With reference to the Himalayan rivers joining the Ganga downstream of Prayagraj from West to East, which one of the following sequences is correct ?

(a) Ghaghara – Gomati – Gandak – Kosi
(b) Gomati – Ghaghara – Gandak – Kosi ✓ UPSC's answer
(c) Ghaghara – Gomati – Kosi – Gandak
(d) Gomati – Ghaghara – Kosi – Gandak

Why the answer is (b)

• Downstream of Prayagraj the Ganga receives its major Himalayan left-bank tributaries in the Uttar Pradesh–Bihar plain.

• The Gomati joins first, near Ghazipur (Kaithi) in eastern Uttar Pradesh.

• Next the Ghaghara (Saryu) joins at Chhapra, just above Patna in Bihar; then the Gandak joins opposite Patna at Hajipur.

• Farthest east, the Kosi joins near Kursela in Katihar district before the Ganga enters West Bengal.

• The west-to-east sequence is therefore Gomati – Ghaghara – Gandak – Kosi, option (b).

Why the other options are wrong

(a) Ghaghara – Gomati – Gandak – Kosi: The Gomati joins before the Ghaghara, not after.
(c) Ghaghara – Gomati – Kosi – Gandak: The Gomati comes first and the Gandak before the Kosi.
(d) Gomati – Ghaghara – Kosi – Gandak: The Gandak joins before the Kosi, not after.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2024, held on 16 June 2024. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.