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canal

Artificial waterway constructed for drainage, irrigation, or navigation. Irrigation canals carry water for irrigation from rivers, reservoirs, or wells, and are designed to maintain an even flow of water over the whole length. Navigation and ship canals are constructed at one level between locks, and frequently link with rivers or sea inlets to form a waterway system. The Suez Canal in 1869 and the Panama Canal in 1914 eliminated long trips around continents and dramatically shortened shipping routes.

Irrigation canals

The River Nile has fed canals to maintain life in Egypt since the earliest times. The division of the waters of the Upper Indus and its tributaries, which form an extensive system in Pakistan and Punjab, India, was, for more than ten years, a major cause of dispute between India and Pakistan, settled by a treaty in 1960. The Murray basin, Victoria, Australia, and the Imperial and Central Valley projects in California, USA, are examples of 19th- and 20th-century irrigation-canal development. Excessive extraction of water for irrigation from rivers and lakes can cause environmental damage.

Ship canals

Probably the oldest ship canal to be still in use, as well as the longest, is the Grand Canal in China, which links Tianjin and Hangzhou and connects the Huang He (Yellow River) and Chang Jiang. It was originally built in three stages: the first was finished around 486 BC, the second (linking the Chang Jiang and Huang He) was constructed from 605 to 610, and the third between 1282 and 1292. It reaches a total length of approximately 1,600 km/1,000 mi. Large sections silted up in later years, but the entire system was dredged, widened, and rebuilt between 1958 and 1964 in conjunction with work on flood protection, irrigation, and hydroelectric schemes. It carries millions of tonnes of freight every year.

Where speed is not a prime factor, the cost-effectiveness of transporting goods by canal has encouraged a revival; Belgium, France, Germany, and the states of the former USSR are among countries that have extended and streamlined their canals. The Baltic-Volga waterway links the Lithuanian port of Klaipeda with Kahovka, at the mouth of the Dnieper on the Black Sea, a distance of 2,430 km/1,510 mi. A further canal cuts across northern Crimea, thus shortening the voyage of ships from the Dnieper through the Black Sea to the Sea of Azov. In Central America, the Panama Canal (1904-14) links the Atlantic and Pacific oceans (64 km/40 mi). In North America, the Erie Canal (1825) links the Great Lakes with the Hudson River and opened up the northeast and Midwest to commerce; the St Lawrence Seaway (1954-59) extends from Montréal to Lake Ontario (290 km/180 mi) and, with the deepening of the Welland Ship Canal and some of the river channels, provides a waterway that enables ocean-going vessels to travel (during the ice-free months) between the Atlantic and Duluth, Minnesota, USA, at the western end of Lake Superior, some 3,770 km/2,342 mi.

Irrigation canals, dug from ancient times, prevented flooding and provided neolithic farming villages with an expanded area of rich alluvial soil, especially in the Tigris-Euphrates valley and along the Nile. Here agricultural surpluses eventually allowed for the rise of civilizations. Navigation canals developed after irrigation and drainage canals; often they link two waterways and were at first level and shallow. Locks were invented to allow passage where great variations in level existed. By the 20th century mechanized tows and self-propelled barges were in use.

Brindley, James Dortmund-Ems Canal

Egypt Grand Canal

Kara-Kum Kiel Canal

Nicaragua Canal Panama Canal

Suez Canal Trent Canal