Test: Lining of Irrigation Canals - Civil Engineering (CE)

A lined canal can be designed smaller in cross- section and also in length. The steeper gradients can be provided because higher velocities are permissible. It can, therefore, help to bring high areas under command.

In large canals, safety ladders are generally provided on side slopes, at suitable intervals along the canal length. These ladders can be used by persons or cattle, that may be swept away with the flowing water in the canal. Such a person, who may otherwise get drowned, may catch hold of one such ladder and can climb it to get out of the canal easily.

Under-drainage arrangements are required in both unlined and lined canals. This is because water can seep through the sides and bottom of a canal, regardless of whether it is lined or not. The purpose of under-drainage is to collect and safely dispose of this seepage water, preventing water-logging of nearby land and possible damage to the canal structure itself. So, it is a necessary requirement for all types of canals.

The best alignment of off-taking channel is that in which the off-taking channel makes zero angle with the parent channel initially and then separates out in transition. The depth of water should always be such that off take channel runs full. The transitions should be properly designed, so as to avoid accumulation of silt. The transition can also be used as metering flume. Thus depth, slope and width will be the correct order of preference of parameters.