CANAL IRRIGATION

UNIT-IV CANAL IRRIGATION
SYLLABUS:
Canal regulations – direct sluice - Canal
drop – Cross drainage works-Canal outlets
– Design of prismatic canal-canal
alignments-Canal lining - Kennedy’s and
Lacey’s Regime theory-Design of unlined
canal

INTRODUCTION:
It is a direct irrigation system, which makes use of a weir
or a barrage, as well as a storage irrigation scheme which
makes use of a storage dam or a storage reservoir,
necessitates the construction.
DISTRIBUTION SYSTEMS FOR CANAL
IRRIGATION:
Main canal
Branch canal
Distributaries (major Distributaries)
Minor Distributaries
Watercourse

Main canal:
 Canal head works are generally situated on the river
flowing valley and canal should reach the ridge line in
shortest possible distance.
 Therefore the canal aligned very carefully and has to
excavate deep cutting below N.S.L
Branch canal:
 These are taken off the water from the main canal on
either side.
 It supply the water to the distributaries.
Distributaries:
 These are smaller canals get water from the branch canal
and distribute their supply through outlets into minors or
water courses.

Minors Distributaries:
 The distance between the distributary outlet and land is
very long, discharge in a minor.(less than 2.5 cumec)
Water courses:
 These are excavated and maintained by the land
cultivators.

Classification of Canal
Nature of
source of
supply
Financial
output
Function of
canal
Boundary
surface of
canal
Permanent
canal
Inundation
canal
Protective
canal
Productive
canal
Power canal
Navigation
canal
Feeder canal
Carrier canal
Irrigation canal
Rigid-boundary
canal
Non-alluvial
canal
Alluvial canal
Permanent
source of
supply
High stage
of supply
Net
revenue
to
nation
Protect
some
area

CANAL REGULATORS
Head regulator:
 It is provided at the head of the off-taking canal, controls
the flow of water entering the new channel.
Cross regulator:
 It is required in the main channel downstream in off-
taking channel, operated when necessary.

MAIN FUNCTIONS OFA HEAD REGULATOR:
 Regulate or control supply the off-taking canal.
 Control the entry of silt into off-taking canal.
 Serve the measuring discharge.
MAIN FUNCTIONS OFA CROSS REGULATOR:
 To control entire canal irrigation system.
 Help to fed the water from upstream to off-taking canal.
 Help to reduce fluctuations and possibilities to reach the
tail end of canal.
 It is combined with bridges and falls, if required.

RIVER TRAINING WORKS:
These are required near the weir site in order to ensure a
smooth and axial flow of water & to prevent the river
from outflanking works due to a change in its course.
It required on a canal headworks are,
(a) guide banks
(b) marginal bunds
(c) spurs or groynes
(a) Guide Banks:
 When a barrage is constructed across a river which flows
through the alluvial soil, guide banks must be constructed
on both sides of canal to protect from soil erosion.

Purposes:
o Protects from effects of scouring and erosion.
o Provides straight approach towards the barrage.
o Controls the tendency of changing the course of river.
o Controls velocity of flow near the structure.
(b)Marginal bunds:
 These are earthen embankments which are constructed
parallel to the river bank one or both banks according to
the condition.
 Top width is 3 to 4m and slope on river side 1.5:1 and
other side 2:1

Purposes:
o Prevent the flood or storage water from entering the
surrounding area may be lead to water logged.
o Retains flood water or storage water within a specified
section.
o Prevents towns and villages from floods.
o Protects valuable agricultural lands.
(c)Spurs or groynes:
(i) Spurs:
 These are temporary structures permeable in nature
provided on the curve of a river to protect the river bank
from erosion.

 These are projected from the river bank and make an
angle of 60 to 750 with river bank.
 The length of the spur is based on the width & sharpness
of the river.
 The function of spur is to break the velocity of flow and
form a water pocket in upstream for sediments get
deposited.
 It has the following types;
(a) bamboo spur
(b) timber spur
(c) boulder spur

(a) Bamboo spur:
• These are like compartment is prepared by bamboo piles
at 15cm c/c.
• Piles are secured by bamboo bracings and hollow space is
filled by sand bags.
• It is permeable in nature and water can seep through its
body.
• This is suitable for small rivers and purely temporary
structures .
• It requires repair work every year & length of bamboo
piles depends upon the bed condition.

