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Columbia Encyclopedia entry: irrigation

Irrigation, in agriculture, artificial watering of the land. Although used chiefly in regions with annual rainfall of less than 20 in. (51 cm), it is also used in wetter areas to grow certain crops, e.g., rice. Estimates of total irrigated land in the world range from 543 to 618 million acres (220 to 250 million hectares), almost half of them in India, Pakistan, and China. The United States had almost 60 million acres (23.8 million hectares) of irrigated farmland in 1991. In many cases irrigation is correlated with drainage to avoid soil salinity, leaching, and waterlogging. Irrigation may also involve preliminary clearing, smoothing, and grading of land. Methods of applying water include free-flooding of entire areas from canals and ditches; check-flooding, in which water flows over strips or checks of land between levees, or ridges; the furrow method, in which water runs between crop or tree rows, penetrating laterally to the roots; the surface-pipe method, in which water flows in movable slip-joint pipes; sprinklers, including large-scale center-pivot and other self-propelled systems; and a variety of water-conserving drip and trickle systems. Since prehistoric times water has been diverted from waterways to fields by ditching. Early improvements for raising water included counterbalanced poles with attached water vessels, and adaptations of the wheel and of a pump called the Archimedes' screw. The use of canals, dams, weirs, and reservoirs for the distribution, control, and storage of water was probably initiated in ancient Egypt. In modern times pumps have facilitated the use of underground as well as surface water. Large-scale 20th-century irrigation projects commonly also include water supply, hydroelectric power, and flood control. Many regions, notably in China, Egypt, Mesopotamia, and India, have been under continuous irrigation from ancient times. Today China, India, the United States, and Pakistan rank highest in irrigated land. In North America, where most of the arid and semiarid land lies west of the 100th meridian, irrigation was first practiced in the Southwest by Native Americans and later by the Spanish, especially in California. As agriculture expanded, early irrigation initiatives by individual farmers or local groups were soon supplemented by commercial projects, until more ambitious water conservation and development schemes involved state and federal governments in vast projects. A drawback to intensive irrigation, especially in areas of high evaporation rates, is that excessive quantities of salts accumulate in the upper layers of the soil as water evaporates from the surface, rendering the soil unfit for crop production.

See J. Keller and R. D. Bliesner, Sprinkle and Trickle Irrigation (1990); B. A. Stewart and D. R. Nelson, Irrigation of Agricultural Crops (1990); W. F. Ritter, ed., Irrigation and Drainage (1991).

Wikipedia search results for: Irrigation

From Wikipedia, the free encyclopedia

Irrigation is an artificial application of water to the soil. It is usually used to assist in growing crops in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed farming. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given area. Irrigation is also a term used in medical/dental...more »

Columbia Encyclopedia search results: irrigation

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Kashka-Darya
Kashka-Darya, river, c.200 mi (320 km) long, Uzbekistan. It is the basis of a wide network of irrigation canals near the towns of Kitab and Kanshi.
Atwater
Atwater, city (1990 pop. 22,282), Merced co., central Calif., in the San Joaquin valley; inc. 1922. It is the processing and commercial center of an irrigated farming area. National wildlife r...
Manzanares
Manzanares, river, c.55 mi (90 km) long; rising in the Sierra de Guadarrama, central Spain, and flowing S past Madrid (where it is canalized) into the Jarama River. The Manzanares is used for ...
Penner
Penner, river, 350 mi (563 km) long, rising in the Eastern Ghats, Karnataka state, S India, and flowing N into Andhra Pradesh state, then E to the Bay of Bengal, near Nellore. The river is use...
Andijan
Andijan or Andizhan, city (1991 pop. 298,000), capital of Andijan region, Uzbekistan, in the Fergana Valley, on the Andijan-Say River. It is an industrial center in an irrigated area that prod...
Ahome
Ahome, city, Sinaloa state, W Mexico, on the Pacific Ocean. Ahome lies along the Inter-American Highway and is linked by rail with Mexico City. Sugarcane, grains, and cotton are grown in the r...
Minuf
Minuf, town (1986 pop. 69,673), N Egypt, between the Rashid (Rosetta) and Dumyat (Damietta) branches of the Nile River. It is the trade center for an irrigated agricultural region that produce...
Nizamabad
Nizamabad, city (1991 pop. 241,034), Andhra Pradesh state, S central India. It is a district administrative center and a market for grain, sugar, and vegetable oil. The district is irrigated b...
Boise project
Boise project, in the Boise, Payette, and Snake river valleys, SW Idaho and E Oregon; developed in 1905 by the U.S. Bureau of Reclamation for irrigation, hydroelectricity, flood control, and r...
Carey Land Act
Carey Land Act, sponsored by Sen. Joseph M. Carey and passed by the U.S. Congress in 1894. The act provided for the transfer to Western states of U.S.-owned desert lands on the condition that ...

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