Morning News According to the Legal Evening News, there was no water in the Forbidden City during the rainstorm in Beijing on July 2 1. Why can't this 600-year-old system building accumulate water in the torrential rain once in 6 1 year? What are the characteristics of its drainage system?
According to an ancient city building expert in Shenyang, the drainage system of the Forbidden City has two sets of systems: bright and dark. Open ditch drainage is the way of spreading the floor to discharge the flood, and then it is discharged into the surrounding rivers through various outlets and nozzles. Underground drainage is to discharge water into the river through underground drainage channels, which is the internal and external Jinshui River. According to its introduction, this is how chengde mountain resort built the drainage system. All in all, in a word, the whole system, by means of light and shade, achieves a goal: summary and discharge.
The drainage system has gone through 600 years.
According to the Records of the History of Yuan Dynasty, in the 28th year of Yuan Dynasty (129 1), July passed, "The capital was destroyed by rain, and twenty thousand troops were sent to build it", and in May of the eighth year of Zheng Zheng, 57 years later, "It rained heavily and the capital collapsed".
Then, the flood continued. According to Ming Yingzong's records, in July of the fifth year of Jingtai (1454), it rained in the capital and nine city walls collapsed. In the thirty-fifth year of Wanli (1607), in June, it rained heavily in Shuntianfu, day and night, lasting for twenty days. Rain drops into the city. Chang 'an Avenue is five feet deep, and the depression is more than ten feet deep. All government offices are immersed in huge water.
According to the above historical data, although Jiumen City Wall collapsed during the Yingzong period of the Ming Dynasty, the Forbidden City was obviously calmer than the Yuan Dynasty, and there was no "bad rain". There was heavy rain in Wanli for 20 consecutive days, and there was water in Chang 'an Avenue, but there was no large area of water in the Forbidden City.
The drainage system of the Forbidden City, which was built in the 18th year of Yongle (1420), has stood the test. What is the reason?
Three lines of defense for flood control outside the city
According to experts, from the topographical point of view, Beijing faces Yanshan in the north, Bohai in the east, high in the northwest and low in the southeast, so the water flows to the southeast. Seen from the Forbidden City, the ground level of Shenwumen in the north gate is 46.05 meters, and that of Wumen in the south gate is 44.28 meters, with a difference of about 2 meters. Its drainage facilities make full use of this topographical feature.
According to experts, the overall feature of this drainage system is that rainwater from east to west will flow into the north-south main ditch and then into the Neijinshui River.
Dredge the drainage system of palaces and courtyards, including trunk lines and branch lines, open ditches, underground ditches, culverts and running ditches. After careful measurement, planning, design and construction, excavation and maintenance are carried out at a fixed time every year. It is worth mentioning that a complete drainage system has been arranged outside the city, reducing the burden in the city.
There are at least three lines of defense outside the Forbidden City: first, the inner city moat, Daming Hao and Taiping Lake in the Ming Dynasty; The second is Xiyuan Taiye Pool and Houhai; The third is the Waijinshui River and Tongzi River (moat) of the Forbidden City. On the one hand, these canals can be used for urban water supply, on the other hand, they can also be used for drainage under flood conditions, ensuring that a large amount of rainwater and flash floods will not flow into the outer Forbidden City.
Jinshuihe main drainage channel
Neijinshui River is the inland river of the Forbidden City. On Nanhegang, east of the northwest corner of the Forbidden City, there is a stone coupon cave, which is the entrance of Neijinshui River into the palace. Equipped with a sluice, the water level can be controlled and closed in case of flood.
According to experts, Neijinshui River is the Yuquan landscape in the western suburbs. Because the western five elements belong to gold, it is named Jinshui River. "The moat water flows into the palace from the Xigou of Shenwumen, along the west to the front of Wuying Hall, under the Jinshui Bridge in front of Taihe Gate, then to the Yuange of Wenjing to Sanmen, and then flows out of the Forbidden City from the southeast of Luanjiaku."
The Neijinshui River is more than 2,000 meters long, and the riverbank and river bottom are paved with white stones. The river twists and turns, either hidden or present, and flows through the whole Forbidden City. It is not only used to beautify the environment and appreciate fish and algae, but also used as a source of building and fire water except well water in the city.
There are more than 90 courtyards in the Forbidden City, which are drained into the nearby underground ditches through the drainage channels of our courtyard, and finally all of them gather in the Neijinshui River, and then flow out to the sluice at the south corner of Donghuamen to join the Waijinshui River.
