Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

land Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% of Earth's surface and includes all continents and islands. Earth's land sur ...

to help grow

crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, Fiber, fibre, or fuel. When plants of the same spe ...

s, landscape plants, and

lawn A lawn () is an area of soil-covered land planted with Poaceae, grasses and other durable plants such as clover lawn, clover which are maintained at a short height with a lawn mower (or sometimes grazing animals) and used for aesthetic an ...

s. Irrigation has been a key aspect of

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

for over 5,000 years and has been developed by many cultures around the world. 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 A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...

growth in

grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...

fields, and prevent

soil consolidation Soil consolidation refers to the soil mechanics, mechanical process by which soil changes volume gradually in response to a change in pressure. This happens because soil is a three-phase material. The first phase consists of soil grains, and a ...

. It is also used to cool

livestock Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The t ...

, reduce

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

, dispose of

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewerage, sewer system. Sewage consists of wastewater discharged fro ...

, and support

mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

operations.

Drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging (anaerobic conditions that harm root gro ...

, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation. There are several methods of irrigation that differ in how water is supplied to plants.

Surface irrigation Surface irrigation is where water is applied and distributed over the soil surface by gravity. It is by far the most common form of irrigation throughout the world and has been practiced in many areas virtually unchanged for thousands of years. ...

, 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 Drip irrigation or trickle irrigation is a type of micro-irrigation system that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surfac ...

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 Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

(extracted from springs or by using wells), from surface water (withdrawn from

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. Irrigation can be supplementary to

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

fall, 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 only occurs in arid landscapes with very low rainfall or when crops are grown in semi-arid areas outside of rainy seasons. The environmental effects of irrigation relate to the changes in quantity and quality of

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

and

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 the altered hydrological conditions caused by the installation and operation of the irrigation scheme. Amongst some of these problems is depletion of underground

aquifers An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

through

overdrafting Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pum ...

. Soil can be over-irrigated due to poor distribution uniformity or

management Management (or managing) is the administration of organizations, whether businesses, nonprofit organizations, or a Government agency, government bodies through business administration, Nonprofit studies, nonprofit management, or the political s ...

waste Waste are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor Value (economics), economic value. A wast ...

s water, chemicals, and may lead to

water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...

. Over-irrigation can cause deep drainage from rising water tables that can lead to problems of irrigation

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

requiring watertable control by some form of subsurface land drainage.

Extent

In 2000, the total fertile land was 2,788,000 km² (689 million acres) and it was equipped with irrigation infrastructure worldwide. About 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 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 hectares, and in 1990, 235 million hectares. By 1990, 30% of the global food production came from irrigated land. McNeill 2000 pp.180–181. Irrigation techniques across the globe includes canals redirecting surface water, McNeill 2000 pp.174. Peterson 2016

pumping, and diverting water from dams. National governments lead most irrigation schemes within their borders, but private investors McNeill 2000 pp.153. and other nations, especially the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, Ekbladh 2002 pp.337.

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, Bosshard 2009. and European countries like the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, 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 of 2000 and more than twice the 1960s land area equipped for irrigation. 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 equipped area for irrigation, far ahead of the United States o fAmerica (27 million ha). China and India also have the largest net gains in equipped area between 2000 and 2020 (+21 million ha for China and +15 million ha for India). All the regions saw increases in the area equipped for irrigation, 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 which otherwise could not support them. Countries frequently invested in irrigation to increase

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

, or

cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...

production, often with the overarching goal of increasing self-sufficiency.

Example values for crops

Water sources

Groundwater and surface water

Irrigation water can come from

(extracted from springs or by using wells), from surface water (withdrawn from

s or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. While floodwater harvesting belongs to the accepted irrigation methods,

rainwater harvesting Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a Rainwater tank, tank, cistern, deep pit (well, shaft, or borehole), Aquifer s ...

is usually not considered as a form of irrigation. Rainwater harvesting is the collection of runoff water from roofs or unused land and the concentration of this.

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 Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...

onto cold surfaces. This is practiced in the vineyards at

Lanzarote Lanzarote (, , ) is a Spanish island, the easternmost of the Canary Islands, off the north coast of Africa and from the Iberian Peninsula. Covering , Lanzarote is the fourth-largest of the islands in the archipelago. With 163,230 inhabi ...

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 saltmarsh crops irrigated with sea water. 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 Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in Climate change mitigation, limiting climate change by reducing the amount of Carbon dioxide in Earth's atmosphere, carbon dioxide in the atmosphe ...

