Silt ejector is provided
- Ain the river far off from the weir on the upstream side
- Bin the river adjacent to the head regulator
- Cin the river on the downstream of the weir
- Din the canal on the downstream of head regulatorCorrect
Solution
Concept
A silt ejector (silt extractor) removes silt that has already entered the canal, so it is placed in the canal just downstream of the head regulator.
Step-by-step solution
1. There are two silt control devices at headworks: the silt excluder and the silt ejector. 2. The silt excluder is placed in the river bed (pocket) upstream of the head regulator. It stops silt from entering the canal. 3. The silt ejector (extractor) is placed in the canal, some distance downstream of the head regulator. 4. It removes the silt that has already entered the canal. 5. So the answer is (D).
Explanation
A silt ejector removes silt that has already entered the canal. It is built in the canal bed a short distance downstream of the head regulator. A silt excluder, in contrast, is built in the river to stop silt from entering the canal.
Why the other options are wrong
A: No silt device is placed far upstream in the river. B: A device in the river near the head regulator is a silt excluder, not an ejector. C: Downstream of the weir in the river has no use for canal silt control.
Shortcut
Excluder = in the river (keeps silt out). Ejector = in the canal (throws silt out).
Common mistake
Students confuse the silt ejector with the silt excluder and choose option B.
Correct answer: D) in the canal on the downstream of head regulator