Irrigation in agriculture is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures worldwide. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation. Irrigation and drainage improvements are not necessarily mutually exclusive. Often both may be required together to assure sustained high-level production of crops. For a discussion of the role of drainage practices in agriculture .
Several irrigation methods differ in how water is supplied to plants. Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. Micro-irrigation is a system that distributes water under low pressure through a piped network and applies it as a small discharge to each plant. Micro-irrigation uses less pressure and water flow than sprinkler irrigation. Drip irrigation delivers water directly to the root zone of plants. Subirrigation has been used in field crops in areas with high water tables for many years. It involves artificially raising the water table to moisten the soil below the root zone of plants.
Irrigation water can come from groundwater (extracted from springs or by using wells), from surface water (withdrawn from rivers, lakes or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. Irrigation can be supplementary to rainfall, which is common in many parts of the world as rainfed agriculture, or it can be full irrigation, where crops rarely rely on any contribution from rainfall. Full irrigation is less common and occurs only in arid landscapes with very low rainfall or when crops are grown in semi-arid areas outside the rainy season.
The environmental effects of irrigation relate to the changes in quantity and quality of soil and water as a result of irrigation and the subsequent effects on natural and social conditions in river basins and downstream of an irrigation scheme. The effects stem from altered hydrological conditions resulting from the installation and operation of the irrigation scheme. Amongst these problems is the depletion of underground aquifers through overdrafting. Soil can be over-irrigated due to poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution. Over-irrigation can cause deep drainage from rising water tables, which can lead to irrigation salinity problems, requiring watertable control through some form of subsurface land drainage.
Extent
The world’s total irrigated land area more than doubled between 1964 and 2023 and by 2023, 23% of all croplands were equipped for irrigation. In 2025, irrigated croplands produce 48% of all crops in value terms, indicating that irrigated land is 3.2 times more productive than rainfed land in value terms. On average, the yield of irrigated land is 76% higher than that of rain fed land.
The global land area equipped for irrigation reached 355 million ha in 2023, an increase of 23% from the 289 million ha of 2000 and more than twice the land area equipped for irrigation in the 1960s. The vast majority is located in Asia (71% in 2023), where irrigation was a key component of the green revolution; the Americas account for 16% and Europe for 8% of the world total. India (76 million ha) and China (75 million ha) have the largest equipped area for irrigation, far ahead of the United States of America (25 million ha). China and India also have the largest net gains in equipped area between 2000 and 2023 (+21 million ha for China and +15 million ha for India).
In 2000, the total fertile land was 2,788,000 km2 (689 million acres), and it was equipped with irrigation infrastructure worldwide. Roughly 68% of this area is in Asia, 17% in the Americas, 9% in Europe, 5% in Africa, and 1% in Oceania. The largest contiguous areas of high irrigation density are found in Northern and Eastern India and Pakistan along the Ganges and Indus rivers; in the Hai He, Huang He, and Yangtze basins in China; along the Nile river in Egypt and Sudan; and in the Mississippi-Missouri river basin, the Southern Great Plains, and in parts of California in the United States. Smaller irrigation areas are spread across almost all populated parts of the world.
By 2012, the area of irrigated land had increased to an estimated total of 3,242,917 km2 (801 million acres), which is nearly the size of India.The World. The World Factbook. Central Intelligence Agency. The irrigation of 20% of farming land accounts for the production of 40% of food production.
Global overview The scale of irrigation increased dramatically over the 20th century. In 1800, 8 million hectares globally were irrigated; in 1950, 94 million; and in 1990, 235 million. By 1990, 30% of the global food production came from irrigated land.McNeill 2000 pp.180–181. Irrigation techniques across the globe include canals redirecting surface water,McNeill 2000 pp.174.Peterson 2016 groundwater pumping, and diverting water from dams. National governments lead most irrigation schemes within their borders, but private investorsMcNeill 2000 pp.153. and other nations, especially the United States,Ekbladh 2002 pp.337. China,Bosshard 2009. and European countries like the United Kingdom,McNeill 2000 pp.169-170. also fund and organize some schemes within other nations.
