Diversion head work

This presentation covered Diversion head work topic. Details topics selection of the suitable site for the
diversion headwork- different parts of
diversion headwork- Causes of failure of
structure on pervious foundation- Khosla’s
theory- Design of concrete sloping glacis weir covered.

1. Diversion Headworks
DIVYA VISHNOI
Assistant Professor

3. •Diversion Headworks:
•Types- selection of the suitable site for the
diversion headwork- different parts of
diversion headwork- Causes of failure of
structure on pervious foundation- Khosla’s
theory- Design of concrete sloping glacis weir

4. CANAL HEADWORKS
•Canal head works
–Structures/works constructed across river and at the
head of the off taking canal
Canal head works
Diversion head works
To raise water level in river and
divert the required quantity
Storage head works
To store water on u/s of river
and divert the required
quantity

5. Diversion Head-Works
•The works which are constructed at the head
of the canal in order to divert the river water
toward the canal, so as to ensure a regulated
continuous supply mostly silt free water with
certain minimum head into the canal, are
known as diversion headworks.

6. Diversion Head-Works

7. Objectives of Diversion Head Works
•The Following are the objective of Diversion
Head works
•To Raise the water level at the head of canal.
•To form a storage by construction of dykes on
both side of banks of the river so that water is
available throughout the year.
•To control the entry of silt into the canal and to
control the deposition of silt at the head of canal.
•To control the fluctuation of water level in the
river during different seasons.

8. Objective of Diversion Head works

9. Objective of Diversion Head works

10. Objective of Diversion Head works

11. Objective of Diversion Head works

12. TYPES OF DIVERSION HEAD WORKS
•1. Temporary diversion head works

–Consists of a bund constructed across river to raise the
water level in the river and will be damaged by floods

•2. Permanent diversion head works

–Consists of a permanent structure such as a weir or
barrage constructed across river to raise water level in the
river

13. Selection of Site for Diversion Head
Works
The following points should be considered to
select a site for this diversion headworks.
•The river should be straight and narrow at the
site
•The elevation of site should be higher than the
area to be irrigated for gravity flow.
•River banks at site should be well defined and
stable.
•Valuable land upstream of the barrier like
weir or barrage should not be submerged.

14. Selection of Site for Diversion Head
Works
•Material of construction should be locally
available.
•Roads or railway communication to the site is
essential to carry the material of construction.
•Site should be close to the cropland to
minimize loss of water due to seepage and
evaporation of canal.
•The site should provide a good foundation for
construction of weir or barrage.

15. Selection of Site for Diversion Head
Works

16. Components of Diversion Headworks

17. Components of Diversion Headworks

18. weir
Divide wall
Scouring sluices
Fish ladder
Fig.( component parts of weir and barrage )
RIVER

19. Components of Diversion Headworks
•The components of diversion headworks are:
•Weir or barrage
•Canal head regulator
•Divide Wall
•Fish Ladder
•Scouring Sluices Under sluices
•Silt excluder
•Silt ejector.
•Marginal embankment or dikes
•Guide bank
•Silt pocket or trap.

20. Weir or Barrage
•Weir is a solid obstruction placed across the
river. Its main function is to raise the water
level so that water can be diverted by canal to
crop field due to difference of head.
•Barrage is practically a low weir with an
adjustable gate over this low weir. Heading up
of water is affected by gate.

21. Weir

22. Weir

23. Weir

24. Barrage

25. Barrage

26. Barrage

27. Comparison Between Weir & a
Barrage

28. Types of Weir

29. Types of Weir
•Weir may be of different types based on material of
construction, design features and types of soil
foundation as:
•Vertical Drop Weir
•A crest gate may be provided to store more water
during flood period. At the upstream and downstream
ends of impervious floor cut off piles are provided.
Launching apron are provided both at upstream and
downstream ends of floor to safeguard against
scouring action. A graded filter is provided
immediately at the downstream end of impervious
floor to relieve the uplift pressure. This type of weir is
suitable for any type of foundation.