(b) Timber spur:
• This is box like compartment is prepared by driving
timber piles at 15cm to 30cm c/c.
• Piles are secured by wooden bracings.
• The hollow space filled by boulders and it is permeable
also stable.
• It is recommended for the rivers with high velocity of
flow.
• The length of timber piles depend on bed condition.

(c) Boulder spur:
• Here boulders are enclosed in G.I wire net in circular
shape.
• The boulders should be heavy, varying from 30kg to 50kg
and wire net made of 4mm diameter G.I wires.
• It laid in river bank towards bed making angle of 600 –
750
• These type is recommended in velocity of flow is very
high.

(ii) Groynes:
 The function of groynes are similar to spur & these are
impervious permanent structures constructed on the
curve of a river to protect river bank from erosion.
 Extend an angle of 600 to 750 with bank and towards
upstream or downstream, sometimes it is perpendicular.
 These are constructed with rubble masonry in trapezoidal
section and surface finished with stone pitching or
concrete blocks.
Stone pitching or concrete blocks are set with rich cement
mortar.
Length of groyne based on width & nature of river.

Top width varies from 3 to 4m, side slope may be 1.5:1 or
2:1
These are provided in series throughout the affected
length of river bank.
Spacing of groynes = 2L (L-length of groyne)
It is recommended for river where the permanent solution
of erosion control necessary.
These are may be designed as follows;
(a) Attracting groyne:
 It is constructed obliquely to bank @ angle 60 – 750
towards downstream.
 Flow of water attracted by bank and bank protected of
stone pitching for safety.

(b) Repelling groyne:
 It is constructed obliquely to bank @ angle 60 – 750
towards upstream.
 So that water pocket formed and silts get deposited.
 Bank protection not necessary because the flow of water
does not touch the bank.
 For safety purpose boulder pitching is provided.
(c) Deflecting groyne:
 It is constructed perpendicular to bank.
 The flow of water deflected from bank by perpendicular
obstruction and eddy current formed upstream of groyne.
 For safety purpose boulder pitching is provided.

Modification of groyne:
(a) Denehy’s groyne or T-headed groyne:
After long investigation, deheny developed a groyne in
shape of T.
Length of head kept as L/2, (L-length of groyne).
All others are same as other groynes.

(b) Hockey head groyne:
The head of the groyne is curved towards the downstream
in shape of a hockey stick & it behaves like a attracting
groyne.
But it allows the water to flow smoothly over the head of
the groyne.

SILT REGULATION WORKS
Special works to reduced the entry of silt into the canal.
(a) Silt excluders
(b) Silt ejectors
(a) Silt excluders:
 Constructed on the bed of river in upstream of head
regulator.
 The clear water enter the head works and silted water
entered the silt excluder.
(b) Silt ejectors:
 It is also called silt extractor, which extract silt from canal
water after silted water travelled a certain distance.

TYPES OF SLUICE GATE
Flap sluice
gate
Vertical
rising SG
Radial SG
Rising
sector SG
Needle SG
Automatic
type(by
pressure)
Plate
sliding
vertical
direction
Cylindrical
surface
act as gate
same
radial, @
bottom &
rotates
center
Thin
needles
formed by
sluices
Wood Cast iron
Stainless
steel
FRP
TYPES OF MATERIALS USED FOR SLUICE GATE

CANAL FALL:
 Generally canals are provided some slope. But sometimes
the ground surface is not uniform, so that the vertical drop
is provided to continue the flow.

NECESSITY OF CANAL FALLS:
 When the slope of ground suddenly changes to steeper
slope, the permissible bed slope can't be maintained.
 So that it required excessive earth filling to maintain the
slope. In such case falls are provided to avoid excessive
earth work in filling.
 Slope of ground is more or less uniform and slope is
greater than permissible bed slope , the canal fall is
provided.
 In cross drainage works the F.S.L of canal is above the
bed level of drainage the canal fall is necessary.

TYPES OF CANAL FALLS:
The followings are the types of canal falls based on the site
condition;
a) Ogee fall
b) Rapid fall
c) Stepped fall
d) Trapezoidal notch fall
e) Vertical drop fall
f) Glacis fall

(a) Ogee fall:
 In this type, ogee curve(combination of convex curve and
concave curve) is provided for carrying the canal water
from higher level to lower level.
 This fall is recommended when the natural ground surface
suddenly changes to steeper slope along the alignment of
canal.
It consists of concrete vertical wall and concrete bed.
Over the concrete bed the rubble masonry is provided in
shape of ogee curve.
Surface of masonry is finished with rich cement
mortar(1:3)
Upstream and downstream side of fall is protected by
stone pitching with cement grouting & the design is based
on site condition.

