Types of irrigation
There are three types of irrigation.
- Gravity flow or surface water flow.
- Tank or reservoir.
- Lift irrigation.
Gravity flow or surface irrigation
The irrigation in which the water flows under gravity from the source to the field is known as gravity flow irrigation.
Due to gravity water flows from higher areas to the lower areas. After which it is distributed in the fields. Silt in the canal water has a fertilizing agent. The whole canal irrigation in our country is gravity irrigation. The gravity flow irrigation is cheaper and quality of water is also good due to presence of soil content.
If the runoff is more than the required amount then headwork and barrages are constructed to store the water.
A headwork consists of a weir, canal head regulator, gate structure (barrage) .
So a headwork is a complete system of structures. Whereas barrage is a part of headwork.
Barrage is constructed in a path of river to block water.
The flow of a river is a seasonal flow. Sometimes more water is required and the source is limited. Sometimes less water is required and the source is high. So in order to regulate flow, the reservoirs are constructed. The function of reservoirs are
- To fulfil the irrigation requirements.
- To generate the hydraulic power.
- Regulate the river flow so as to avoid flood.
In some areas, small dams instead of canals are constructed for the irrigation purposes.
When the main source is at the lower level than the supply level. Then water is supplied through some mechanical means. This is known as lift irrigation.
This can be done by the following methods.
- Lift from canals.
- Open wells.
- Tube wells.
Lift from canals (Rivers)
Pumps are used to lift the water from canals or rivers at lower level to the area at higher level for irrigation purpose.
In villages there are some open holes whose depth intercepts the water table. So the water is taken out from lower level to the surface for irrigation purpose by adopting different mechanical means.
It is the lifting of water by pumping from underground reservoir. Extensive surface irrigation results in an increase in the ground water level due to percolation and seepage which causes water logging in large areas. Irrigation by this method will reduce the yield. Tube well offers a remedial measure by providing sub surface drainage.
Tube well irrigation can be obtained more quickly than from surface water project. Large costs involve in making canals for the construction of headworks, whereas less cost is involved in constructing tubewells.