Competition for water resources

Until the 1960s, there were fewer than half the number of people on the planet as of 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 Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. These resources can be either Fresh water, freshwater from natural sources, or water produ ...

is much more intense, because there are now more than seven billion people on the planet, increasing the likelihood of

overconsumption Overconsumption describes a situation where consumers overuse their available goods and services to where they can't, or don't want to, replenish or reuse them. In microeconomics, this is the point where the marginal cost of a consumer is greater ...

of food produced by water-thirsty animal agriculture and

intensive farming Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of arable farming, crop plants and of Animal husbandry, animals, with higher levels ...

practices. This creates increasing competition for water from industry,

urbanisation Urbanization (or urbanisation in British English) is the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It can also ...

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. Successful agriculture is dependent upon farmers having sufficient access to water. However,

water scarcity Water scarcity (closely related to water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity. One is ''physical.'' The other is ''economic water scarcity''. Physic ...

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 only happens in arid landscapes experiencing very low rainfall or when crops are grown in semi-arid areas outside of any rainy seasons.

Surface irrigation

Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In ''surface'' (''furrow,'' ''flood'', or ''level basin'') irrigation systems, water moves across the surface of agricultural lands, in order to wet it and infiltrate into the soil. Water moves by following gravity or the slope of the land. Surface irrigation can be subdivided into furrow,'' border strip or basin irrigation''. It is often called ''flood irrigation'' when the irrigation results in flooding or near flooding of the cultivated land. Historically, surface irrigation is the most common method of irrigating agricultural land across most parts of the world. The water application efficiency of surface irrigation is typically lower than other forms of irrigation, due in part to the lack of control of applied depths. Surface irrigation involves a significantly lower capital cost and energy requirement than pressurised irrigation systems. Hence it is often the irrigation choice for developing nations, for low value crops and for large fields. Where water levels from the irrigation source permit, the levels are controlled by dikes (

levee A levee ( or ), dike (American English), dyke (British English; see American and British English spelling differences#Miscellaneous spelling differences, spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural ...

s), usually plugged by soil. This is often seen in terraced rice fields (rice paddies), where the method is used to flood or control the level of water in each distinct field. In some cases, the water is pumped, or lifted by human or animal power to the level of the land. Surface irrigation is even used to water urban gardens in certain areas, for example, in and around

Phoenix, Arizona Phoenix ( ) is the List of capitals in the United States, capital and List of cities and towns in Arizona#List of cities and towns, most populous city of the U.S. state of Arizona. With over 1.6 million residents at the 2020 census, it is the ...

. The irrigated area is surrounded by a

berm A berm is a level space, shelf, or raised barrier (usually made of Soil compaction, compacted soil) separating areas in a vertical way, especially partway up a long slope. It can serve as a terrace road, track, path, a fortification line, a b ...

and the water is delivered according to a schedule set by a local irrigation district. A special form of irrigation using surface water is spate irrigation, also called floodwater harvesting. In case of a flood (spate), water is diverted to normally dry river beds (wadis) using a network of dams, gates and channels and spread over large areas. The moisture stored in the soil will be used thereafter to grow crops. Spate irrigation areas are in particular located in semi-arid or arid, mountainous regions.

Micro-irrigation

''Micro-irrigation'', sometimes called localized irrigation, low volume irrigation, or trickle irrigation is a system where water is distributed under low pressure through a piped network, in a pre-determined pattern, and applied as a small discharge to each plant or adjacent to it. Traditional drip irrigation use individual emitters, subsurface drip irrigation (SDI), micro-spray or micro-sprinklers, and mini-bubbler irrigation all belong to this category of irrigation methods.

Drip irrigation

Drip irrigation, also known as microirrigation or trickle irrigation, functions as its name suggests. In this system, water is delivered at or near the

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

zone of plants, one drop at a time. This method can be the most water-efficient method of irrigation, if managed properly; evaporation and runoff are minimized. The field water efficiency of drip irrigation is typically in the range of 80 to 90% when managed correctly. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer. The process is known as fertigation. Deep percolation, where water moves below the root zone, can occur if a drip system is operated for too long or if the delivery rate is too high. Drip irrigation methods range from very high-tech and computerized to low-tech and labor-intensive. Lower water pressures are usually needed than for most other types of systems, with the exception of low-energy center pivot systems and surface irrigation systems, and the system can be designed for uniformity throughout a field or for precise water delivery to individual plants in a landscape containing a mix of plant species. Although it is difficult to regulate pressure on steep slopes, pressure compensating emitters are available, so the field does not have to be level. High-tech solutions involve precisely calibrated emitters located along lines of tubing that extend from a computerized set of valves.

