**5. Conclusions**

In this paper, a harmonious evaluation index system was constructed with WEF as the research object. The evolutionary characteristics of the representative elements of each of the subsystems were analyzed. The harmony degree of the nine provinces along TYR was studied and the harmony regulation of WEF was carried out. This paper draws several conclusions, as follows:

(a) The representative elements of the subsystem have different distribution characteristics. The per capita water resources of TYR were 1248.98 m<sup>3</sup> . It shows the distribution characteristics were high in the west and low in the east. The carbon emissions were much higher in the east than in the west. Among them, Shanxi and Shandong had larger carbon emissions. The per capita output of grain is increasing. Among them, Inner Mongolia, Henan, and Shandong had larger per capita grain production. Based on this result, each province can identify its own strengths and weaknesses. This is very useful for the provinces to maintain their strengths and make up for their shortcomings;


Due to the complex and variable relationships of WEF, the harmonious analysis of WEF in this paper is superficial and macroscopic. Facing the needs of high-quality development of TYR, there are still some shortcomings in this paper. (a) The analysis of temporal and spatial evolution of the subsystems is inadequate. Considering the research focus, this paper selects only one representative element for each subsystem in the practical application. It can be systematically studied in further research. (b) Whether the indicator system can entirely represent the relationship of WEF needs to be further explored. This is a problem that all of the indicator systems need to face, and the representativeness of the indicator system for different regions or countries needs to be analyzed according to the actual national context. (c) Lack of consideration of inter-provincial transfer of resources, which should be deepened in future studies. (d) There are some shortcomings in the schemes setting and these schemes only provide some guidance. There is a lack of specific schemes.

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

**Funding:** This research was funded by the National Key Research and Development Program of China (No. 2021YFC3200201) and the Major Science and Technology Projects for Public Welfare of Henan Province (No. 201300311500).

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

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** The authors are grateful to the editors and the anonymous reviewers for their insightful comments and suggestions.

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

#### **References**

1. Yu, L.; Xiao, Y.; Zeng, X.; Li, Y.; Fan, Y. Planning water-energy-food nexus system management under multi-level and uncertainty. *J. Clean. Prod.* **2020**, *251*, 119658. [CrossRef]

