The Huaihe River, the sixth largest river in China, flows from west to east, with the Yellow River in the north and the Yangtze River in the south. It is 700 kilometers in length and 400 kilometers in width, covering 270,000 square kilometers, of which the Huaihe water system covers 190,000 kilometers, and the water system of the Si, Jin and Shu rivers cover 80,000 kilometers.

Starting in the Tongbai Mountains, it has its upper reaches in Henan Province, middle reaches in Anhui Province, and lower reaches in Jiangsu Province. Its trunk is about 1,000 kilometers long and its drainage area about 270,000 square kilometers.

The Huaihe River is divided into three sections: the upper reaches flow from the source to the mouth of Honghe River between Henan and Anhui provinces, with a total length of 360 kilometers and a drainage area of 30,000 square kilometers; the middle reaches, from Honghe River to Hongze Lake, are 490 kilometers in length and 160,000 square kilometers in drainage area; and the lower reaches, 30,000 square kilometers.     

With the passage of time, the waters of the Huaihe River converged to form two large lakes, Hongze and Gaoyou, of which the Hongze Lake is the fourth largest freshwater lake in China. In its high-water season the Huaihe River flows through the Hongze and Gaoyou lakes and the Grand Canal into the Yangtze River near Yangzhou City before emptying into the sea.

Since the founding of the People's Republic of China in 1949, many reservoirs and flood-detention projects have been built in its upper and middle reaches, new courses have been laid out in its lower reaches and its outlet to the sea has been widened. In this way, the greater part of its water now flows into the Yangtze River and the rest into the Huanghai Sea through the new channels.