Sprinkler irrigation

Crop sprinklers Rio Vista California 15 Jul 2004-002

In ''sprinkler'' or overhead irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns. A system using sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a ''solid-set'' irrigation system. Higher pressure sprinklers that rotate are called ''rotors'' and are driven by a ball drive, gear drive, or impact mechanism. Rotors can be designed to rotate in a full or partial circle. Guns are similar to rotors, except that they generally operate at very high pressures of 275 to 900 kPa (40 to 130 psi) and flows of 3 to 76 L/s (50 to 1200 US gal/min), usually with nozzle diameters in the range of 10 to 50 mm (0.5 to 1.9 in). Guns are used not only for irrigation, but also for industrial applications such as dust suppression and

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidder, skidding, on-site processing, and loading of trees or trunk (botany), logs onto logging truck, trucks

Center pivot

Center pivot irrigation is a form of sprinkler irrigation utilising several segments of pipe (usually galvanized steel or aluminium) joined and supported by

truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...

es, mounted on wheeled towers with sprinklers positioned along its length. The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc. These systems are found and used in all parts of the world and allow irrigation of all types of terrain. Newer systems have drop sprinkler heads as shown in the image that follows. most center pivot systems have drops hanging from a U-shaped pipe attached at the top of the pipe with sprinkler heads that are positioned a few feet (at most) above the crop, thus limiting evaporative losses. Drops can also be used with drag hoses or bubblers that deposit the water directly on the ground between crops. Crops are often planted in a circle to conform to the center pivot. This type of system is known as LEPA (Low Energy Precision Application). Originally, most center pivots were water-powered. These were replaced by hydraulic systems ('' T-L Irrigation'') and electric-motor-driven systems (Reinke, Valley, Zimmatic). Many modern pivots feature GPS devices.

Irrigation by lateral move (side roll, wheel line, wheelmove)

A series of pipes, each with a wheel of about 1.5 m diameter permanently affixed to its midpoint, and sprinklers along its length, are coupled together. Water is supplied at one end using a large hose. After sufficient irrigation has been applied to one strip of the field, the hose is removed, the water drained from the system, and the assembly rolled either by hand or with a purpose-built mechanism, so that the sprinklers are moved to a different position across the field. The hose is reconnected. The process is repeated in a pattern until the whole field has been irrigated. This system is less expensive to install than a center pivot, but much more labor-intensive to operate – it does not travel automatically across the field: it applies water in a stationary strip, must be drained, and then rolled to a new strip. Most systems use 100 or 130 mm (4 or 5 inch) diameter aluminum pipe. The pipe doubles both as water transport and as an axle for rotating all the wheels. A drive system (often found near the centre of the wheel line) rotates the clamped-together pipe sections as a single axle, rolling the whole wheel line. Manual adjustment of individual wheel positions may be necessary if the system becomes misaligned. Wheel line systems are limited in the amount of water they can carry, and limited in the height of crops that can be irrigated. One useful feature of a lateral move system is that it consists of sections that can be easily disconnected, adapting to field shape as the line is moved. They are most often used for small, rectilinear, or oddly-shaped fields, hilly or mountainous regions, or in regions where labor is inexpensive.

Lawn sprinkler systems

A lawn sprinkler system is permanently installed, as opposed to a hose-end sprinkler, which is portable. Sprinkler systems are installed in residential lawns, in commercial landscapes, for churches and schools, in public parks and cemeteries, and on

golf course A golf course is the grounds on which the sport of golf is played. It consists of a series of holes, each consisting of a teeing ground, tee box, a #Fairway and rough, fairway, the #Fairway and rough, rough and other hazard (golf), hazards, and ...

s. Most of the components of these irrigation systems are hidden under ground, since aesthetics are important in a landscape. A typical lawn sprinkler system will consist of one or more zones, limited in size by the capacity of the water source. Each zone will cover a designated portion of the landscape. Sections of the landscape will usually be divided by

microclimate A microclimate (or micro-climate) is a local set of atmosphere of Earth, atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as a few square m ...

, type of plant material, and type of irrigation equipment. A landscape irrigation system may also include zones containing drip irrigation, bubblers, or other types of equipment besides sprinklers. Although manual systems are still used, most lawn sprinkler systems may be operated automatically using an irrigation controller, sometimes called a clock or timer. Most automatic systems employ electric

solenoid valve A solenoid valve is an electromechanically operated valve. Solenoid valves differ in the characteristics of the electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the ...

s. Each zone has one or more of these valves that are wired to the controller. When the controller sends power to the valve, the valve opens, allowing water to flow to the sprinklers in that zone. There are two main types of sprinklers used in lawn irrigation, pop-up spray heads and rotors. Spray heads have a fixed spray pattern, while rotors have one or more streams that rotate. Spray heads are used to cover smaller areas, while rotors are used for larger areas. Golf course rotors are sometimes so large that a single sprinkler is combined with a valve and called a 'valve in head'. When used in a turf area, the sprinklers are installed with the top of the head flush with the ground surface. When the system is pressurized, the head will pop up out of the ground and water the desired area until the valve closes and shuts off that zone. Once there is no more pressure in the lateral line, the sprinkler head will retract back into the ground. In flower beds or shrub areas, sprinklers may be mounted on above ground risers or even taller pop-up sprinklers may be used and installed flush as in a lawn area.

