Conclusion and discussion

China started the history of drainage from its early age especially at the age of early urban formation, and then it was developed with the rural and urban development. The ancient founders of cities always choose the riverside as the site for building their cities for convenient water supply. However, it is easy to be understood normally in the world history that early civilizations almost emerged from the riversides. Hence, what we learnt from the wisdom of the Chinese ancestor in designing a city was that they did not just build the city close rivers but also designed and built the city with drainage system. Hereafter, it was developed to be an integrated water system with the functions of water supply, use and drainage. Normally, the water system was combined with river，city rivers, draining aqueducts, ponds, town-rounding fosse, draining rivers，etc. Thus, this system had performed the functions of water supply, use and drainage of a city thereby working as a water cycle system.

The systematic water system design and construction in the history of the urban development has been remarkable. The water system of the urban history not only focused on water supply and other single purpose, but it also considered it as a systematic design and construction which included water supply，use and drainage which are the constituents of a water cycling system. Accordingly, the systematic idea and construction of water system was the essential factor of the ancient urban construction in China that has enhanced all ancient major cities' development from their early age even till nowadays to thousands of years.

The strategic design and construction of drainage system is also the outstanding feature of the ancient urban construction. For example, city rivers，sewers, ponds and town-rounding fosses were built and linked to the urban water system serving as the function of water circulation and especially that of drainage. Today, there are many historical draining structures which are still functioning in many cities. The meaning of“strategic design”is that people not only designed the urban water system systematically for multi-purpose use but was also strongly considered to encounter possible flood after a longtime. With the case of the storm flooding in Beijing in July 21, 2011, the storm mainly hit the area of West No.3 Rounding-town Express Way and West No.4 Roundingtown Express Way. Nevertheless, the area of the old town where located inside No.2 Rounding-town Express Way with the ancient draining structures which was not heavy affected. The drainage system in this area was built in Ming Dynasty and has been used for more than 500 years. So far, the drainage system in the area which was heavily hit in July 21, 2011 was built just about 20 years ago. The outstanding paradigm is the royal palace and the Forbidden City. However, there were no hit by this storm event and many old structures nearby were also in same condition. What was more outstanding was that there were no records of storm flooding regarding the historical structures in the past 600 years. However, it is strongly relying on the consummate drainage system incorporated together with the palace construction.（Fig.9, 10）

China has been involved in rapid urbanization in recent decades; conse quently, all the cities have gone in a quick enlarging process. Compared to the difference of the drainage in the old time and current age, the focus in ancient time was mainly on storm flood draining and not the waste water due to limited population and simple livelihood at that time. However, there were no special concern for waste water, but the situation in this current age is mainly focused on waste water, and rainstorm is even been neglected in many cities. It is a common status that many cities have planned the reconstruction of waste water disposal facility but rainstorm disposal is not included at same time. Today, the situation of the cities in China is quite different from that of old times; therefore，it is difficult to expect the old drainage facilities to perform all functions including rainstorm disposal. But even so, it is still valuable to learn from history by having a systematic and strategic design and reconstruction of the water system in the enlarging urban construction. Also, it is very important to put water supply, waste water disposal and rainstorm treatment on a coequal basis.

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（Published at The Finnish Journal of Environmental History, No.1, 2015.

本文载《芬兰环境史》2015年第1期）