By 2021, the global land area equipped for irrigation reached 352 million ha, an increase of 22% from the 289 million ha in 2000 and more than twice the land area equipped for irrigation in the 1960s. The vast majority is located in Asia (70%), where irrigation was a key component of the green revolution; the Americas account for 16%, and Europe for 8% of the world total. India (76 million ha) and China (75 million ha) have the largest irrigated area, far ahead of the United States of America (27 million ha). China and India also had the largest net gains in equipped area between 2000 and 2020 (+21 million ha in China and +15 million ha in India). All regions saw increases in irrigated area, with Africa growing the fastest (+29%), followed by Asia (+25%), Oceania (+24%), the Americas (+19%), and Europe (+2%).
Irrigation enables the production of more crops, especially commodity crops in areas that otherwise could not support them. Countries frequently invested in irrigation to increase wheat, rice, or cotton production, often with the overarching goal of increasing self-sufficiency.
Example values for crops +Approximate values of seasonal crop water needsCropCrop water needs mm / total growing periodSugarcane1500–2500Banana1200–2200Citrus900–1200Potato500–700Tomato400–800Barley/oats/wheat450–650Cabbage350–500Onions350–550Pea350–500
Water sources
Groundwater and surface water
Irrigation water can come from groundwater (extracted from springs or by using wells), from surface water (withdrawn from rivers, lakes or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection.
While floodwater harvesting is an accepted irrigation method, rainwater harvesting is usually not considered a form of irrigation. Rainwater harvesting is the collection of runoff water from roofs or unused land and its concentration.
Treated or untreated wastewater
Other sources Irrigation water can also come from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection.
In countries where humid air sweeps through at night, water can be obtained by condensation onto cold surfaces. This is practiced in the vineyards at Lanzarote using stones to condense water. Fog collectors are also made of canvas or foil sheets. Using condensate from air conditioning units as a water source is also becoming more popular in large urban areas.
, a Glasgow-based startup has helped a farmer in Scotland to establish edible salt marsh crops irrigated with seawater. An acre of previously marginal land has been put under cultivation to grow samphire, sea blite, and sea aster; these plants yield a higher profit than potatoes. The land is flood irrigated twice a day to simulate tidal flooding; the water is pumped from the sea using wind power. Additional benefits are soil remediation and carbon sequestration.
Competition for water resources
Until the 1960s, there were fewer than half as many people on the planet as there are in 2024. People were not as wealthy as today, consumed fewer calories and ate less meat, so less water was needed to produce their food. They required a third of the volume of water humans presently take from rivers. Today, the competition for water resources is much more intense, because there are now more than seven billion people on the planet, increasing the likelihood of overconsumption of food produced by water-thirsty animal agriculture and intensive farming practices. This creates increasing competition for water from industry, urbanisation, and biofuel crops. Farmers will have to strive to increase productivity to meet growing demands for food, while industry and cities find ways to use water more efficiently.Chartres, C. and Varma, S. Out of water. From Abundance to Scarcity and How to Solve the World's Water Problems, FT Press (USA), 2010
Successful agriculture depends on farmers having adequate access to water. However, water scarcity is already a critical constraint to farming in many parts of the world.
Irrigation methods There are several methods of irrigation. They vary in how the water is supplied to the plants. The goal is to apply the water to the plants as uniformly as possible, so that each plant has the amount of water it needs, neither too much nor too little. Irrigation can also be understood whether it is supplementary to rainfall, as happens in many parts of the world, or whether it is 'full irrigation, whereby crops rarely depend on any contribution from rainfall. Full irrigation is less common and occurs only in arid landscapes with very low rainfall or when crops are grown in semi-arid areas outside rainy seasons.
Surface irrigation