The River That Made the City a Port

The Hai River's main channel is short and its measurement is disputed, which is itself informative. It runs from the Zibei confluence, or Sanchahekou, to the Dagu mouth, and the sources give its length as 76, 72 or 73 kilometres depending on the authority; the city's own account uses 73 kilometres from Sanchahekou to the Bohai and calls the river the mother of Tianjin. A river whose length cannot be agreed is a river that has been repeatedly engineered. What is not disputed is its function: it takes the water of five upstream rivers and more than three hundred smaller streams and delivers them to the sea at one point, and a city built at that point controls the traffic.

The basin is the reason the channel matters so much. The Hai system covers 318,000 square kilometres and stretches across seven provinces, autonomous regions and municipalities: Beijing, Tianjin, Hebei, Shanxi, Henan, Shandong and Inner Mongolia. Five large rivers, the North Canal, the Yongding, the Daqing, the Ziya and the South Canal, gather into the single channel that reaches the sea inside Tianjin. That geometry produces both the city's advantage and its danger: all the water of a vast region passes one point, so the same channel carries the grain fleet in a dry year and floods the streets in a wet one. In the 1939 flood the low-lying parts of central Heping District stood under nearly two metres of water.

The river is older than its name. Haihe first appears in 1613, in farm rules written by the scholar Xu Guangqi, which means that for most of the city's history the water was called something else: the sources record that in the Song it was treated as the lower Jie River, in the Jin and Yuan as the Zhigu and Dagu rivers. The name changed when the understanding of the river changed, from a reach of a border waterway to a system with its own identity. A basin-wide water board, the Hai River Engineering Bureau, carried out the Tianjin embankment, the river cut-offs and channel dredging, which is how a natural channel became a managed one.