Hose-end sprinklers

Hose-end sprinklers are devices attached to the end of a garden hose, used for watering lawns, gardens, or plants. They come in a variety of designs and styles, allowing you to adjust the water flow, pattern, and range for efficient irrigation. Some common types of hose-end sprinklers include: Oscillating Sprinklers: These spray water back and forth in a rectangular or square pattern. They are good for covering large, flat areas evenly. Impact (or Pulsating) Sprinklers: These create a rotating, pulsating spray, which can cover a circular or semi-circular area. They are useful for watering large lawns. Stationary Sprinklers: These have a fixed spray pattern and are best for smaller areas or gardens. Rotary Sprinklers: These use spinning arms to distribute water in a circular or semi-circular pattern. Traveling Sprinklers: These move along the hose path on their own, watering as they go, ideal for covering long, narrow spaces. Each type offers different advantages based on garden size and shape, water pressure, and specific watering needs.

Subirrigation

Subirrigation has been used for many years in field crops in areas with high

water table The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...

s. It is a method of artificially raising the water table to allow the

to be moistened from below the plants'

zone. Often those systems are located on permanent grasslands in lowlands or river valleys and combined with drainage infrastructure. A system of pumping stations, canals, weirs and gates allows it to increase or decrease the water level in a network of ditches and thereby control the water table. Subirrigation is also used in the

commercial Commercial may refer to: * (adjective for) commerce, a system of voluntary exchange of products and services ** (adjective for) trade, the trading of something of economic value such as goods, services, information or money * a dose of advertising ...

greenhouse A greenhouse is a structure that is designed to regulate the temperature and humidity of the environment inside. There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight pass an ...

production, usually for potted plants. Water is delivered from below, absorbed by upwards, and the excess collected for recycling. Typically, a solution of water and

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s floods a container or flows through a trough for a short period of time, 10–20 minutes, and is then pumped back into a holding

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...

for reuse. Sub-irrigation in greenhouses requires fairly sophisticated, expensive equipment and management. Advantages are water and nutrient conservation, and labor savings through reduced system maintenance and

automation Automation describes a wide range of technologies that reduce human intervention in processes, mainly by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machine ...

. It is similar in principle and action to subsurface basin irrigation. Another type of subirrigation is the self-watering container, also known as a sub-irrigated planter. This consists of a planter suspended over a reservoir with some type of wicking material such as a polyester rope. The water is drawn up the wick through capillary action. A similar technique is the wicking bed; this too uses capillary action.

Efficiency

Modern irrigation methods are efficient enough to supply the entire field uniformly with water, so that each plant has the amount of water it needs, neither too much nor too little. Water use efficiency in the field can be determined as follows: * Field Water Efficiency (%) = (Water Transpired by Crop ÷ Water Applied to Field) x 100 Increased irrigation efficiency has a number of positive outcomes for the farmer, the community and the wider environment. Low application efficiency infers that the amount of water applied to the field is in excess of the crop or field requirements. Increasing the application efficiency means that the amount of crop produced per unit of water increases. Improved efficiency may either be achieved by applying less water to an existing field or by using water more wisely thereby achieving higher yields in the same area of land. In some parts of the world, farmers are charged for irrigation water hence over-application has a direct financial cost to the farmer. Irrigation often requires pumping energy (either electricity or fossil fuel) to deliver water to the field or supply the correct operating pressure. Hence increased efficiency will reduce both the water cost and energy cost per unit of agricultural production. A reduction of water use on one field may mean that the farmer is able to irrigate a larger area of land, increasing total agricultural production. Low efficiency usually means that excess water is lost through seepage or runoff, both of which can result in loss of crop nutrients or pesticides with potential adverse impacts on the surrounding environment. Improving the efficiency of irrigation is usually achieved in one of two ways, either by improving the system design or by optimising the irrigation management. Improving system design includes conversion from one form of irrigation to another (e.g. from furrow to drip irrigation) and also through small changes in the current system (for example changing flowrates and operating pressures). Irrigation management refers to the scheduling of irrigation events and decisions around how much water is applied.