(b) Rapid fall:
 This is suitable when the slope of natural ground surface
is even and long.
 It consists of slope varies from 1 in 10 to 1 in 20.
Curtain walls are provided on the upstream and
downstream side of slopes.
Sloping bed is provided with rubble masonry.
The upstream and downstream side of fall is also
protected by rubble masonry.
The surface finished with cement mortar 1:3

(c) Stepped fall:
 It consists of series of vertical drops in form of steps.
 This fall is suitable where the sloping ground is very long
and requires long glacis(easy slopes) to connect the higher
bed level to lower bed level.
This is practically modification of the rapid fall.
The sloping glacis(easy slope) divided to numbers of
drops, so that the flowing water may not cause to damage
the canal bed.
Brick walls are provided at each of the crops.
The bed of canal protected by rubble masonry and the
surface finished with cement mortar 1:3

(d) Trapezoidal notch fall:
 The body wall is constructed across the canal and wall
consists of several trapezoidal notches in b/w the side
piers.
The body wall constructed with masonry or concrete.
An impervious layer is provided to resist the scoring
effect of falling water.
The upstream and downstream side of fall is protected by
stone pitching with cement grouting.
The size and number of notches depends upon the full
supply discharge of the canal.

(e) Vertical drop fall:
 It consists of a vertical drop walls which constructed with
masonry work.
 The water eastern is provided on the downstream side
which acts as a water cushion to dissipate the energy of
falling water.
A concrete floor if provided @ downstream to control the
scouring effects.
Curtain walls are provided on upstream and downstream
side.
Stone pitching provided with cement grouting provided to
protect from scouring.

(f) Glacis fall:
 It consists of a straight glacis provided with a crest.
 A water cushion is provided on downstream to dissipate
the energy of falling water.
Sloping glacis constructed with cement concrete.
Curtain walls and toe walls are provided on upstream and
downstream sides.
The space b/w the toe walls and curtain walls is protected
by stone pitching.
This type of fall is suitable for drops up to 1.5m.

CROSS DRAINAGE WORKS
Suitable structures must be constructed at the crossing
point for easy flow of water of canal and drainage in
respective directions.
NECESSITY OF CROSS-DRAINAGE WORKS
 The water-shed canals do not cross natural drainages and
there is some obstacles like natural drainages.
 Some points, the water of canal and drainage get
intermixed.
 The site condition of crossing point, the water of canal
and natural drainage may get mixed so need some
structures.

TYPES OF CROSS-DRAINAGE WORKS
TYPE-I:
a) Aqueduct
b) Siphon aqueduct
TYPE-II:
a) Super passage
b) Siphon super passage
TYPE- III:
a) Level crossing
b) Inlet and outlet

TYPE-I:
a) Aqueduct:
 It is like a bridge where a canal is taken over the deck
supported by piers instead of a road or railway.
 The canal may be a rectangular or trapezoidal.
Inspection road is provided along the side of the trough.
The bed and banks of drainage below the trough is
protected by boulder pitching with cement grouting.
The trough design is according to full supply discharge of
canal.
Free board is 0.50m
Height and section of piers designed based on H.F.L and
velocity of flow & it is a stone masonry or RCC.

b) Siphon Aqueduct:
 Bed of the drainage is depressed below the bottom level
of canal trough by providing sloping apron on both sides
of the crossing.
Sloping apron is constructed by stone pitching or cement
concrete.
Section of below the canal is constructed by cement
concrete to form tunnel, it is act as a siphon.
Cut off walls and boulder pitching are provided on both
sides to prevent scouring.
The other components are same as aqueduct.

TYPE-II:
a) Super passage:
 It is opposite of the aqueduct.
 Here the drainage is passing above the canal & it is may
be a rectangular or trapezoidal shapes supported by piers.
The section of drainage trough is based on the high flood
discharge.
Free board is 1.5m & trough constructed by RCC.
Bed and banks of canal below the drainage is protected by
boulder pitching or lining with concrete slabs.
Foundation of piers will be same as in the case of
aqueduct.

b) Siphon super passage:
 It is opposite to the siphon aqueduct & the canal passes
below the drainage trough.
 Section of trough is designed based on high flood
discharge.
 The bed of the canal is depressed below the bottom level
on both sides(made like sloping apron).
Sloping apron may be constructed with stone pitching or
concrete slabs.
Section of canal below the trough is constructed with CC
in form of tunnel which acts as siphon.
Cut off walls provided on U/S and D/S side of sloping
apron and other components are same as siphon aqueduct.

