**6. Conclusions**

The contribution of recycled moisture to precipitation was estimated using the linear mixing model in different seasons for different elevations. The results showed that the contribution rate of recycled moisture to precipitation was higher in the spring, summer, and autumn (2.05~16.5%) and low in winter (1.62~3.32%). In the high-elevation areas (>2400 m), the contribution rate of recycled moisture to precipitation was higher than the foothills area (2100~2400 m). The contribution of the *fTr* moisture was higher than that of the *fEv* to precipitation in the mountain areas. The contribution of recycled moisture increased with the elevation in the Qilian mountains. The water obtained from the xylem of plants contains organic pollutants (methanol and ethanol) that may cause of greater uncertainty in *fTr* in different studies. The quantification of the contribution rate of recycled moisture requires the cooperation of multi-source data, but the high-elevation regions often lack systematic mufti-element observation data. To better understand the contribution mechanism and influencing factors of recycled moisture, a long-term field monitoring system should be established to obtain comprehensive first-hand data. This study can provide a reference for the study of recycled moisture in other mountain areas.

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

**Funding:** This research was funded by National Natural Science Foundation of China (41867030, 41661005, 41971036).

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

**Data Availability Statement:** We have made public the stable isotope data of precipitation that support the results of this study (Zhu, Guofeng, 2020. Data sets of isotopes of different water bodies at different altitudes in Qilian Mountains, Mendeley Data, V2, doi:10.17632/bhxp9mjtv4.2) and Meteorological datasets can be found at http://data.cma.cn.

**Acknowledgments:** The work was supported by the National Natural Science Foundation of China (41867030, 41661005, 41971036). We thank Hanxiong Pan, Xinggang Ma, Dongdong Chen, Kai Wang, Yang Shi, Zhiyuan Zhang, Leilei Yong for assistance during fieldwork. We sincerely thank Marit Greenwood for the writing suggestions.

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

### **References**


**Ting Li 1, Gyuwon Lee <sup>2</sup> and Gwangseob Kim 1,\***


**Abstract:** This study aimed to calculate and analyze total overflows that accumulate in urban manholes in the target drainage basin of Samsung-dong, Seoul in heavy rainfall events with different temporal distribution characteristics, using the EPA's Storm Water Management Model (EPA-SWMM model). Inundation behaviors were analyzed using the two-dimensional flood model (FLO-2D). The extreme rainfall events were produced using different exceedance probability Huff distributions for different durations and return periods, such as from 1 to 3 h and 10 years, 50 years, 80 years, 100 years, respectively. The inundation model was validated using the actual flood observations on 21 September 2010 in the Samsung-dong drainage basin. The total overflow amount showed considerable differences according to the different time distribution characteristics, such as the temporal location of the storm peak and the concentration level of the storm. Furthermore, the inundation behaviors were also related to the temporal characteristics of storms. The results illustrated that the consideration of the temporal distribution characteristics of extreme rainfall events is essential for an accurate understanding of the rainfall–runoff response and inundation behavior in urban drainage basins.

**Keywords:** extreme rainfall event; huff method; optimum inundation map; EPA-SWMM; FLO-2D; Samsung-dong
