Ancient history Archaeological investigations have found evidence of irrigation in areas lacking sufficient natural
rainfall to support
rainfed agriculture. Some of the earliest known use of the technology dates to the 6th millennium BCE in
Khuzistan in the south-west of
Iran. The site of
Choga Mami, in present-day Iraq on the border with Iran, is believed to be the earliest to show the first canal irrigation in operation at about 6000 BCE. Irrigation was used to manipulate water in the alluvial plains of the
Indus Valley Civilization, with its application estimated to have begun around 4500 BCE and to have drastically increased the size and prosperity of their agricultural settlements. The Indus Valley Civilization developed sophisticated irrigation and water-storage systems, including artificial
reservoirs at
Girnar dated to 3000 BCE, and an early
canal irrigation system from 2600 BCE. Large-scale agriculture was practiced, with an extensive network of canals used for irrigation. Farmers in the
Mesopotamian plain used irrigation from at least the third millennium BCE. They developed
perennial irrigation, regularly watering crops throughout the
growing season by coaxing water through a matrix of small channels formed in the field.
Ancient Egyptians practiced
basin irrigation using the
flooding of the Nile to inundate land plots which had been surrounded by
dikes. The flood water remained until the fertile sediment had settled before the engineers returned the surplus to the
watercourse. There is evidence of the ancient Egyptian
pharaoh Amenemhet III in the
twelfth dynasty (about 1800
BCE) using the natural lake of the
Faiyum Oasis as a reservoir to store surpluses of water for use during dry seasons. The lake swelled annually from the flooding of the
Nile. s restoring and developing the old
Mughal irrigation system in 1847 during the reign of the
Mughal Emperor Bahadur Shah II in Indian subcontinent The
Ancient Nubians developed a form of irrigation by using a
waterwheel-like device called a
sakia. Irrigation began in Nubia between the third and second millennia BCE. It largely depended upon the flood waters that would flow through the
Nile River and other rivers in what is now the Sudan. In
sub-Saharan Africa, irrigation reached the
Niger River region cultures and civilizations by the first or second millennium BCE and was based on wet-season flooding and water harvesting. Evidence of
terrace irrigation occurs in pre-Columbian America, early Syria, India, and China. The
noria, a water wheel with clay pots around the rim powered by the flow of the stream (or by animals where the water source was still), first came into use at about this time among
Roman settlers in North Africa. By 150 BCE, the pots were fitted with valves to allow smoother filling as they were forced underwater.
Sri Lanka The irrigation works of ancient
Sri Lanka, the earliest dating from about 300 BCE in the reign of King
Pandukabhaya, and under continuous development for the next thousand years, were one of the most complex irrigation systems of the ancient world. They included underground canals and artificial reservoirs to store water. These reservoirs and canal systems were used primarily to irrigate
paddy fields, which require a lot of water to cultivate. Most of these irrigation systems still exist undamaged to this day in
Anuradhapura and
Polonnaruwa, thanks to their advanced and precise engineering. The system was extensively restored and further extended during the reign of King
Parakrama Bahu (1153–1186
CE).
China tunnel at
Turpan, Xinjiang, China The oldest known
hydraulic engineers of
China were
Sunshu Ao (6th century BCE) of the
Spring and Autumn period and
Ximen Bao (5th century BCE) of the
Warring States period, both of whom worked on large irrigation
projects. In the
Sichuan region belonging to the
state of Qin of ancient China, the
Dujiangyan Irrigation System devised by the Qin Chinese hydrologist and irrigation engineer
Li Bing was built in 256 BCE to irrigate a vast area of farmland that today still supplies water. By the 2nd century CE, during the
Han dynasty, the Chinese also used
chain pumps which lifted water from a lower elevation to a higher one. These were powered by manual foot-pedal, hydraulic
waterwheels, or rotating mechanical wheels pulled by
oxen. The water was used for
public works, providing water for urban residential quarters and palace gardens, but mostly for irrigation of
farmland canals and channels in the fields.
Korea Korea,
Chang Yŏngsil, also known as Jang Yeong-sil, a Korean engineer of the
Joseon dynasty, under the active direction of the king,
Sejong the Great, invented the world's first
rain gauge,
uryanggye () in 1441. It was installed in irrigation tanks as part of a nationwide system to measure and collect rainfall for agricultural applications. Planners and farmers could better use the information gathered in the survey with this instrument.
