Spatial-temporal evolution characteristics of water quality in Haihe River Basin

Recent developments in society and economy have been accompanied by adverse changes in water resources in Haihe River Basin, with increasingly serious water pollution. Water quality monitoring data at 7 automatic monitoring sections in Haihe River Basin from 2004 to 2016 were therefore analyze for overall temporal and spatial variations. Environmental factors (pH, DO, COD_Mn and NH₃-N) were analyzed by Mann-Kendall non-parametric test, change trend and abrupt points were obtained. Scatter plot was used to intuitively determine variation law of each factor for the Tianjin Sanchakou section during the year. Mean and standard deviation of pH, DO, COD_Mn, NH₃-N at each section were calculated and spatial distribution of water quality was then analyzed and compared. Water quality in Haihe River Basin was found to show a trend of improvement from 2004 to 2016, sudden changes were observed in 2006 to 2007, largely due to very little precipitation. Spatial analysis revealed best water quality at Gangnan Reservoir, worst at Chenggou Bay in Liaocheng. Water quality at tributary has been found to be generally better than at main stream, upstream better than downstream.