Third year civil engineering subject- WRE

1. CANALS
Prof. M. B Chougule ( department of civil engineering)
DKTE’S Y.C.P Ichalkaranji

2. .
• canal
• A canal is defined as an artificial channel constructed on the
ground to carry water from a river or another canal or a
reservoir to the fields.
• CLASSIFICATUION OF CANAL
• A)Classification based on alignment:
• 1) ridge canal
• 2) ridge canal
• 3) side long / side slope canal.
• B)Classification based on position:
• 1) Main Canal
• 2) Branch Canal
• 3) Major Distributary
• 4) Minor distributary
• 5) Water Course 6) Head Work

3. .
• CONTOUR CANAL:-
• when canals are to be laid in hilly area it is not possible
to align along which is at top of hill. In such cases canals
are aligned generally along contours.
• The canal taking off from reservoir follows contours
alignment such that canal which is aligned parallel to
the contours of area is known as contour canal.
• Contour canal have large number of CD works but no
falls.
• A contour canal can irrigate only one side as ground
level at other side is quite high.
• Contour canals need not to follow same contour along
its length.
• To contour canals longitudinal slope is given to enable
the water to flow by gravity.

5. .
• Advantages:-
• A) suitable in hilly area.
• B) to contour canal longitudinal slope is given to enable
the water to flow by gravity.
• Disadvantages:-
• A) large number of cross drainage works.
• B) can irrigate only one side.
• RIDGE CANAL/ RIDGE ALIGNMENT:-
• it is also called as watershade canal. These types of
canal are generally laid along ridge or naturally
watershade line as canal runs on watershade it can
irrigate on both sides and thus irrigates area on sides.
• These canals are very economical. No CD works is
required.

6. .
• Advantages:-
• A) it can irrigate on both sides.
• B) economical.
• C) no CD work
• Disadvantages:-
• A) velocity of water needs to be controlled.
• B) scouring of bed due to higher velocity.

7. .
• SIDE SLOPE CANALS:-
• In this type of alignment canal is not aligned along
either ridge or contour but it is aligned across
contour.
• These canals runs nearly parallel to natural drain
similar to contour canal. It also irrigates area on
only one side.
• These type of canal are not intercepted by cross
drainage works.

9. .
• Canal network:-

10. .
• i) Head regulator: When the canals are branched or taking off
from reservoir or main canals in the distribution system head
regulator is provided at the head of canal, to divert necessary
discharge from reservoir to canal or main canal to branch
canal, to control, regulate or measure the discharge, to
control the silt entry in the taking off canal ,to stop the supply
of water when not needed (end of rotation) or for repair at
down stream.
• (ii)Cross regulator: When it is required to raise the water level
in main canal in order to regulate the flow in branch canal ,to
stop the flow in case of repair on down stream. To divert silty
overflow water in to the near by river or stream during flood
control cross regulator is provided.
• (iii) Escape: At the end of main canal or to allow escape of the
silty water into the waste channel and then to natural drain
during rainy season escapes are provided.
• (iv )Outlets: To admit water into the, distributaries, minors,
water courses, field channels etc. Out lets

11. PARTS OF CANAL SYSTEM:-
• A) main canal B) branch canal. C) major distributor.
• D) minor distributor. E) water course. c.

12. .
• A) main canal:- the canal taking off from a river or
reservoir i.e. from source is called as main canal.
• Function is to carry the total water and to distribute
it to canal system.
• It is largest canal in system and no direct irrigation is
normally done from main canal.
• B) branch canal:- it is canal takes off from main
canal on either side. Very little direct irrigation is
done from them.
• These canal act as a feeder canals for major
distributor. The discharge capacity of branch canal is
usually varies from 5 to 25 cumec.
• It helps to make irrigation water available in
different parts of distribution.

13. .
• C) major distributor:- it is generally takes off from main
canal which supplies water to other distributor.
• The discharge capacity of major distributor varies from
0.25 to 5 cumec in some cases it may be 10 cumecs.
• These are generally used for direct irrigation and their main
function is to distribute water to water courses.
• D) minor distributor/ minor:- minor distributor generally
takes off from major distributor or from main canals or
another distributor and supplies water to water course.
• Its discharge capacity is less than 0.25 cumecs. These are
also used for direct irrigation.
• E) water course:- these are small channels which takes
water from the outlet of distributor or minor distributor
and supply it to the agricultural fields.

