## 5 Conclusions  
In this study, the attributions of the evapotranspiration (ET) and gross primary production (GPP) changes including climate variables, elevated atmospheric carbon dioxide (eCO\({}_{2}\)), land-use and coverage change (LUCC) were quantified in the six catchments in the water source region of the Xiong'an New Area using the improved water-carbon coupled DTVGM ecohydrological model. The ecohydrological model could capture the ET and GPP variations reasonably in the study area. The modelling experimental scenarios show that annual ET and GPP increased significantly, particularly in the spring and summer seasons. At the annual scale, increasing precipitation dominated the ET uptrend absolutely and air temperature also contributed to the ET uptrend. The eCO\({}_{2}\) concentration and solar dimming were found to be the main causes for the ET decrease. For the GPP changes, eCO\({}_{2}\), increasing precipitation and rising temperature dominant the GPP increases. Compared to climate change, the LUCC has small effects on both ET and GPP in terms of the few changes in land coverage. At the seasonal scale, the modelling results show different effects in the four seasons. Overall, precipitation, temperature and eCO\({}_{2}\) are the main causes for ET and GPP changes. However, the decreasing humidity was found to be the dominant factor for ET increase in winter, while solar dimming imparts strong effects on ET decreases in autumn. It should also be noted that the contribution of the interactive effects cannot be neglected at the seasonal scale, particularly in terms of the considerable decreases in ET and GPP in spring, increases in ET in autumn and winter and increase in GPP in winter. This study highlights the importance of considering water-carbon coupling on the attribution of ET and GPP and the differentiation of the effects by the abovementioned influence factors at the annual and seasonal scales.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/rs14051187/s1](https://www.mdpi.com/article/10.3390/rs14051187/s1)]([https://www.mdpi.com/article/10.3390/rs14051187/s1](https://www.mdpi.com/article/10.3390/rs14051187/s1)).  
S.Z.: Formal analysis, Investigation, Methodology, Writing--original draft. H.D.: Conceptualization, Methodology, Writing--review and editing. J.X.: Conceptualization, Writing--review and editing. J.W.: Investigation, Visualization. L.Y.: Data Curation. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This study was supported by the National Natural Science Foundation of China (No.51809008), Youth Innovation Promotion Association, CAS (2021385) and the Central Guidance on Local Science and Technology Development Fund of Chongqing City (No.2021000069).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are openly available through the Resource and Environment Science and Data Center, China Meteorological Data Sharing Service System and Global Land Evaporation Amsterdam Model Datasets.  
**Acknowledgments:** We thank the anonymous reviewers for their constructive feedback.  
**Conflicts of Interest:** The authors declare no conflict of interest.