Fig 1.
Geological map of the Yangtze River basin and studying stations.
Table 1.
Location and description of 17 environmental monitoring stations.
Fig 2.
Changes of number of different grades of river water based on 17 stations in the Yangtze River basin from 2004 to 2015.
The dashed lines are the trend lines for each Grade.
Fig 3.
Weekly probability distribution functions for regional mean concentrations in the Yangtze River basin, between 2004 and 2015 for the three time periods: 2004–2007 (black curve), 2008–2011 (green curve), and 2012–2015 (red curve).
(a) pH, (b) CODMn (mg/L), (c) NH3-N (mg/L), and (d) DO (mg/L).
Table 2.
Univariate statistics of the water quality parameters.
Fig 4.
Spatial distribution of seasonal Mann-Kendall trends (the value of Z) at 17 stations in the Yangtze River basin, between 2004 and 2015.
(a) pH, (b) CODMn (mg/L), (c) NH3-N (mg/L), and (d) DO (mg/L).
Table 3.
Seasonal trends (the value of Z) of stations with positive or negative trends for water quality parameters in the Yangtze River basin during 2004–2015.
Fig 5.
Mann-Kendall trends (the value of Z) for 52 weekly water qualityat 17 stations in the Yangtze River basin, between 2004 and 2015.
(a) pH, (b) CODMn (mg/L), (c) NH3-N (mg/L), and (d) DO (mg/L).
Fig 6.
Comparison of the long-term trend of pH, DO, CODMn, NH4-N at environmental stations 7 (left) and 13 (right). The last two sub-graphs are for trends of river discharges at Yichang and Hukou respectively. The coefficients of determination (R2) between the weekly data and the DHR model are given in each panel.
Table 4.
Seasonality analysis: The results of the DHR seasonal cycle extracted from the weekly time series (see the main text for more detail on how the seasonality analysis was carried out).
Fig 7.
Spatial distributions of mean concentrationsat 17 stations, with GDP of 2010 (Chinese yuan /km2), population of 2010 (person/km2), mean precipitation between 2001 and 2010 (mm), and land use of 2010.
(a) pH, (b) CODMn (mg/L), (c) NH3-N (mg/L), and (d) DO (mg/L).
Fig 8.
Main pollutant emission in industrial waste water in main cities from 2005 to 2013.