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Irrigation

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Irrigation is the practice of applying controlled amounts of water to land.

Fields SW from Sevilla
Fields SW from Sevilla

This process helps grow crops, maintain landscapes, and revegetate disturbed soils. It is especially vital in dry areas or during times of below-average rainfall. Beyond simple plant growth, irrigation serves many specialized roles. It can protect crops from frost and suppress weed growth in grain fields. It also prevents soil consolidation and can be used to cool livestock. In some settings, it helps reduce dust, dispose of sewage, or support mining operations.

There are several distinct methods used to supply water to plants. Surface irrigation, also known as gravity irrigation, is the oldest form.

LevelBasinFloodIrrigation
LevelBasinFloodIrrigation

In this method, water moves across agricultural lands by following the slope of the land. It can include furrow, border strip, or basin irrigation. Sprinkler irrigation uses pipes to move water to central locations. High-pressure devices then distribute the water overhead.

TravellingSprinkler
TravellingSprinkler

Micro-irrigation is a more precise system using a piped network under low pressure. Drip irrigation is a specific type of micro-irrigation that delivers water directly to the root zone.

Dripperwithdrop
Dripperwithdrop

Finally, subirrigation involves artificially raising the water table to moisten soil below the root zone.

Water for these systems comes from many different sources. Most water is drawn from surface water, such as rivers, lakes, or reservoirs.

Pump-enabled Riverside Irrigation in Comilla, Bangladesh, 25 April 2014
Pump-enabled Riverside Irrigation in Comilla, Bangladesh, 25 April 2014

It can also come from groundwater extracted from springs or wells. Some regions use non-conventional sources like treated wastewater or desalinated water. In certain climates, people use fog collection with canvas or foil sheets.

Vale do São Francisco Pernanbuco
Vale do São Francisco Pernanbuco

Even air conditioning condensate or seawater can be used in innovative ways. For example, a farmer in Scotland uses wind power to pump seawater for salt marsh crops.

Irrigation has a long and expanding history. Humans have used these techniques for over 5,000 years.

David Roberts ancient fountain
David Roberts ancient fountain

The global scale of irrigation increased dramatically during the 20th century. In 1800, only 8 million hectares were irrigated worldwide. By 1950, this grew to 94 million hectares. By 1990, it reached 235 million hectares.

Bisse
Bisse

By 2021, the global land area equipped for irrigation reached 352 million hectares. This is more than twice the land area equipped for irrigation in the 1960s.

The significance of irrigation to the global food supply is massive. While irrigated land is a fraction of all farmland, it is highly productive. Specifically, the irrigation of 20% of farming land accounts for 40% of total food production.

Share of agricultural land which is irrigated, OWID
Share of agricultural land which is irrigated, OWID

Different crops have very different water needs during their growing periods. For example, sugarcane requires 1500–2500 mm of water. In contrast, onions only need about 350–550 mm. Understanding these specific requirements is essential for efficient management.

Irrigation is distributed unevenly across the globe. Asia contains the vast majority of irrigated land, accounting for 70% of the total.

Area Equipped For Irrigation By Region
Area Equipped For Irrigation By Region

India and China have the largest irrigated areas, with 76 million and 75 million hectares respectively. The United States follows with 27 million hectares. Other major areas include the Mississippi-Missouri river basin and the Nile river in Egypt and Sudan. These regions often use irrigation to increase the production of wheat, rice, or cotton to reach self-sufficiency.

However, irrigation also presents environmental challenges that must be managed. Over-irrigation can lead to poor distribution uniformity and wasted water. This can cause water pollution from leaked chemicals. It can also lead to the depletion of underground aquifers through overdrafting. Rising water tables from over-irrigation may cause irrigation salinity problems. To fix this, farmers often use subsurface land drainage to control the water table. Managing these hydrological changes is a key part of modern agriculture.

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🖼️ Images & Media (18)
File:Fields SW from Sevilla.jpg
Fields SW from Sevilla.jpg
File:Share of agricultural land which is irrigated, OWID.svg
Share of agricultural land which is...
File:Area Equipped For Irrigation By Region.svg
Area Equipped For Irrigation By Region.svg
File:Bisse.jpg
Bisse.jpg
File:Pump-enabled Riverside Irrigation in Comilla, Bangladesh, 25 April 2014.jpg
Pump-enabled Riverside Irrigation in...
File:Vale do São Francisco Pernanbuco.jpg
Vale do São Francisco Pernanbuco.jpg
File:LevelBasinFloodIrrigation.JPG
LevelBasinFloodIrrigation.JPG
File:Residential flood irrigation in Phoenix, Arizona, in the United States of America.jpg
Residential flood irrigation in Phoenix,...
File:Dripperwithdrop.png
Dripperwithdrop.png
File:dripirrigation.gif
dripirrigation.gif
File:Crop sprinklers Rio Vista California 15 Jul 2004-002.jpg
Crop sprinklers Rio Vista California 15...
File:TravellingSprinkler.JPG
TravellingSprinkler.JPG

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