Canal lining: Meaning, importance, types, advantages and disadvantages

Canal lining refers to the process of covering the sides and bottom of an irrigation canal with a material such as concrete, asphalt, plastic, or clay to reduce water loss due to seepage or evaporation. By lining canals, the water can be conveyed more efficiently and with less waste, which can help to increase the water supply available for irrigation or other uses.

Canal lining can be particularly important in areas with high evaporation rates or porous soils that allow water to seep out of the canal, reducing the amount of water that reaches the crops. The type of lining material used can depend on various factors, including the local climate, soil conditions, and the availability of materials.

In addition to reducing water loss, canal lining can also improve the durability and longevity of the canal, reducing the need for costly maintenance and repairs.

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See also: What is Inundation canal?

Canal lining: Important role

1. It is used to reduce the amount of canal water lost by seepage.
2. Additionally, it stops the canal’s bed and sides from scouring and silting.
3. It is also used to speed up water flow through canals. As a result, the canal section’s discharge likewise increases.
4. By lining the canal, the water logging issue may also be avoided.
5. Additionally, weeds and other unwelcome vegetation are prevented from growing along the canal’s bed and sides by lining it.
6. The expense of maintaining the canal is reduced by lining it.

Canal lining: Types

Earthen-type lining

Earthen-type canal linings are further divided into the following two groups:

Compacted earth lining:- Compacted earth lining is chosen whether earthen materials are on the job site or already there. This canal lining can be expensive if the earthen material is not already on the site. This liner is made from earthen material that has been compacted since compaction and minimises the size of soil voids by displacing water and air. The density, shear strength, and compressive strength of the soil are all increased along with its permeability when the void size of the soil is reduced.

Soil cement lining– This canal lining may be created using cement, sand, and water, which hardens into a substance like concrete. Soil Cement Lining Cement should make up 2-8% of the soil’s volume. In the case of large channels, the soil cement layer is occasionally coated with coarse earth to offer extra strength or to prevent erosion. A 50mm layer of soil, straw, or hessian sacks should be placed on top of the soil cement liner to properly cure it and protect it from weathering for seven days. It should also be kept wet. Two techniques are used to construct soil cement canal lining: dry mixing and plastic mixing.

Hard surface-type canal lining

Hard surface-type canal linings can be further categorised into the following categories:-

Cement concrete lining: These are the most common forms of canal linings because they are hydraulically effective, robust, long-lasting, and impermeable. Large and small canals with high or low flow velocities can use these canal linings. There are two types of cement concrete linings: plain cement concrete lining and reinforced cement concrete lining. Reinforced concrete linings are more durable and can sustain higher hydrostatic pressure than normal cement concrete linings.

Brick or tile lining: In this kind of canal lining, the bed and sides of the canal are lined with bricks or tiles installed using cement mortars to give the surface a smooth finish.

Plastic lining: This innovative technique or canal lining uses thin plastic sheets to stop the seepage of canal water. Three sorts of plastic sheets are utilised in this form of canal lining. These are polyvinyl chloride, high-density polyethene, and low-density polyethene. The thin, manageable plastic sheets used in this form of canal lining have several benefits, including quick construction and resistance to various contaminants.

Boulder lining: As the name implies, many boulders or stone blocks are utilised for the canal lining in this form of lining. Blocks of dressed stone are not found in nature. Uneven blocks are then dressed following the specifications. Dressed stone blocks are preferred over rough stone blocks or boulders because rough stone blocks give higher resistance to the flowing water in the canal. As a result, this style of canal lining is chosen in locations where head loss is not a major factor and where there are reasonably priced stones and blocks to choose from.

Prefabricated cement concrete lining: This kind of canal lining is recommended in areas with inexpensive labour, simple access to aggregates, and convenient transportation. This method of canal lining is favoured over in situ concrete lining because it allows for more control over moulding, mixing, and curing. Also, its construction took less time.

Concrete asphalt lining: Gravel and asphalt are used to create the lining material in this canal lining. This canal liner has a service life of 15 to 20 years and a thickness range of 2 to 4 inches. When built appropriately, asphalt concrete linings are similar to portland cement concrete linings in many ways.

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Canal lining: Advantages

Among the key benefits are the following:

Reduced seepage: The primary benefit of canal lining is water loss reduction due to seepage. The amount of water provided can be lost by seepage in unlined canals by 25 to 50 per cent. Canal lining is costly but justified since it aims to stop most seepage-related water losses.

Prevention from water logging- Water logging is induced owing to the rise in the water table by the seepage losses from the canals. The groundwater table is impacted by water logging, which renders the terrain unsuitable for irrigation. By lining canals, this issue of water logging may be avoided.

Increase in command area- Lining the canals reduces the seepage losses of the water used for irrigation from the canals. Due to lined canals’ far higher water carrying capacity than unlined canals, this aids in expanding the area of a field that is irrigated, thus expanding the command area.

Increased channel capacity: Lining a canal can also enhance a channel’s capacity. A lined canal’s surface is frequently smooth and allows faster water movement than an unlined canal. A channel’s capacity rises as flow velocity does. Hence, a canal’s liner will increase the channel’s capacity.

Reduced maintenance: Lined canals have substantially greater maintenance costs than lined canals. Unlined canals have far higher silt volume deposition, significantly raising maintenance costs. The strong water flow in lined canals prevents silt from quickly depositing on the canal bed, in contrast to unlined canals.

Protection against flooding: Unlike unlined canals, lined canals’ beds and sides can survive flooding. Unlined canals’ beds and sides are readily washed away by water under flood conditions, whereas lined canals’ beds and sides are shielded by a hard layer that inhibits deterioration.

Canal lining: Disadvantages

Some of its drawbacks include:

1. Canal lining requires a large initial expenditure.
2. The risk of shifting the outlet is substantial since it necessitates tearing apart and replacing the lining.
3. The building phase of the lined canal is longer.
4. For canal lining, skilled labour and advanced construction tools are needed.

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