CANAL IRRIGATION

BY:- PROF. SAGAR R. RAUT

M.TECH. (STRUCTURAL ENGG.) B.E. (CIVIL ENGG).

CANAL:-

A canal is an artificial channel generally

trapezoidal in shape constructed on the ground

to carry water to the field either from the river

of from a reservoir.

Classification of CANAL:-

CANALS

NATURE OF SOURCE OF

SUPPLY

1. PERMANENT 2.

INUNDATION CANAL

FINANCIAL OUTPUT

1. PRODUCTIVE CANAL 2. PROTECTIVE CANAL

FUNCTION

1. IRRIGATIONAL CANAL 2.

CARRER CANAL 3. FEEDER CANAL

4. NAVIGATION

CANAL 5. POWER CANAL

BOUNDRY SURFACE

OF CANAL

1. ALLUVIAL CANAL 2. NON

ALLUVIAL CANAL 3. RIGID

BOUNDRY CANAL

DISCHARGE & ITS RELATIVE

IMPORTANCE

1. MAIN 2. BRANCH 3. MAJOR

DISTRICUTORY 4.MINOR

DISTRUBUTORY 5. WATER COURSE

CANAL ALIGNMENT

1. CONTOUR

2.WATERSHED 3. SIDE

SLOPE

Classification of CANAL:- Classification based on the nature of source of

supply:- 1. Permanent Canal.

2. Inundation Canal.

Classification based on the financial output:- 1. Productive Canal2. Protective Canal

Classification of CANAL:- Classification based on function of the canal:-

1. Irrigation Canal2.Carrier Canal3. Feeder Canal4. Navigation Canal5. Power Canal

Classification based on boundary surface of canal:- 1. Alluvial Canal2. Non- Alluvial Canal3. Rigid Boundary Canal

Classification of CANAL:- Classification based on discharge and its relative importance

in a given network of canal:- 1. Main Canal.2. Branch Canal.3. Major Distributary .4. Minor Distributary .5. Water Course .

Classification based on Canal Alignment:- 1. Contour Canal .2. Watershed Canal (Ridge Canal).3. Side Slope Canal.

Canal Alignment:- General consideration for alignment:- 1. It should be aligned in such a way that maximum area is

served with the least length. And its cost including CD- work is minimum.

2. A shorter length of canal has less loss of head due to friction and smaller loss of water due to seepage and evaporation, so that additional area can be brought under cultivation.

3. The alignment should be kept straight as far as possible, it will result in minimum losses.

4. It should have minimum CD work.

Canal Alignment:- General consideration for alignment:- 5. It should not passes through the village, town, forest or

costly lands, otherwise heavily compensation shall have to given.

6. It should be such that heavy cutting and feeling (embankment) are avoided.

7. It should through passes the ridge so that both side of canal can be irrigated.

8. The alignment should be such that as far as possible a balanced depth of cutting and filling is achieved.

9. The alignment should not be made in rocky, brackish or cracked strata.

A canal section will be economical when earth work involved at a particular section has an equal amount of cut and fill. Usually a canal section has a part in cutting and part in filling as shown in fig.

If the amount of cut is equal to the amount of fill, it has to be paid for once only.

Definition:- For a given C/S there is always only one depth of

cutting for which the cutting and filling will be equal. The depth is known as balancing depth.

Balancing Depth:-

Balancing Depth:-

If :- h = vertical height of top of bank from the bed of canal.b = bed width of the channel.t = top width of the canal bank.n:1 = side slope of bank in filling.z:1 = side slope of canal in cutting.d = full supply depth of canal.y = depth of cutting.

Balancing Depth:-

Area of the cut = by + zy2

= y(b + zy)

Area of fill = 2[(h – y)t + n(h-y)2 ]Equating the area of cut and fill:y(b + z y) = 2[(h – y)t + n(h-y)2 ]

b y+ zy2 = 2th + 2nh2 – 2nhy – 2ty – 2nhy + 2ny2

y2 (2n – z) – (b + 4nh + 2t)y + 2h(t + nh) =0

From this equation the balancing depth of the canal may be determined.

Balancing Depth:-

A canal is usually constructed with side slope of 1:1 in cutting and a slope 1.5:1 in filling.Putting n = 1.5 and z =1 in above equation.We get;

y2 – (b/2 + 3h + t)y + h (t + 3/2 h)=0

Balancing Depth:-

A canal is generally taken in such a way that its section is partly in cutting and partly in filling in order to approach close to balancing depth. Many times however the canal has to be carried through deep cutting or filling. A canal structure may, therefore, either :1. In Cutting 2. In Filling 3. In Partial Cutting and Filling.

Cross-section of canal:-

Cross-section of canal:-

Cross-section of canal:-

Cross-section of canal:-

Components of canal:-

• Side slopes• Berms• Free board• Land width• Dowla or Dowel• Spoil banks • Borrow pit

Components of canal:- • Side slopes:- – The side slope constructed on both sides of the canal for

allowing the water to flow in between them. As the canal is to be constructed in cutting and embankment or both.

Sr. No. Type Of Soil Slope In Cutting Slope In banking

1 Clayey Soil 1.5 : 1 2 : 1

2 Sandy Soil 3 : 1 4 : 1

3 Loamy Soil 1.5 : 1 2 : 1

4 Gravel Soil 0.75 : 1 1.25 : 1

5 Hard Rock 0.25 : 1 ----

6 Soft Rock 0.5 : 1 ----

Components of canal:- • Berms:-

– This is horizontal distance, which is left at G.L.

between the top edge of cutting & toe of bank.

