Tuesday, February 21, 2012
China - Mount Qingcheng and the Dujiangyan Irrigation System
Mount Qingcheng and the Dujiangyan Irrigation System.
Sent by Doris, a postcrosser from Guangzhou, China.
This is from UNESCO : The Dujiangyan Irrigation System, begun in the 2nd century BC, is a major landmark in the development of water management and technology, and is still discharging its functions perfectly. It graphically illustrates the immense advances in science and technology achieved in ancient China. The temples of Mount Qingcheng are closely associated with the foundation of Taoism, one of the most influential religions of East Asia over a long period of history.
In 256 BC Li Bing, Shu Kingdom magistrate of the Qin dynasty, selected the mountain outlet of the Minjiang River, with its abundant water flow, as the site for an irrigation system. This involved cutting the Lidui platform, digging canals to avoid the risk of flooding, and opening up a navigation route; at the same time the neighbouring farmland would be irrigated, creating a 'Land of Abundance'.
During the Tang dynasty (618-907) large-scale water conservancy and irrigation projects were carried out. The system was rationalized during the Song dynasty (960-1279) into three main water-courses, three canals and fourteen branches, with coordinated maintenance and water control. During the Yuan dynasty (1206-1368) additional projects were carried out, and this process continued throughout the Ming dynasty (1368-1644). Incessant warfare at the end of the Ming dynasty and the early years of the Qing dynasty (1644-1913) resulted in the system falling into disrepair, but this was eventually set to rights.
In AD 142 the philosopher Zhang Ling founded the doctrine of Taoism on Mount Qingcheng, and in the following year he took up permanent residence in what became known as the Celestial Cave of the Tianshi (the name given to the spiritual head of the Taoist religion). During the Jin dynasty (265-420) a number of Taoist temples were built on the mountain, and it became the centre from which the teachings of Taoism were disseminated widely throughout China.
The irrigation system consists of two principal components, the Weir Works and the irrigated area. The Weir Works form the heart of the system. It receives water from the upper valley of the Minjiang River. There are three main elements. The Yuzui Bypass Dyke is located at the outfall of the Minjiang River. Water from the upper valley is diverted into the Outer and Inner Canals: the former follows the course of the Minjiang River and the latter flows to the Chengdu plain through the Baopingkou Diversion Passage. It serves the essential function of bypassing the considerable amount of silt brought down by the river. It makes full use of the bend, directing surface water with low concentrations of silt into the Inner Canal and the heavily silted deeper water into the Outer Canal.
The Feiyashan Floodgate is situated between the lower end of the Yuzui Bypass Dyke and the V-Shaped Dyke. Its upper end is 710 m from the Bypass Dyke and 120 m from the Baopingkou Diversion Passage. The principal function of the Floodgate is to transfer overflow, together with silt and pebbles, from the Inner to the Outer Canal. When water flow in the Inner Canal is low, the Floodgate ceases its draining function and transfers water into the Weir Works to ensure the supply of irrigation water to the Chengdu Plains. The Baopingkou Diversion Passage lies between the Lidui Platform south of Dujiangyan City and the cliff facing it, an enormous engineering project that dates back to the beginning of the Irrigation System in the 3rd century BC. It is able to control and maintain the water flow to the Chengdu irrigated plains automatically, even in periods of drought or flooding.
Mount Qingcheng dominates the Chengdu plains. There are eleven temples on Mount Qingcheng of special significance in the field of Taoist architecture because, unlike Mount Wudang temples, they do not reproduce the features of imperial courts but the traditional architecture of western Sichuan. The Erwang Temple west of Dujiangyan City was considerably enlarged during the Song dynasty (960-1279) and substantially reconstructed in the 17th century. It is constructed of wood and is located on a commanding point of the mountain, overlooking the river. The carvings inside the temple record the history and achievements of water control.