Tashan Weir: Difference between revisions
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Tashan weir divided the Yinjiang river into two: fresh water is stored in the Tang rivers, irrigating 240,000 mu of farmland in seven townships of the area, while the salty tide is blocked. When floods occur upstream, the weir can overflow and, combined with the other hydraulic projects downstream, achieve the purpose of flood diversion. It has been calculated that for a 20-year flood, the Tashan weir, in combination with the downstream hydraulic projects, can divert about 70% of the flood. |
Tashan weir divided the Yinjiang river into two: fresh water is stored in the Tang rivers, irrigating 240,000 mu of farmland in seven townships of the area, while the salty tide is blocked. When floods occur upstream, the weir can overflow and, combined with the other hydraulic projects downstream, achieve the purpose of flood diversion. It has been calculated that for a 20-year flood, the Tashan weir, in combination with the downstream hydraulic projects, can divert about 70% of the flood. |
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[[File:River System Map in Ancient Ningbo.svg|thumb|Ancient network of the different Ningbo water courses, with Sun and Moon lakes highlighted]] |
[[File:River System Map in Ancient Ningbo.svg|thumb|Ancient network of the different Ningbo water courses, with Sun and Moon lakes highlighted]] |
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After the 1970s, two large reservoirs were built on the upstream tributaries of the Yinjiang river, and the importance of Tashan weir was greatly reduced, but it still performs irrigation and flood control functions. |
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In total, the hydraulic system of Tashan Weir (the dam, two flows, and ancillary facilities) has been irrigating nearly 16,000 hectares of land for centuries, and continues to do so even today. The Ningbo area experienced rapid growth due to the stable water supply that the dam provided. |
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==Construction== |
==Construction== |
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Revision as of 14:41, 17 October 2024
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它山堰 | |
 | |
 | |
| 29°46′11″N 121°20′50″E / 29.769607°N 121.347248°E | |
| Location | Tashanyan Village, Yinjiang Town, Haishu District, Ningbo, Zhejiang, China |
|---|---|
| Designer | Wang Yuanwei |
| Type | Dam |
| Length | 110 metres (360 ft) |
| Completion date | 833 |
Tashan Weir (Chinese: 它山堰; pinyin: Tuōshān yàn) also called Tuoshan Weir or Tuoshanyan[1] is an ancient dam that was erected under Emperor Tang Wenzong during the Tang dynasty in 833. The dam is located in Tashanyan Village, Yinjiang Town, Haishu District, Ningbo, Zhejiang, China. Originally designed under the supervision of Wang Yuanwei, then magistrate of Yin County, the dam was constructed to prevent tidal sea water from accessing the banks of the Fenghua River and to store water during periods of severe drought. The dam later became part of a large-scale irrigation system serving Ningbo City. This infrastructure is particularly notable because it is recognized as a historical site protected by the state.[2]
History
Prior to the dam's construction, the surrounding area experienced devastating floods from torrential rains every summer and autumn due to the sub-tropical climate. In addition, salty water from Fenghua river, which is a tidal river and connected with Yinjiang river through all the tributaries of the latter, would reach farthest to 3 kilometers upstream of Yinjiang Town, and caused the freshwater resources of the upper Yinjiang river largely unusable for irrigation and other purposes. To address these recurring challenges, Wang Yuanwei, the magistrate of Yin County, spearheaded the construction of the Tashan Weir on the Yinjiang River. Completed in 833 A.D. during the Tang Dynasty, this innovative hydraulic project was designed to permanently mitigate the harmful effects of tidal saltwater intrusion on farmland and to reduce the risks posed by flooding.
Tashan weir divided the Yinjiang river into two: fresh water is stored in the Tang rivers, irrigating 240,000 mu of farmland in seven townships of the area, while the salty tide is blocked. When floods occur upstream, the weir can overflow and, combined with the other hydraulic projects downstream, achieve the purpose of flood diversion. It has been calculated that for a 20-year flood, the Tashan weir, in combination with the downstream hydraulic projects, can divert about 70% of the flood.
After the 1970s, two large reservoirs were built on the upstream tributaries of the Yinjiang river, and the importance of Tashan weir was greatly reduced, but it still performs irrigation and flood control functions.
Construction
The dam is about 110 meters long and its top is approximately 5 meters wide. Its outer part is composed of roughly regular stones (2 to 3 meters long and 0.2 to 0.35 meters thick) while its internal structure consists of a mixture of stone and wood. To consolidate the structure, molten iron was directly injected in some sections. The dam was designed to adjust according to the flow of the river and to mitigate risks associated with natural geological erosion. Maintenance and restructuring work have been continuously carried out, from the imperial dynasties to the present day.
The design of the facility ensured that in cases of excessive rain, 70 percent of the flood water flows to the Zhang River (inner river) while the remaining 30 percent discharges to the Nantang River (outer river).[3] This proportion of water flow is reversed during periods of drought, achieved through the use of water gates between the inner and outer rivers.
Legacy
Tashan Weir was officially declared a Major Historical and Cultural Site Protected at the National Level on January 13, 1988 (Number 3-55). It is also recognized as one of the four most important water conservation projects of imperial or pre-imperial China, along with the Zhengguo Canal, Lingqu Canal, and Dujiangyan. A temple with a statue representing Wang Yuanwei and ten builders of Tashan Weir was built nearby, and important ceremonies and cultural festivities are regularly held there.
Gallery
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View from the northern bank of the river -
First edge of the dam -
Second edge of the dam -
View from the west -
View from the east -
Holes where molten iron was introduced -
Temple dedicated to Wang Yuanwei -
Stele marking the emplacement of the temple -
Statue of Wang Yuanwei
See also
References
Citations
- ^ The 它 of 它山堰 is read as "Tuō" and not as "Tā"
- ^ angelakis, Andreas; Mays, Larry; Koutsoyiannis, Demetris; Mamassis, Nikos (2012). Evolution of Water Supply Through the Millennia. London: IWA Publishing. p. 198. ISBN 9781843395409.
- ^ Angelakis et al., p. 198.
Bibliography
- Andreas N. Angelakis, Larry W. Mays, Demetris Koutsoyiannis, Nikos Mamassis, Evolution of Water Supply Through the Millennia.
- Han Zhang, China’s Local Entrepreneurial State and New Urban Spaces: Downtown.
- Yongxiang Lu, A History of Chinese Science and Technology, Volume 3.