Canal Irrigation Management, Canal Regulation and Outlet Regulations

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Canal Irrigation Management, Canal
Regulation and Outlet Regulations
Presentation
on
By
Chethan B J
2019-28-003
Course Teacher:
Dr. Asha Joseph
Professor
Department of IDE
KCAET, Tavanur

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 An open canal, channel, or ditch, is an open waterway whose
purpose is to carry water from one place to another.
 Channels and canals refer to main waterways supplying water to
one or more farms.
 Field ditches have smaller dimensions and convey water from the
farm entrance to the irrigated fields.
Introduction

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• Draws its supplies from a river only during the
high stages of the river
• Continuous source of water supply
• Also called as Perennial canals
Types of Canals
Based on the Source of supply
Permanent
Canal
Inundation
Canal

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• Feeds two or more canals
• Used to carry water for generation of
hydroelectricity
• Used for transport of goods
• Carries water from its source to agricultural fields
Types of Canals
Based on Function
Irrigation
Canal
Navigation
Canal
Power
Canal
Feeder
Canal

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• Aligned at right angles to contours i.e. along
the side slopes
• Contour channels follow a contour, except for
giving the required longitudinal slope to canal
• The canal which is aligned along any natural
watershed (ridge line)
Types of Canals
Based on Alignment
Watershed or
Ridge Canal
Contour
Canal
Side Slope
Canal

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Fig. Alignment of a Watershed
or Ridge Canal
Fig. Alignment of a Contour
Canal
Fig. Alignment of a Side Slope
canal
(Source: Irrigation Engineering and hydraulic
Structures by S K Garg)

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Types of Canals
Based on Distribution
Main Canal
Major
Distributary
Watercourses
Branch Canal
Minor
Distributary

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Main Canal
 This canal takes off from the river and derives water through a regulator.
 Direct flow irrigation from such a channel is not possible as its water surface is
below the general ground surface.
 Main function- To take the required amount of irrigation water at the head and
to deliver it in the canal system below.
Branch Canal
 All offtakes from main canal with head discharge of 30 cumecs and above are
termed as branch canals.
 The main canal is branched to cover the whole area. The bifurcated canals are
called branch canals or simply branches.

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Major Distributary
Minor Distributary
Water Course
All offtakes from main canal or branch canal with head discharge from 2.5-30
cumecs are termed as branch canals.
All offtakes from major distributary with head discharge less than 2.5 cumec
are termed as branch canals.
Small channels which carry water from the outlets of a major or minor
distributary or a branch canal to the fields to be irrigated.

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(Source: Irrigation Engineering and hydraulic
Structures by S K Garg)

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• Lining of impervious material on its bed and banks
to prevent seepage of water.
• Concrete, Brick, Burnt clay tile, Boulder etc.
• Bed and banks made up of natural soil.
• Water velocities >0.7 m/s are not tolerable.
• High seepage and conveyance water losses.
• Profuse growth of aquatic weeds retards the flow.
Types of Canals
Based on Lining
Unlined
Canals
Lined
Canals

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Fig. Unlined Canal Fig. Lined Canal

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Cross Section of Irrigation Canals
Fig. Typical cross-section of an irrigation canal

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Losses of water in canals
Evaporation
Seepage
Percolation
Absorption

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Canal Regulations Works
 Canal regulation – The process of regulating water from a
reservoir or diversion head works through a canal system for a
dependable supply of water for irrigation requirement.
 The canal system plays a key role in regulating the irrigation
water.
 The structures constructed on a canal to control and to regulate
the discharge, velocity, depth etc. are known as canal regulation
works.
 Regulation structures – To control the amount of water passing
into canal.

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Fig. Canal structures for flow regulation and control

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Canal regulation structures may be described as follows:
 Drops and falls: To lower the water level of the canal.
 Cross regulators: To head up water in the parent channel to divert
some of it through an off take channel, like a distributary.
 Distributary head regulator: To control the amount of water
flowing into off take channel.
 Canal escapes: To allow release of excess water from the
canal system.

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Canal Drops and Falls
 A canal fall is structure constructed on a channel to lower
down the water level and bed level of the channel.
 The canal fall consists of a combination of a water lowering
structure and an energy dissipating device.
 Location of fall judiciously worked out such that there should be
a balance between the quantities of excavation and filling.
 Height of the fall has to be decided, since it is possible to provide
larger falls at longer intervals or smaller falls at shorter intervals.

