Spatial-Temporal Variations of the Water Quality and the Pollutants Sources in the Yangtze River (Hubei Province)

The water quality in the Yangtze River in Hubei Province (YRHP) is deteriorating, but little attention has been paid to the water pollution of YRHP. This paper aimed to analyze the water quality and the pollutants sources of YRHP. The results showed that: (1) Total nitrogen (TN) was found to be the primary pollution parameter. The concentrations of TN and total phosphorus (TP) were higher in non-flood seasons than in flood seasons; (2) The water pollution index (WPI) ranged from 52.93 to 107.58 with an average of 83.04 ± 20.87, corresponding to the water quality of Grade V. The WPI values were found to be higher during non-flood seasons than during flood seasons. The relatively high WPI values were mainly concentrated in areas with Wuhan City as the core; (3) In areas where the pollutants loads were consistent with WPI, agricultural pollution was identified as the primary source of pollutants. In areas with low pollutants loads but high WPI, the poor water quality in mainstream was affected by the poor water quality in tributaries. In areas with high pollutants loads but low WPI, the relatively good water quality was related to the high percentage of woodland or the large afforestation area.