TYPE-III:
a) Level crossing:
 It is arrangement provided to regulate the flow of water
through the drainage and the canal when they cross each
other approximately in the same bed level.
Crest wall:
 It is provided across the drainage just at the upstream side
of crossing point & top level is full supply of canal.
Drainage regulator:
 It is provided across the drainage just at the downstream
side of crossing point & it consists adjustable shutters.
Canal regulator:
 It is provided across the drainage just at the downstream
side of crossing point & it consists adjustable shutters.

b) Inlet and outlet:
 Crossing of small drainage with small channel no
hydraulic structure is constructed.
 Simple openings only provided for their respective
directions.
Inlet is provided in the channel bank simply by open cut
and the drainage water is allowed to join the channel.
Inlet and outlet ends are protected by stone pitching.

CANAL ESCAPES:
It is a side channel constructed to remove the surplus
water from an irrigation channel into a natural drain.

CANALALIGNMENT:
Canal has to be aligned, produce minimum losses,
irrigated to entire area with short length and economical
manner.
FACTORS TO BE CONSIDERED FOR CANAL
ALIGNMENT:
 Most economical way to distributing the water to land.
 Minimum number of cross drainage works.
 The alignment of canal should be occupied by
distributaries.
 Length of inlet and outlet should be minimum.
 Contour alignment should be changed to minimize the
cross drainage works.

 Alignment should avoid the valuable properties.
 Alignment should be minimum cutting and filling.
 Acute curves are minimum.
 Idle and branches of canals are minimum.
 Alignment should not be made in rocky and strong strata.
Types of canal alignment:
i) Watershed canal or ridge canal
ii) Contour canal
iii) Side-slope canal
i) Watershed canal or ridge canal:
 The dividing ridge line between the catchment areas of
two streams(drains) is called watershed or ridge line.

 The main streams are divided into two streams by
watershed(ridge line).
 The canal which is aligned along the natural watershed is
known as watershed canal or ridge canal.
 Aligning the canal on ridge ensures gravity irrigation on
both sides of the canal.
 Canal aligned on the watershed saves the cost of
construction of cross-drainage works.

ii) Contour canal:
 In hilly regions the watershed canals are not possible. So
the contour canal alignment was take place.
 Contour channels are follow a contour except longitudinal
slope of the canal.
 The river slope is much steeper than the canal bed slope,
the canal encompasses more and more area itself.
 It irrigates only one side because the area on the other side
is higher.

iii) Side-slope canal:
 It is aligned at right angles to the contours.
 The canal runs parallel to the natural drainage works the
cross drainage works are not necessary.

CANAL LINING:
 An impermeable layer is provided at the bed and sides of
canal to improve the life & discharge capacity of canal.
 Irrigation loss is generally occurred in canals are 30-40%.
TYPES OF CANAL LININGS
Earthen type lining Hard surface lining
Compacted
earth lining
Soil
cement
lining
Cement
concrete
lining
Brick
lining
Plastic
lining
Boulder
lining

1.EARTHEN TYPE LINING:
a) Compacted earth lining:
 If suitable earthen material available near the construction
site or in-situ, it is the efficient method of canal lining.
 Compaction reduces the permeability of soil, pore sizes,
voids and increases the density , compressive strength and
shear strength of soil.
 Also reduction of volume and settlement of surface
occurred.
 Proper compaction is essential for increase the stability
and decrease the erosion and seepage losses.

b) Soil cement lining:
 It is the mixture of cement ,sandy soil and water to make
the harden material like concrete.
 Cement content should be from 2-8% of soil by volume.
 The construction of soil-cement linings two methods are;
i) dry-mix method
ii) plastic mix method
 Sometimes the coarse soil is covered the soil-cement layer
for protection of erosion.
 Soil-cement lining is protected from weather for 7 days
by spreading approximately 50mm of soil.
 Proper curing takes place for 28 days with water
sprinkling and some other methods.

