Research on water quality characteristics and variation of mainstream of Yangtze River before and after impoundment of Three Gorges Reservoir

In order to analyze the variation trend of water quality in the mainstream of Yangtze River before and after impoundment of Three Gorges Reservoir,5 representative sections were selected and the water quality conditions were analyzed and the monitoring data of 2010 and the historical data from 1998 to 2009 were compared.The research results show that the water quality of the mainstream is good at present,annual water quality in III classification;mainly in III classification before impoundment and mainly in II~III classification after impoundment;from upstream to downstream,the water quality gradually improved.The indexes such as TP,CODMn,lead are the main factors influencing water quality and their concentration decrease more than that before impoundment,and the excessive water pollution is mitigated.