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City drainage in ancient China reflects spirit of craftsmanship

(Chinese Social Sciences Today)
A 2,200-year-old Qin Dynasty sewage system was discovered in Xi’an, Shaanxi Province, the capital city of the Qin. Photo: FILE


China’s city drainage system dates back to the Neolithic era. It consisted largely of channels, trenches, pools, culverts, and natural rivers and lakes within or outside the cities. The relatively developed ancient drainage system in China reflects the prosperity of Chinese civilization and its ever-present spirit of craftsmanship.
Advanced water system
The ancient city of Pingliangtai, located in Henan Province, dates back about 4,300 years. It is one of the earliest cities found in China and a monumental representative of the construction of ancient city drainage facilities. There were already pottery drainage pipes within the city.
Later in the Shang Dynasty (1600–1046 BCE), cities had more developed city drainage systems than Pingliangtai, and many were discovered with cleverly-installed draining channels made by wood and stone.
Then from the Western Zhou Dynasty (1046–771 BCE) to the Spring and Autumn and Warring States periods (770–221 BCE), pottery pipes not only became more popular, but reached a very high level of craftsmanship. Some fine pottery pipes were found in the capital site of Yan State, modern-day Hebei province.
In the Qin and Han dynasties (221 BCE–220 CE), city drainage construction was more common. In his poem “On the Ah Fang Palace,” Tang poet Du Mu wrote, “The Wei River swelling with grease—it was made by the waste of ointment.” As we can see, the drainage system of the Qin palace was connected to the Wei River. Moreover, pentagon-shaped pipe sections were often discovered in excavations of Ah Fang Palace. Compared with square-shaped pipe sections, this kind of pipe structure could better withstand surface pressure.
In the capital city Chang’an of the Han Dynasty, located at the northwestern side of the modern city of Xi’an, the city planning was scientific and reasonable. The city drainage system mainly consisted of the trenches and open channels. At the end of some channels, there were discharging pools to ensure that no water would accumulate after rainstorms.
In the capital city Chang’an of the Tang Dynasty (618–907), located in the modern city of Xi’an, there was a unified drainage system. Drainage systems within the palace were the finest. A set of iron grid gates were installed every few sections to prevent clogging and pollution. The first gate was for blocking larger pollutants. The second gate filtered out smaller pollutants with rhombus-shaped holes. The culvert could be cleaned from above through openings near the water gates.
In the Song Dynasty (960–1279), people’s understanding of city drainage and flood prevention was further deepened. The capital city Dongjing of the Northern Song Dynasty, modern-day Kaifeng, had a very developed water system, including three layers of trenches, four major channels crossing within the city, small channels around the lanes and alleys, and lakes and reservoirs outside of the city.
The design of the drainage system in Dadu, capital of the Yuan Dynasty (1206–1368), was planned simultaneously with the entire city. The water routes showed fully developed measures, design and construction. In the Ming and Qing dynasties (1368–1911), Beijing was built and expanded based on Dadu, so the drainage channels and culverts were kept and dredged.
Why drainage matters
The drainage system in ancient China was relatively complete and widely used. The reasons why the drainage system flourished in ancient times are as follows.
One is the impact of urban development. During the Warring States period, the population of the seven states was about 20 million. By the end of the Western Han Dynasty, the population had reached more than 59 million, the first peak of China’s population growth. In the mid-Tang era, the national population was about 60 to 70 million. In the first year of Emperor Xianfeng of the Qing Dynasty in 1851, China’s population peaked at 430 million. 
The rapid growth of the population and the prosperity of commerce led to the emergence of many small, medium and large cities throughout history. With the increase of cities and the expansion of city scale, the drainage pressure was enormous, giving rise to a large number of drainage system constructions.
Second, ancient Chinese dynasties not only stressed the importance of the construction of drainage facilities, but also made numerous drainage-related rules and laws. All the dynasties had officials assigned specifically to the matter of water management. Their titles and responsibilities were different in different periods.
In the Xia, Shang and Zhou dynasties (c. 2070–221 BCE), an official with the title “Sikong” was in charge of water and land related matters. There was another official titled “Chuanheng” in charge of managing the rivers and lakes.
