Yongding River flows into Bohai Sea. Yongding River, known as flood control, flood control, Sanggan River, Lugou River, Hunhe River and Wuding River in ancient times, is one of the seven major water systems in Haihe River Basin. The upper reaches of Yongding River flows through the Loess Plateau, and the river has a large sediment concentration, so it is called "Little Yellow River" and "Hunhe River". The lower reaches of the river form an overground river due to sediment deposition, and its migration is uncertain, so it used to be called "Wuding River".

Yongding River flows through Inner Mongolia, Shanxi and Hebei provinces, Beijing and Tianjin, and 43 counties and cities, and joins the North Canal at Qujiadian. Part of the flood flows from the North Canal into the Haihe River, and most of the flood flows into the Bohai Sea through Yongding New River in Beitang Town, Tianjin Binhai New Area.

The average natural runoff in Yongding River mountainous area for many years is 2.08 billion cubic meters, including 65.438+0.97 billion cubic meters above Guanting. Runoff distribution is extremely uneven during the year, and runoff accounts for 30 ~ 60% of the whole year in general flood season.

Historically, Yongding River is the most seriously flooded river in Haihe River system. During the 834 years from the Jin Dynasty to the founding of the People's Republic of China, the Yongding River burst 8 1 time and changed its course 9 times. During the more than 250 years since dykes were built in the lower reaches of the Qing Dynasty, the crevasse overflowed 78 times, with an average flood in less than 4 years.