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 1869 and the Panama Canal 1914 eliminated long trips around continents and dramatically shortened shipping routes.
Irrigation canals fed from the Nile have maintained 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 1960; the Murray basin, Victoria, Australia, and the Imperial and Central Valley projects in California, US, are examples of 19th- and 20th-century irrigation canal development.
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 485 BC–AD 283, reaching a total length of 1,780 km/1,107 mi. Large sections silted up in later years, but the entire system was dredged, widened, and rebuilt 1958–72 in conjunction with work on flood protection, irrigation, and hydroelectric schemes. It carries millions of metric tons of freight every year.
Where speed is not a prime factor, the cost-effectiveness of transporting goods by canal has encouraged a revival and Belgium, France, Germany, and the 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 the north 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 linked the Great Lakes with the Hudson River and opened the northeast and Midwest commercially; the St Lawrence Seaway 1954–59 extends from Montréal to Lake Ontario (290 km/180 mi) and, with the deepening of the Welland 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, US, at the western end of Lake Superior, some 3,770 km/2,342 mi.
Irrigation canals, dug from ancient times, provided flood control as well as neolithic farming villages with an expanded area of rich alluvial soil, especially in the Tigris-Euphrates valley and along the Nile, where 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. Soon, those with inclined planes had towpaths along which men and animals towed vessels from one level to the next. Locks were invented to allow passage where great variations in level exist. By the 20th century mechanized tows and self-propelled barges were in use.
1. Long and narrow strip of water made for boats or for irrigation.
2. (Astronomy) An indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion. + prikaži više

ETYM Old Eng. chanel, canel, Old Fren. chanel, French chenel, from Latin canalis. Related to Canal.
1. A relatively narrow body of water linking two larger bodies; SYN. sound.
2. A path over which electrical signals can pass; SYN. transmission channel.
3. (Often plural) A means of communication or access; SYN. communication channel, line.
1. A path or link through which information passes between two devices. A channel can be either internal or external to a microcomputer.
2. In communications, a medium for transferring information. Depending on its type, a communications channel can carry information (data, sound, and/or video) in either analog or digital form. A communications channel can be a physical link, such as the cable connecting two stations in a network, or it can consist of some electromagnetic transmission on one or more frequencies within a bandwidth in the electromagnetic spectrum, as in radio and television, or in optical, microwave, or voice-grade communication. Also called: circuit, line. See also analog, band, bandwidth, digital, electromagnetic spectrum, frequency.
3. A single color within a digital color space. For example, the rgb color space contains three channels—red, green, and blue—and all colors within the rgb color space are created with a combination of one or more of those three color channels. In cmyk there are four channels—cyan, magenta, yellow, and black. Color management and graphics applications rely on control and manipulation of individual color channels. See also color space. + prikaži više

ETYM French, from Late Lat. conductus escort, conduit. Related to Conduct.
A passage for water (or other fluids); SYN. channel.

ETYM Latin ductus a leading, conducting, conduit, from ducere, ductum, to lead. Related to Duke, Douche.
1. A bodily passage or tube conveying a secretion or other substance; SYN. canal, channel.
2. A continuous tube formed by a row of elongated cells lacking intervening end walls.
3. An enclosed conduit for a fluid.

1. A long hollow object (usually cylindrical) used to hold and conduct liquids or gases; SYN. tubing.
2. A system of electrodes arranged in an evacuated glass or metal envelope; SYN. vacuum tube, thermionic vacuum tube, thermionic tube, electron tube, thermionic valve.
3. (Anatomy) Any hollow cylindrical body structure; SYN. tube-shaped structure. + prikaži više