North America at Jang Yeong-sil Science Garden in
Busan The earliest agricultural irrigation canal system known in the area of the present-day
United States dates to between 1200 BCE and 800 BCE and was discovered by Desert Archaeology, Inc. in Marana, Arizona (adjacent to Tucson) in 2009. The irrigation-canal system predates the Hohokam culture by two thousand years and belongs to an unidentified culture. In North America, the Hohokam were the only culture known to rely on irrigation canals to water their crops, and their irrigation systems supported the largest population in the Southwest by CE 1300. The Hohokam constructed simple canals, combined with
weirs, for their agricultural pursuits. Between the 7th and 14th centuries, they built and maintained extensive irrigation networks along the lower
Salt and middle
Gila Rivers that rivaled the complexity of those used in the ancient Near East, Egypt, and China. These were constructed using relatively simple excavation tools, without the benefit of advanced engineering technologies, and achieved drops of a few feet per mile, balancing erosion and siltation. The Hohokam cultivated cotton, tobacco, maize, beans, and squash varieties and harvested an assortment of wild plants. Late in the Hohokam Chronological Sequence, they used extensive dry-farming systems, primarily to grow
agave for food and fiber. Their reliance on agricultural strategies based on canal irrigation, vital in their less-than-hospitable desert environment and arid climate, provided the basis for the aggregation of rural populations into stable urban centers.
South America The oldest known irrigation canals in the Americas are in the desert of northern Peru in the Zaña Valley near the hamlet of
Nanchoc. The canals have been
radiocarbon dated to at least 3400 BCE and possibly as old as 4700 BCE. The canals at that time irrigated crops such as
peanuts,
squash,
manioc,
chenopods, a relative of
Quinoa, and later
maize.
Modern history The scale of global irrigation increased dramatically over the 20th century. In 1800, 8 million hectares were irrigated; in 1950, 94 million hectares, and in 1990, 235 million hectares. By 1990, 30% of the global food production came from irrigated land. One of the main attractions of irrigation in the West was its increased dependability compared to rainfall-watered agriculture in the East. Proponents argued that farmers with a dependable water supply could more easily get loans from bankers interested in this more predictable farming model. Most irrigation in the
Great Plains region derived from underground
aquifers. Euro-American farmers who colonized the region in the 19th century tried to grow the commodity crops they were used to, such as
wheat,
corn, and
alfalfa, but rainfall limited their yields. Between the late 1800s and the 1930s, farmers used
wind-powered pumps to draw groundwater. These windpumps had limited power, but the development of gas-powered pumps in the mid-1930s pushed wells deep into the
Ogallala Aquifer. Farmers irrigated fields by laying pipes across the field with
sprinklers at intervals, a labor-intensive process, until the advent of the
center-pivot sprinkler after World War II, which made irrigation significantly easier. By the 1970s, farmers drained the aquifer ten times faster than it could recharge, and by 1993, they had removed half of the accessible water. Large-scale federal funding and intervention pushed through the majority of irrigation projects in the West, especially in
California,
Colorado,
Arizona, and
Nevada. At first, plans to increase irrigated farmland, largely by giving land to farmers and asking them to find water, failed across the board. Congress passed the
Desert Land Act in 1877 and the
Carey Act in 1894, which only marginally increased irrigation. Only in 1902 did Congress pass the
National Reclamation Act, which channeled money from the sale of western public lands, in parcels up to 160 acres large, into irrigation projects on public or private land in the arid West. The Congressmen who passed the law and their wealthy supporters supported Western irrigation because it would increase American exports, 'reclaim' the West, and push the Eastern poor out West for a better life. While the National Reclamation Act was the most successful piece of federal irrigation legislation, its implementation did not go as planned. The
Reclamation Service chose to push most of the Act's money toward construction rather than settlement, so the Service overwhelmingly prioritized building large dams like the
Hoover Dam. Over the 20th century, Congress and state governments grew more frustrated with the Reclamation Service and the irrigation schemes.