2.Hard surface lining:
a) Cement concrete lining:
 This method is widely used for lining but it is costly.
 They are tough, durable, relatively impermeable and
hydraulically efficient.
 It can be suitable for small and large channels and both
high and low flow velocities.
 It has several procedures;
i) cast in-situ lining
ii) shotcrete lining
iii) precast concrete lining
iv) cement mortar lining

b) Brick lining:
 The canal sides are lined with bricks laid in cement
mortar.
c) Plastic lining:
 As a modern technique use of plastic as a lining material.
i) low density poly ethylene
ii) high molecular high density polythene
iii) polyvinyl chloride
 These are low in weight, easy for handling, transport.
 These are prepared subgrade of the canal & to anchor on
banks ‘V’ trenches are provided.
 The film is then covered with productive soil cover.

b) Boulder lining:
 This type of lining is constructed with dressed stone
blocks laid in mortar.
 This type of lining is limited to the situation where loss of
head is not an important consideration and where stones
are available at moderate cost.

CANAL DESIGN:
a) Kennedy’s theory
b) Lacey’s regime theory
a) Kennedy’s equation:
 For design of canal, the following equations are used;
Continuity equation:
Q = Area x Velocity
Kutter’s equation:

Kennedy’s equation,
Vo = 0.55 m D0.64 (Kennedy’s regime equation)
Design procedure:
Case 1: Given Q,N, m and S (from L-section)
Step -1: Assume a trial value of ‘D’ in meters
Step -2: Calculate the velocity Vo from the equation.
Vo = 0.55 m D0.64
Step -3: Get area of section ‘A’ from the continuity equation.
A= Q/ Vo
Step-4: Knowing ‘D’ and ‘A’ calculate bed width ‘B’ from
geometry of canal section & side slope assumed 0.5:1 when
the canal run for some time.

A = BD + D2 / 2
From which ‘B’ can be calculated.
Step-5: Calculate the perimeter and hydraulic mean depth
from following relations,
𝑷 = 𝑩 + 𝑫 𝟓
R = A / P = (BD+D2/2) / (B+D√5)

Step-6: Calculate the actual mean velocity of flow(V) from
kutter’s equation.
If V= Vo, assume depth is correct.
If not, repeat evaluations with a changed value of ‘D’
till V=Vo
Case-2: Given Q, N, m and B/D ratio.
Step-1: Calculate ‘A’ interms of ‘D’
Let, B/D = x (or) B= Dx
𝑨 = 𝑩𝑫 +
𝑫 𝟐
𝟐
= 𝑿𝑫 𝟐 +
𝑫 𝟐
𝟐
= 𝑫 𝟐(𝑿 + 𝟎. 𝟓)
Step-2: The value of velocity Vo is known in terms of ‘D’ by
kennedy’s equation,
Vo = 0.55 m D0.64

Substitute the values of ‘Vo’ and ‘A’ in the continuity
equation and solve ‘D’.
Q= A * Vo = 𝐷2(𝑋 + 0.5) * 0.55 m D0.64
Q= 0.55m(x + 0.5) D2.64
Hence , 𝑫 =
𝑸
𝟎.𝟓𝟓𝒎 𝒙+𝟎.𝟓
1/2.64
Hence, D is determined.
Step-3: Calculate ‘B’ and ‘R’ from relations:
B = xD and R = (BD+D2/2) / (B+D√5)
Step-4: Calculate the velocity Vo from kennedy’s equation
Vo = 0.55 m D0.64
Step-5: Knowing ‘Vo’ and ‘R’, determine the slope ‘S’ from
kutter’s equation. The equation can be solved by trail and
error.

DRAWBACKS IN KENNEDY’S THEORY:
1. Kennedy did not notice the importance of B/D ratio.
2. Silt grade and silt charge were not defined.
3. He aimed to find out only the average regime conditions
for the design of channel.
4. He did not give any slope equation.
5. He used kutter’s equation for determination of mean
velocity and therefore the limitations of kutter’s equation
got incorporated in kennedy’s theory of channel design.

b) Lacey’s regime theory:
 Silt is kept in suspension by vertical component of eddies
generated at all points of forces normal to the wetted
perimeter.
Regime channel:
 A channel is said to in regime, if there is neither silting
nor scouring.
 According to lacey there may be three regime conditions;
i) True regime
ii) Initial regime
iii) Final regime

i) True regime:
 Discharge is constant
 Flow is uniform
 Amount is silt is constant
 Type and size of silt is always same
 Channel flowing through a material which can be scoured
as easily as it can be deposited and transported.
But in practice all these conditions can never satisfied.
Therefore the artificial channels can never be in ‘true
regime’ they can either be in initial or final regime.

ii) Initial regime:
 Bed slope varies
 Cross section or wetted perimeter remains unaffected.
iii) Final regime:
 All the variables such as perimeter, depth, slope, etc. are
free to vary and achieve permanent stability.

