The 36 Weirs of Baishaxi Stream, located in the Jinhua City of Zhejiang Province, is an ancient weir complex with the functions of flood control, water storage, and the utilization of water power.

History

In 27 AD, Lu Wentai, a general of the Eastern Han Dynasty decided to retreat to peaceful village life. He left the capital with 36 subordinates and went quietly to a place called Fucang, or today’s Wucheng District of Jinhua City, Zhejiang Province. They found this place enjoyed fertile soil but suffered from frequent drought and flood. To solve the problem, they built at Gaoru Village the Baisha Weir to facilitate irrigation, thereby starting the construction of the weir complex along the Baishaxi Stream. For the next over one hundred years, their descendants and local residents applied the experience accumulated from building the Baisha Weir to the construction of the weir complex. From the upstream to the downstream, the 36 weirs cover a river section as long as 45km and form a water level difference of 168m. These weirs have ensured stable crop yields despite drought and excessive rain.

During the construction process, local people acquired a comprehensive understanding of the natural conditions of the Baishaxi Stream. Considering its characteristics of large vertical drop, rapid flow, and abundant deep pools, local people chose to build weirs at the pools and dig canals for irrigation. In this way, a water use system combining pools, weirs, ponds, wells, and springs was established, and water supply was thereby guaranteed.

Irrigation System

Most of the 36 weirs are located at natural deep pools. Based on the theories of modern hydraulics, this could not only improve their water storage and diversion capacity but also reduce the impact of water flow. The establishment and renovations of the cascade weirs have fully tapped the local natural resources such as pines and bamboos which were respectively made into reinforcing stakes and cages filled with stones. Besides, building cascade low weirs, relatively easier and less risky, has reflected the ancient Chinese philosophies of water management and harmonious coexistence between man and nature.

In the past two millennia, local people have accumulated abundant experience in weir management and annual repair. The local government laid down the general rules of weir management, clarifying water rights and repair responsibilities, coordinating the operation of the 36 weirs, and guaranteeing the fairness of water use in dry months. The Regulations on the Management of the Wantan Weir, amended in 1908, includes the detailed layout of the weir’s canal network, and information such as the location of the weir, the water distribution system, and water diversion facilities.

Also, each weir had its own “water user association”. The “association” was responsible for formulating detailed rules of weir management. Elected by local villagers, its head was usually a respectable gentleman who was in charge of handling weir-related affairs and settling water use disputes. Local people formed close water communities centred on land, water, man, and money. During the annual repairs, people followed the principle of dredging the pond thoroughly and keeping the weirs low, which helped to improve the water diversion capacity of canals and prolong the service life of the weir body. In the inscriptions of a stone tablet of the Ming Dynasty, the author Zhao Chongshan states that people at that time are already aware of the importance of the first weir of the cascade—they believe the first weir, occupying the key position, has a great impact on all the weirs downstream, which means it is the priority of repair in the cases of silting-up and destruction by flood.

As a kind of very advanced production tool in the ancient time, water-powered machine trip-hammer has been employed ever since the completion of the weir complex along the Baishaxi Stream. According to historical records, more than 150 water-powered trip-hammers were built in the 120 villages of the Baishaxi Stream Basin. High crop yields and advanced grain-processing technology have given birth to the brilliant culture of liquor making. In the Tang and Song Dynasties, there was a liquor shop by the Bailong Bridge famous for its fine spirits. Today, the local village is still called Gufang, meaning liquor shop. Besides, also in the Tang and Song Dynasties, the machine trip-hammers were also used to crush kaolin, the raw material of porcelain, supporting the development of local porcelain making business and boosting the local economy. The huge benefits generated by the 36 weirs along the Baishaxi Stream have made an enormous impact on regional development. Historically, there were more than 6000 water-diverting weirs built in this area as imitations of the 36 weirs. Together, these irrigation facilities have turned central Zhejiang Province one of the most important grain production bases of China.

After the foundation of the People’s Republic of China, Shafan Reservoir and Jinlan Reservoir were built along the Baishaxi Stream, leading to the inundation of some ancient weirs. Today, 21 out of the 36 ancient weirs are still diverting water for irrigation, and the guaranteed rate of water supply is further improved. Reservoirs, weirs, and canals have formed a complete irrigation system that covers 18500ha of farmland.

To commend the outstanding contribution made by Lu Wentai, the founder of the weir complex, successive governments of different dynasties gave him 7 honorary titles, including 4 dukedoms and 3 princedoms. To show their gratitude, local people have built more than 100 temples to worship him. Temple fairs are held every year to commemorate and praise his outstanding achievement and carry forward his spirit.