In the Han Dynasty, the Sikong was still in charge of matters of water and land. There were also local water-related officials in some prefectures close to rivers and lakes.
In the Tang Dynasty, the Minister of Craft was in charge of the construction of all facilities, and the Minister of Water was in charge of all water-related matters such as irrigation and navigation. Under the Minister of Water, there was a “water supervisor,” who was in charge of making water related policies. The Song, Yuan, Ming and Qing dynasties all had water officials similar to the Tang’s.
The continuous progress of science and technology boosted the construction and development of ancient drainage systems. Though drainage facilities existed in the pre-Qin era, their construction technology was relatively simple. In the Qin, Han, Wei and Jin dynasties, circular drainage pipes appeared, which were undoubtedly a great leap compared with square and pentagon shaped pipes in the pre-Qin period. With the same material, the cross-sectional area of a circular pipe is the largest, and so is the flow. Therefore, in the case of heavy rain, it can quickly drain the water. As for stress, the circular pipe bears a uniform force compared with other shaped pipes, and it is not easily damaged when buried underground.
Again, the overall layout of Chang’an city in the Han dynasty presented a network structure of “from the inside to the outside, from the small to the big,” which was beneficial to having a clear and distinct drainage system, thus ensuring the smooth drainage of the whole city. In the Tang Dynasty, the iron gates at the outlet of the pipes, where the culvert meets the river, were valuable for preventing clogging. By the Ming Dynasty, the drainage system of the palace was even built with stone or copper, which indicates a great technological improvement.
Spirit of craftsmanship
Chinese people uphold the spirit of craftsmanship. As the Book of Rites puts it, “A mistake of a hair’s breadth will lead to an error of a thousand li.” And again, as the Book of Poetry puts it, “As smooth as ivory neatly made, as carefully polished as a jade.” The principles of attention-to-detail, delicate work and pursuit of excellence are well embodied in the construction of ancient drainage systems. 
In the 600 years since the establishment of the Forbidden City, it has never been in danger of flooding, which is a fact inseparable from the meticulous design, construction and maintenance of its drainage system. Before the construction of the Palace Museum, the soil foundation was laid and tamped down, which was equivalent to laying a huge sponge under the Palace Museum to absorb water and speed up the infiltration of rainwater into the ground. The bluestone bricks laid on the road are also good for rainwater drainage. The above ground and underground drainage systems then work together to ensure the smooth drainage of the palace. It can be seen that the planning and layout of the drainage system in the Palace Museum is very meticulous and rigorous, which fully demonstrates the ingenuity of craftsmen and embodies the spirit of excellence and meticulous craftsmanship. 
From the pottery pipes and discharge pools found in archeological excavations, we can still imagine the level of completion of drainage systems in ancient times. For example, the Han pottery pipes excavated in Luoyang City, Henan Province, were products of jointed sections. Each section had one broader end and one narrower end. In this way, the gap is small, not easy to leak and the construction is simple. This craft has been used for thousands of years in China and is still in use today. China was the first country to use this kind of jointed sections.
At the same time, there were discharging pools at the outlets of the pipes because people realized that, as time goes by, pipes would accumulate sediment and debris. Only by regularly dredging the pipe can clogging be reduced. These designs are unprecedented and fully reflect the innovative spirit of craftsmen at that time.
Again, around mid-Northern Song Dynasty, a relatively complete drainage system—Fu and Shou Culverts—was developed. The water gates were cleverly designed, able to open and close automatically according to the water level. When the water level is higher in the culvert, the sewer water pushes the water gate, forcing it to open and discharge; when the water level is higher in the river, the river water would push the water gate, forcing it to close and preventing river water from entering the culvert. Fu and Shou Culverts are still the main drainage routes used today.  
Lastly, during city planning in ancient times, planners always considered the need for drainage and flood-defense. Many city drainage systems were designed and constructed simultaneously with the walls and palaces. The size of a drainage system was decided based on not only the present size of the city, but also the potential expansion of the city. Therefore, some thousand-year-old drainage systems are still in use today. According to the historical records, dredging was practiced every year in Dongjing in the Song Dynasty. People’s hard-work and dedicated spirit during these times cannot be overlooked.
Zhuang Huafeng and Huang Wei are from the School of History and Society at Anhui Normal University. 
edited by YANG XUE