Lacey’s equations:
Fundamental equations;
𝑉 =
2
5
𝑓𝑅 𝑜𝑟 𝑓 =
5𝑉2
2𝑅
Where, f= 1.76√D50
D50 – average grain/particle size in ‘mm’
Af2 = 140 V5
V = 10.8 R2/3 S1/2
Derived equations;
𝑃 = 4.75 𝑄
𝑉 =
𝑄𝑓2
140
1/6

S= f3/2 / (4980 R1/2) [upper indus basin, f=0.8 to 1.3]
S= f5/3 / (3340 Q1/6) [sindh plain, f=0.7 to 0.8]
V= 1/ Na( R3/4 S1/2) [Lacey’s Non-regime flow equation]
Lacey’s Normal regime scour depth = 0.473(Q/f)1/3
[𝑃 = 4.75 𝑄]
For other values of active river width,
Lacey’s normal scour depth = 1.35(q/f)1/3 , q=Q/L
Where, q= discharge intensity
L= actual river width at the given site

Lacey’s channel design procedure:
Step-1: Calculate the velocity from equation,
𝑉 =
𝑄𝑓2
140
1/6
Where,
Q = cumecs
V = m/s
f = silt factor, f=1.76√dmm [dmm – avg particle size]
Step-2: Workout the hydraulic mean depth (R),
R= (5/2) (V2/f) [V = m/sec; R= m]
𝐷 = 𝑃 − (𝑃2 − 6.944𝐴)/3.742
B=P - √5 D

Step-3: Compute area of channel section, A= Q/V
Step-4: Compute wetted perimeter, P = 4.75 √Q
Step-5: Knowing these values, the channel section is known
and finally the bed slope ‘S’ determined by following
equation,
S= f5/3 / (3340 Q1/6)
Drawbacks in Lacey’s theory:
The concept of true regime is only theoretical and cannot
be achieved practically.
Various equations are derived by considering various silt
factor.
Concentration of silt is not taken into account.
Silt grade and charge are not clearly defined.

Equations are empirical and based on the available data
from a particular type of channel.
Characteristics of regime of channel may not be same foe
all cases.

COMPARISON BETWEEN KENNEDY’S AND
LACEY’S THEORIES
S.No KENNEDY THEORY LACEY’S THEORY
1
Silt carried by the
flowing water is kept
vertical component,
generated from bed of
channel.
Silt carried by the flowing
water is kept vertical
component, generated from
entire wetted perimeter.
2 Relation between ‘V’
and ‘D’
Relation between ‘V’ and
‘R’
3 Critical velocity ratio
‘m’ is introduced to
make different channels
with different channels.
Silt factor ‘f’ is introduced to
make different channels with
different channels.

S.No KENNEDY THEORY LACEY’S THEORY
4 Kutter’s equation is
used for finding the
mean velocity.
Theory gives an equation for
finding the mean velocity.
5 No equation for bed
slope.
It gives an equation for
finding the mean velocity.
6 Design based on trial
and error method.
It does not involve trial and
error method.

DESIGN OF UNLINED CANAL:
 Unlined canals exist mostly in underdeveloped countries
when lining cannot be easily afforded.
Uniform flow formulae:
a) Chezy’s formula:
𝑉 = 𝐶 𝑅𝑆
Where, V – Velocity of flow (m/s)
S – longitudinal slope of channel (energy slope)
C – chezy’s co-efficient.
C

Where,
N – kutter’s co-efficient (based on nature of bed and sides of
channel)
R – hydraulic mean radius (A/P)
‘C’ also determined by Bazin’s equation;
𝐶 =
87
1 +
𝐾
𝑅
Where, K – Bazin’s co-efficient

b) Kutter’s formula:
Where,
V – Velocity of flow (m/s)
S – longitudinal slope of channel
N – rugosity coefficient
R - hydraulic mean radius (A/P)

Value of ‘N’ in kutter’s equation:
c) Manning’s Formula:
V= (1/n)R2/3 S1/2
Where,
n – manning’s roughness coefficient
S.No Condition of channel Value of N
1 Very good 0.0225
2 Good 0.0250
3 Indifferent 0.0275
4 Bad 0.0300

Values of manning’s roughness coefficient
Material n
Concrete 0.012
Gravel bottom with sides-
concrete 0.20
Moderated stone
Natural clean, straight natural
stream
0.030
Natural stream with heavy bush
and timber
0.100

CANAL IRRIGATION

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CANAL IRRIGATION