Canal Regulation Works

What is Canal
•
Fall?
Whenever the available 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
below. Such a drop in a natural canal bed will
not be stable and, therefore, in order to retain
this drop, a masonry structure is constructed.
Such a structure is called a Canal Fall or a
Canal drop.
Canal
Fall
 Canal
Irrigation canals Fall
are designed for a prescribed bed
slope so that velocity becomes non silting or non
scouring. But if the ground topography is such that in
order to maintain the canal designed slope, indefinite
filling from falling ground level is to be made. This
indefinite filling is avoided by constructing a hydraulic
structure in the place of sudden bed level. This
hydraulic structure is called canal fall or drop. Beyond
the canal fall, canal again maintains its designed slope.
 Canal
Fall
• Thus, a canal fall or drop is an irrigation structure
constructed across a canal to lower down its bed
level to maintain the designed slope when there is a
change of ground level to maintain the designed
slope when there is change of ground level. This
falling water at the fall has some surplus energy. The
fall is constructed in such a way that it can destroy
this surplus energy.
 Necessity of Canal
Falls
• When the slope of the ground suddenly changes to
steeper slope, the permissible bed slope can not be
maintained. It requires excessive earthwork in
filling to maintain the slope. In such a case falls are
provided to avoid excessive earth work in filling
Necessity of Canal
Falls
 Necessity of Canal
Falls
• 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
Falls
• 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
Falls
 Types of Canal Fall
• Depending on the ground level conditions and shape
of the fall the various types of fall are:
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
withprovide
to an aim smooth transition and to
disturbance
reduce 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.
Ogee
Fall
 Types of Canal Fall
Stepped Fall
• It consists of a series of vertical drops in the form of
steps. This steps is 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 bed of the canal within
the fall is protected by rubble masonry with surface
finishing by rich cement mortar.
Stepped
Fall
 Types of Canal Fall
Vertical Fall (Sarda Fall)
• In the simple type, canal u/s bed is on the level of
upstream curtain wall, canal u/s bed level is
below the crest of curtain wall. In both the cases,
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 is provided. This
type of fall is used in Sarda Canal UP and
therefore, it is also called Sarda Fall.
Vertical Fall
 Types of Canal Fall
Rapid Fall
• When the natural ground level is even and
rapid, this rapid 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.
Rapid
Fall
 Types of Canal Fall
Straight Glacis Fall
• It consists of a straight glacis provided with a
crest wall. For dissipation of energy of flowing
water, a water cushion is provided. Curtain
walls are provided at toe and heel. Stone
pitching is required at upstream and
downstream of the fall.
Straight Glacis
Fall
 Types of Canal Fall
Trapezoidal Notch Fall
• It was designed by Reid in 1894. In this type a
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.
Upstream and downstream side of the fall is
protected by stone pitching finished with cement
grouting
Trapezoidal Notch Fall
 Types of Canal Fall
Well or Cylinder Notch 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 Fall
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,
Montague Type Fall
Montague Type Fall
 Types of Canal Fall
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
Inglis or Baffle
Fall
 Canal
• It is a side Escape
channel constructed to remove
surplus water from an irrigation channel (main
canal, branch canal, or distributary etc.) into a
natural drain.
• The water in the irrigation channel may become
surplus due to -
• Mistake
• Difficulty in regulation at the head
• Excessive rainfall in the upper reaches
• Outlets being closed by cultivators as they
find the demand of water is over
 Canal
• Escape
It is the structure required to dispose of surplus or
excess water from canal from time to time. Thus, a
canal escape serves as safety valve for canal system. It
provides protection to the canal from possible damage
due to excess supply which may be due to mistake in
releasing water at head regulator or heavy rainfall
that makes sudden regular demand of water. The
excess supply makes the canal banks vulnerable to
failure due to overtopping or dangerous leaks.
Therefore, provision for disposing this surplus water
in form of canal escapes at suitable intervals along the
canal is essential. Moreover emptying canal for
repair
and maintenance and removal of sediment deposited
in the canal can also be achieved with the help of
canal escapes.
 Escapes are usually of the
following three types.
Surplus Escape
• It is also called regulator type. In this type sill
of the escape is kept at canal bed level and
the flow is controlled by a gate. This type of
escapes are preferred now-a-days as they
give better control and can be used for
employing the canal for maintenance.
Surplus Escape
Surplus
Escape
 Escapes are usually of the
following
Tail Escape three types.
• A tail escape is provided at the tail end of the
canal and is useful in maintaining the
required FSL in the tail reaches of the canal
and hence, they are called tail escape.
Tail Escape
 Escapes are usually of the
following three types.
Scouring Escape

• This escape is constructed for the purpose of scouring

of excess silt deposited in the head reaches from time
to time. Hence, it is called scouring escape. Here the
sill of the regulator is kept at about 0.3 m below the
canal bed level at escape site. When deposited silt to
be scoured, a higher discharge than the FSL is
allowed to
enter the canal from the head works. The gate of the
escape is raised so as to produce scouring velocity
which remove the deposited silt. This type of
Escape
has become obsolete as silt ejector provided in the
canal can produce better efficiency.
Scouring Escape
 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.
• Function:
• Tocontrol the entry of water either from the reservoir
or from the main canal.
• To control the entry of silt into off taking or main canal.
• To serve as a meter for measuring discharge of water.
 Head Regulator
• Construction: The components of head regulator
depends upon the size of canal and location of head
regulator. It consists of one or more gated research
openings with barrels running through the bank.
For large canals head regulators are flumed to
facilitate the measurement of discharge.
Head Regulator
 Cross Regulator
• Cross Regulator
• A Regulator Constructed in the main canal or parent
canal downstream of an off take canal is called cross-
regulator.
• It is 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
Cross Regulator
 Cross Regulator
Construction: For Cross Regulators abutments
with grooves and piers are constructed parallel
to the parent canal. The sill of regulation is kept
little higher than the u/s bed level of canal
across which it is constructed. Vertical lift gates
are fitted in the grooves. The gates can be
operate from the road.
Canal regulators
Canal regulators