Introduction to the reservoir dam: 45 meters high, it stores water from the Yongding River in the Huailai Basin formed by the alluvial waters of Sanggan River, Yanghe River and Guishui above the dam. It covers an area of ​​230 square kilometers and controls 97% of the Yongding River basin. The area's runoff has a storage capacity of 2.27 billion cubic meters (the storage capacity has been reduced year by year due to sedimentation in recent years). In addition to relieving the threat of flooding in Ping and Tianjin areas, the reservoir dam also supplies urban water in Beijing and provides irrigation for more than 20,000 hectares of farmland in the southeastern suburbs of Beijing.