The Practice of the Urban Water System

Early cities emerged at about 3000 BC according to the archeological discovery. The Shan Town which is today's Zhengzhou is at a very important stage（Dong, 2011）. The archeological evidence shown that water facilities were built including the town construction, especially the sewers. Earliest sewer facility was discovered in the old town, Pingliangtai（around 2000 BC）of Henan province. Thus, what was remarkable by the discovery was that earthenware was used to build the downcomer inside the town. Also, some earthen pipelines which was used for building a drainage system underground were found（Fig.3）Henan Institute for Cultural Relic, 1983.

A very clear golden age of the early urban development was the Spring-Autumn and the Fighting-state periods（around 700—100 BC）. During this period, many cities were formed and developed in the Yellow River Basin. The archeological evidences showed that water facilities such as drainage were incorporated during the urban construction. For example, the earthen sewer was found in the ruins of the Yan Xia Du town（燕下都）, today's Yi county of Hebei province（Dong, 2011）.

In 221 BC, Qin Empery, the first unitive country in the Chinese history was built in today's centre China. Mr. Qin Shi Huang, the emperor of Qin built the capital at Xian Yang city, Shanxi province. Today, the old city had disappeared long time ago, but according to the historical documents, it was a very large city at that time, and archeological discovery in recent years found that consummated drainage facilities was built in the city. It was also remarkable that earthen pipeline was popularly used as sewer facility. For example, archeological digging in the palace ruins showed that a drainage facility combined with 4 pools and earthen downcomer were built in the palace. It gathers the rain water and waste water from the palace by the downcomers and raceways（uncovered）to the pools, and uses pipeline to direct water into rivers. Another important discovery in Shanjailing ruins in Qin dynasty, shangxi Province in 2010 was that the earthen pipes used as downcomer in the residential area were out of the major cities. In addition, some earthen pipelines which were discovered includes a pipe elbow. The pipe elbow is a type of earthenware which is very rare to find（Fig.4, 5）.

（Shanxi Provincial Relics Bureau, 2010.）

Furthermore, the drainage facilities designed and built was an important advancement in the urban water system in history. It shows that people not just consider water supply naturally, but on the fact that drainage also brought the city into an age of integrated urban water system construction.

From Han Dynasty（202 BC—220 A. D.）, the urban construction of China was going into a new age. Taking more than 400 years construction and development, Han had become one of the flourished tops of the dynasties in Chinese history. Also, many major cities were built with complex urban water system.

The founder of Han Dynasty founded its capital Chang'an city near today's Xi'an city, Shanxi province. According to the historical documents, this city was developed to be a very large city quickly after it was founded. It has also existed as the capital city for 15 dynasties until 907 A. D. Chang'an city was 35 km2 in size at that time with a population of five hundred thousand Yang，1989. The archeological discovery showed a complex water system which was built in the city, and which combines the functions of water supply, drainage，storage of water, and ship transportation. However, the main constructions of the water system are described below.

Water Supply: The water supply of the city was from the river naturally. The city was found at the south side of Wei Shui（渭水）River, but the water supply was from the Jue Shui（泬水）River because the location of the town was higher than the Wei Shui River. Jue Shui River flows from the south of the city and flows to the north into the town. It flows across the palaces and the city（this part was called Ming river, meaning open ditch, 9 km of length）, and then out of the town into the Wei Shui river. Furthermore, other branch of Jue Shui River also flows across part of the town, and then into the Wei Shui river. However, for the purpose of improving water supply, a big pond was built to receive water from Jao Shui River（交水）. This pond is a very famous pond called“Kunming Pond”. After this pond was built, an aqueduct was built to introduce water into the town for urban water supply.

Urban Rivers: There are many rivers or canals inside the town which serves as water cycling system. For example, the main water supply source, Jue Shui River, flows into the town directly. Firstly it passes through the palaces for water supply, and then, it separates into two ways to the residential areas, and finally into other rivers. As mentioned above, there are also aqueducts built from Kunming Pond or other sources to introduce water into the town. Hence, the aqueduct from the Kunming Pond was called“Kunming Aqueduct”, which is the important water supply canal to the city. In addition, the urban river cycling inside the town to supply water to the town also performs the function of drainage.

The Ponds: There are 10 big ponds which are built for rainwater sluice in summer and water storage supply in winter. According to the documentary, the ponds was also use for training water war for the army, but fortunately, it became the waterscapes of the city mainly, and gave adequate space for the citizens to enjoy water most periods.

