All the different sources of irrigation in India are divided into two major divisions; viz. Flow irrigation and Lift irrigation.
The water of a reservoir or tank usually remains at a higher level, and when a channel is connected to it, water automatically flows down the channel which serves the purpose of a canal for irrigating the land. In this case the water level remains higher than the fields. Such irrigation is known as the flow irrigation and it is generally possible in the plain areas.
But where the farm lands lie at a higher level and the canals or tanks lie at a lower level, it becomes necessary to lift the water by pump etc. to irrigate land. Water is lifted from wells and tanks by a crude country method (by tend) and from tube-wells by pumps for irrigation.
Nowadays the ground water is used for irrigation by lifting it by means of electric or diesel pump sets. Water is also lifted from wells tanks or rivers by pumps and irrigation is done through channels. This method of irrigation is known as the Lift Irrigation. Now a day’s sprinkle irrigation is being very much popular as more land can be irrigated with less water in this method.
The Irrigation Projects of India are classified into three types according to their capacity of irrigation.
They are (i) Major Irrigation Projects, (ii) Medium Irrigation Projects and (iii) Minor Irrigation Projects.
Irrigations in India carried are on in three different ways according to their sources, such as (i) by canals, (ii) by wells, and (iii) by tanks. Out of the total area under irrigation, 40 per cent are irrigated by canals, 40 per cent by wells and 12 per cent by tanks. The rest 8 per cent of land are irrigated by other methods.
1. Irrigation by Canals:
This is the most convenient method of irrigation. About half of the total area under irrigation by canals is situated in Punjab, Haryana, Uttar Pradesh and Andhra Pradesh. It is easy to dig canals in these areas since the land is level and soil soft.
There are two types of canals; such as: perennial canals and inundation canals. Artificial reservoirs are created by constructing annicuts. Barrages or dams across rivers for perennial canals. Irrigation is being done in the Mahanadi delta area by constructing barrages at Naraj and at Jobra of Cuttack city across the Mahanadi and at Choudwar across the river Birupu.
When there is excessive flow of water in the rivers in flood, the extra water flows in the canals rising from those rivers. Such canals are effective only during floods; hence those are known as the inundation canals. This type of canal is very few in number in the country, more in Punjab than elsewhere.
There are many perennial canals in different regions of the country and the most famous of those are the Upper Bari Doab Canal and the Sir hind Canal in Punjab, the West Yamuna Canal and the Chakra Canal in Haryana. The Chakra Canal is the largest canal of the country. This canal serves the purpose of irrigation in the states of Punjab and Haryana. The Rajasthan Canal (The Indira Gandhi Canal) of Rajasthan is the longest canal of Asia. The northwestern part of Rajasthan is being irrigated by it. The other important canals are the Shard Canal, the Beta Canal, the Upper Ganga and the Lower Ganga Canals of Uttar- Pradesh.
Many canals have been dug out of the rivers Krishna, Godavari und Tungabhadra of Andhra Pradesh. The other important canals are the Son Canal of Bihar, the Damodar Canal of West Bengal, the Mahanadi and the Rushikulya Canals of Orissa, the Mettur and the Periyar Canals of Tamilnadu. The Krishnarajsagar, the Tungabhadra and the Ghataprava Canals of Karnataka.
2. Irrigation by Wells:
The rain-water sinks down easily in the areas where the soil is soft and porous. So water is available at a lower depth when wells are dug and it helps irrigation. Primarily irrigation is carried on by wells in the western part of Uttar Pradesh, some parts of Bihar and in the blank cotton soil area of the Deccan.
In addition to it, in the coastal strip of Tamilnadu and Andhra Pradesh, some parts of Rajasthan, Haryana and Gujarat irrigation is also carried on by wells. Some or the other type of lift irrigation is required-for using the well-water for irrigation. Old methods like inot or ieiida are still practiced in many areas.
Power-driven pumps have become very popular in most parts. In some areas cattle or camels are used to lift water by the Persian wheels. The power-driven (electric or diesel) pumps can also lift water from a much greater depth from tube-wells. Now a days wind mills also lift water from the wells for irrigation purpose.
Irrigation by wells is more expensive, so more profitable farming of vegetables is carried on in those areas.
3. Irrigation by Tanks:
Tank irrigation is the most feasible and widely practiced method of irrigation all over the Peninsula, where most of the tanks are small in size and built by individuals or groups of farmers by raising bonds across seasonal streams.
The soil of this plateau is hard and stony and its land is undulated and so, it is not easy to dig canals or wells in those areas. There are big tanks which have been created by raising high bonds on one side of the valley of hills. Small channels are dug out of both the sides of the tanks to irrigate lands. There are big reservoirs like Nizam Sagar, Usman Sagar, Hossain Sagar, Krishna raj Sagar etc. in the peninsular India. Besides, in rural areas of the Peninsula there are large numbers of small tanks for irrigation, but such tanks dry up during acute drought period and don't help in irrigation.
Underground Water Resources:
A huge quantity of water has been stored under the ground since long. Now an organisation named the Central Underground Water Board has been set up in order to utilize this water. A map has been prepared by this organisation after surveying all over the country. This map shows the regions where underground water is easily available and at what depth.
Nowadays pure drinking water is being supplied by deep bored tubewells in the rural areas where pure drinking water is not available and in the coastal strip of Orissa having brined water. Lift irrigation is being carried on by sinking deep bored tube wells in the areas having scarcity of water for agriculture. People had not such idea regarding the underground water before India attained independence. So the underground water resources had not been developed.
Multipurpose River-Valley Projects:
Many multipurpose river valley projects have been developed in our country in order to utilize the vast water-resources of our rivers. Many purposes can be solved by creating reservoirs by constructing strong dams and embankments or bonds in the river beds.
Flood control, irrigation, generation of hydro-electricity, navigation, soil conservation, afforestation, pisciculture, water supply etc. have been the chief aims of these multipurpose projects. So these projects have been turned as Multipurpose River-Valley Projects. In addition to this, these projects have also been spots of tourist interest to attract tourists. Owing to generation of hydro-electricity, power supply has been cheap and convenient and growth of industry has been possible in our country.