Abstract: The approach to managing the Yongding River and lakes in the Jingnan plain in Kangxi and Yongzheng periods stressed allowing the river to carry silt.However, during the Qianlong reign, the approach was changed to regulate the runoff, such as pumping water out of the river embankment by artifi cial measures, in order to maintain the river and lake wetlands. The methods applied in Qianlong reign made the river water fl ow freely, so that the silt carried by the river could deposit in the fl oodplain outside the embankments. These changes in river management obtained good results because it prevented the river-borne silt from blocking the lake in the river way and thereby prevented fl oods that could destroy the people's villages. The change of the theory and practice of managing the Yongding River suggested an increasingly serious confl ict between humans and water resources. Over time human activity made the management of Yongding River more difficult.