Fig. 1: Trajectories and spatial distribution of COD and DO concentration changes across China’s ten major river basins.
From: Natural and anthropogenic imprints on seasonal river water quality trends across China
Histograms showing the percentage of sub-watersheds with significant changes (p < 0.05) in COD (a) and DO (b) concentrations from 2006 to 2020. Dark gray indicates increasing concentration trends, while light gray represents decreasing trends. The red dashed line marks no change in concentration. c Quadrant chart illustrating four distinct trajectories of COD and DO concentration changes in sub-watersheds. Colored circles denote significant trends (p < 0.05), while gray circles indicate non-significant trends (p > 0.05). d Bar chart showing the number of watersheds corresponding to each of the four concentration change trajectories. e Spatial distribution of the four concentration change trajectories across China’s ten major river basins. Colored circles represent significant trends (p < 0.05), and gray circles denote non-significant trends (p > 0.05). f Distribution of river networks and monitoring stations, with green lines indicating our first-order rivers and gray dots indicating monitoring stations.