Water Heritage

The structure that was ahead of its times in terms of project formulation, engineering design, construction techniques, dimensions of the structure itself, quantum of water diverted, and size of the command.

The 36 Weirs of Baishaxi Stream refer to the 36 weirs built on the same river. From the Shafan Weir on the upper reaches to Zhongji Weir on the lower reaches, the 36 Weirs are located on a belt extending 45 km with a drop of 168m in elevation. The 36 Weirs of Baishaxi Stream is a pioneering project in terms of engineering planning and construction scale. 

The structure must have made an outstanding contribution to enhancing food production, livelihood opportunities, rural prosperity, and poverty alleviation in a region.

The construction of the 36 Weirs makes important contributions to agricultural development and growth in food output. Historically, more than 6,000 water-diverting weirs were built in imitation of these 36 Weirs in the neighbouring areas to promote the local agricultural development. During the Tang and Song dynasties, the water-powered trip-hammers of the 36 Weirs were used to crush kaolin that was the raw material for porcelains in the kilns of Wu Prefecture along the banks of Baishaxi Stream. The 36 Weirs made important contributions to the local economic development.

The structure was innovative in its ideas at the time of its construction.

The 36 Weirs of Baishaxi Stream is the earliest weir irrigation project in Zhejiang Province and even in China. To make it easier to build every single weir and extend their life cycle, the constructors innovatively adopted the concept of scattered distribution to build these 36 weirs stage by stage to divert water for irrigation purpose.

The structure contributed to the evolution of efficient and contemporary engineering theories and practices.

The terraces-deep pool is a topographic feature naturally formed in mountain rivers. Such a characteristic of Baishaxi Stream was discovered and scientifically used by constructors of the 36 Weirs. The weirs were built along the lower reaches of each deep pool to use the energy dissipation of water currents to reduce the impact of water flow, and to increase water storage of the weir in dry months. The principle of “dredging the pool thoroughly and keeping the weirs low” was summarized during the annual repairs of weirs for increasing water storage of deep pools, improving the water-diversion capacity of canals, increasing the energy dissipation effects of deep pools and protecting the safety of weirs.

The structure is an example of attention to environmental aspects in its design and construction.

The main building materials of the 36 Weirs of Baishaxi Stream were pebbles, rectangular stone slabs, iron and others. Cost-efficient and easy to repair, these locally obtained materials played an important role. Importance was also attached to environmental protection in engineering construction. The way of “building weirs at the pools” enhance energy dissipation in pools along Baishaxi Stream, consolidates riverbed of Baishaxi Stream and increases the capacity of streams and pools in sorting bed material load in river courses. Such a way is conducive to forming the biodiversity in the region of Baishaxi Stream and plays an important role in ecological restoration.

The structure was unique in some positive and constructive way.

A total of 36 weirs were built in a way of scattered distribution on one river. “Building weirs at the pools” represented a pioneering and unique concept of construction at that time.

The structure bears the stamp of a cultural tradition or a civilization of past the past.

Rulers of different dynasties conferred honorary titles to Lu Wentai, the founder of 36 Weirs, for controlling water for irrigation. These titles include 4 dukedoms and 3 princedoms.  He was conferred the title of Duke of Wuwei in AD 880 in the Tang Dynasty. The imperial mandate reads that “The prayer for rain was always effective when the drought was worrisome, even the plague of locusts that ran rampant would disappear within the regions benefiting from the 36 weirs.” He was also conferred the title of Prince of Baoning in 908 in the Later Liang Dynasty (AD 907–923) with imperial mandate reading “(The 36 weirs) warded off evil-doers of the Han Dynasty and relieved the farmland in the Wu Region of drought”; Duke of Zhaoli and a plaque bearing the inscriptions of Zhaoli in 1113 in the Song Dynasty (AD 960–1279); Duke of Lingkuang in 1183 and the title of Duke of Fuying in 1201 in the Song Dynasty; the Prince of Guangji in 1217, and the title of Prince of Zhonglie in 1358 in the Yuan Dynasty (1206–1368).

More than 100 poems by well-known poets of successive dynasties sing the praise of the 36 Weirs of Baishaxi Stream. Lu Wentai was respectfully called “Lord Baisha” by the local residents of more than 120 villages along the Baishaxi Stream. They remembered him for his great contributions to building weirs to harness water. Around 100 Baisha Temples have been constructed. The influences of Baisha Culture derived from these memorial buildings are still felt today. 