When water flows in the canal at FSL (Full Supply

Level), silt particles are deposited on the berms and

make the final side slope to 1.5:1

Components of canal:- • Free Board:- – It is the vertical distance between FSL and the top of

bank. It is provided to ensure that water does not overtop the bank. The magnitude of the free board in a channel is governed by the consideration of the channel size and location, rain water inflow wind action soil characteristics etc.

I.S. 7112- 1973 recommends a minimum freeboard =

0.5m

Components of canal:- • Land Width:- – The total land required for the construction of

channel is divided into the two parts.1. Permanent Land 2. Temporary Land

Components of canal:- • Dowel or Dowla:- – A Dowel or Dowla is provided on the side of a service

road between the service road and channel.

– The top of the dowel is kept above the FSL in the channel the Dowel are provided as a measure of safety for automobile driven on the service road.

– They acts as a kerbs on the side of the road way towards the canal.

Components of canal:- • Spoil Banks:-

–When the quantity of earth obtained from

excavation or cutting is deposited near the

cutting in the form of bank known as spoil

bank.

Components of canal:- • Borrow Pit:-

–When the earth work in filling exceeds excavated quantity at particular section borrow pit are required to make good requirement of filling.

Numerical

1. What is balancing depth? Find out the balancing depth for canal having bed width 18m. FSD of 3m, top width of bank is 6m & 3m side slope in cutting 1.5 : 1 and in banking 2:1 and freeboard = 1m.

2. Calculate the economical depth of cutting for the C/S of canal the bed width is 5m and top width of banks is 2m. Side slope for excavation is 1:1 and of banking is 1.5:1. h= 2.92m

CANAL LINING

Canal Lining• It is the treatment given to the canal bed and

banks to make the canal section impervious. The lineds

• Canal lining is the process of reducing seepage loss of irrigation water by adding an impermeable layer to the edges of the trench.

• Seepage can result in losses of 30 to 50 percent of irrigation water from canals, so adding lining can make irrigation systems more efficient. Common lining materials include compacted earth, concrete, and plastic membranes.

Advantages of Lining Water Conservation:

Lining a canal results in reduction in water losses, as water losses in unlined irrigation canals can be high.

No seepage of water into adjacent land or roads: If canal banks are highly permeable, the seepage of

water will cause very wet or waterlogged conditions, or even standing water on adjacent fields or roads. Lining of such a canal can solve this problem.

Advantages of Lining Canal linings improve command:

Lining makes it possible to maintain high velocity in the canal. Generally lined canals are designed with normal value of silt factor (f= 1.2) and maximum permissible velocity (from 1.8 m/sec to 2.5 m/sec).

For these values of f and V steepest practicable longitudinal slope may be adopted. Even then this slope will be flatter than the slope of unlined canal.

Advantages of Lining

Thus this flat slope raises the FSL in general and brings the high area of land under command which have not been irrigated before.

Another advantage of maintaining high velocities can be recognized from the fact that “lined canals require smaller sections to convey same amount of water as that carried by unlined canals”.

Advantages of Lining Canal linings increase available head for power generation.

Canal linings make the canal section stable.

Canal linings prevent bank erosion and breaches.

Canal linings assure economical water distribution

Canal linings reduce maintenance costs

Types of Canal LiningHard Surface Lining

Cast Insitu Cement Concrete Lining

Shotcrete or Plastic Lining

Cement Concrete Tile Lining or Brick Lining

Asphaltic Concrete Lining

Boulder Lining

Exposed and Hard Surface Linings

Earth type canal lining.

Buried Membrane Linings

Types of Canal Lining

Exposed and Hard Surface Linings:- It includes all linings exposed to wear, erosion and

deterioration effect of the flowing water, operation and maintenance equipment and other hazards.

Such linings are constructed across of cement concrete and mortars, asphaltic materials, bricks, stones and exposed membranes.

Although the initial cost of all these linings is generally high, the reinforced cement concrete linings are costliest and are usually recommended for use only where structural safety is the primary consideration

Types of Canal Lining

Exposed and Hard Surface Linings:- 1. Cast in situ cement concrete lining2. Shotcrete or plastic lining.3. Cement concrete tiles lining or Brick

lining.4. Asphalt concrete lining.5. Boulder lining. 6. Exposed Membrane Linings.

Types of Canal Lining

Earth type canal lining.Thick compacted earth lining is durable and

can withstand considerable external hydrostatic pressure. Bentonite has shown considerable promise for use as a good lining material.

Bentonite containing large percentage of montmorillonite, is characterised by high water absorption accompanied by swelling and imperviousness. It can be used as 5.0 cm thick membrane covered by protective blanket or as a mixed inplace layer of soil bentonite and well compacted.

Types of Canal Lining

Buried Membrane Linings Hot-applied asphaltic, prefabricated

asphalt materials, plastic film and a layer of bentonite or other types of clays protected by earth or gravel cover are cheap linings. These linings can be provided immediately after completion of excavation or even later. Membrane linings are susceptible to damage by weed root and permissible water velocity is limited to avoid erosion. The life of the lining is uncertain.

Types of Canal Lining

Cast In-situ Cement Concrete Lining

Shotcrete & Plastic Lining

Canal Lining

CONCRETE LINING

Canal Lining

Concrete tiles canal lining

Canal LiningBrick canal lining

PREFABRICATED CHANNEL SECTION

Canal LiningGEOPOLYMER CANAL LINING

THANK YOU!!!!