Calculation and discussion of non- point source pollution loads in Danjiangkou Reservoir Area

Correctly estimating the non- point source pollution loads in Danjiangkou Reservoir Area is important to the environmental protection of the water source area. The Digital Filter method is used to separate the base flows of Hanjiang River,Tianhe River,Duhe River,Danjiang River,Laoguan River and Qihe River in the reservoir basin according to the daily discharge data. Based on the daily flow,the base flow and monthly typical pollutant concentration in 2013,a flux model is set up to calculate the background pollution loads,point- source pollution loads and non- point source pollution loads respectively. The calculation results show that in 2013,the inflow discharge of the 6 rivers accounted for 95. 9% of the total inflow,and the total pollution loads of CODMnand TP from the 6 rivers are 58. 2 thousand t and 1. 86 thousand t,while the non- point source pollution loads are 39. 82 thousand t and 1. 544 thousand t,so the non- point source pollution is the decisive factor; Hanjiang River is the largest pollutants contributor to Danjiangkou Reservoir and followed by Duhe River; the non- point source pollution enters into the river channel with rainfall,so the pollution load concentrates in the flood season,CODMnand TP accounted for 80. 8% and90. 9% of the total pollutants in the reservoir in flood season of 2013.