Q. With reference to the Himalayan rivers joining the Ganga downstream of Prayagraj from West to East, which one of the following sequences is correct? (UPSC Prelims 2024)
Answer: Gomati - Ghaghara - Gandak - Kosi
Notes: The correct answer is [B] Gomati - Ghaghara - Gandak - Kosi. The Ganga river receives several major Himalayan tributaries on its left bank as it flows through the Indo-Gangetic plains toward the east.

• Gomati (1st from West): Originating from Gomat Taal in Pilibhit, Uttar Pradesh, it joins the Ganga near Varanasi, which is downstream of Prayagraj.
• Ghaghara (2nd from West): A major left-bank tributary that originates in the glaciers of Mapchachungo. It joins the Ganga at Chhapra, Bihar, located further east of the Gomati confluence.
• Gandak (3rd from West): Formed by the Union of Kaligandaki and Trishuli in Nepal, it enters the Indian plains in Champaran and joins the Ganga at Sonpur, near Patna.
• Kosi (4th from West): Known as the "Sorrow of Bihar," this antecedent river joins the Ganga at Kursela in the Katihar district, which is the easternmost among the four options provided.

The general West-to-East sequence of major left-bank tributaries is: Ramganga (upstream of Prayagraj), followed by Gomati, Ghaghara, Gandak, Bagmati, and Kosi.