SPATIOTEMPORAL DISTRIBUTIONS OF WATER QUALITY OF DRAINAGE DITCHES AND ITS POLLUTION SOURCE ANALYSIS FROM 2014 TO 2019 IN QINGTONGXIA IRRIGATION DISTRICT
To understand the spatiotemporal variation characteristics of water quality of the main drainage ditches in the Qingtongxia Irrigation district in the middle and upper reaches of the Yellow River,and reveal the pollution sources and spatial distribution of typical pollutants.The spatiotemporal distributions of total phosphorus(TP),ammonia nitrogen(NH3-N),chemical oxygen demand(COD)and permanganate index(CODMn)concentrations in the 12 main drainage ditch of irrigation district from 2014 to 2019 were explored.The pollution sources and its spatial distribution in the region of drainage ditches were revealed by the output coefficient method.The results were showed as follows.(1)The overall water quality of the drainage ditches in the irrigation district was the surface water quality grade Ⅳ standard and some even worse than the grade Ⅴ during study period.The concentrations of ammonia nitrogen and total phosphorus exceeded the standard seriously.The concentration of pollutants in the non-irrigation period was significantly higher than the irrigation period.(2)On the spatial scale,the water quality of drainage ditch along the direction of the Yellow River first decreased,then increased and then decreased.The water quality of Yinxin ditch,Zhong ditch and Yonger ditch near Yingu Bridge was worse than the grade Ⅴ standard.(3)On the source of pollutants,the total phosphorus load into the river in the study area mainly came from non-point source pollution(86.7%)and concentrated in Qingtongxia,Helan county and Pingluo county,while the ammonia nitrogen load mainly came from point source pollution(66.8%).COD load into the river was concentrated in Yinchuan city and Litong district and from point source and non-point source accounting for 48.1%and 51.9%,respectively.Therefore,the study area should focus on Yinxin ditch,Zhong ditch and Yonger ditch in drainage ditch control.Strictly controlling of point source discharge in winter is the key to improving the water quality of main ditches in irrigation areas.Qingtongxia,Helan and Pingluo cities are given priority in the planting source pollution prevention and control,while Litong district is given priority in the livestock and poultry breeding source pollution prevention and control.Yinchuan city is given priority in the urban living source pollution prevention and control.
water qualityexport coefficient methodspatiotemporal distributionpollution source analysisQing-tongxia irrigation district
NETL
NSTL
万方数据