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Fig. Typical location for providing canal fall or drop

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 When slope of ground suddenly changes to steeper slope,
permissible bed slope cannot be maintained.
 Slope of ground is more or less uniform and slope is greater than
permissible bed slope of canal.
 In cross drainage work, when difference between level of canal
and that of drainage is small or when F.S.L of canal is above bed
level.
Necessity of canal falls

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Types of canal falls
1. Ogee fall:
 An ogee curve provided for carrying canal water from higher
level to lower level.
 It is recommended when natural ground surface suddenly
changes to a steeper slope along the alignment of the canal.
 Upstream and downstream of the fall is protected by stone
pitching.

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Fig. (a). Ogee type fall made of rubble masonry, (b). Same type fall but made of concrete
and equipped with a stilling basin for energy dissipation

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2. Rapid fall:
 Slope of natural ground surface is
even and long.
 Consists of long glacis with
longitudinal slope.
 Curtain walls are provided on the
upstream and downstream side of
the sloping glacis.
 Used for timber traffic.
 These falls are not popular
because of high construction cost.
Fig. Rapid falls

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3. Trapezoidal notch fall:
 Body wall is constructed across the
canal.
 Body wall consists of several
trapezoidal notches between side
piers and intermediate piers.
 Notches are kept at the upstream bed
level of canal.
 Body wall is constructed with
masonry or concrete.
Fig. The notch fall

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4. Vertical drop fall:
 Vertical drop fall constructed with
masonry work.
 Water flows over the crest of wall.
 Concrete floor – To control scouring
effect.
 Curtain wall provided on both
upstream and downstream side.
 Provided at Sardar canal, UP.
 Also called as Sardar fall.
Fig. Vertical drop fall

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Head Regulator
Regulators Constructed at the off taking point are called head
regulators. When it is constructed at the head of main canal it is
known as canal head regulator. And when it is constructed at the
head of distributary, it is called distributary head regulator.
Fig. Head Regulator
Functions:
 To control the entry of water from parent
canal to the off taking channel.
 To control the entry of silt into off taking or
main canal.
 To serve as a meter for measuring
discharge of water.

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Canal Regulator
 Includes the cross regulator and the distributary head regulator
structures for controlling the flow through a parent canal and its off-
taking distributary.
 Helps to maintain the water level in the canal on the upstream of
the regulator.
 Generally constructed at a distance of 9 to 12 km along the main
canal and 6 to 10 km along branch canal.
Functions:
i. To Control the flow of water in canal system.
ii. To feed the off taking Canals.
iii. To enable closing of the canal breaches on the d/s.
iv. To provide roadway for vehicular traffic.

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Cross Regulator
Fig. Cross Regulator
 Angle at which a distributary canal off-takes
from the parent canal has to be decided
carefully.
 The best angle is when the distributary takes off
smoothly.
 Another alternative is to provide both channels
(off-taking and parent) at an angle to the original
direction of the parent canal.
 When it becomes necessary for the parent
canal to follow a straight alignment, the edge of
the canal rather than the center line should be
considered in deciding the angle of off-take.

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Fig. Distributary head regulator and parent canal cross regulator showing combination
with glacis fall and bridge.

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 To prevent excessive entry of silt deposition at the mouth of the off-
take, the entry angle should be kept to between 600 and 800.
 For the hydraulic designs of cross regulators, one may refer to the
Bureau of Indian Standard code IS: 7114-1973 “Criteria for
hydraulic design of cross regulators for canals”.
 The distributary should preferably be designed to draw sediment
proportional to its flow, for maintaining non-siltation of either the parent
canal or itself.
 Three types of structures have been suggested as discussed below
along with the relevant Bureau of Indian standard codes.

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Silt Vanes
Fig. View of silt vanes for diverting
the sediment bed load of parent
canal away from offtake
 Thin, vertical, curved parallel walled
structures – reinforced concrete.
 Height of vanes – 1/4th
to 1/3rd
of depth
of flow in parent canal.
 Thickness – as small as possible.
 Spacing – 1.5 times the vane height.
 To minimize silting tendency, the
pitched floor on which the vanes are
built should be about 0.15 m above
the normal bed of the parent canal.

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Groyne walls or Curved wings
Fig. View of groyne wall (curved wing)
 Projected out into parent canal.
 Groyne wall extends upstream into the
parent canal to cover 3/4th
of full width of
offtake.
 Proportional distribution of flow into off
taking canal is expected to divert
proportional amount of sediment.
 Height – at least 0.3m above the FSL of
parent canal.
BG - Projected length of the groyne wall
BC - Bed width of the off taking canal
BG = (0.75 to 1.00) BC

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Fig. View of Skimming platform
Skimming Platform
 RCC slab resting on low height piers on
the bed of the parent canal, and in front of
the off- taking canal.
 Creates a kind of low tunnel at the bed of
the parent canal.
 Floor of the off-taking canal being above
the level of the platform thus only takes
suspended sediment load coming along
with the main flow in the parent canal.
 Suitable where parent channel is deep
and offtake is small.
 Tunnels – 0.6 m deep.

