The Forbidden City has two independent drainage systems. In recent years, plastic bags are often cleared from underground ditches.

　　Recently, Beijing ushered in heavy rainfall, and the Forbidden City reappeared "Jiulong Spitting Water". The Beijing News reporter saw in the Palace Museum today (July 31) that the grand Palace Museum complex was safe and sound in the rainstorm with the exquisite drainage system.

　　The rainwater drainage system of the Forbidden City was built in the Ming Dynasty, and the length of ancient rainwater ditches preserved to this day is more than 15 kilometers, of which the length of underground ditches is nearly 13 kilometers. All the drainage ditches in the Forbidden City lead to the Neijinshui River, which is connected with the moat 52 meters wide outside the Forbidden City wall, and is also connected with the surrounding Waijinshui River, Zhongnanhai and other water systems.

　　On July 31, rainwater flowed down the drainage system of the Wumen Tower of the Forbidden City. Beijing News reporter Li Muyi photo

　　After heavy rainfall, there was short-term water accumulation, and mineral water bottles and plastic bags were cleared out of the underground ditch.

　　On July 22, a sudden heavy rainfall caused short-term water accumulation in some areas of the Forbidden City, which became the focus of public attention.

　　Di Yajing, director of the World Heritage Monitoring Department of the Palace Museum, said that the precipitation on July 22 was the first heavy precipitation encountered by the Palace Museum since the summer of this year. The 24-hour precipitation reached 93.5 mm, which was close to the level of heavy rain, and the maximum hourly rainfall intensity reached 50.4 mm at 8 o'clock, reaching the level of heavy rain. "We launched the highest-level emergency plan at the first time, conducted carpet inspections and investigations in all areas of the hospital, and found hidden dangers to be disposed of at the first time."

　　"After the inspection, there was a serious water accumulation in the open area, which was located on the west side of the courtyard of Cining Palace. Due to the strong rain, the water accumulation reached 17 cm in a short time. The staff of the Forbidden City quickly discharged the water after the rain through artificial drainage and other measures; There are 8 mild water accumulations with a maximum water depth of 6 cm, which are completely discharged within half an hour after the rain. " Di Yajing said.

　　Through the repeated investigation of the stagnant water area, the staff of the Forbidden City observed that the drainage capacity on the west side of Cining Palace was significantly lower than in previous years, and then conducted a comprehensive inspection, and dug up the junction point between the branch ditch and the culvert in the back wall of the enclosure, and cleaned up a lot of silt, mineral water bottles, plastic bags and other sundries from the culvert. Through the on-site analysis, the staff initially judged that because of the short-term heavy rain, the ridge dust washed off the roof, and rushed into the drainage ditch together with a small number of mineral water bottles, plastic bags and other debris discarded by the audience, blocking the drainage outlet.

　　"At present, we have completed the cleaning of the culvert, restored the drainage capacity of the courtyard, and repaired the branch ditch structure." Di Yajing said, "According to the records and experience, we have also summarized the areas and buildings that are prone to water accumulation and rain leakage in the Forbidden City, and strengthened its inspection and maintenance. For example, Cining Palace is an area that we pay more attention to, because its drainage ditch is connected with the branch ditch outside the courtyard through the house with a large depth, and it is very difficult to clean it. Therefore, we will go to the site for inspection in almost every rain and after rain, and no obvious water accumulation has been found. Generally, the water in the courtyard can be discharged within 30 minutes after heavy rain. "

　　On July 31, the open ditch drain on the west side of Cining Palace. Beijing News reporter Li Muyi photo

　　In recent years, when maintaining the drainage system, plastic bags and clothes have been found.

　　"The rainwater drainage of the Forbidden City still uses the ancient rainwater system of the Forbidden City and is naturally discharged to Jinshui Hanoi. Everyone said that there would be no water in the Forbidden City in 600 years. In fact, it is more accurate to say that even if there is water in the Forbidden City, it can be drained quickly. To achieve this effect, on the one hand, it relies on the good ancient rainwater system of the Forbidden City, on the other hand, the post-cleaning and maintenance work is also an indispensable link in flood control. " Yu Xiang, deputy director of the administrative department of the Palace Museum, said.