Challenges

Environmental impacts

1960- Groundwater loss - depletion - Central Valley of California

Negative impacts frequently accompany extensive irrigation. Some projects which diverted surface water for irrigation dried up the water sources, which led to a more extreme regional climate. McNeill 2000 pp.164-165. Projects that relied on groundwater and pumped too much from underground aquifers created

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

and salinization. Salinization of irrigation water in turn damaged the crops and seeped into drinking water. Pests and pathogens also thrived in the irrigation canals or ponds full of still water, which created regional outbreaks of diseases like

malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...

and

schistosomiasis Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever is a neglected tropical helminthiasis, disease caused by parasitism, parasitic Schistosoma, flatworms called schistosomes. It affects both humans and animals. It affects ...

. McNeill 2019. Worster 1992 pp.112-13. McNeill 2000 pp.171. Governments also used irrigation schemes to encourage migration, especially of more desirable populations into an area. Parker 2020 Visser 2018 Worster 1992 pp.156-57. Additionally, some of these large nationwide schemes failed to pay off at all, costing more than any benefit gained from increased crop yields. Pisani 2002 p.5. McNeill 2000

Overdrafting Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pum ...

(depletion) of underground

: In the mid-20th century, the advent of diesel and electric motors led to systems that could pump

out of major

aquifer An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

s faster than

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

s could refill them. This can lead to permanent loss of aquifer capacity, decreased water quality, ground subsidence, and other problems. The future of food production in such areas as the

North China Plain The North China Plain () is a large-scale downfaulted rift basin formed in the late Paleogene and Neogene and then modified by the deposits of the Yellow River. It is the largest alluvial plain of China. The plain is bordered to the north by th ...

, the

Punjab region Punjab (; ; also romanised as Panjāb or Panj-Āb) is a geopolitical, cultural, and historical region in South Asia. It is located in the northwestern part of the Indian subcontinent, comprising areas of modern-day eastern Pakistan and no ...

in India and Pakistan, and the

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

of the US is threatened by this phenomenon.

Technical challenges

Irrigation schemes involve solving numerous engineering and economic problems while minimizing negative environmental consequences.ILRI, 1989, Effectiveness and Social/Environmental Impacts of Irrigation Projects: a Review. In: Annual Report 1988, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 18 – 34 . On line

/ref> Such problems include: * Ground

(e.g.

New Orleans, Louisiana New Orleans (commonly known as NOLA or The Big Easy among other nicknames) is a Consolidated city-county, consolidated city-parish located along the Mississippi River in the U.S. state of Louisiana. With a population of 383,997 at the 2020 ...

) * Underirrigation or irrigation giving only just enough water for the plant (e.g. in drip line irrigation) gives poor soil salinity control which leads to increased

soil salinity Soil salinity is the salt (chemistry), salt content in the soil; the process of increasing the salt content is known as salinization (also called salination in American and British English spelling differences, American English). Salts occur nat ...

with consequent buildup of toxic salts on soil surface in areas with high evaporation. This requires either leaching to remove these salts and a method of

drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging (anaerobic conditions that harm root gro ...

to carry the salts away. When using drip lines, the leaching is best done regularly at certain intervals (with only a slight excess of water), so that the salt is flushed back under the plant's roots. * Overirrigation because of poor distribution uniformity or

wastes water, chemicals, and may lead to

. * Deep drainage (from over-irrigation) may result in rising water tables which in some instances will lead to problems of irrigation

requiring watertable control by some form of subsurface land drainage. For example in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, over-abstraction of fresh water for intensive irrigation activities has caused 33% of the land area to be at risk of salination. * Drainage front instability, also known as viscous fingering, where an unstable drainage front results in a pattern of fingers and viscous entrapped saturated zones. * Irrigation with saline or high-sodium water may damage soil structure owing to the formation of

alkaline soil Alkali, or alkaline, soils are clay soils with high Soil pH, pH (greater than 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable ...

. * Clogging of filters: algae can clog filters, drip installations, and nozzles. Chlorination, algaecide, UV and ultrasonic methods can be used for algae control in irrigation systems. * Complications in accurately measuring irrigation performance which changes over time and space using measures such as productivity, efficiency, equity and adequacy. * Macro-irrigation, typical in intensive agriculture, where also are used agrochemicals, often causes

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

Social aspects

* Competition for surface water rights and territory defense. * Assisting smallholders in sustainably and collectively managing irrigation technology and changes in technology.

History

Ancient history

Archaeological investigation has found evidence of irrigation in areas lacking sufficient natural rainfall to support crops for 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 Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

. 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 as a means of manipulation of water in the alluvial plains of the

Indus valley civilization The Indus Valley Civilisation (IVC), also known as the Indus Civilisation, was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE, and in its mature form from 2600 BCE ...

