Canal Design and Regulation MCQ with answer and solution

Concept

A cross regulator is built across the parent canal. It can close the supply to the downstream reach during repairs.

Step-by-step solution

1. A head regulator is at the head of a canal. It controls the flow entering that canal from the river or parent canal. 2. A distributary head regulator controls the flow going from the parent canal into a branch or distributary. 3. A cross regulator is built across the parent canal, just downstream of an offtake. 4. Closing its gates stops flow to the downstream reach of the parent canal. This allows repairs there. 5. So the answer is the cross regulator.

Explanation

A cross regulator is built across the parent canal itself. It raises the water level upstream so that offtaking channels get enough water. It can also cut off supply to the downstream part of the canal during repairs or rotation.

Why the other options are wrong

B: A distributary regulator controls flow into the distributary, not the parent canal downstream. C: A head regulator controls flow at the start of a canal, not downstream of the parent canal. D: A stream regulator is not the standard structure for this job.

Shortcut

Cross regulator = across the parent canal = controls the parent canal downstream.

Common mistake

Students confuse the head regulator (at the canal entry) with the cross regulator (across the parent canal).