Table of Contents
- Canal lining is a treatment given to the canal bed and banks, so as to render the canal section impervious.
- Since imperviousness of the canal section is achieved mostly by making canal section pucca.
- Either by cement concrete or bricks, the lined canals are also sometimes know pucca canals.
- Lined canals are mostly referred to as pucca canals.
- It has been estimated that seepage losses in irrigation canals.
- May amount from 30% to 50% of the water admitted in the canals at diversion headworks.
- This much loss of water in unlined channels cannot be afforded.
- As resources of water in India are limited in relation to irrigable area available.
- Hence in order to reduce or rather eliminate the seepage losses, lining of canals is the need of the hour.
Advantages of Lining Following are the benefits of lined canals:
- Seepage losses are practically eliminated or reduced to minimum.
- Maintenance cost of the canals is reduced.
- Canals can be run with increased velocity.
- Section of the canal is considerably reduced as due to increased velocity.
- Same discharge can be passed through smaller sectional area.
- Cost of earth work is reduced, as smaller section will have to be constructed.
- Silting does not take place, as canals are run at considerably larger velocities than silting velocity.
- No scouring occurs anywhere in the canal section.
- Less width of land is required for the canal.
- Weed growth in the canal is reduced.
- Harmful salts from adjoining soils do not get dissolved in the canal water.
- More head for power generation becomes available as lined canals can be laid at a flatter gradient.
- This measure also helps in bringing more areas under command.
- Possibilities of canal breaches are eliminated.
- Additional areas may be brought under irrigation from the water saved by the lining.
- Possibilities of waterlogging of adjoining areas are reduced.
- Losses due to evaporation are reduced, as due to increased velocity, water takes less time to reach the outlet.
Disadvantages of Canal Lining
Following are the disadvantages of the canal lining:
- It requires a very heavy initial expenditure.
- When lining gets old it generally develops cracks.
- Leakage through cracks is very difficult to check.
- Joins in lining always create problems.
- Position of outlets cannot be shifted easily.
- Lined canals do not have berms.
- If some person or animal happens to fall in the canal, it is very difficult to pull him cut.
- To overcome this difficulty there should be stepped sections at regular intervals along the length of the canal.
- Lined canals are generally seep.
- Only that man can enjoy bath in the canal who knows swimming.
- As seepage of water is almost completely stopped.
- Rows of trees cannot be grown along the canal as in the case of Kucha canals.
- In order to run with greater velocity, lined canals may have to be given increased longitudinal slopes.
- This may result in loss of command in the area.
- Lining materials like clay, bitumen, etc. get easily destroyed under the feet of animals crossing the canal.
- In order to justify the lining of canal it is essential to analyse on one hand.
- The extra capital cost of providing lining and on the other hand an evaluation of the benefits of lining.
- For lining to be economically feasible, the capitalized value of benefits should be equal to or greater.
- Than the extra cost involved in providing lining.
- In other words, the capitalized value of benefits divided by the extra capital cost.
- Of providing lining should always be more than one.