, the application of which is estimated to have begun around 4500 BCE and drastically increased the size and prosperity of their agricultural settlements. The Indus Valley Civilization developed sophisticated irrigation and water-storage systems, including artificial

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

s at Girnar dated to 3000 BCE, and an early

canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...

irrigation system from 2600 BCE. Large-scale agriculture was practiced, with an extensive network of canals used for the purpose of irrigation. Farmers in the

Mesopotamia Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of ...

n plain used irrigation from at least the third-millennium BCE. They developed ''perennial irrigation'', regularly watering crops throughout the

growing season A season is a division of the year marked by changes in weather, ecology, and the amount of daylight. The growing season is that portion of the year in which local conditions (i.e. rainfall, temperature, daylight) permit normal plant growth. Whi ...

by coaxing water through a matrix of small channels formed in the field. Ancient Egyptians practiced ''basin irrigation'' using the

flooding of the Nile The flooding of the Nile (commonly referred to as ''the Inundation'') and its silt Deposition (geology), deposition was a natural cycle first attested in Ancient Egypt. It was of singular importance in the history and culture of Egypt. Governments ...

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 A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

.''p19'' Hill, A History of Engineering in Classical and Medieval Times There is evidence of the ancient Egyptian

pharaoh Pharaoh (, ; Egyptian language, Egyptian: ''wikt:pr ꜥꜣ, pr ꜥꜣ''; Meroitic language, Meroitic: 𐦲𐦤𐦧, ; Biblical Hebrew: ''Parʿō'') was the title of the monarch of ancient Egypt from the First Dynasty of Egypt, First Dynasty ( ...

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 The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

. 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 The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the longest river i ...

and other rivers in what is now the Sudan. In

sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...

, irrigation reached the

Niger River The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through Mali, Nige ...

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. In the Zana Valley of the

Andes Mountains The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, archaeologists have found remains of three irrigation

radiocarbon-dated Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE. These canals provide the earliest record of irrigation in the

New World The term "New World" is used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...

. Traces of a canal possibly dating from the 5th millennium BCE were found under the 4th-millennium canal.

Ancient Persia The history of Iran (also known as Persia) is intertwined with Greater Iran, which is a socio-cultural region encompassing all of the areas that have witnessed significant settlement or influence exerted by the Iranian peoples and the Iranian ...

(modern-day

) used irrigation as far back as the 6th millennium BCE to grow barley in areas with insufficient natural rainfall. The Qanats, developed in ancient

Persia Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

about 800 BCE, are among the oldest known irrigation methods still in use today. They are now found in Asia, the Middle East, and North Africa. The system comprises a network of vertical wells and gently sloping tunnels driven into the sides of cliffs and steep hills to tap groundwater. 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 into the water.

Sri Lanka

The irrigation works of ancient

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

, 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. In addition to underground canals, the Sinhalese were the first to build completely 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 up to now, in

Anuradhapura Anuradhapura (, ; , ) is a major city located in the north central plain of Sri Lanka. It is the capital city of North Central Province, Sri Lanka, North Central Province and the capital of Anuradhapura District. The city lies north of the cur ...

and

Polonnaruwa Poḷonnaruwa, (; ) also referred as Pulathisipura and Vijayarajapura in History of Sri Lanka, ancient times, is the main town of Polonnaruwa District in North Central Province, Sri Lanka. The modern town of Polonnaruwa is also known as New Town, ...

, because of the advanced and precise engineering. The system was extensively restored and further extended during the reign of King Parakrama Bahu (1153–1186 CE).

China

The oldest known

hydraulic Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...

engineers of

were Sunshu Ao (6th century BCE) of the

Spring and Autumn period The Spring and Autumn period () was a period in History of China, Chinese history corresponding roughly to the first half of the Eastern Zhou (256 BCE), characterized by the gradual erosion of royal power as local lords nominally subject t ...

and Ximen Bao (5th century BCE) of the

Warring States The Warring States period in Chinese history (221 BC) comprises the final two and a half centuries of the Zhou dynasty (256 BC), which were characterized by frequent warfare, bureaucratic and military reforms, and struggles for gre ...

period, both of whom worked on large irrigation

project A project is a type of assignment, typically involving research or design, that is carefully planned to achieve a specific objective. An alternative view sees a project managerially as a sequence of events: a "set of interrelated tasks to be ...

s. In the

Sichuan Sichuan is a province in Southwestern China, occupying the Sichuan Basin and Tibetan Plateau—between the Jinsha River to the west, the Daba Mountains to the north, and the Yunnan–Guizhou Plateau to the south. Its capital city is Cheng ...

region belonging to the

state of Qin Qin (, , or ''Ch'in'') was an ancient Chinese state during the Zhou dynasty. It is traditionally dated to 897 BC. The state of Qin originated from a reconquest of western lands that had previously been lost to the Xirong. Its location at ...

