The second phase of the Daxing Airport flood detention basin, situated along the Yongxing River in southern Beijing, is nearing the completion of its project acceptance procedures. Positioned across the river from the already operational first phase, these two basins will transform into a massive "storage reservoir" during the flood season, safeguarding the adjacent Daxing International Airport, protecting nearby villages, and alleviating pressure on the upstream and downstream river channels.

According to the Beijing Water Authority, following the "23·7" catastrophic flooding in the Haihe River basin, Beijing has constructed and improved eight flood detention and storage areas, adding approximately 35 million cubic meters of new storage capacity. This enhancement significantly strengthens flood defense capabilities for the Yongding River and North Canal basins.

Two Basins, North and South, Protect the Airport and Surrounding Areas

The Daxing Airport flood detention basin is located on the northwest side of the airport. On a map, the Yongxing River stretches like a 30.8-kilometer ribbon, channeling runoff from Daxing New Town, Panggezhuang, and the airport economic zone downstream to the southeast past the airport's northern edge, eventually emptying into the Yongding River in Hebei Province. Consequently, the basin acts as a critical shield for the airport, intercepting floodwaters and ensuring the safety of the airport and its neighboring communities.

Wang Xuepeng, deputy director of the Niantan Water Affairs Office under the Daxing District Water Authority, explained that the detention basin is divided into two phases. Phase one is situated on the southern bank of the Yongxing River, while phase two, located on the northern bank, consists of a southern and a northern section connected by an underground culvert. Phase one was completed in December 2020 with a storage capacity of 3.3 million cubic meters. Phase two, which began construction in 2024 and finished in 2025, is scheduled to pass its engineering acceptance soon. This new phase adds a total storage volume of 2.9 million cubic meters, with the southern section holding 550,000 cubic meters and the northern section 2.35 million cubic meters. Combined, the two phases offer a total flood storage space of 6.2 million cubic meters, equivalent to the capacity of three Kunming Lakes.

"The Donglianggezhuang sluice gate is a critical control point in the entire system, and the discharge flow must not exceed 110 cubic meters per second," Wang noted. If upstream inflows surge and the flow at this gate surpasses this threshold, the detention basin will be activated. "In the event of extreme rainfall and significant upstream inflows, phase one will be filled first. If its capacity is insufficient, the phase two flood diversion gates will be opened."

The southern and northern sections of phase two operate via gravity flow. Floodwaters enter the southern section through a three-bay diversion gate, and as the water level rises, they automatically flow through the northern connecting culvert into the larger northern section, requiring no manual gate operation. Once the rain subsides and river flow stabilizes, the drainage gates are opened to release the stored floodwater back into the Yongxing River.

Phase One Played a Crucial Role During a Real Flood Event

Both phases of the Daxing Airport flood detention basin resemble green, landscaped ecological parks. In the distance, wild ducks flutter up from the reeds, while overhead, planes taking off from Daxing Airport streak across the sky. During construction, existing trees like Chinese pines and ginkgoes were carefully relocated to protect them. Now that work is complete, these plants have been returned to their original home, and new saplings have been added, creating the current forested embankment landscape.

To ensure the airport's normal operations, the detention basin cannot hold permanent water, which would attract waterfowl and pose a risk to flight safety. Therefore, it must be kept empty before the flood season each year. Although phase two has yet to be officially used, phase one has already been tested in real conditions. Wang recounted that during the "23·7" catastrophic flood, upstream floodwaters surged into the Yongxing River, and the phase one gates were opened to store water, reaching a maximum depth of 23 meters and successfully containing the flood.

Now, as phase two is about to pass its acceptance, the two phases will work in tandem to manage floodwaters. Specifically, when the phase one diversion gates are fully open and the water level at the Donglianggezhuang gate continues to rise, the phase two diversion gates will be opened to keep the water level at Donglianggezhuang from increasing. When phase one reaches its maximum storage level of 24 meters, its gates will be closed, and the phase two gates will be progressively fully opened to maintain the river level. This coordinated operation ensures the Yongxing River's flood conveyance capacity remains unobstructed, guaranteeing a safe flood season.

Enhanced Flood Defense for the Yongding River and North Canal Basins

Flood detention basins are a vital component of major river flood control systems, working alongside reservoirs, river channels, and embankments to manage floodwaters. They are often referred to as the "trump card" of basin flood control. Their primary function is to temporarily receive and store excessive floodwaters from extreme storms, diverting surplus flow, reducing peak discharge, and minimizing overall flood damage.

According to the Beijing Water Authority, in the wake of the "23·7" flood, Beijing has built or upgraded eight such basins. These include the Daxing International Airport flood detention project phase two, the Mentougou Liushui LianTong detention project, the Baoyangcheng detention basin, the Nankou and Shagouhe detention basin, the Wenyu River Park Shunyi phase two detention project, the Bahekou detention basin construction project, and the Xiyuhe detention basin project. Together, they add approximately 35 million cubic meters of storage, significantly boosting the flood defense capacity of the Yongding River and North Canal basins.