Irrigation systems are often designed to maximize efficiency & minimize labour & capital requirements. There are three broad classes of irrigation system:
- Pressurized distribution.
- Gravity flow distribution.
- Drainage flow distribution.
Pressurized distribution
The pressurized systems include sprinkler, trickle, in which water is conveyed to & distributed over the fields through pressurized pipe networks.
Gravity flow distribution
This system conveys & distributes water at the field level by a free surface, overland flow regime.
Drainage flow distribution
Irrigation by control of the drainage system sub irrigation is not so common but is interesting. Relatively large volumes of applied irrigation water percolate through the root zone & become a drainage or ground water flow. By controlling the flow at critical points, it is possible to raise the level of the ground water to within reach of the crop roots.
To supply water the entire field uniformly so that each plant would get sufficient amount of water, there are various types of irrigation techniques that differ in how the water obtained from the source is distributed within the field. These are:
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Surface Irrigation
In this irrigation system water moves over & across the land by simple gravity flow in order to wet it & to infiltrate into the so 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.
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Ditch Irrigation
This is the simplest & oldest irrigation system & it is still common in many parts of the world. The only technology essential is the manpower or machines to dig ditches or furrows between the rows of plants. Water is added to the ditches by means of gravity flow, pumps & siphons.
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Localized Irrigation
It is a system where water is distributed under low pressure through a piped network, in a pre-determined pattern, & applied as a small discharge.
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Drip Irrigation
This is also known as trickle irrigation. Water is delivered at or near the root zone of plants; drop by drop. This method can be the most water efficient method of irrigation.
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Overhead Irrigation
This is the artificial application of water to crops from above. Central pivot systems, which are in wide use in areas of flat terrain, have sprinklers spaced along very long aluminum or steel pipes that extend in two directions from a central supply point. Sprinkler systems are another very common overhead irrigation system. In these systems, water is piped to a point within the area to be irrigated.
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Sub-Irrigation
This is also called as seepage irrigation used for many years in the fields where water table is high. This method artificially raises the water table by allowing the soil to be moistened from below the plants‟ root zone.
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Manual Irrigation
This system has low requirements for infrastructure & technical equipment but needs high labour inputs by using buckets or watering cans.
