ca·nal

Canals are waterways channels, or artificial waterways, for water conveyance, or to service water transport vehicles. They may also help with irrigation. It can be thought of as an artificial version of a river. Canals carry free surface flow under atmospheric pressure. In most cases, the engineered works will have a series of dams and locks that create reservoirs of low speed current flow. These reservoirs are referred to as slack water levels, often just called levels. The oldest known canals were irrigation canals, built in Mesopotamia circa 4000 BC, in what is now Iraq and Iran.

In ancient China, large canals for river transport were established as far back as the Spring and Autumn Period (8th–5th centuries BC), the longest one of that period being the Hong Gou (Canal of the Wild Geese), which according to the ancient historian Sima Qian connected the old states of Song, Zheng, Chen, Cai, Cao [曹国], and Wei [卫国].

The Caoyun [漕运] System of canals was essential for imperial taxation, which was largely assessed in kind and involved enormous shipments of rice and other grains. By far the longest canal was the Grand Canal of China, still the longest canal in the world today and the oldest extant one. It is 1,794 kilometres (1,115 mi) long and was built to carry the Emperor Yang Guang between Zhuojun [涿郡] (Beijing) and Yuhang [余杭] (Hangzhou). The project began in 605 and was completed in 609, although much of the work combined older canals, the oldest section of the canal existing since at least 486 BC. Even in its narrowest urban sections it is rarely less than 30 metres (98 ft) wide.

The Panama Canal is an artificial 82 km (51 mi) waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean. The Suez Canal is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea.

 

The South-to-North Water Diversion Project in China is the largest of its kind ever undertaken. The project involves drawing water from southern rivers and supplying it to the dry north. This massive scheme has already taken 50 years from conception to commencement and is expected to take almost as long to construct. Planned for completion in 2050, it will eventually divert 44.8 billion cubic metres of water annually to the population centres of the drier north. [link]

南水北调西线工程简称西线调水，是从长江上游调水至黄河。即在长江上游通天河、长江支流雅砻江和大渡河上游筑坝建库，坝址海拔高程2900-4000米，采用引水隧洞穿过长江与黄河的分水岭巴颜喀拉山调水入黄河。

Karez [坎儿井] is a water conservancy system in the arid region of Xinjiang, where wells are connected by underground channels. Water from a karez is used for water supply and irrigation. 坎儿井在《史记》中有记载(井渠)。维吾尔语则称之为“坎儿孜”。应为波斯语：Karez , (Persian; literally, an underground irrigation channel),an underground structure for collecting groundwater and conveying it to the surface. Such structures are in use in the mountainous and foothill areas of Middle Asia and Transcaucasia [外高加索]. 波斯是伊朗在欧洲的古希腊语和拉丁语的旧称译音，即波斯是伊朗的古名。

六级/考研单词: canal, convey, irrigate, dam, reservoir, slack, seldom, autumn, goose, accord, indispensable, imperial, evaluate, immense, grain, emperor, divert, undertake, construct, billion, subway, literal