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UPSC Prelims 2008 · Indian Geography · Rivers, Lakes and Dams
Consider the following pairs: Tributary River — Main River Which of the pairs given above is/are correctly matched?
- Chambal — Narmada
- Sone — Yamuna
- Manas — Brahmaputra
- (a) 1, 2 and 3
- (b) 1 and 2 only
- (c) 2 and 3 only
- (d) 3 only
Show the answer and explanation
Answer: (d) 3 only
Only Manas–Brahmaputra is correct.
Statement by statement
1. ✗ WRONG The Chambal flows north into the Yamuna.
2. ✗ WRONG The Son joins the Ganga near Patna.
3. ✓ CORRECT The Manas is a major north-bank tributary of the Brahmaputra.
The idea
A drainage divide can send neighbouring rivers into different main systems. Match a tributary by its downstream junction, not by the river nearest its source. The receiving river may then be a tributary itself, creating more than one level in the network.
Why the others are wrong
(a) Chambal and Son are mismatched.
(b) Both are wrong.
(c) The Son joins the Ganga.
The trap
The Chambal rises near the Narmada (Mhow) but flows the other way.
Elimination technique
Chambal’s Yamuna junction makes pair 1 false and removes (a) and (b). Son meets Ganga rather than Yamuna, removing (c); check Manas to confirm (d).
Also know
Chambal, Sindh, Betwa and Ken feed the Yamuna. Son joins the Ganga separately, while Yamuna meets it at Prayagraj. Manas drains Himalayan foothills through Bhutan and Assam. A right or left bank is identified while facing downstream, not by which side appears on a north-up map.
🔒 Yamuna right bank: Chambal, Sindh, Betwa, Ken. Ganga right bank: Yamuna, Son.
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