Types of canals | Classification of canals | Alignment of canals

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What is Canal?

There different types of canals based on different purposes which I have described below one by one. An artificial waterway constructed to allow the passage of boats or ships inland or to convey water for irrigation.

Types of canals

Types of canals / classification of canals

A) According to function; canal is classified into;

1) Irrigation canal

This Types of canals carries water directly to the agricultural fields.

2) Navigation canal

The canal which is utilized for navigation besides doing irrigation.

3) Power canal

The canal which is utilized for power generation.

4) Feeder canal

It is constructed with the idea of feeding two or more canal.

5) Carrier canal

A carrier canal besides doing irrigation carries water for another canal.

B) Based on financial output, canal is classified into;

1) Productive canal

The types of canals which yields net revenue to the nation after full development of the irrigation in the area is known as productive canal.

2) Protective canal

The canal which is constructed with the idea of protecting a particular area from famine is termed as productive canal.

Based on nature of source, canal is classified into;

4) Permanent canal

A canal is said to be permanent when provision of a regular graded channel and masonry works for regulation and distribution is justified by a well assured source of supply.

5) Inundation canal

They draw their supplies from the river when there is a high stage in the river. They are not provided with any head works for diversion of river water to the canal.

C) Based on discharge and relative importance;

  1. Main canal
  2. Branch canal ( Discharge > 5 cumec )
  3. Major distributary ( discharge ¼ to  5 cumec )
  4. Minor distributary ( discharge < ¼ cumec )

D) Based on canal alignment;

  1. Watershed canal
  2. Contour canal
  3. Side slope canal

E) Based on lining

  1. Unlined canal
  2. Lined canal
These are the different types of canals. Now let us discuss about the different components of canal.
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Components of canal irrigation system

The components of canal irrigation system are as follows;

1) Head work

The headworks comprise of all the works to store divert and controls the river water and regulate supplies into the canal.

The headworks comprise of all the works to store divert and controls the river water and regulate supplies into the canal.

2) Canal network

It may consists of main canal branch, canal, distributaries, water canal etc.

  • Main ( major ) canal

It is the headworks taking off from the head work. No direct irrigation is usually carried out from the main canal.

  • Branch canal

When irrigation canal reaches the area which is to be irritating, it gets divided into branches going to different parts of the area. These branches are called branch canal.

  • Major distributaries

These are small channel taking off from the branch canals or something from the main canal.

  • Minor distributaries

These discharge are usually lessthan 0.25 cumecs. They supplies water to the water courses through the outlets provided along them.

  • Water courses

It is small channel connecting outlets to the fields. Farmers normally construct it.

3) Structures in canals

It consists of cross drainage structures, canal falls, canal escapes, cross regulators, distributary head regulators, outlets,etc.

  • Cross drainage structures

These are structures constructed at the crossing of canal and natural drainage so as dispose of drainage water takes place without interrupting the continuous canal supply.

  • Canal fall

Whenever the available natural ground slope is steeper than the design slope the difference is adjusted by a fall structures called canal drop or canal fall.

  • Cross regulators

It is a structure provided on the parent channel just downstream of the off take p[oint of the off taking channel to raise water level in the parent channel so that thje full supply can be taken into off taking channel evem when the parent channel is running full.

  • Distributary head regulator

A distributary head regulator is provided at the head of each distributor and branch channel.

  • Outlet

An outlet is usually pipe embedded in the bank of channel with discharging capacity in proportion to the area to be controlled from that canal.

Alignment of canal

Canal has to be aligned in such a way that it covers the entire area proposed to irrigated with shortest possible length and at the same time its cost including the cost of cross drainage is minimum. The alignment of canal should be done on the basis of following approach.

  1. The alignment should be done such that (1) Minimum number of C/D works (2) Most economical way of distributing the water to the land (3) as high command area as possible.
  2. The alignment of canal on watershed is preferred since it is most economical .
  3. The length of main canal should be minimum between two points.
  4. Alignment should avoid villages, roads, cart tracks, cremation places, places of worship and other valuable properties.
  5. Ideal length of canal should be minimum and branches should be economically planned.
  6. The alignment should not be made in a salty rocks or cracked strata.

Based on the alignment of canal irrigation, canal can be of the following three ways.

1) Watershed or ridge canal

Watershed or rigid canal is highest line between two drainage areas. It is aligned along a watershed or runs for most of its length on watershed. When a channel is on the watershed it can command areas on both banks.

Advantages

  1. It can command areas on both banks so large area can be brought under cultivation.
  2. No drainage can intersect watershed and hence the necessary of construction of cross drainage structures are avoided.

Disadvantages

  1. The depression in the ridge line may also necessitate construction of canal bridge, siphons.
  2. In head reach it is not economical to align in ridge.
  3. If watershed is passing through village  or towns this canal may have to leave the watershed for some distance.

2) Contour canal

A channel is aligned parallel to contour except for the necessary longitudinal slope is called a contour canal. Such type of canal is constructed  in hilly areas.

Advantages

  1. It is economical than ridge canal when ridge is very higher than river flows.
  2. It is suitable for contour farming.

Disadvantages

  1. It irrigates only one side of the canal so it serve the small area.
  2. As the drainage flow is always a right angle to contours such a canal would have more cross drainage structures.

3) Side slope canal

It is a channel aligned roughly at the right angle to contours. Such a channel is roughly parallel to the natural drainage and hence does not intercept cross drainage and hence no cross drainage structure is required.

Largest man made canal in the world

The largest man-made canal in the world is the Suez canal. It is a sea-level waterway in Egypt. It is connecting the Mediterranean sea to the Red Sea through the Isthmus of Suez.

It was constructed by the Suez Canal Company between 1859 and 1869 and officially opened on 17 November 1869. An estimated 1.5 million people had worked on this project. 

This canal allows the relation between Europe and Asia. And also from the Indian Ocean to the North Atlantic Ocean without any obstacle between them.

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