Water quality variation and its causes in six drinking water source regions in Nanjing reach of Yangtze River

The variation tendency of the water quality in the drinking water source regions of six waterworks in the Nanjing reach of the Yangtze River was evaluated in this study.The causes of pollution in the drinking water source regions with poor quality of water were analyzed.The results show the following:(1) The water function zone where the water intake of Shangyuanmen waterworks is located has the worst water quality,followed by the water source regions of the Yuangu and Pukou waterworks.The water quality in the water source regions of the Pukou,Shangyuanmen,Chengbei,and Yuangu waterworks has seriously deteriorated since 2008.(2) The causes for the deterioration of water quality in the drinking water source regions mainly include the construction of drainage pumping stations,industrial sewage discharge,and the standard-exceeding discharge from the wastewater treatment plants.(3) Total phosphorus is one of the main factors causing pollution of the drinking water sources,and it has had an increasingly significant influence on the water quality.