Abstract: Xuliujing is located on the south side of the Changjiang River and in Changshu of Jiangsu Procince. The section of the river at Xuliujing is considered to be the starting point of the estuary of the Changjiang River. To explore laws and main causes of the changes in water pollution at the Xuliujing Section, analysis was done of data on flows available for trends of the variations of flow rate and water quality of the Changjiang River at the Xuliujing Section during the period from 1997 to 2011. The Changjiang River is in the flood season from May to Sseptember , and turns into the non-flood season from October to April of the following year . The average flow rate of the fourteen years was 27927±4699m³•s^-1, with the highest occurring in 1998 and the lowest in 2011. The flow rate at the Xuliujing Section was significantly higher (1.73-2.95 fold) in the flood season than in the non-flood season. By contrast,annual average index (COD_Mn) decreased and was positively related to flow rate. The annual average biological oxygen demand (BOD₅) showed a trend of decreasing from 1997 to 2011 and being higher in the non-flood season than in the flood season. In most years between 1997 and 2011, the concentration of ammonia nitrogen (NH₃-N) was higher in the non-flood season than in the flood season and was the lowest in 1998 and the highest in 2002. The variation of the concentration of total phosphorus (TP) was similar to that of NH₃-N during 1997-2011. The major pollution factors exceeding the standard limits were nitrogen and phosphorus.

Key words: flow rate, water quality, Xuliujing, Changjiang River