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 Han dynasty was an Dynasties of China, imperial dynasty of China (202 BC9 AD, 25–220 AD) established by Liu Bang and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–206 BC ...

, the Chinese also used chain pumps which lifted water from a lower elevation to a higher one.Needham, Joseph (1986). ''Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering''. Taipei: Caves Books Ltd. Pages 344–346. These were powered by manual foot-pedal, hydraulic waterwheels, or rotating mechanical wheels pulled by

oxen An ox (: oxen), also known as a bullock (in BrE, British, AusE, Australian, and IndE, Indian English), is a large bovine, trained and used as a draft animal. Oxen are commonly castration, castrated adult male cattle, because castration i ...

.Needham, Volume 4, Part 2, 340–343. The water was used for

public works Public works are a broad category of infrastructure projects, financed and procured by a government body for recreational, employment, and health and safety uses in the greater community. They include public buildings ( municipal buildings, ...

, providing water for urban residential quarters and palace gardens, but mostly for irrigation of

farmland Agricultural land is typically land ''devoted to'' agriculture, the systematic and controlled use of other forms of lifeparticularly the rearing of livestock and production of cropsto produce food for humans. It is generally synonymous with bot ...

canals and channels in the fields.Needham, Volume 4, Part 2, 33, 110.

Korea

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

, Jang Yeong-sil, a Korean engineer of the

Joseon dynasty Joseon ( ; ; also romanized as ''Chosun''), officially Great Joseon (), was a dynastic kingdom of Korea that existed for 505 years. It was founded by Taejo of Joseon in July 1392 and replaced by the Korean Empire in October 1897. The kingdom w ...

, under the active direction of the king,

Sejong the Great Sejong (; 15 May 1397 – 8 April 1450), commonly known as Sejong the Great (), was the fourth monarch of the Joseon, Joseon dynasty of Korea. He is regarded as the greatest ruler in Korean history, and is remembered as the inventor of Hangu ...

, invented the world's first

rain gauge A rain gauge (also known as udometer, ombrometer, pluviometer and hyetometer) is an instrument used by meteorologists and Hydrology, hydrologists to gather and measure the amount of liquid precipitation in a predefined area, over a set period of t ...

, ''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

The earliest agricultural irrigation canal system known in the area of the present-day

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 various simple canals combined with weirs in their various agricultural pursuits. Between the 7th and 14th centuries, they built and maintained extensive irrigation networks along the lower

Salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

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 ''Agave'' (; ; ) is a genus of monocots native to the arid regions of the Americas. The genus is primarily known for its succulent and xerophytic species that typically form large Rosette (botany), rosettes of strong, fleshy leaves. Many plan ...

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

peanut The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...

s, squash,

manioc ''Manihot esculenta'', common name, commonly called cassava, manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America, from Brazil, Paraguay and parts of the Andes. Although ...

, chenopods, a relative of

Quinoa Quinoa (''Chenopodium quinoa''; , from Quechuan languages, Quechua ' or ') is a flowering plant in the Amaranthaceae, amaranth family. It is a herbaceous annual plant grown as a crop primarily for its edible seeds; the seeds are high in prote ...

, and later

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

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. Irrigation techniques across the globe included canals redirecting surface water, groundwater pumping, and diverting water from dams. National governments led most irrigation schemes within their borders, but private investors and other nations, especially the

, and European countries like the

, funded and organized some schemes within other nations. Irrigation enabled the production of more crops, especially commodity crops in areas that otherwise could not support them. Countries frequently invested in irrigation to increase

, or

production, often with the overarching goal of increasing self-sufficiency. In the 20th century, global anxiety, specifically about the American cotton monopoly, fueled many empirical irrigation projects: Britain began developing irrigation in

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

, the

Ottomans Ottoman may refer to: * Osman I, historically known in English as "Ottoman I", founder of the Ottoman Empire * Osman II, historically known in English as "Ottoman II" * Ottoman Empire The Ottoman Empire (), also called the Turkish Empir ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

, the France, French in Algeria, the Portugal, Portuguese in Angola, the Germany, Germans in Togo, and Soviet Union, Soviets in Central Asia. Negative impacts frequently accompany extensive irrigation. Some projects that diverted surface water for irrigation dried up the water sources, which led to a more extreme regional climate. Projects that relied on groundwater and pumped too much from underground aquifers created

and salinization. Salinization of irrigation water damaged the crops and seeped into drinking water. Pests and pathogens also thrived in the irrigation canals or ponds full of still water, which created regional outbreaks of diseases like

and

. Governments also used irrigation schemes to encourage migration, especially of more desirable populations into an area. Additionally, some of these large nationwide schemes failed to pay off at all, costing more than any benefit gained from increased crop yields.