30. Vertical Drop Weir

31. Vertical Drop Weir

32. Vertical Drop Weir

33. Types of Weir
•Sloping Weir of Concrete:
•This type is suitable for soft sandy foundation.
It is used where difference in weir crest and
downstream riverbed is not more than 3 m.
Hydraulic jump is formed when water passes
over the sloping glacis. Weir of this type is of
recent origin.

34. Sloping Weir of Concrete

35. Sloping Weir of Concrete

36. Types of Weir
•Parabolic Weir:
•A parabolic weir is almost similar to spillway
section of dam. The weir body wall for this
weir is designed as low dam. A cistern is
provided at downstream.

37. Types of Weir

38. Types of Weir
•Dry Stone Slopping Weir:
•It is dry stone or rock fill weir. It consists of
body wall and upstream and downstream dry
stones are laid in the form of glacis with some
intervening core wall.

39. Dry Stone Slopping Weir

40. Dry Stone Slopping Weir

41. Barrage
•When the water level on the upstream side of
the weir is required to be raised to different
levels at different time, then the barrage is
constructed. Practically a barrage is an
arrangement of adjustable gates or shutters at
different tiers over the weir. The water level
can be adjusted by the opening of gates.

42. Barrage

43. Divide Wall
•The Divide Wall is a long wall constructed at right angle to the
weir or barrage, it may be constructed with stone masonry or
cement concrete. On the upstream side, the wall is extended
just to cover the canal regulator and on the down stream side,
it is extended up to the launching apron. The functions of the
divide wall are as follows,
•(a) To form a still water pocket in front of the canal head so
that the suspended silt can be settled down which then later
can be cleared through the scouring sluices from time to time.
•(b) It controls the eddy current or cross current in front of the
canal head.
•(c) It provides a straight approach in front of the canal head.
•(d) It resists the overturning effect on the weir or barrage
caused by the pressure of the impounding water.

44. Divide Wall

45. Scouring Sluices or Under Sluices
•The Scouring sluices are the openings provided
at the base of the weir or barrage. These
openings are provided with adjustable gates.
Normally, the gates are kept closed. The
suspended silt goes on the depositing in front of
the canal head regulator. When the silt
deposition becomes appreciable the gates are
opened and the deposited silt is loosened with an
agitator mounting on a boat. The muddy water
flows towards the downstream side through the
scouring sluices. The gates are closed. But, at the
period of flood, the gates are kept opened.

46. Under Sluices

47. Scouring Sluices or Under Sluices

48. Fish Ladder
•The Fish Ladder is provided just by the side of the
divide wall for the movement of fishes. Rivers are
important source of fishes. There are various types of
fish in the river. The nature of fish varies from type
to type. But in general, the tendency of fish is to
move from upstream to downstream in winters and
from downstream to upstream in monsoons. This
movement is essential for their survival.

49. Fish Ladder
•Due to construction of weir or barrage, this
movement gets obstructed, and is detrimental to
the fishes. For the movement of the fishes along
the course of the river, the fish ladder is essential.
In the fish ladder, the baffle walls are
constructed in the zigzag manner so that the
velocities of flow within the ladder does not
exceed 3 m/s. The width, length, and height of
the fish ladder depends on the nature of the river
and the type of the weir or barrage.

50. Fish Ladder

51. Fish Ladder

52. Canal Head Regulator
•A structure which is constructed at the head of
the canal regulator to regulate the flow of water
is known as canal head regulator. It consists of a
number of piers which divide the total width of
the canal into a number of spans which are
known as bays. The pier consists of a number of
tiers on which the adjustable gates are placed.
The gates are operated from the top by suitable
mechanical device. A platform is produced on
the top of the piers for the facility of operating
the gates. Again some piers are constructed on
the downstream side of the canal head to support
the roadway.

