Canal irrigation is an important means of irrigation and is more common in the Northern Plains because:
1. The rivers are perennial
2. The water is stored in reservoirs by building dams across rivers
3. This water is then distributed to the fields by a network of canals
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1. Perennial Canals are the canals that have water in them throughout the year as they draw out water from perennial rivers or artificial lakes which have water in them. These are common in northern India where rivers are perennial.
2. Inundation Canals: These canals are taken out of rivers without building dams or weirs at their head, to regulate the flow of water. The excess water during floods flows into them.
Canals can be an effective source of irrigation in areas of low level relief, deep fertile soils, perennial source of water and extensive area. Therefore these are common in the Northern Plains in the states of Uttar Pradesh, Punjab, Haryana, Rajasthan and Bihar which account for about half of the canal irrigated area of the country. In the south Andhra Pradesh, Madhya Pradesh, Orissa and Tamil Nadu are important.
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Merits of Canal Irrigation
1. Canals bring down a lot of sediments from the rivers which make the soil fertile.
2. Most of the canals provide perennial irrigation and supply water as and when needed.
3: Although initial cost is much higher, Canal irrigation is quite cheap in the long run.
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Demerits of Canal Irrigation
1. Canals are generally not deep and since they are open they may dry up.
2. The water soaks into the ground and leads to the problem of water-logging.
3. The marshy areas near the canals act as breeding grounds for mosquitoes.
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4. Excessive flow of water brings the salt to the surface making the soil infertile.