The Drainage System: Drainage systems were built inside the town. They include the sewers, open ditches, channels, ponds and moats, and draining rivers. There are many earthen pipes and underground sewer which has been found. However, by archeological discovery shown, a sewer system was built in the palaces, and the residential areas then were linked to the urban rivers（Li et al, 1981）. In 2008, a major sewer was found in the old Chang' an city. It was built with bricks of 2m wide and 40m length, Hence, we can see how large a sewer system was built in Han city（Fig.6, 7）（Feng, 2008）.

The water systems are connected to each other through Water Supply Rivers, ponds, drainage sluiceways, moat and Drainage Rivers. However, not only wastewater can be drained, but also rainstorm water could be sluiced.

The Town Moat: Outside the town, a moat（length of 26km）was built around the town. It was connected with the main urban river, Ming River, and also performs the function of rainwater sluice from the town（Wu, 2009）.

Additionally, the water system include parts of the water supply rivers or aqueducts, urban rivers and channels, ponds, sewers, moat and draining rivers, which combines to form a perfect urban water system. An important point was that the water system in Chang'an City also created a model of urban water system which influenced many Chinese cities subsequently. Consequently，Cheng'an city was not just as a flourishing city historically, but also at a very important stage in the history of urban construction of water system in China（Zheng, 2013）.

Another paradigm is the East Capital of North Song Dynasty（960—1127），today's Kaifeng City. In this age, urban design and construction has been improved more effectively for water supply and drainage. Being built close to Yellow River, Kaifeng City was around 50 km2 in size at that time. Also, there were four rivers: Bian River, Jingshui River, Cai River, and Wuzhang River flowing cross the city, which performs the functions of water supply and drainage. At the early age of this city, flooding risk became a great threat due to seasonal water change and water introduced directly into the city from Yellow River by Bian River as the main source of urban water supply. However, this situation also brought about the design and construction of the city more conditionally for drainage. The water system of Kaifeng was consisted of（1）rivers-mentioned above that there were four rivers flowing cross the city as well as series of urban river connecting to each other which performs the function of water supply and drainage.（2）moats-it was recorded that there were three rings of moats which extended from the palace to the urban area.（3）ponds-There were four ponds inside the city, which are: Ningxiang（凝祥）, Qiongling（琼林）, Jinming（金明）, and Yujing（玉津）（J. H. Dong, 2004）.（4）the sewer system-It was documented that there were a complex sewer system built in the urban area. Some of them were underground channels, while some were ditches along the streets. In four royal streets especially, ditches were built along with all of them. However, the water system of Kaifeng City perfectly met the demand of water through the rivers at same time. It was greatly achieved for urban drainage due to its closeness to the Yellow River mainstream. Thus, the water system performs drainage functions by connecting all the sections above to each other to regulate the flow of water seasonally. For example, the capacity of sluice of the three moats was 17.65 millions m3, and included four urban rivers with a total of around 18.52 millions m3. However, it effectively reduced the flooding risk（Wu, 2009）commonly from the Yellow River or by rainstorm.

Furthermore, not just the capital cities were built with typical urban water system modeled from Han Chang'an city, the sub-cities also had their own water system. Shaoxi City is a paradigm. Being located at the west of Zhejaing Province, Shaoxi City is a very famous city not just because of its long and important history or local culture, but also has a typical urban water system. The history of Shaoxi city was dated back to 2500 years ago, According to the historical documents, the city was built by Wu kingdom, a local kingdom at that time. From the original history of the city, the city was found with abundant water. There are 43 rivers from the Kuai Ji Mountains to the north flat, bring abundant water to this region. Consequently, the city was built with convenient water resource. However, this city does not just have a natural source of water, but the urban water system was an artificial one. In East Han Dynasty, a lake called lake Jian was built by the governor to store water for urban water supply. After it was built, a supply river was also built from the north lake into the town. This river goes to the south of the lake again after flowing into the town. In Tang Dynasty（618—907 A. D.）, the Zhe Dong canal was built to link Shaoxin town. It brought more water resource to the city. In Song Dynasty（960—1279A. D.），the water system of the city was formed with supply rivers, urban rivers，moats, lakes, and rivers. What was remarkable was that many urban rivers were built inside the town. Also, after a river has been built, the streets and houses were built close to the riversides, therefore forming a water net inside the town. In Qing Dynasty（1636—1912 A. D.）, a complete water system was combined with 33 rivers inside the town, 60km of total length, and two moats（inside and outside town）, 27 lakes and ponds, and they are all linked to each other as well as to water systems outside the town. For instance, 8 out of 9 town-wall gates were mainly for river cross, as there were linkage of the rivers with Zhe Dong canal, lake Jian, and other rivers. Therefore, water system perfectly performs the function of water supply, cycle, use, drainage, and transportation; thus, it also sustained the local social life（Qiu, 2012）.