Yuluyong Tunnel and Culvert
Summarize the Neijinshui River
The Forbidden City covers an area of 72 hectares. Siheyuan are all high in the middle and low in the side, high in the north and low in the south. When it rains, it first flows into the stone trough under the foundation of the surrounding houses, that is, the open ditch. Obstacles such as steps or buildings are provided with voucher holes, that is, ditch holes, which are convenient for surface water to pass through obstacles. The water on the ground or open ditch flows into the ground through the water inlet. The water inlet is mostly carved into the shape of copper coins (big money) in the Ming and Qing Dynasties, that is, five holes are carved on the Chinese side of the outer circle, which can be filled with water, so it is called the money eye.
Take the first three halls of the Forbidden City, the Hall of Supreme Harmony, the Hall of Zhonghe and the Hall of Baohe as examples. The first three halls are built on a three-story platform with a height of 8.13m, and there are holes at the bottom of railings around the platform to discharge rainwater. There is also a beautifully carved stone faucet under each observation post, named "cicada's head", whose mouth is a round hole drilled through and is also a hole for auxiliary drainage. On rainy days, rainwater is sprayed from the 1 142 drainage hole, showing a "thousand dragons spraying water" landscape, falling layer by layer and flowing into the courtyard, so that there is no water on the countertop. There is a stone trough drain around the abutment.
There is a north-south imperial road in the front three halls and the back three palaces. East, West, Sixth Palace and other courtyards also have north-south tunnels. Imperial roads and tunnels are both high in the middle and low on both sides. With the terrain, rainwater can be discharged directly from the middle to both sides.
For example, after the Imperial Road of the Hall of Supreme Harmony is determined, in order to ensure smooth drainage, it is necessary to determine the direction of water flow and find a good slope in front of the paved ground, and collect rainwater into the open drainage ditches on the east and west sides, also known as the Lotus Leaf Ditch, and introduce it into the ditch gate in the southeast corner of the courtyard, and then flow into the Neijinshui River through the trench under the berth.
The courtyards of the East, West and Six Palaces are basically two entrances, and there are long streets between the courtyards. The tunnel divides the yard into two drainage areas, and the backyard drains into the front yard. In order to make the drainage smooth, it is necessary to determine the slope of the water flow gap between the front yard and the back yard in advance, commonly known as flooding. Rainwater flows from the ditch gates on the east and west sides of the front yard, through the open ditch, into the dark ditch of the long street, and then into the trunk line through the branch line, and meets at the Neijinshui River.
Because of pavilions, rockeries, pavilions and fish ponds, the imperial garden is the most complicated place for drainage in the Forbidden City. The specific way is to divide the imperial garden into two drains, east and west, and then subdivide several small drains. Take the lowest point of each small area as the water inlet of the culvert. Underground ditches are connected with each other, and then connected with the main ditches outside the park to form an underground drainage pipe network.
Internal and external drainage of multiple vertical and horizontal ditches
In the north wall of the Forbidden City, outside the Red Palace wall, that is, in front of the East-West Joint House, there is an east-west Dagan ditch, about 1.5m deep and about 60-70cm wide. Cover with rectangular slate. For every 20-odd stone slabs, there are 4 stone slabs with four notches cut on both sides. Together, there are 16 small holes for rainwater to leak in. The western end of the ditch is connected with the Jinshui River of the Chenghuang Temple, from which rainwater is discharged. The eastern end extends southward along the palace wall, becoming a north-south longitudinal main canal, and rainwater flows into the Jinshui reach of the Qing History Museum.
In addition, there are three ditches that directly enter the Neijinshui River from north to south. A passage in the Hibernation and Ningshou Palace of the East Sixth Palace leads to the latitude ditch of Shenwumen in the north, bypasses the Imperial Tea House in the south in the east, and flows into the Neijinshui River in the east of Wenhua Hall in the south. Among them, the branch passes through the south group room of Fengxian Hall in the west. Go through the southwest corner. From the east side of the arrow pavilion to the south, the inner gold water is injected from the west wall of Wenhua Hall.
Article 4 The North-South Ditch runs from the southwest corner of Ganqingmen Courtyard, passes through the inner right gate and enters the South Library of hall of mental cultivation, then exits Longzongmen from the South Library, turns south, and flows into Neijinshui River at the Broken Hongqiao in the east of Wuying Hall.
In addition, there are short-distance north-south longitudinal ditches in the alleys such as Dongyi, Dong Er, Yi Xi and Scheer, which are respectively connected with the horizontal ditches in Gan Qing Gate, east and west of Gan Qing Palace, and the horizontal ditches in the courtyard. By using the natural gap of high in the middle, low around, high in the north and low in the south, and high in the middle and low at both ends of some small ditches, rainwater is quickly collected and discharged into inland rivers and out of the palace.