Classification of canals based on the nature of source of supply & Inundation canal
Based on the nature of supply, there are following types of canals.
- Perennial canal/Permanent canal.
- Non-perennial canal.
- Inundation canal/rainy canal.
Perennial canal/Permanent canal
These are the canals which get continuous supplies by permanent source of supply like a river or reservoir.
These irrigate the field throughout the year with equitable rate of flow.
These are the canals which irrigate the field for only one part of the year. They irrigate usually during summer season or at the beginning and the end of winter season.
These canals take-off water from the rivers which do not assured supply throughout the year.
Inundation canal/rainy canal
These are the earliest form of water conveyance channels. They take off water directly from the river. They are not provided with permanent head works, like a weir or barrage across the river. These canals work only when water in the river rises during high flow season. When water become less, these canals become inoperative. Similarly, if river changes its course, the canal would stop drawing water and ultimately dry up. Therefore, unlike a barrage controlled perennial canal, an inundation canal suffers from the unpredictable behavior of the river.
Most of the inundation canals located in South Asian sub-continent were constructed in the 17th century AD, the Mughal era. Some of the canals are functioning till now. However, most of them cease to function. They have been converted into barrage controlled perennial canals. These canals are generally excavated parallel to the river course. Some of the inundation canals had a very large capacity of 300 cumecs. There were also small inundation canals drawing few hundred cumecs.