14. .
• These are owned constructed controlled and maintained by
cultivators.
• Some times these are constructed by the government on behalf of
irrigators but its maintenance is carried out by irrigators only.
• F) head work:- the works those are constructed to store, divert and
control the river water regulate the supply in to the canal.

15. .
• FIXING ALIGNMENT OF CANAL:-
• Following points should be considered while fixing the
alignment of canal:-
• 1. Along the alignment of canal, the cross – drainage works
• should be minimum.
• 2. The alignment of canal should be such that, water should
flow under gravity.
• 3. The canal alignment should be such that, the quantity of
• earthwork in cutting should be equal to the quantity of
• earthwork in filling.
• 4. The alignment of canal should be such that, it can cover
• maximum command area.
• 5. The length of main canal should be minimum.
• 6. The number of curves should be minimum.
• 7. The alignment should not made in a rocky cracked strata.

16. .
CROSS SECTION OF CANAL IN, FILLING AND IN PARTIAL CUTTING & FILLING:-
in cutting:-

19. Cross Section of Canal in Partial
Cutting and Filling

20. .
• CANAL LINING:-
• means providing impervious thin layer of 2.5 to 15 cm thickness to
protect the bed and sides of canal.
• Generally of RCC or CC bricks, Stones etc.
• Materials used in canal lining.
• 1) Cement Mortar, lime Mortar 2) Concrete
• 3) Stone masonry 4) Brick
• 5) Sodium carbonate 6) Asphalt
• 7) Precast concrete block

21. .
• Types of canal lining:-
• a. Cement concrete Lining: Concrete as a lining material gives
excellent hydraulic properties. The thickness of lining is governed
by the requirement of imperviousness and structural strength. The
thickness is provided is from 5 to 10 cm for M15and 7.5 cm to 15
cm for M10 concrete. The concrete used for lining has mix ratio
1:4:8 or 1:3:6 or 1:4:6.
• b. Shotcrete Lining: Mixture of cement and sand (1:4) is shot at
the sub grade through a nozzle. The thickness of this type of lining
varies from 2.5 to 6.5 cm. Shotcrete consumes large amount of
cement. Shotcrete can be placed on irregular subgrade and fine
dressing of subgrade is not required.
• c. Precast concrete Lining: This type of concrete lining consists of
precast slabs usually 90 cm x 30 cm in size. The thickness of each
slab is from 5 to 6.5 cm. The blocks are manufactured with an
interlocking arrangement. The slabs are laid on well prepared and
compacted subgrade.
• d. Cement mortar lining: Thickness for this of lining is kept from 1
to 4 cm. A large amount of cement is consumed in this type of
lining and it is very costly.

22. .
• e. Brick Lining: This type of lining consists of single or double layer
of brick masonry or a layer of brick masonry followed by a layer of
tiles laid is mortar. The first layer is laid on 12 mm layer of 1:6
cement mortar. A 12 mm thick layer of plaster in 1:3
• cement mortar is laid over the first layer. Then the second layer is
laid over it in 1:3 cement mortar.
• f. Asphaltic lining: It is controlled mixture of asphalt and grade
aggregate mixed and placed at a high temperature of 200c and
covered with 30 cm layer of earth material for a protection. The
mix is placed either by hand or by equipment similar to that
concrete.
• g. Clay Puddle Lining: Clay puddle is produced from by first
exposing clay to weathering. It is then mixed with water to bring it
to the saturation and pugged thoroughly by trampling under man’s
or cattle’s feet. This thickness of lining is 30 cm. It is then protected
by layer of earth material.
• h. Sodium carbonate Lining: The mixture consists of clayey soil
(10%) and sodium carbonate (6%). The thickness of lining is kept as
10 cm. this type of lining is used for small canal and water course.

