Canal Lining is an impermeable layer provided for the bed and sides of the canal to improve the life and discharge capacity of the canal usually constructed in 2.5 to 15 cm thick layer of lining material such as RCC or CC brick, stone, etc.
It also prevent waterlogging across the lower areas of the canal.
Here we will learn about canal lining, types of canal lining, advantages & disadvantages of canal lining.
Introduction to canal lining:
An irrigation canal or channel requires an additional amount to spend on lining construction but in long times, it is the lining that helps control seepage through banks and bed.
This additional water provided through the lining process can justify the additional cost incurred on the channel lining.
In canal system while the water flows towards the irrigable area, it can cause damage due to seepage i.e. crops will not get the required amount of water, which affects the crop yield.
Therefore it is necessary to provide an impervious layer on the bed and side of the canal to minimize losses.
Types of Canal Lining:
1.Cement or lime concrete lining:
The lining provided with concrete is called concrete lining, it is very useful because it allows a high reduction in seepage losses.
It is strong, durable and used for any thickness for both small and large canals.
High velocity is possible due to cross-section and strong pavement which prevents silting tendency in the canal.
Its maintenance cost is low.
2.Cement mortar lining:
In this type of lining, seepage losses are reduced from 90 to 95%, commonly used due of its durability, impermeability, and hydraulic efficiency.
The materials used in this lining are Portland cement, sand graves & water.
Sometimes for special purposes admixtures are added to it for required result.
3.Stone masonry lining:
This type of lining is suitable where large quantities of stones are available.
It is sometimes plastered to make the surface proper.
When bricks are used for lining it is called brick lining.
It is economical and gives reasonable protection from seepage but is not impermeable as a solid lining has low resistance to corrosion.
In the shotcrete lining of cement mortar, pressure is applied through the nozzle on the surface of the canal.
It is a mixture of cement and sand used to resurface the old lined surface, thickness of this lining varies from 3.5 cm to 5 cm.
In this type of lining, asphalt cement is used along with sand and gravel provides a smooth flexible surface.
It absorbs heat and encourages weed growth due to rapid degradation.
7.Precast concrete block lining:
In such lining, concrete blocks are poured into factories to prepare the bed.
It has high durability hydraulic efficiency, the thickness of such lining can vary from 5 to 6.5.
Properties of Canal Lining:
- Strength: The material should be quite strong to withstand various pressures behind the lining.
- Easy in construction: The material selected can be used in any difficulty in giving the desired shape.
- Resistance to the growth of weeds: It is able to resist the growth of weeds and attack burrowing animals.
- Durability: It is durable and provides sufficient resistance against forces such as weathering, chemical attack, and wearing.
- Hydraulic efficiency: The surface of the lining material should be smooth for higher hydraulic efficiency.
- Reparability: The lining material can be easily repaired.
- Water tightness: To reduce seepage losses the lining material should be water.
Advantages of Canal Lining:
The various advantages of canal lining as follows:
1.Reduction in losses due to seepage:
The lining prevents dripping, in the end more water can be irrigated with the same amount of water and valuable water is saved.
2.Prevention of waterlogging:
Seepage is the main cause of waterlogging if the canal is lined the seepage is reduced thus helps in protection from waterlogging.
3.Low maintenance cost:
The maintenance of lined canal is less as compared to the unlined canal.
4.Prevention of weed growth:
The lining prevents the growth of weeds.
5.Stepper bed slope:
The hard surface lining can maintain high velocity which means the stepper bed slope can be provided.
The lining canal is less likely to split because the lining is more stable and stronger as well as silting is less due to higher velocity.
7.Low evaporation losses:
Water can reach the area quickly due to the high velocity thus the evaporation losses are minimum.
8.Less salt problem:
As canal water does not come in contact with harmful salt present in natural soil, salt problem reduced to some extent.
Disadvantages of Canal Lining:
The various disadvantages of canal lining as follows:
1.High initial cost:
The initial cost of the lined canal is high.
2.Leakage from the joint:
There may be a possibility of leakage through the joint.
3.Difficult to repair:
If it is damaged it is difficult to repair.
4.Difficult to shift outlet:
Due to the strong lining, it is difficult to shift the outlet at a later stage.
- Transfer of the outlet is not possible if necessary, as the lining is a permanent construction.
- These lined channels are without a berm, so it is safely provided by a berm for traffic on the service road is absent.
Also read: Cross Drainage Work, Open Channel Flow & River Training Works
Canal lining also used to prevent weed growth, which might spread in an irrigation system that reduce water flow.
By making a canal less permeable, the speed of water will increase leading to greater overall discharge.