing the date of surface water, groundwater, Luanhe River water and STNWTP water. We thank Paul Seward, PhD, from Liwen Bianji, Edanz Group China (www.liwenbianji.cn/ac), for editing the English text of a draft of this manuscript.

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