A canal may have to transport a considerable amount of sediment load which damages lining by abrasion. Cement concrete and stone boulder linings provide better abrasion resistance as compared to brick tile lining.

The one which shows maximum annual benefit-cost ratio is most economical lining. It may have a higher cost initially but longer life than anor type of lining having a lesser value of annual benefit-cost ratio.

Asphaltic concrete lining has been under evolution. It is used in very few places. This concrete is a careful mixture of asphalt and graded stone aggregate, and is mixed and applied under elevated temperature. This is a flexible lining and readily confirms to subgrade.

Before laying concrete subgrade should be levelled dressed and moistened thoroughly so that moisture is not taken from concrete laid. To avoid this inverted filter blanket is laid over subgrade before laying concrete. And to make this blanket effective and to prevent ingression of concrete being laid on blanket a tar paper is placed over filter blanket, before placing of cement concrete.

The expenditure on Annual repair (A.R) and Maintenance (M.O) costs are reduced with lining of a canal. The expenditure maybe due to removal of weeds and plants, minor repairs like covering cracks, leakages, and undulations in bed, removal silt deposited on bed. So, refore if lining is done expenditure (costs) can be reduced.

Using Manning?s equation: V = 1/n.R^2/3.S^1/2
2 = 1/0.015 x R^2/3 x 1/5000^1/2
R = 2.80 m.

With help of lining canals can be designed for both in smaller cross section and shorter in length. Steep gradients can be provided as higher velocities are allowed, and flat slopes can also be provided without silting action on lined canals. Therefore, due to se reasons command area can be increased.

Safety ladders are generally provided in large canals on both banks which consists of a number of ladder rungs at different elevations along canal length. In case any person or cattle that may be swept away with flowing water may catch hold one such ladder rung and can climb higher rungs to get out of canal to prevent mselves from drowning.

The choice of suitable lining for different size of a canal depends on canal slopes and alignments, size and importance of canal, climate of area, initial expenditure, etc. In-situ cement concrete lining in bed and on sides is generally preferred for canals when bed width is greater than 8 m.

Pressure relief valve is a flap valve opening upwards into canal. It helps in releasing hydrostatic pressure as soon as differential head exceeds safe pressure. These valves open out as soon as differential pressure goes beyond 10 cm.