Question 78 from UPSC CSE 2024 - Geograph y

Question

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

IASCODEX · Accepted Answer

Correct Option: B. Gomati, Ghaghara, Gandak, Kosi

Strategy: The strategy involves mentally tracing the Ganga's eastward flow downstream of Prayagraj and visualizing the sequence of Himalayan tributaries.
*   Identify the westernmost river among the options (Gomati is west of Ghaghara).
*   Establish the correct west-to-east confluence order: Ghaghara enters near Chhapra, Gandak joins at Sonpur, and Kosi merges in Katihar.
*   Eliminate options that do not respect this established sequence to arrive at the correct answer.

Key Info: The major Himalayan rivers joining the Ganga downstream of Prayagraj are the Gomati, Ghaghara, Gandak, and Kosi, each entering sequentially from west to east:

*   **Gomati River**
    *   Originates in Pilibhit, Uttar Pradesh.
    *   Flows southeast through Sitapur, Lucknow, Barabanki, Sultanpur, and Jaunpur.
    *   Joins the Ganga near Varanasi, making it the westernmost major tributary in this context.
*   **Ghaghara River**
    *   Rises from the Mapchachungo glaciers in Tibet; known as Karnali in Nepal.
    *   Enters India near Bahraich, Uttar Pradesh; after receiving the Sarda (Kali) river, it flows southeast.
    *   Joins the Ganga at Chhapra in Bihar.
*   **Gandak River**
    *   Comprises Kali Gandak and Trishulganga, originating in the Nepal Himalaya between Dhaulagiri and Everest.
    *   Enters Bihar, India, and meets the Ganga at Sonpur, near Patna.
    *   Historically known for frequent course changes and fertile alluvial deposition.
*   **Kosi River**
    *   The easternmost of these tributaries; originates as the Arun in Tibet, flows through Nepal collecting the Sapt Kosi rivers.
    *   Emerges onto the plains and enters India in Bihar, meeting the Ganga in the Katihar district.
    *   Frequently called the 'Sorrow of Bihar' due to its floods.

The sequence from west to east, after the confluence at Prayagraj, is thus: Gomati, Ghaghara, Gandak, and Kosi, matching option B. These rivers contribute significant alluvial soil crucial for agriculture but also pose flood threats due to shifting courses and heavy siltation.

IASCODEX · Answer

Option A: Ghaghara, Gomati, Gandak, Kosi

IASCODEX · Answer

Option C: Ghaghara, Gomati, Kosi, Gandak

IASCODEX · Answer

Option D: Gomati, Ghaghara, Kosi, Gandak