This document discusses various types of canal structures used in irrigation systems including falls, regulators, outlets, cross drainage works, and escapes. Falls are structures used to lower water levels across canals. There are several types of falls including ogee, rapid, stepped, notch, vertical drop, and glacis. Regulators are used to control water flow between main canals and distributaries. Outlets supply water from distributaries to field channels. Cross drainage works allow streams to pass over or under canals. Escapes are side channels that remove excess water from canals to prevent damage from breaches.

1. Canal structures
Asst Prof: Mitali Shelke
St. John College of Engineering and Management, Palghar
Department of Civil Engineering

2. Canal falls:
A fall is an irrigation structure constructed across a Canal to lower down its water level and destroy
the surplus energy liberated from falling water which may otherwise scour the bed and banks of the
canal.
Arrangements are made to dissipate the excess energy liberated from the falling water.
Development of falls:
1. Ogee fall
2. Rapid fall
3. Stepped fall
4. Notch fall
5. Vertical drop fall
6. Glacis type fall

3. Classification of falls:
Class I : falls designed to maintain the depth discharge relation
Class II : falls designed to maintain a fixed supply level in the channel above the
work
Class III : falls designed to admit the variations of the surface level above the work
at the will of the operator
Class IV : miscellaneous types

4. Head regulator and cross regulator:
• Head regulator and cross regulator regulate the supplies of the off taking
channel and the parent channel respectively.
• Distributary head regulator is provided at the head of distributary and controls
the supply entering the distributary.
• It is a necessary link between the parent channel and the distributing channel
• A cross regulator is provided on the main Canal at the downstream of the off
take to head up the water level and to enable the off taking channel to draw the
required supply.

5. Canal outlets:
An outlet is a small structure which admits water from the distributing channel to a water
course or field channel.
Outlet is a sort of head regulator for the field channel delivering water to the irrigation field.
The efficiency of the canal network mostly depends upon functioning of the outlets and other
regulation works, Hence a Canal outlet should fulfill following requirements:
1. The outlet should be strong
2. The outlet should be designed such that the farmer cannot temper with its functioning
3. It should be cheap
4. The design should be simple
5. It should be possible for the outlet to work efficiently with a small working head
6. The outlet should draw its fair share of silt carried by the distributing channel
7. Outlet should be a fairly constant discharge.

6. Types of outlets:
1. Non modular outlet
2. Semi module or flexible module
3. Rigid module

7. Cross drainage works:
• It is a structure carrying the discharge of a natural stream a cross a canal
intercepting the stream.
• When a canal is to be taken to the watershed it crosses a number of natural
streams in the distance between the reservoir to the watershed.
• When a canal is aligned as a contour canal, a number of cross drainage works
are necessary.
• A cross drainage work is generally very costly and should be avoided as far as
possible by:
1) diverting one stream into another
2) changing the alignment of the canal so that it crosses below the junction of two
streams.

8. Types of cross drainage works:
1. Cross drainage works carrying Canal over the drainage.
2. Cross drainage works carrying drainage over the canal
3. Cross drainage works admitting the drainage water into the canal
Selection of suitable type of cross drainage work:
• The factors which affect the selection of suitable type of cross drainage works
are:
1. Relative bed levels and water levels of the canal and the drainage
2. Size of the canal and the drainage.

10. Canal escapes:
• An escape is a side channel constructed to remove surplus water from an irrigation channel (main
Canal, branch Canal or distributary) into a natural drain.
• The supplies shall be reduced or stopped from the head works but the effect of this reduction is
felt only after a certain time.
• Therefore in order to avoid damage some immediate action is required and this is achieved by
means of an escape, generally called a ‘surplus water escape’.
• The importance of such an escape is realised more in case a breach occurs in a channel.
• If a breach occurs immediately information is sent to the head so as to close down the channel
supplies.
• But the water already contained in the channel from the head to the breach site will cause wide
spread damage if allowed to pass through the breach.

11. • In such circumstances the escape existing on upstream of the breach is opened and most
of the water is allowed to escape.
• Hence it can be stated that “escapes are the safety values of canals and must be
provided at regular intervals depending upon the importance of the channel and
availability of a suitable drainage for the disposal of the escaped water.”
• The minimum capacity of the escape is generally kept as half of the channel capacity at
the point of the escape.
Types of Canal Escapes:
1. Wier type
2. Regulator type