Canal Head Regulation

1. Canal Regulation Works
Dr. Muhammad Ajmal
Lecturer Agri. Engg. UET Peshawar

2. Contents
 Introduction of Canal Regulation Works
 Canal Fall- Necessity and Location - Types of Falls
 Canal outlets, Types and Functions
 Cross Regulator and Distributory Head Regulator
 Cross Drainage works and their Functions
 Monitoring of flows - telemetry system

3. Introduction to Canal Head Regulation
 Any structure constructed to regulate the discharge, full supply
level or flow velocity in a canal is known as a regulation work.
 These structures are necessary for the efficient working and
safety of an irrigation channel.
 The various regulation works may be classified as follows:
1) Canal Fall
2) Head Regulator
3) Cross Regulator
4) Canal Escape
5) Canal Outlet

4. Canal Fall
 A fall is an irrigation structure constructed across a canal to lower
down its water level and destroy the surplus energy liberated
from the falling water which may otherwise scour the bed and
banks of the canal.
 If natural ground slope is steep than the designed bed slope
of the channel, the difference is adjusted by constructing
vertical ‘falls’ or ‘drops’ in the canal bed at suitable intervals, as
shown in figure on next slide.
 A drop in a natural canal bed will not be stable. In order to retain
this drop, a masonry structure is constructed. Such a structure is
called a Canal Fall or a Canal drop.

5.  Irrigation canals are designed for a prescribed bed slope so that
velocity becomes non silting or non scouring.
 This slope may vary from 1 in 4000 for a discharge of about 1.5
m3/s to about 1 in 8000 for a discharge of 3000 m3/s.
 This slope is quite flat in comparison to the available ground
slope of an average value of 5 to 20 cm/km length (i.e., 1 in 200
to 1 in 50).
 The ground slope in nature is always very much steeper than
the design bed slope of irrigation canal, based on the silt
theories.
Necessity of Canal Fall

6. Necessity of Canal Fall
 When the ground slope suddenly changes to steeper slope,
the permissible bed slope can not be maintained and requires
excessive earthwork in filling to maintain the slope.
 In this case, falls are provided to avoid excessive earth work in
filling and dissipate the excess energy liberated from falling
water.

7.  When the slope of the ground is more or less uniform
and the slope is greater than the permissible bed slope of
canal.
Necessity of Canal Fall

8.  In cross-drainage works, when the difference between bed level
of canal and that of drainage is small or when the F.S.L of
the canal is above the bed level of drainage then the canal
fall is necessary to carry the canal water below the stream or
drainage.
Necessity of Canal Fall

9.  Depending on the ground level conditions and shape of the fall
the various types of fall are:
1) Ogee Fall
 The ogee fall was constructed by Sir Proby Cautley on the
Ganga Canal.
 This type of fall has gradual convex and concave surfaces
i.e. in the ogee form.
 The gradual convex and concave surface is provided with an
aim to provide smooth transition and to reduce disturbance
and impact.
 A hydraulic jump is formed which dissipates a part of
kinetic energy.
 Upstream and downstream of the fall is provided by Stone
Pitching.
Types of Canal Falls

10. Types of Canal Falls

11. 2) Rapid Fall
 When the natural ground level is even and rapid, this type of
fall is suitable.
 It consists of long sloping glacis.
 Curtain walls are provided on both u/s and d/s sides.
 Rubble masonry with cement grouting is provided from u/s
curtain wall to d/s curtain wall.
 Masonry surface is finished with a rich cement mortar.
Types of Canal Falls

12. Types of Canal Falls

13. 3) Stepped Fall
 It consists of a series of vertical drops in the form of steps.
 These steps are suitable in places where sloping ground is
very long and require a long glacis to connect the higher bed
level u/s with lower bed level d/s.
 It is practically a modification of rapid fall.
 The sloping glacis is divided into a number drops to bring
down the canal bed step by step to protect the canal bed and
sides from damage by erosion.
 Brick walls are provided at each drop.
 The canal bed within the fall is protected by rubble masonry
with surface finishing by rich cement mortar.
Types of Canal Falls

14. Types of Canal Falls

15. 4) Vertical Fall (Sarda Fall)
 In shape very similar to the ogee fall but without having
variation in construction as gradual convex to concave. In
other words with an abrupt change from u/s to d/s.
 A cistern is formed to act as water cushion.
 Floor is made of concrete u/s and d/s side stone pitching with
cement grouting.
 This type of fall is used in Sarda Canal UP and therefore, it is
also called Sarda Fall.
Types of Canal Falls

16. Types of Canal Falls

17. 5) Straight Glacis Fall
 It consists of a straight glacis provided with a crest wall.
 For energy dissipation of flowing water, a water cushion is
provided.
 Curtain walls are provided at toe and heel.
 Stone pitching is required at u/s and d/s of the fall.
Types of Canal Falls

18. Types of Canal Falls

19. 6) Trapezoidal Notch Fall
 It was designed by Reid in 1894.
 The body or foundation wall across the channel consisting of
several trapezoidal notches between side pier and intermediate
pier is constructed.
 The sill of the notches are kept at upstream bed level of the canal.
 The body wall is made of concrete.
 An impervious floor is provided to resist the scouring effect of
falling water. U/s and d/s side of the fall is protected by stone
pitching finished with cement grouting.
Types of Canal Falls

20. Types of Canal Falls

21. 7) Well or Cylinder Notch or Pipe Fall
 In this type, water of canal from higher level is thrown in a
well or a cylinder from where it escapes from bottom.
 Energy is dissipated in the well in turbulence.
 They are suitable for low discharges and are economical also.
Types of Canal Falls

22. Types of Canal Falls
Figure: Well or Cylinder Fall

23. 8) Montague Type Fall
 In the straight glacis type profile, energy dissipation is not
complete. Therefore, montague developed this type of profile
where energy dissipation takes place.
 His profile is parabolic and is given by the following
equation,
Types of Canal Falls

24. Types of Canal Falls

25. 9) Inglis or Baffle Fall
 Here glacis is straight and sloping, but baffle wall provided on
the downstream floor dissipate the energy.
 Main body of glacis is made of concrete.
 Curtain walls both at toe and heel are provided.
 Stone pitching are essential both at u/s and d/s ends
Types of Canal Falls

26. Types of Canal Falls