53. Canal Head Regulator

54. Canal Head Regulator

55. Silt Excluder
•When silt pocket is formed in front of the canal head
by constructing the divide wall, then it is found that
the lower layer of water contains heavy silt and the
upper layer contains very fine silt. The fine silt is
very fertile and it may be allowed to enter the canal.
But the heavy silt causes sedimentation in the
pocket.. To eliminate the suspended heavy silt, the
silt excluder is provided. It consists of a series of
tunnels starting from the side of the head regulator
up to the divide wall.

56. Silt Excluder
•The tunnel nearest to the head regulator is
longest, and the successive tunnels decrease in
length, the tunnel nearest to the divide wall is
shortest. The tunnels are covered by R.C.C. Slab.
The top level of the slab is kept below the sill
level of the head regulator. So, the completely
clear water is allowed to flow in the canal
through the head regulator. The suspended
heavy silt carried by the water enters the silt
excluder tunnels and passes out through the
scouring sluices.

57. Silt Excluder
•Silt excluders are those works which are
constructed on the bed of the river, upstream
of the head regulator. The clearer water
enters the head regulator and silted water
enters the silt excluder. In this type of
works, the silt is, therefore, removed from the
water before in enters the canal.

58. Silt Excluder

59. Silt Ejectors
•Silt ejectors, also called silt extractors, are
those devices which extract the silt from
the canal water after the silted water has
•Traveled a certain distance in the off-take
canal. These works are, therefore, constructed
on the bed of the canal, and little distance
downstream from the head regulator.

60. Silt Ejectors

61. Marginal Embankments or dykes
•The marginal embankments or dykes are earthen
embankments which are constructed parallel to the
river bank on one or both the banks according to the
condition. The top width is generally 3 to 4 m and side
slope is generally 1 ½ : 1 to 2: 1. The height of the
embankment depends on the highest flood level. A
suitable margin is provided between the toe of the
embankment and the bank of the river. To resist the
effect of erosion on the embankment, wooden piles are
driven along the river banks throughout the length of
dyke. The length of the dyke is protected by boulders
pitching with cement grouting and the downstream
side is protected by turfing.

62. Marginal Embankments or dykes
•The Marginal Bunds are constructed for the
following purposes.
•(a) It prevents the flood water or storage
water from entering the surrounding area.
•(b) It retains the flood water or storage water
within a specified section.
•(c) It Protects the towns and village from
devastation during the heavy flood.
•(d) It protects valuable agricultural lands.

63. Marginal Embankments

64. Guide Bank
When a barrage is constructed across a river which
flows through the alluvial soil, the guide banks must
be constructed on both the approaches to protect the
structure from erosion. It is an earthen embankment
with curved head on both the ends.
The Guide Bank serves the following purposes.
•It protects the barrage from the effect of scouring and
erosion.
•It controls the tendency of changing the course of the
river.
•It controls the velocity of the flow near the structure.

65. Guide Bank

66. Guide Bank

67. Guide Bank
•Components of Guide Banks are
•Upstream curved head
•Downstream curved head
•Shank portion which joins upstream and
downstream curved end
•Sloping apron
•Launching apron
•Pile protection

68. RTU Questions
•Explain the term ”Diversion Head Work” and
clearly mention its different functions.
•Explain Bligh’s Creep Theory in details.
•What is weir? How does it differ from a barrage
structure?
•What are the functions of a canal head regulator?
•Compare the weir and barrage with relative
advantages?
•Draw the neat sketch of silt excluder and label it.
Also explain the functions of silt excluder?

69. References
•Irrigation Engineering & Water Power Engineering
–By Prof B.C.PUNMIA
–Laxmi Publication
•Irrigation Engineering & Hydraulic Structures
–By Prof. Santosh Kumar Garg
–Khanna Publishers
•Irrigation, Water Power Engineering & Hydraulic Structures
–By Prof K.R. Arora
–Standard Publishers Distributions

•Internet Websites
•http://www.aboutcivil.org/
•http://nptel.ac.in/courses/105105110/

70. Thanks
GHT