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Irrigation

Irrigation (also referred to as watering of plants) 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 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,[1] 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.

This article is about irrigation for agriculture and landscapes. For other uses, see Irrigation (disambiguation).

There are several methods of irrigation that 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Irrigation water can come from groundwater (extracted from springs or by using wells), from surface water (withdrawn from rivers, lakes or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection.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 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 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 the altered hydrological conditions caused by the installation and operation of the irrigation scheme. Amongst some of these problems is 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 that can lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage.

Field Water Efficiency (%) = (Water Transpired by Crop ÷ Water Applied to Field) x 100

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.[34] Water use efficiency in the field can be determined as follows:


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.

Ground (e.g. New Orleans, Louisiana)

subsidence

Underirrigation or irrigation giving only just enough water for the plant (e.g. in drip line irrigation) gives poor which leads to increased soil salinity 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 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.[48]

soil salinity control

because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution.[49]

Overirrigation

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.[50][51] For example in Australia, over-abstraction of fresh water for intensive irrigation activities has caused 33% of the land area to be at risk of salination.[52]

salinity

also known as viscous fingering, where an unstable drainage front results in a pattern of fingers and viscous entrapped saturated zones.

Drainage front instability

Irrigation with or high-sodium water may damage soil structure owing to the formation of alkaline soil.

saline

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.

[53]

Macro-irrigation, typical in , where also are used agrochemicals, often causes eutrophication.

intensive agriculture

The hub of a center-pivot irrigation system

The hub of a center-pivot irrigation system

Leaks in micro-irrigation drip lines

Leaks in micro-irrigation drip lines

Sprinkler irrigation of blueberries in Plainville, New York, United States

Sprinkler irrigation of blueberries in Plainville, New York, United States

Irrigation in Tamil Nadu, India

Irrigation in Tamil Nadu, India

Irrigation ditch in Montour County, Pennsylvania, USA

Irrigation ditch in Montour County, Pennsylvania, USA

Water gardens in Sigiriya, Sri Lanka

Water gardens in Sigiriya, Sri Lanka

Micro-sprinkler

Micro-sprinkler

Deficit irrigation

Gezira Scheme

Irrigation management

Irrigation statistics

Leaf Sensor

Lift irrigation scheme

List of countries by irrigated land area

Surface irrigation

Tidal irrigation

Water use in alluvial fans

All pages with titles containing irrigation

Sources[edit]

 This article incorporates text from a free content work. Licensed under CC BY-SA IGO 3.0 (license statement/permission). Text taken from World Food and Agriculture – Statistical Yearbook 2023​, FAO, FAO.

International Commission on Irrigation and Drainage (ICID)

at the Water Quality Information Center, U.S. Department of Agriculture

Irrigation

: FAO's global information system on water and agriculture

AQUASTAT