Fig. 1. Distribution map of key lakes and reservoirs in the study area

Fig. 2. The processing workflow for lake and reservoir water level data

Fig. 3. The reservoir capacity curve based on the water level-area relationship of key lakes and reservoirs

Fig. 4. Comparison of differences in water surface area extracted from Landsat 8 and Sentinel-1 images with that extracted from Sentinel-2 images

Fig. 5. Time series of CryoSat-2 and multi-source altimetry data for four large lakes （2013~2022）

Fig. 6. Scatter plot of water levels obtained from DAHITI and Hydroweb compared to the water levels derived from CryoSat-2 data

Fig. 7. Changes in total water volume of key lakes and reservoirs from 2013 to 2022

Fig. 8. Distribution map of average eutrophication levels in key lakes and reservoirs from 2013 to 2022

Fig. 9. Changes in the number of key lakes at different eutrophication levels from 2013 to 2022

Fig. 10. Changes in the number of key reservoirs at different eutrophication levels from 2013 to 2022

Fig. 11. Types of changes in eutrophication levels in lakes

Fig. 12. Types of changes in eutrophication levels in reservoirs

Fig. 13. Time series of water volume changes in lakes under different eutrophication levels from 2013 to 2022

Fig. 14. Time series of water volume changes in reservoirs under different eutrophication levels from 2013 to 2022

Fig. 15. Monthly time series of water volume and water quality for key lakes and reservoirs

Fig. 16. Relationship between water volume changes and water quality changes in Baiyangdian

Fig. 17. Relationship between water volume changes and water quality changes in Jiefangcun Reservoir