Question

A contour canal is _______.

• A. Irrigates only on one side
• B. Does not needs bank on higher side
• C. Is generally aligned parallel to the contour of the area
• D. all options are correct

Answer 1

The correct option is D all options are correct

A contour canal irrigates only on one side because the area on the other side is higher.
$\text{Note:}$ Irrigation canal can be aligned in any of the following three ways.
$\text{(a) Watershed canal or ridge canal}$

• The divide line between the catchment area (the area form which rain water flows into a drain or a stream) is called watershed or the ridge.
• Canal which is aligned along any natural watershed is called a watershed canal or ridge canal.
• aligning the canal on the ridge ensures gravity irrigation on both sides of the canal.
• No cross-drainage work are required since the drainage flows away from the ridge.
• This type of canal is preferred in plain areas where land slopes are relatively flat and uniform.

$\text{(b) Contour canal}$

• It is impossible to take the canal on the top of higher ridge in hilly areas as ridge line may be hundred of meters above the river.
• In such conditions, contour canals are usually constructed.
• Contour canals follow a contour, except for giving the required longitudinal slope.
• It irrigates only on one side because the areas on the other side is higher.
• This type of canal necessitate the construction of cross drainage works as the drainage flow is always at right angles to the ground contour.

$\text{(c) Side slope canal}$

• A side slope canal is that which is aligned at right angles to the contour.
• In such canals, flow runs parallel to natural drainage.
• Usually, flow in such canals does not intercept the drainage channel thus avoid the construction of cross-drainage works.