American West

Irrigated land in the

increased from 300,000 acres in 1880 to 4.1 million in 1890 to 7.3 million in 1900. Two thirds of this irrigation sources from

or small ponds and reservoirs, while the other one third comes from large dams. 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

region derived from underground

s. Euro-American farmers who colonized the region in the 19th century tried to grow the commodity crops that they were used to, like

, maize, corn, and alfalfa, but rainfall stifled their growing capacity. Between the late 1800s and the 1930s, farmers used windpump, 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 irrigation sprinkler, sprinklers at intervals, a labor-intensive process, until the advent of the center pivot irrigation, 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 Newlands Reclamation Act, 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, the implementation of the act did not go as planned. The United States Bureau of Reclamation, 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 Haynes Newell, 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 River, 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 Soviet Central Asia, 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 paddy fields, 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. Peterson 2016. 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, Joseph Stalin, Stalin and other Soviet leaders prioritized large-scale, ambitious hydraulic projects, especially along the Volga, 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. The Russians built dams on the Don (river), Don and Kuban (river), Kuban Rivers for irrigation, removing freshwater flow from the Sea of Azov and making it much saltier. Depletion and salinization scourged other areas of the Russian irrigation project. In the 1950s, Soviet officials began also diverting the Syr Darya and the Amu Darya, which fed the Aral Sea. Before diversion, the rivers delivered of water to the Aral Sea per year, but after, they only delivered . Because of its reduced inflow, the Aral Sea covered less than half of its original seabed, which made the regional climate more extreme and created airborne salinization, lowering nearby crop yields. By 1975, the USSR used eight times as much water as they had in 1913, mostly for irrigation. Russia's expansion of irrigation began to decrease in the late 1980s, and irrigated hectares in Central Asia capped out 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

Different irrigation schemes with various goals and success rates have been implemented across Africa in the 20th century but have all been influenced by colonial forces. The Tana River (Kenya), 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 rebellion, 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 Gaddafi, 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 created an irrigation department and began investing in water storage infrastructure and irrigation. The government used irrigation and dam-building to further social goals like poverty relief by creating construction jobs for poor whites and 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 Dam, Kammanassie project, and Buchuberg irrigation scheme on the Orange River all followed in the same vein in the 1920s and 30s. In Egypt, modern irrigation began with Muhammad Ali of Egypt, Muhammad Ali Pasha in the mid-1800s, who sought to achieve Egyptian independence from the

through increased trade with Europe—specifically cotton exportation. His administration proposed replacing the traditional flooding of the Nile, 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, which 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 history of Egypt under the British, 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 Low Dam, 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 'Urabi revolt, 1879-1882 'Urabi revolt.#refRoss2017, Ross 2017 p. 37-38.

Examples by country

Gallery

Center-pivot irrigation.jpg, upThe hub of a center-pivot irrigation system Irrigation drip leaks.jpg, Leaks in micro-irrigation drip lines Irrigated blueberries4046.jpg, Sprinkler irrigation of Blueberry, blueberries in Plainville, New York, United States Peanuts irrigation.jpg, Irrigation in Tamil Nadu, India Irrigation ditch in Montour County, Pennsylvania.JPG, upIrrigation ditch in Montour County, Pennsylvania, USA Sigiriya WaterGardens.JPG, Water gardens in Sigiriya, Sri Lanka Sprinkler Irrigation - Sprinkler head.JPG, Micro-sprinkler

References

Sources

* * * * * * * * * * * *

Sources

External links

International Commission on Irrigation and Drainage (ICID)

Irrigation
at the Water Quality Information Center, U.S. Department of Agriculture
AQUASTAT
FAO's global information system on water and agriculture {{Authority control Irrigation, Agricultural soil science Agronomy Environmental issues with water Land management Water management

Extent

Global overview

Example values for crops

Water sources

Groundwater and surface water

Treated or untreated wastewater

Other sources

Competition for water resources

Irrigation methods

Surface irrigation

Micro-irrigation

Drip irrigation

Sprinkler irrigation

Irrigation by lateral move (side roll, wheel line, wheelmove)

Lawn sprinkler systems

Hose-end sprinklers

Subirrigation

Efficiency

Challenges

Environmental impacts

Technical challenges

Social aspects

History

Ancient history

Sri Lanka

China

Korea

North America

South America

Modern history

American West

Soviet Central Asia

Africa

Examples by country

Gallery

See also

References

Sources

Sources

External links