　　Yu Xiang introduced that in the early flood season, from May to June every year, the staff will carry out daily cleaning of the municipal sewage of ancient rainwater in the hospital and make preparations for flood control; In the middle of the flood season, from July to August, in addition to the daily cleaning work, the Forbidden City also has a flood control and rescue team of ten people to clean up the water accumulation area in the courtyard at any time; From September to October in the late flood season, the staff will clean up the ancient rainwater and municipal sewage after the rain, sum up the problems in the flood season, and repair the hidden dangers together with the ancient construction department and the repair department.

　　When the Forbidden City was built, a complicated and perfect drainage system was designed, and strict regulations were made for the repair and maintenance of the drainage system in the Ming and Qing Dynasties. "However, in the design, construction, repair and maintenance of the drainage system in the Forbidden City, the conventional silt such as ridge ash and dead leaves on the roof are mainly considered. For these pollutants, the drainage network can be basically kept smooth through rainwater scouring and daily cleaning." Yu Xiang said that in recent years, during daily maintenance, staff found a large number of sundries such as plastic bags, mineral water bottles, papers, and even towels and clothes in the drainage system. These products of modern industry can't be washed away by rain like mud, but they are very easy to block in narrow and difficult-to-find and clean parts such as the corner of drainage culvert and the joint between branch culvert and culvert. Once several points are blocked, some drainage facilities may often work poorly.

　　On July 31, the continuous rainfall in Beijing made the Forbidden City once again present the spectacular scene of "Jiulong Spitting Water". Beijing News reporter Li Muyi photo

　　The Forbidden City has two independent drainage systems.

　　Among natural disasters, flood has always been the key risk that ancient buildings need to deal with, and flood is also one of the most frequent and serious natural disasters in Beijing.

　　Since ancient times, cities and ancient buildings in Beijing have designed flood control and drainage systems, and the Forbidden City is no exception. Di Yajing introduced that at present, the Forbidden City has two sets of drainage systems that are independent of each other. Among them, the municipal sewage system of the Forbidden City was built in the 1950 s to ensure the toilet problem after the Forbidden City was opened to the audience, and it was built after professional planning and design and examination and approval by higher-level units; The rainwater drainage is still discharged to Jinshui Hanoi by using the ancient rainwater system.

　　Rainwater drainage in the Forbidden City is a complex system. Courtyard is generally high in the middle and low in the side, high in the north and low in the south. The water in the courtyard is led into the culvert through money holes or discharged into the open ditches on both sides of the courtyard. When the open ditches meet the abutment and buildings, stone coupon holes are opened from below, so that water flows through, and the open ditches and the open ditches communicate with the palaces and courtyards, and finally the water is led into the Jinshui River and merged into the urban rivers.

　　These ditch systems were built in the Ming Dynasty, and the scale of the project exceeded the Jinshui River on the ground. It was stipulated in the Ming and Qing dynasties that the ditches in the palace should be cleaned on time every year. For example, in the Qing dynasty, this work was mostly carried out in March every year. The continuous dredging and maintenance of the past dynasties can keep it basically unblocked for 600 years.

　　The First Historical Archives of China has a collection of "Playing for Sending Personnel to Dredge the River Blockage in the Forbidden City (Qing Dynasty)". Photo courtesy of the Palace Museum

　　Di Yajing introduced that as the most complete preserved ancient wooden palace complex in the world, after the establishment of the Forbidden City, the flood control work has always been the top priority of the Forbidden City's architectural protection and cultural relics protection, and a flood control working group has been set up to prevent floods. In the daily management, not only the information system of infrastructure pipe network including drainage system is established, but also the yard patrol is conducted in time to record the drainage blocking points after the rain, and the drainage ditch inspection, scouring and cleaning are carried out in spring, summer and autumn every year.

　　Fang Xiaomei, director of the Open Management Office of the Palace Museum, said that the Palace Museum will prepare all kinds of flood control materials in advance. When the door is closed in the evening, the staff will issue disposable raincoats to the audience who don't have rain gear and help them leave. According to the Emergency Plan for the Opening of Meteorological Disasters in the Palace Museum, after receiving the notice from relevant departments, the Hall of Supreme Harmony, the Hall of Zhonghe, the Hall of Baohe, the Palace of Ganqing, the Hall of Jiaotai, the Hall of the Emperor, the Hall of Xianruo, the front and rear halls of Shoukang Palace and the east annex of the front hall will be closed.

　　Beijing News reporter Guo Wei

　　Editor Fan Yijing proofreads Liu Yue.