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Canal Escapes
 Structures – To release excess water from a canal.
 The excess water in a canal results in the water level rising above
the full supply level which may cause erosion and subsequent
breaches.
 Escapes also built at the tail end of minors at the far ends of a
canal network.
 These are required to maintain the required full supply level at the
tail end of the canal branch.

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Weir Escapes
Fig. Weir escape
 These are constructed in the form of weirs, without any gate or
shutter and spills over when the water level of the canal goes
above its crest level.

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Fig. Sluice escape
Sluice or Surplus Escapes
 Gated escapes – very low crest
height.
 These sluices can empty the
canal much below its full
supply level and at a very
fast rate.
 In some cases, these
escapes act as scouring
sluices to facilitate removal
of sediment.

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Canal Outlets
 Canal outlets also called Farm turnouts or modules.
 These are small structures built on the bank of distributary channel
through which water is supplied to a water course.
 Outlet for a water course serves the same purpose as a distributary
head regulator serves for the distributary.
 The outlet is the connecting link between the distributary
maintained by the department and a water course maintained by
the cultivators.
 It is used for the measurement of discharge being supplied to the
water course.

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 Discharge through an outlet is usually less than 0.085 cumecs.
 An outlet plays an important role in the equal distribution of
available water to all the cultivators.
Fig. Canal Outlets

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Requirements of a good canal outlet
 It should be simple in design, construction and maintenance.
 It should be strong and durable.
 It should not have any movable part which is likely to be easily
damaged.
 The outlet should be such that it is not easily tempered with by the
cultivators to increase the discharge in the water course.
 It should be able to work efficiently and draw its full discharge even
under a small working head.
 It should draw its due share of silt.

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 It should not be expensive.
 Its design should be such that it can be easily constructed by the
local workers.
 The design is such that, it draws discharge according to the
fluctuations of the discharge in the distributary.

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Criteria for selection of outlet capacity
 Method of regulation of supply in the main canal
 Method of distribution of water to cultivators
 Source of supply
 System of working of the distributary
 System of assessment

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Non modular outlets
Semi modular outlets
Modular outlets
Open Sluice, Submerged pipe outlets, Inclined pipe outlets.
Pipe outlets discharging freely into air, Venturi flume outlet, Open flume outlet,
Adjustable orifice semi module outlet.
Gibb’s rigid module, Khanna’s rigid module
Classification of outlets

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Non modular outlets
These outlets operate in such a way that the flow passing through
them is a function of the difference in water levels of the distributing
channel and the watercourse.
Advantages:
 It can work under very small available head.
 It can pass the required discharge with a working head as small
as 3 cm.

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Disadvantages:
 Discharge through the outlet varies as the water level either in
the distributary or the water course or both varies.
 The discharge varies from outlet to outlet because of different
flow condition.
 In the case of low supply in the distributary, the outlet at the tail
end will not get adequate discharge when the outlet in the head
reaches draw full discharge.

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Semi modular outlets
 Discharge through these outlets depend on the water level of the
distributing channel.
 Discharge is independent of the water level in the watercourse so
long as the minimum working head required for their working is
available.
 The only disad
vantage of a semi-modular canal outlet is that it
involves comparatively greater loss of head.

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Fig. Adjustable orifice semi module

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Modular outlets
 The discharge through modular outlets is independent of the
water levels in the distributing channel and the watercourse,
within reasonable working limits.
 This type of outlets may or may not be equipped with moving
parts.
 If an outlet is desired to be located at upstream of a regulator or a
raised crest fall, a modular outlet would be a suitable choice.

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Fig. Khanna’s rigid module

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[Anonymous], Irrigation Engineering Principles, CE IIT, Kharagpur,
Available:https://nptel.ac.in/courses/105105110/pdf/m3l10.pdf
Garg, S. K. 1996. Irrigation engineering and hydraulic structures,
(12th
Ed.), Khanna Publishers.
Michael, A. M. and Ojha, T. P. 2018. Principles Of Agricultural
Engineering, Water Power and Water Resources Engineering: Vol.
2,(5th
Ed.), Jain Brothers, New Delhi.
References

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