23. .
• i. Stone block lining: This consists of undressed stone
block set in mortar laid over prepared sub grade. The
lining is able to check seepage effectively but has a
considerable resistance to flow of water.
• j. Pre-fabricated light weight membrane: They are
matted fibers of asbestos or jute and are coated with
asphalt. It is laid on a smooth and prepared subgrade,
and is covered with layer ofearth material.
• k. Bentonite and clay membrane: This consists of
bentonite or clay blanket 4 cm thick laid over a
prepared subgrade and covered with earth.
• l. Road oil lining: The road oil sprinkled on subgrade in
thickness of about 1.5 mm is sufficient enough to
saturate subgrade to depth 8 cm. the subgrade is then
rolled so that oil enters the soil pores.

24. .
• Purposes of lining :
• 1. To reduce the seepage losses in canal.
• 2. To prevent scouring of bed sides.
• 3. To improve the discharge of canal by increasing
the velocity of flowing water.
• 4. To prevent water logging.
• 5. To increase the capacity of canal.
• 6. To increase the command area.
• 7. To control the growth of weeds.
• 8. To protect the canal from the damage by flood.

25. .
• Advantages :
1. It reduces the loss of water due to seepage and hence the
duty is enhanced.
2. It controls the water logging.
3. It provides smooth surface and hence the velocity of flow can
be increased.
4. Due to the increased velocity the discharge capacity of canal
is also increased.
5. Due to the increased velocity the evaporation also is reduced.
6. It eliminates the effect of scouring in the canal bed.
7. The increased velocity eliminates the possibility of silting in
the canal bed.
8. It controls the growth of weeds along the canal sides and bed.
9. It provides the stable section of the canal.
10. It prevents the sub soil salt to come in contact with the canal
water.
11. It reduces the maintenance cost of canal.

26. .
• Disadvantages
• 1. The initial cost of canal lining is very high.
• 2. It involves much difficulty for repairing the
damaged section of lining.
• 3. It takes too much time to complete the project
work.
• 4. It becomes difficult if the outlets are required to
be shifted or new outlets are required to be
provided because dismantling of the lined section is
difficult
• 5. there might be chances of leakage through joint.

27. .
• properties of good lining material :
• 1) Water tightness
• 2) Low cost & subsequent less maintenance cost
• 3) Strength & durability
• 4) Prevention of weeds growth
• 5) Ease of constructing with local material
• 6) the lining material should be should be such that
it can be easily repaired.
• 7) it should be able to resist the growth of weeds
and attack of burrowing animals.
• 8) the surface of lining material should be smooth
for higher hydraulic efficiency.

28. .
• Define balancing depth in canals:-
• The depth of particular cross section in which the
amount of cutting and filling is equal is known as
balancing depth.
• This section is economical.
• It is found out by following procedure:-
• Let
• h=vertical height of top bank from bed of canal.
• b= bed width of canal.
• t= top width of canal bank.
• z:1= side slope of canal in cutting.
• n:1= side alope of bank in filling.
• d= full supply depth of canal.

29. .
• Area of cutting= by + zy²
• Area of filling = 2 [ (h-y)t + h(h-y)² ]
• Equating area of cutting to area of filling:-
• Y(b+zy)= 2 [ (h-y)t + h(h-y)² ]
• As per design consideration
• In cutting side slope= 1:1
• And in filling = 1.5:1
• Putting n =1.5 and z= 1
• Y= depth of cutting
The depth y from ground line and bed level is
calculated.

31. .
• HYDRAULIC DESIGN:-
• In hydraulic design of canal following values are to be
found out:
• 1) bed width (b) 2) velocity (v)
• 3) supply level (d) 4) afflux etc.
• All these factors depends on :-
• 1) Design discharge (R)/(Q) 2) bed slope (S)
• 2) coefficient of rugocity (N) 4) side slope (Z)
• 5) Side slope in cutting (n)
• Bed slope:- steeper the bed slope higher or more the
velocity. Velocity should be such that it neither scour
the bed and does not allows the silt to deposit such
velocity is known as ‘critical velocity’ (V₀)

