What is canal lining of canal?
An impervious layer that is provided at the bed and sides of the canal to increase the life, discharge, and hydraulic efficiency of the channel is known as canal lining. Here we will discuss Requirements, Advantages, Disadvantages, and Types of Canal lining.
Types of channel
- Unlined channel and
- Lined channel
In unlined channel are earthen channel. there is no coating on its side and bottom. But in lined channel the bottom and sides are coated with materials like cement plaster, concrete, stone etc to reduce the water loses, seepage and percolation.
Function of lining
The lining of the canal means laying the stable (in erodible) material on the earthen surface of the channel such as concrete, tiles, asphalt, etc. The seepage losses channel reduces the potential of the supplied water. So, the main objective of lining is to reduce the seepage loss and maintain the potential of irrigation water.
The advantages of canal lining are as follows
i) Seepage control:- Seepage losses can be considerably reduced by lining the channels. But the cost of the channel is increased by 2 to 2.5 times of the unlined channels.
The heavy seepage losses also necessitate the higher capacity of the impounding reservoir and bigger dams. The lining of channels, therefore, reduces the impounding capacity of the reservoir and also its cost.
ii) Prevention of waterlogging:- Seepage losses through the unlined channels considerably increases the water table in the surrounding fields up to or near to the ground level to bring the roots of crops within the capillary fringe.
This enhances the alkali effects on the ground surface and hence makes the ground unfit for cultivation. Lining reduces the seepage and minimizes this effect on the ground surface.
iii) Increase in channel capacity:- Lining of the channel produces a smooth surface and hence reduces the resistance of flow. The flow-through unlined channel is resisted by the vegetation on the sides and bottom.
The water on the lined channel flows faster and greater discharge can be achieved through the same section. Hence lining the channel increases the channel capacity.
iv) Increase in the commanded area:- A lined channel can be designed not only smaller in cross-section but also smaller in length. A steeper gradient can be provided so that short alignment can be selected.
A flatter gradient can also be provided without silting on a lined channel. So the lined channel helps to bring a high area under command.
v) Reduction in maintenance cost:- Due to less seepage loss, no vegetation, and less silting property of lined channel. its maintenance cost can be considerably reduced.
vi) Elimination of flood dangers:- An unlined channel founded in the weaker foundation is always in danger and there may also danger of outbursts due to a smaller cross-section in the unlined channel. A strong concrete lining removes all such dangers.
Requirements of good canal lining
iv) Structural Stability (SS)
Shortly we can write as DRESS.
i) Durability:- A good canal lining must be able to withstand the following:
- Natural wear and tear
- Effect of the velocity of water
- Rain, sunshine, frost, and thawing
- Thermal and moisture change
- The chemical action of salts
- The damaging effect of cattle traffic, weed, and rodent growth.
ii) Repairability:- The lining should be such that it can be repaired easily and economically. For this Brick tile, boulder and precast slab linings are preferred to easily repairable than that of cast in situ concrete lining.
iii) Economy:- The type of lining selected should not only be economic in initial cost but also in repair and maintenance cost.
iv) Structural Stability (SS):- The lining should be strong enough to withstand the differential sub-soil water pressure due to sub-grade getting saturated through seepage or rain or due to sudden drawdown of the channel.
v) Impermeability:- The lining should be such that the see-page losses are reduced to a considerable extent.
vi) Hydraulic efficiency:- The lining should have a low coefficient of rugosity so that the channel has a high discharge carrying capacity and the channel section is hydraulically more efficient.
vii) Resistance to erosion:- The lining should be able to withstand abrasion due to sediment transported by flowing water. Cement concrete and boulder linings provide better abrasion resistance as compared to brick tile lining.
Types of Canal Lining
A) Rigid types of canal Lining
- STONE PITCHED LINING
- BURNT CLAY TILE/BRICK LINING
- PRECAST CEMENT CONCRETE IN-SITU CEMENT CONCRETE LINING
- STONE MASONRY LINING
- SOIL CEMENT LINING
- SHOTCRETE LINING
- ASPHALTIC CEMENT/CONCRETE LINING
B) Hard Surface Lining
- CEMENT CONCRETE LINING
- PRECAST CONCRETE LINING
- CEMENT MORTAR LINING
- BRICK LINING / BURNT TILE LINING
- STONE BLOCKS / UNDRESSED STONE LINING
- ASPHALTIC LINING
- BURIED MEMBRANE LINING
C) Earth Types of canal Lining
- SOIL CEMENT LINING
- CLAY PUDDLE LINING
- SODIUM CARBONATE LINING
ADVANTAGES OF CANAL LINING
- Prevents water seepage through the surface of the canal.
- Helps in preventing Water-Logging
- Increases discharge carrying capacity of the channel.
- Increases channel life and reduces the maintenance cost.
- Increases Gross area under cultivation.
- Silting is prevented as velocity is increased.
- Prevents or Reduces Weed Growth.
- Increase available head for power generation due to flatter gradient.
DISADVANTAGES OF CANAL LINING
- A heavy initial investment is required.
- Difficult to shift the outlets as the lining is permanent.
- Difficult to repair the damaged lining.
- The berm is absent in Lined channels, so safety to vehicular and gets reduce and pedestrian track get reduces.
I hope this article on “Requirements, Advantages, Disadvantages, and Types of Canal lining” remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Ranjeet Sahani