Types of Open Channel

• It is of two types:

A. Unlined open channels:

• If any artificial line is not made to flow water, it is called as unlined channel.
• They are built strong enough to carry the required flow of water safely.
• Should have ample capacity to carry the discharge at an erosive velocity.
• Permanent irrigation channels shouldn’t have side slopes steeper than 1 ½ horizontal to 1 vertical.
• In Stiff clay, however steep slope up to ½ to 1 are possible.
• Loose sand should have flat slope of about 2 to 1.

Advantages of unlined open channels

1. Easily understood and accepted by farmers.
2. Can be built and maintained by unskilled persons and requires no special equipment and materials.
3. Requires no initial cost.

Disadvantage of unlined open channels

1. It may transfer weed seed and weed to the field.
2. May be disturbed by plants and other materials, thus more seepage loss occurs.
3. Soil erosion may be found on the sides of the channel.

B. Lined channel:

• Earthen channels are lined with impervious materials to prevent excessive seepage and growth of weeds in channels.