32. .
• it is given by, (V₀) = 0.55d² ( Kennedy equation )
• (V₀) = critical velocity in m/s²
• d= depth of flow in m.
• Critical velocity ratio:-
• It is the ratio of actual velocity (v) to the critical velocity.
• C.V.R= V/ V₀ ( for unlined canal its value is in between 0.9 to 1.2)
•
• Coefficient of rugosity (N):-
The general value adopted are:
For stone lining - 0.022
For unlined canal – 0.030
For concrete canal – 0.01 to 0.016

33. .
• Side slope for design:-
• It depends on lining of canal, whether the canal is lined
or unlined.
• 1) in case of lined canal actual side slope to which lining
is laid should be adopted.
• 2) for unlined canal it is taken as 1:0.5
• design procedure:-
• for unlined canal-
• 1) adopt side slope 1V = 0.5H and N=0.03
• 2) assume ratio of b/d between 2 to 4 (b=4, d=1)
• 3) by using trial and error method assume a set of ‘b’ &
‘d’ & calculate values of area (A) perimeter (P), ( R) and
velocity (V) by using following equation
• A=(b-zd) ∙ d

34. .
• P= b + 2d √ 1+ z²
• R= A (m)
P
V= 1 R⅔ S½ ( S= Bed Slope)
N
calculate value 0.64
V₀= 0.055d
If it is less than 0.9 reduce depth and if it more than 1.2
increase depth.
4) After satisfying with above step:-
find out discharge Q= AV (cumecs)
And after that check your calculated discharge if it is in
the range if design discharge assume design is ok
otherwise repeat with deiferent values of b and d

35. .
• FOR LINED CANAL:-
• 1) take side slope as 1:1 and value of N as per type
of lining.
• 2) use condition of economic section.
• i.e. b=2d √(1-z²) -2 zd and R= d/2
• 3) find out values of A,V & R (from above formulea)
• 4) and Q design = A ∙ V from this value of b and d
can be obtained.

36. .
• Maintenance work of canal:
• Removal of silt: The silt should be removed properly during
closure period either manually or with machines, and if it is more
than canal should be closed and then silt should be removed. silt
can be removed by increasing velocity of canal water by addition
of more water in it. It also removed by providing silt ejector in
canal.
• 2. Weed growth: weed affects efficiency of canal and hence weeds
and plants should be removed from canal from their roots.
• 3. Strengthening of canal bank: The banks should be strengthened
properly. If any holes made by insects are found, it should be
properly closed. Leakage if any found should be properly treated,
if scouring of banks noticed proper measures should be adopted.
• 4. Maintenance of service road: Canal roads are inspected after
• Heavy rains and necessary repair. Work should be started if found
any deterioration.
• 5. Overflow of canal banks: After rainy season proper attention is
given towards canal banks as banks may get deteriorated due to
heavy rains or flood and then apply necessary treatment.
•

37. .
• C. D. work:
The work constructed to pass the canal water safely
under/over the drainage water is called as cross drainage
work.
or
• Irrigation structures constructed for carrying the canal water
safely over or under the drainage water are called cross
drainage work.
• When a canal is taken off from the reservoir, it meets various
natural drainages before reaching the watershed line. In this
range cross drainage works are required to be constructed.
• Different types of C.D. works:
• i. Aqueduct
• ii. Super passage
• iii. Level crossing
• iv. Inlet and outlet

38. .
• Selection of suitable type of CD work.
• The bed level of irrigation canal and natural drainage.
• Economy of the construction.
• The total discharge carried by canal and drain.
• If the bed level of canal is above HFL of the drain then as
aqueduct should be preferred if drainage is of medium size
culvert should be preferred.
• If FSL of canal is below the drainage bed super passage should
be provided.
• When sufficient headway is not available even by changing
alignment of canal, syphon aqueduct should be preferred.
• When drain bed level is lower and FSL of canal higher than
drain bed level, canal syphon or syphon super passage should
be preferred.
• When Canal & drain bed level are practically at the same level
and the flow is for short period without much silt, level crossing
should be preffered.

40. .
• i) Aqueduct:
• a) The irrigation structure constructed for passing the canal water
safely over the drainage water is called an aqueduct.
• b) Aqueducts are constructed where the discharge of drain is more in
comparison to canal discharge and when canal bed level is
sufficiently above HFL in the drain.

