Importance of canal lining

Canal lining is an impervious layer (concrete, brick, soil-cement, stone, plastic film) on the bed and sides of a canal. It is important because:

1. Controls seepage loss. Unlined canals can lose 20-40% of the water; lining saves most of it, so more land can be irrigated with the same supply.
2. Prevents waterlogging. Reduced seepage keeps the water table down in the command area and avoids salinity.
3. Allows higher velocity. The smooth boundary ($n \approx 0.014$-$0.016$) and non-erodible surface permit a larger velocity, so a smaller cross-section, less land acquisition and less earthwork for the same discharge.
4. Reduces maintenance. No scour of bed and banks, less silting, and little weed growth.
5. Gives stable alignment. Canals can be run through sandy, porous or steep ground and at higher embankments; breaches are fewer.
6. Increases command and improves water control. Higher discharge at the tail and quicker water delivery.
7. Economic. Savings in water, maintenance and drainage normally exceed the annual cost of the lining.