Frederick Newell, head of the Reclamation Service, proving uncompromising and challenging to work with, falling crop prices, resistance to delay debt payments, and refusal to begin new projects until the completion of old ones all contributed. The
Reclamation Extension Act of 1914, transferring a significant amount of irrigation decision-making power regarding irrigation projects from the Reclamation Service to Congress, was in many ways a result of increasing political unpopularity of the Reclamation Service. In the lower
Colorado Basin of
Arizona,
Colorado, and
Nevada, the states derive irrigation water largely from rivers, especially the
Colorado River, which irrigates more than 4.5 million acres of land, with a less significant amount coming from groundwater. In the 1952 case
Arizona v. California, Arizona sued California for increased access to the Colorado River, under the grounds that their groundwater supply could not sustain their almost entirely irrigation-based agricultural economy, which they won. California, which began irrigating in earnest in the 1870s in
San Joaquin Valley, had passed the
Wright Act of 1887 permitting agricultural communities to construct and operate needed irrigation works. The Colorado River also irrigates large fields in California's
Imperial Valley, fed by the National Reclamation Act-built All-American Canal.
Soviet Central Asia When the
Bolsheviks conquered
Central Asia in 1917, the native
Kazakhs,
Uzbeks, and
Turkmens used minimal irrigation. The Slavic immigrants pushed into the area by the Tsarist government brought their irrigation methods, including waterwheels, the use of
rice paddies to restore salted land, and underground irrigation channels. Russians dismissed these techniques as crude and inefficient. Despite this, tsarist officials maintained these systems through the late 19th century without other solutions. Before conquering the area, the Russian government accepted a 1911 American proposal to send hydraulic experts to Central Asia to investigate the potential for large-scale irrigation. A 1918 decree by
Lenin then encouraged irrigation development in the region, which began in the 1930s. When it did,
Stalin and other Soviet leaders prioritized large-scale, ambitious hydraulic projects, especially along the
Volga River. The Soviet irrigation push stemmed mainly from their late 19th century fears of the American cotton monopoly and subsequent desire to achieve cotton self-sufficiency. They had built up their textile manufacturing industry in the 19th century, requiring increased cotton and irrigation, as the region did not receive enough rainfall to support cotton farming. By 1975, the USSR used eight times as much water as it had in 1913, mostly for irrigation. Russia's expansion of irrigation began to decline in the late 1980s, and irrigated hectares in Central Asia peaked at 7 million.
Mikhail Gorbachev killed a proposed plan to reverse the Ob and Yenisei for irrigation in 1986, and the breakup of the USSR in 1991 ended Russian investment in Central Asian cotton irrigation.
Africa Various irrigation schemes with different goals and success rates were implemented across Africa in the 20th century, but were all influenced by colonial forces. The
Tana River Irrigation Scheme in eastern
Kenya, completed between 1948 and 1963, opened up new lands for agriculture. The Kenyan government attempted to resettle the area with detainees from the
Mau Mau uprising. Italian oil drillers discovered Libya's underground water resources during the
Italian colonization of Libya. This water lay dormant until 1969, when
Muammar al-Gaddafi and American
Armand Hammer built the
Great Man-Made River to deliver the Saharan water to the coast. The water largely contributed to irrigation but cost four to ten times more than the crops it produced were worth. In 1912, the
Union of South Africa established an irrigation department and began investing in water storage infrastructure and irrigation systems. The government used irrigation and dam-building to further social goals such as poverty relief by creating construction jobs for poor whites and by developing irrigation schemes to increase white farming. One of their first significant irrigation projects was the
Hartbeespoort Dam, begun in 1916 to elevate the living conditions of the 'poor whites' in the region and eventually completed as a 'whites only' employment opportunity. The
Pretoria irrigation scheme,
Kammanassie project, and Buchuberg irrigation scheme on the
Orange River all followed in the same vein in the 1920s and 30s. His administration proposed replacing the traditional
Nile basin irrigation, which took advantage of the annual ebb and flow of the Nile, with irrigation barrages in the lower Nile, which better suited cotton production. Egypt devoted 105,000 ha to cotton in 1861, a figure that increased fivefold by 1865. Most of their exports were shipped to England, and the United States Civil War-induced cotton scarcity in the 1860s cemented Egypt as England's cotton producer. As the Egyptian economy became more dependent on cotton in the 20th century, controlling even small Nile floods became more important. Cotton production was more at risk of destruction than more common crops like
barley or wheat. After the
British occupation of Egypt in 1882, the British intensified the conversion to perennial irrigation with the construction of the
Delta Barrage, the
Assiut Barrage, and the first
Aswan Dam. Perennial irrigation decreased local control over water and made traditional subsistence farming or the farming of other crops incredibly difficult, eventually contributing to widespread peasant bankruptcy and the
1879-1882 'Urabi revolt. ==Examples by country==