41. .
• AQUEDUCT IS FURTHER CLASSIFIED AS:-
• 1) pipe aqueduct
• 2) box culvert/ irrigation slab drain
• 3) masonry aqueduct
• 4) siphon aqueduct
• 5) siphon culvert
• 6) irrigation culvert

42. .
• Pipe aqueduct:- in this case canal water is taken through pipe.
In the pipeline aqueduct the diameter of pipe depends on discharge.
It is adopted when canal section is very small and width of drain is
more.
• Box culvert:- the culvert are similler to ordinary bridges only
differance is that the road is replaced by canal. Culverts are provided
under following situation.
• When stream discharge is less as compaired to canal discharge. In
culverts thickness of slab is generally 30 to 50 cm. It consist of
abutment of UCR or concrete and piers accordingly to necessity.

43. .
Masonry aqueduct:- in this type of aqueduct it is constructed
with masonry and the width of drainage is very large and drain water
passes through it. Roadway is provided on one side of canal and
inspection path on other side. Wing wall are also provided on
upstream and downstream side.
Siphon aqueduct:- when HFL of the drainage is above or
touches CBL ( canal bed level ) but lower than FSL and drainage
is small this type of aqueduct is preferred. In this type canal is at
higher level than the drainage.
• It consist of pipe aligned normal to the canal at sufficient depth
below CBL. The canal is flumed and taken cross through trough.
• The water flows under hydrostatic pressure through this
depression in order to avoid deposition of silt a small slope is
provided to give self cleaning velocity.

45. .
• Siphon culvert:- in this type of culvert the bed of
drainage is depressed. These are not preferred if
discharge through drainage is more.
• Irrigation culvert:- these culvert belongs to class of
cross drainage work. These are located at nallaha,
strem, torrent, river where it crosses the canal
alignment. These are preferred when width of
drainage varies from 2.5 to 16m. Arch roof is
provided instead of R.C.C slab.

46. .
• ii) Super passage:
• a) When the drainage water at a point of crossing is taken over the
canal, the structure is called super passage.
• b) Super passages are constructed when the discharge is small in
comparison with the canal discharge and when sufficient clearance is
available between the FSL of canal and drain bed.
• It is classified as:
• 1) pipe super passage
• 2) siphon super passage

48. .
• Pipe super passage:- in this case pipe is provided for carrying
drainage water over the canal. Pipe super passage is provided only if
discharge is less.
• The main disadvantage of these type of super passage is that if silt is
deposited it is difficult to clear it off.
• Siphon super passage:- in this type the bed of canal is
depressed so that FSL should not touch the roof of water way.

49. .
• iii) Level crossing:
• a) When the canal bed level and drain bed level practically the same,
drain water is taken into the canal and it is allowed to intermingle
with the canal water. Such type of cross-drainage work is known as
level crossing.
• b) It is constructed where RL of canal bed and RL of natural drain are
practically the same. Also when the discharge of drain and that of the
canal is approximately of the same magnitude, duration of the flood
in drain is short and no other structure is economically feasible.

50. .
• iv) Inlet and outlet:
• a) Inlet admits water of stream into the canal and it flows mixed with
canal water and then excess discharge is allow to pass through outlet.
• b) The capacity of inlet and outlet must be same and sides and beds
of canal must be protected by stone pitching.

55. .

57. .
• 2- Suggest suitable type of cross drainage works with neat labeled
sketches (any two).
• 1.Nallah bed level is well above canal FSL
• 2. Nallah and canal bed levels are almost equal with heavy flood
discharge in Nallah
• 3. Canal Bed Level = 435.0 m
• . Nallah bed level = 433.0 m
• . Nallah HFL = 436.0
• i.Nallah bed level is well above canal FSL :-Super passage

58. .
• ii. Nallah and canal bed levels are almost equal with heavy flood
discharge in Nallah

59. .
• iii.Canal Bed Level = 435.0 m
• Nallah bed level = 433.0 m
• Nallah HFL = 436.0