Engineering utility vis-à-vis designed utility

In AD 27, Lu Wentai, a general of the Eastern Han Dynasty decided to retreat to peaceful village life. He left the capital with 36 subordinates and went quietly to a place called Fucang, or today’s Tingjiu Village, Shafan Township, Wucheng District of Jinhua City, Zhejiang Province. They found this place enjoyed fertile soil but suffered from frequent drought and flood. To solve the problem, they built at Gaoru Village the Baishaxi Weir to facilitate irrigation, thereby starting the construction of the weir complex along the Baishaxi Stream.    

For the next over 100 years, their descendants and local residents applied the experience accumulated from building the Baisha Weir to the construction of the weir complex. From the upstream to the downstream, the 36 weirs cover a river section as long as 45km and form a water level difference of 168m. It is recorded in Annals of Jinhua Prefecture of successive dynasties that “Baisha Weir is 4.3m wide and 60m long.”

Major maintenance and repairs have been made to the 36 weirs in successive dynasties. Some weirs are built with rectangular stone slabs; some others are built with cages filled with pebble stones. However, the location of each weir remains unchanged, and the water-diverting canals remain unchanged. During the drought that raged in the year of AD 238 in the period of the Three Kingdoms (AD 220–280), the Baishaxi Stream Basin registered a bumper harvest thanks to the irrigation by the 36 weirs, in contrast to the total crop failure resulted from the scorched farmland in the peripheral areas. Local people in Baishaxi Stream Basin were full of gratitude and respect to the 36 weirs and their constructors. 

In his Inscriptions on Stone Tablet of Water Conservancy Works on Baishaxi Stream, Zhao Chongshan, a man from Lanxi under Jinhua Prefecture in the Ming Dynasty (1368 – 1644), recorded that “there are 36 weirs on Baishaxi Stream. They were built long ago and provide substantial benefit. The area irrigated by them has a perimeter of about 100km, covering thousands of acres of fields. The first weir is the most critical one. There are 18 weirs upstream, and the first weir is the 19^th weir. Other weirs on upstream and downstream are not liable to be destroyed so long as the first weir is not destroyed. Occupying a critical position, the first weir plays a decisive role in the overall situation of the 36 Weirs of Baishaxi Stream. That’s why it is more important than other weirs regarding the protection of the system.” According to the above records, the local people in the Ming Dynasty attached high importance to the repair and protection of the first weir. The General Record of the First Weir on Baishaxi Stream, also known as the Rules of Protecting and Utilizing the First Weir on Baishaxi Stream, is still well-preserved. A lot of experience summarized in the book conforms to the requirements of the Scientific Outlook on Development advocated today.

The Wantan Weir was rebuilt in the Qing Dynasty. The Regulations on the Management of the Wantan Weir – The 36 Weirs at Bailong Bridge in Jinhua was recompiled in 1908. The book includes a detailed layout of the weir’s canal network and records an agreement on how local government mediated conflicts concerning the use of water among villagers and reasonably allocated the operation of the 36 weirs. 

In September 1960, Jinlan Reservoir was built at the place where the Baishaxi Stream flows out of the mountain. The water of the reservoir inundated six weirs on Baishaxi Stream, including the Zaoli Weir, the Shanglanbei Weir, the Moshi Weir, the Zhucun Weir, the Xidong Weir and the Shirenshan Weir. With the rapid industrialization and urbanization, it was necessary to meet the needs of people living in the city proper of Jinhua City to drink clean water. In 1992, based on sufficient argumentation, the municipal government of Jinhua City decided to build Shafan Reservoir at a place 20km upstream of Jinlan Reservoir. The dam of Shafan Reservoir is at the site of the Shafan Weir, or the first one of the 36 weirs.  

Of the 36 weirs, 21 are still functioning. The bamboo cages filled with stones have been replaced by concrete and masonry. The building of two reservoirs further guarantees the rate of water supply. Reservoirs, weirs, and canals have formed a complete irrigation system that has increased the irrigation area from 8,000ha to 18,533ha.

Present State of Conservation

The 36 Weirs of Baishaxi Stream have been playing an irreplaceably important supporting role in maintaining of social-economic development and ecological environment since ancient times. Over the past decades, the building of Jinlan Reservoir and Shafan Reservoir on Baishaxi Stream has inundated some of the ancient weirs. Due to the building of reservoirs, however, Baishaxi Stream has become a source of water for Jinhua City, and the flooding and pollution of Baishaxi Stream have been put under effective control. As the irrigation area of the 36 weirs are subject to possible shrinking with the development of urbanization, the administrative authority over the 36 weirs formulated “Plan for Protecting 36 Weirs”, in which the requirements for managing and protecting the ancient weirs are specified, and the display centre and signboards of the weirs have been built. Overall, the risks facing the 36 weirs of the Baishaxi Stream are under control.