## 5 Conclusions  
This study was based on the improved SWAT model and comprehensive EQ assessment model. It analyzed the spatial and temporal distribution and evolutionary characteristics of the URB's hydrological process factors and EQ and identified their synergy relationships and their internal and external change-driving mechanisms. The main conclusions of this study are as follows:  
1. Besides snowmelt, the URB's hydrological process factors, such as precipitation, ET, surface runoff, lateral flow, and groundwater recharge, are all on the rise; the change rate of the downstream hydrological process factors is higher than that of the upstream factors. 2. During 2001-2019, the URB's EPI, ESI, and EBCI showed an increasing trend. The EPI and EBCI were higher in the upstream and southern part of the downstream, whereas the ESI of the downstream is higher than that of the upstream. The multi-year average value of the URB's EQ was 53.66, which is a medium level. The overall EQ trend improved, accounting for 95.14% of the total basin area, of which, of these, 19.75% were dominated by significant increases, mainly in the upstream and northern part of the downstream. 3. The synergistic relationship between the hydrological process factors and EQ is strong. The degree of synergy between the URB's EQ and the hydrological process factors was higher than 0.7 during the study period. Moreover, this relationship showed obvious spatial heterogeneity, with a decreasing distribution pattern from upstream to downstream areas. The URB's EQ improved with an increase in precipitation, surface runoff, lateral flow, and groundwater recharge. Furthermore, the ecological protection measures proposed by the government have accelerated the improvement of the ecosystem, which plays an important role in promoting soil and water conservation  
Figure 13: Land-use/cover net change in the URB in different periods: (**a**) 2000–2005, (**b**) 2005–2010, (**c**) 2010–2015, and (**d**) 2015–2020. and EQ. Local governments should continue to strengthen the implementation of ecosystem protection strategies. Overall, this study focused on the whole hydrological cycle process and evaluated EQ in an integrated way, with three aspects, i.e., EPI, ESI, and EBCI. On this basis, we analyzed the synergistic evolutionary relationship between hydrological processes and EQ in arid and semi-arid regions. This study contributes to theoretical support for understanding the synergistic relationship between ecological changes and hydrological processes in arid and semi-arid regions and provides new ideas for related studies. In this study, the external drivers of hydrologic processes and EQ were not discussed comprehensively. Therefore, the quantitative effects of industrial and mining exploitation, agricultural irrigation, and extreme weather on the relationship between hydrological processes and ecosystem quality should be considered in future studies. Conceptualization, methodology, and writing--original draft preparation, H.C.; conceptualization, supervision, inspection, review, and editing, F.M., C.S. and M.L. ; investigation and validation, H.Z., S.B. and G.L. ; investigation, Y.B. All authors have read and agreed to the published version of the manuscript. This work was jointly supported by the National Natural Science Foundation of China (Nos. 42261079, 42101030, 41861014 and 41961058), Natural Science Foundation of Inner Mongolia Autonomous Region (Nos. 2022 MS04004, 2020B803042 and 2020B804009), Key research, development and achievement transformation project of Inner Mongolia Autonomous Region (No. 2022 YFDZ0061), Development Plan for Young Scientific and Technological Talents in Higher Education Institutions of Inner Mongolia Autonomous Region (Nos. NJYT23019 and NJYT22027), Fundamental Research Funds for the Inner Mongolia Normal University (Nos. 2022 JBQN093 and 2022 JBJB014). Not applicable. The authors would like to thank the editors and anonymous reviewers for their valuable comments and suggestions, which improved the quality of the manuscript.