60. .
• 3- Suggest the suitable type of CD work and draw the sketch of it
under each of the following sititutions.
• i) Canal bed level and Nala Bed level are same
• ii) Canal bed level is above HFL of Nala
• iii) Nala bed level is above FSL of canal.
• iv) HFL of Nala is between FSL of canal & bed level of Canal.
• i) Canal bed level and Nala Bed level are same:

61. .
1. The RL of canal bed & RL of Nala are pratically same.
2. The discharge of Nala & that of canal is app of the same magnitude.
3 No other structure is economically feasible.
ii) Canal bed level is above HFL of Nala

62. .
• 1. The discharge of Nala is more in comparison to Canal discharge.
• 2. The bed level of canal is sufficiently above the high flood level of
Nala.
iii) Nala bed level is above FSL of canal

63. .
• 1. The bed level of drainage is above the full supply level of canal.
• 2. The water of the canal passes clearly below the drainage.
iv) HFL of nala is between FSL of Canal and bed level of canal

64. .
• 1. The nala bed is at higher level than FSL of canal.
• 2. The clearance between Nala bed * FSL of canal is
either insufficient or the Nala bed is lower than FSL
of canal but higher than the bed of canal.

65. .
Canal falls and rapids:-
Canal fall and rapids are constructed when it is necessary to lower
bed so as to avoid heavy banking. This situation occurs when ground
slope is steeper than bed gradient. Falls should be located on
downstream of take off.

68. .
• Falls:- if this lowering is achieved at one section vertically downward
the structure is called as fall.
• Rapid:- if the lowering is achieved in small length by providing steep
slope it is called rapid or chute.
• Drop:- the vertical distance between upstream water level and
downstream water level in canal is called as drop.
• The falls are classified into following types:-
• 1) ogee fall 3) vertical fall with cistern.
• 2) vertical stepped fall 4) trapezoidal notch fall
• 3) rapid fall
• 1. To lower the canal bed level according to the slope of
• ground
• 2. To maintain the designed bed slope of the canal.
• 3. To avoid heavy banking.
• 4. It gives the consideration of economy in cost of
• excavation of channel.

69. .
• Escapes:-
• Irrigation structure constructed to escape excess water from the
canal to some natural drainage are called escape.
• These are located at 5 to 10 km along major canal.
• Escape consist of head wall parallel to the bank. It has opening to
allow canal flow water through pipe and gate. The other end is
attached to waste canal which is lined for some distance. This waste
canal takes discharge to nearby valley.
• The escape are provided at a distance depending upon importance of
canal
• Necessity
• 1. To remove surplus water from canal into some natural drain or
nallah.
• 2. To avoid damage to the channel by surplus water.
• 3. To provide safety valves of canal
• 4. To save downstream section of canal from overflow of banks.

70. .
• The escapes are classified as:-
• 1) scouring escape- provided in head reaches of main canal to scour
out the deposited bed silt
• 2) surplus escape:- provided to dispose off surplus water from canal.
• 3) tail escape:- provided at tail of branch canal

71. .
• Cross regulator:-
• The regulator constructed in or across parent canal
on downstream of major branch or distribution
head regulator is called as cross regulator.
• Function :-
• 1. To control flow of water in the canal system.
• 2. To feed the off taking canals.
• 3. To enable closing of canal the canal branches on
the downstream side.
• 4. To provide roadway for vehicular traffic.
• For cross regulator pier & abutment with grooves
are constructed parallel to parent canal and vertical
lift gates are fitted in to these grooves.

72. .
• Canal outlets:-
• it is a structure constructed to allow water in to
field canals or ditches through which water is
supplied to water course.
• It may be used for measurement of discharge
supplied to cultivator.
• The discharge is less than 0.085cumecs.
• It plays as important role in equal distribution of
water.
• Function:-
• 1. To admit water from the distributor or parent
channel to field channel.
• 2. To draw proportionate quantity of silt.

