Dynamic Analysis of the Water Quality of the Rivers around Nansi Lake

This paper chooses 23 monitoring sections of 23 rivers flowing into Nansi Lake or the water diversion route of Nansi Lake,analyzes the variation trends of water quality of the rivers from the aspects of annual variation,intra-annual variation and different years based on the monitoring data from 2000 to 2010,and screens out the rivers of the worst water quality and the best water quality in the years of 2000 and 2010 respectively.The results show that from 2000 to 2010 annual averages of CODCr and NH3-H presented a mainly downward trend,five-year moving average presented a downward trend,the reduction ratios of CODCr and NH3-H reached 74.4% and 93.1% in 2010 compared with those in 2000,the water quality of 73.9% monitoring sections had been improved from 2005 to 2010 and the overall water quality of the rivers had been greatly improved;however,the average CODCr had not reached the water quality Ⅲ standards and the worst water quality rivers were mainly located in the industrial and urban areas.The results also show that the water quality of the monitoring sections presented a certain intra-annual variation because of the impacts of hydrology,non-point source pollution and point source pollution.