Tashan Weir

Tashan Weir

Tashan Weir is a National Key Cultural Relics Protection Unit.

Tashan Weir is an ancient water conservancy project built on the Yin River, a tributary of the Yong River in China, serving as a hub for preventing salinity intrusion, storing fresh water, and irrigating farmland. Located beside Tashan Mountain in Yinzhou Town, Yinzhou District, Ningbo City, Zhejiang Province, at the outlet of the Zhangxi Stream, it lies southwest of Ningbo City in Zhejiang Province. Constructed in the seventh year of the Dali era (833 AD) of the Tang Dynasty by then-county magistrate Wang Yuanwei, it is collectively known as one of China’s Four Great Ancient Hydraulic Engineering Projects, alongside the Zhengguo Canal, Lingqu Canal, and Dujiangyan Irrigation System. It is also a National Key Cultural Relics Protection Unit.

Before the weir was built, ocean tides could flow upstream along the Yong River to the Zhangxi Stream, causing farmland to become salinized due to seawater backflow and making urban water supply difficult. Between the Siming Mountains and Tashan Mountain at the mountain pass where the Yin River originates upstream in Yinzhou, a spur overflow dam with 36 steps on both the upper and lower sides was constructed using stone slabs. The dam crest is 42 zhang long, built from 80 stone slabs, with a hollow body supported by large wooden beams. Located beside Tashan Mountain in Yinzhou Town, Yinzhou District, it is recognized as one of China’s Four Great Ancient Hydraulic Engineering Projects alongside the Zhengguo Canal, Lingqu Canal, and Dujiangyan Irrigation System, and is a National Key Cultural Relics Protection Unit. Tashan Weir was first built in the seventh year of the Tang Dynasty's Dali era, with a total length of 134.4 meters, a height of about 3.05 meters, and a width of 4.8 meters.

The weir surface is entirely built with stone slabs, while the body of the weir features a wood-and-stone structure, including a massive plum wood beam over a meter in diameter lying within the weir, which has remained unrotted for over a thousand years, earning it the name "Plum Beam of Tashan Weir." The slope of the weir body, the layer of clay mixed with crushed stones, the planar layout of the weir, and the multi-tier energy dissipation and scour prevention methods created a miracle of ancient hydraulic engineering. The first two features were pioneering achievements in ancient water conservancy projects in China, predating similar foreign technologies by over 200 years. After enduring more than 1,160 years of wind, rain, snow, and flood impacts, Tashan Weir remains largely intact and continues to function in blocking salinity, storing fresh water, and draining floods. Around the weir, remnants such as the Backsand Sluice, water measurement ruler, Tashan Temple, and the “Fragrance Left on a Stone Tablet” stele can still be found today. The weir body, structured with wood and stone, is said to have once contained a massive plum wood beam that remained unspoiled for a millennium, hence known as the "Plum Beam of Tashan Weir."

Tashan Weir serves as the headworks for diverting fresh water and blocking salinity. It intercepts the Yin River, channeling water from the upstream Zhangxi Stream. One route leads into the Nantang River, passing through Dongqiao, Hengzhang, Beidu, Lüshe, Shiqi, and Duan Tang via the South Gate of the city, then into the Sun and Moon Lakes, further distributed through branch canals to meet urban water needs. The other route flows north into Xiaoxi Port, reaching Meiyuan and Shenjiao. These two water routes distribute through branches to connect various waterways across the western Ningbo plains, irrigating thousands of hectares of farmland across seven local townships. The weir was ingeniously designed with a unique structure and precise construction. During floods, 70% of the water is directed into the river and 30% into the stream; during droughts, the ratio is reversed. Along the inner and outer rivers and downstream of the Nantang River, three sluices—Wujin, Jidi, and Xingchun—are built to control storage and drainage.

Around 1068, then-county magistrate Yu Daning built the Fengpeng Sluice near Beidu. In 1242, regional governor Chen Kai, aiming to prevent siltation in the inland port, constructed the Backsand Sluice 150 meters northwest of the weir. Due to changes in the ancient river course, it now exists only as a historical relic, with four exposed groove pillars remaining on the ancient riverbed. The second pillar from the west is inscribed with a water measurement ruler marked with scales used to determine water levels for release and storage. The third pillar is engraved with the words “Backsand Sluice,” and both sides of the stone pillar are carved with sluice grooves for mounting sluice gates. Around 1255, regional inspector Wu Qian built three dams east of Yinzhou Town—one by the river, one by the stream, and one between them. One dam by the stream remains; it was rebuilt in 1924, and the Stone Flood Bay Levee, 302 meters long and 4.16 meters high, was constructed. Shaped like a bow, it curves inward toward the stream and outward toward the river, located between Guangxi and the Yinzhou Sluice, forming the second flood diversion levee of Tashan Weir. In 1987, a new Flood Bay Drainage Sluice was built, though the original levee still retains its ruins. Other structures include the Guantang and Goujing Levees. By the late Qing Dynasty and early Republican period, auxiliary projects had expanded to nine dams, five weirs, and thirteen levees. After the founding of the People’s Republic of China, renovations of old sluices, weirs, and levees further improved their functionality.

Tashan Weir, together with the Zhengguo Canal, Lingqu Canal, and Dujiangyan Irrigation System, is known as one of China’s Four Great Ancient Hydraulic Engineering Projects. For over a thousand years, despite numerous floods, it remains largely intact and continues to function in blocking salinity, storing fresh water, diverting water, and draining floods. It has drawn extensive research both domestically and abroad. In June 1982, the Yinzhou County Government designated it as a County-Level Key Cultural Relics Protection Unit. On December 28, 1988, the State Council declared it a National Key Cultural Relics Protection Unit.

Address: Outlet of the Zhangxi Stream beside Tashan Mountain, Yinzhou Town, Yinzhou District, Haishu District, Ningbo City

Type: Ancient Hydraulic Engineering Site

Recommended Visiting Time: About 1 hour

Phone: 0574-88431213

Opening Hours:

Open all day

Ticket Information:

Free admission.

Yinzhou Town: Yinzhou Town is located at the eastern foot of the Siming Mountains and is a major town on the western edge of the Yinxī Plain. It is a historic and cultural town with a history of a thousand years, situated 25 kilometers from downtown Ningbo. It borders Dongqiao Town and Gulin Town to the east, Zhangshui Town and Longguan Township to the west, Fenghua’s Jiangkou and Xiaowangmiao to the south, and Hengjie Town to the north. The town spans 5 kilometers from east to west and 10 kilometers from north to south. The Yong-Jin Expressway runs nearby, the district road Heliang Highway crosses the town center, and the Yinzhou-Hengzhou Highway and the Luyin Branch Road run directly from north to south. It is just minutes away from Ningbo Lishe Airport and the Hangzhou-Ningbo Expressway. The town covers an administrative area of 95,879 mu (approximately 63.9 square kilometers), comprising 12... [More detailed information on Yinzhou Town++]

Further Reading:

· World Heritage Irrigation Structure

· Third Batch of National Key Cultural Relics Protection Units