The Hai River previously called Bai He (Chinese: 白河; pinyin: Bái Hé; literally "white river"; Pei Ho in Western sources), is a river in China which flows through Beijing and Tianjin into the Bohai Gulf of the Yellow Sea.
The He River is formed at Tianjin by five rivers, the Southern Canal, Ziya River, Daqing River, Yongding River, and the Northern Canal. The southern and northern canals are parts of the Grand Canal. The Southern Canal is joined by Wei River at Linqing. The Northern Canal joins with the Bai He (or Chaobai River) at Tongzhou. The Northern Canal (sharing channel with Bai He) is also the only waterway from the sea to Beijing. Therefore, the early westerns also called the Hai He as Bai He.
At Tianjin, through the Grand Canal, the Hai connects with the Yellow and Yangtze rivers. The construction of the Grand Canal greatly altered the rivers of the Hai He basin. Previously, the Wei, Ziya Yongding and Bai Rivers flowed separately to the sea. The Grand Canal cut through the lower reaches of these rivers and fused them into one outlet to the sea, in the form of the current Hai He.
Hai He is 1,329 km long from the longest tributary. However, from Tianjin to its mouth, Hai He is only around 70km. Its basin has an area of approximately 319,000 km² (123,000 square miles). Its annual flow is only half that of the Yellow River or one-thirtieth that of the Yangtze River.
Like the Yellow River, the Hai is exceedingly muddy because of the powdery soil through which it flows. The silt carried by the water deposites in the lower reach, sometimes causing water to overflow. The floods from the five major triburaries only has one shallow outlet to the sea, which makes the flood even stronger. Because China's capital and the second largest city Beijing, the third largest city Tianjin are both located in the Hai He Basin, Hai He flood will cause a significant loss. To allevate flooding, reservoirs are built and artificial channels dug to divert floods directly into the sea. For example, the Chaobai river is diverted to the Chaobai Xin river ('Xin' means new) and is no longer joined with the Northern Canal.
In recent years, due to the industial and urban development in the Hai He basin, the volume of flow is greatly decreased. Many smaller triburary and some of the major triburaries dries out for the most of time during a year. The less water flow further worsens water pollution. The water shortage in the Hai He basin is expected to be solved by the South-North Water Transfer Project.