73. .
• Requirements of good canal outlet:-
• 1) it should be simple in construction as well as
maintenance.
• 2) it should be cheap, strong and durable.
• 3) it should draw proportionate water according to
discharge.
• 4) it should not be easily tempered by cultivator to
increase in the water course.
• 5) it should draw proportionate silt.
• Types of outlet:-
• 1) non modular outlet
• 2) semi modular outlet/ flexible outlet
• 3) modular outlet/ rigid module.

75. .
• 1) non modular outlet:-
• The discharge through non modular outlet depends on the
difference in water level of distributor and water course.
• The most commonly used type of the outlet is the non
modular outlet also called as pipe outlet.

76. .
• 2) semi modular outlet/ flexible outlet:-
• The discharge in this outlet depends on the water
level in the distributor only and is independent of
water level in water course. Kennedis venturi flume
are the example of semi modular type outlet.
• 3) modular outlet/ rigid module:-
• Module is type of structure specially designed to
maintain discharge irrespective of water level in
distributor and the water course.
• The gibb’s module is the best example of modular
type outlet.

79. .
• Canal regulation work:-
• The masonry structure constructed in or across the
canal to regulate the discharge, full supply level and
velocity in canal is called as canal regulation work.
• It includes:-
• 1) head regulator
• 2) cross regulator
• 3) canal escape
• 4) canal fall and rapids
• 5) outlets

80. .
• Head regulator:
• In the distribution system canals are branched from main canals to
this point or junction to this point. Masonry structure constructed is
called the head regulator.
• It divert necessary discharge from reservoir to canal or main canal to
branch canal, to control, regulate or measure the discharge, to
control the silt entry in the taking off canal, to stop the supply of
water when not needed (end of rotation) or for repair at
• Function:-
• 1) it regulates the discharge.
• 2) it divert proportionate quantity of silt to off taking canal.
• 3) it helps to measure discharge.
• Head regulator consist of rectangular opening with barrels running
through bank.
• The upstream abutment is given curved shape while it is normal on
downstream side to divert water and silt.

88. .
• Water logging:
• The condition of soil when it becomes completely saturated with
water and becomes unfit for the growth of plants is called water
logging.
• Effects of water logging:-
• Absence of areation of soil in the root zone of plant.
• Difficulties in the process of cultivation.
• Growth of water- weeds.
• Increase in the level of salts.
• Restriction in root growth.
• Lower soil temperature.
• Plant diseases
• Difficult in field operation.
• Crop yield get reduced.

89. .
• .: Causes of water logging
• i) Over irrigation by farmers under wrong impression that
more water will fetch more crop yield.
• ii) Bad tilling creating depressions and ponds in the field.
• iii) Improper land grading.
• iv) Seepage through vast network of unlined canals.
• v) leakage through badly maintained structures and cracks.
• vi)Irrigation of unsuitable soils (deep clayey soil)
• vii)Inadequate surface drainage which leads to stagnation of
water in the area
• viii)Obstruction to natural drainage due to road, railway or
canal embankment which leads to flooding of land and then
water logging.
• ix) Natural obstruction to the flow of ground water.
• x) Seepage through reservoir leads to water logging on d/s
and u/s side.

90. .
• Remedial measures:
• i)Provide an efficient drainage system to permit quick flow of
rain and reduce the water logging.
• ii)Reduce the percolation from canals –by Lining of irrigation
channels to make canal surface impervious, Lowering of full
supply level of irrigation channel to reduce seepage loss from
embankment. Construct intercepting drains to collect the
seepage water and carry it to nearby natural stream quickly in
short period
• iii)Restrict the irrigation by educating the people regarding
water requirement of crop ,wastage of water , modern and
efficient methods.
• iv)Remove obstruction in natural drainage.v)Prevent seepage
of water from reservoir.
• vi)Reduce ground water storage by pumping out water from
wells.
• viii)Apply sprinkler and drip or any other micro irrigation
system.

91. .
• Following are the precautions to prevent a land
from getting waterlogged:
• i) Reducing the intensity of irrigation
• ii) Providing intercepting drains
• iii) Lining of canals
• iv) Providing intercepting drains
• v) Improving natural drainage of the area
• vi) Providing intercepting drains
• vii) Provision of an efficient drainage system
• viii) Improving natural drainage of the area