Koshi River

·         Origin: The Koshi River system originates in the Himalayas of Tibet and Nepal and is formed by several major tributaries.

• Major Tributaries: The three major tributaries traditionally associated with the upper Koshi system are Sun Koshi, Arun and Tamor.
• Confluence: These rivers converge in eastern Nepal to form the Koshi (Saptakoshi).
• India Entry: The Koshi enters India through Bihar and flows through the northern part of the State.
• Tributary of Ganga: The Koshi is a left-bank tributary of the Ganga.
• High Sediment Load: It carries enormous quantities of sediment from the young and rapidly eroding Himalayas.
• “Sorrow of Bihar”: Frequent changes in its course and devastating floods have earned the Koshi the name “Sorrow of Bihar.”
• Floodplain: Its large sediment load causes channel shifting and floodplain formation, increasing flood vulnerability in Bihar.
• Transboundary River: The Koshi basin is shared by China (Tibet), Nepal and India.
• Hydropower Potential: Its steep Himalayan tributaries provide significant hydropower potential.
• Koshi Agreement: India and Nepal signed the Kosi Agreement in 1954, subsequently amended in 1966, concerning flood control, irrigation and related works.

UPSC Prelims Practice Question — English

Q. With reference to the Koshi River, consider the following statements:

1. The Koshi is a left-bank tributary of the Ganga.
2. Arun, Sun Koshi and Tamor are major rivers associated with the Koshi system.
3. The Koshi enters India through Bihar.
4. Its high sediment load contributes to frequent changes in its course.

Which of the statements given above are correct?

A. 1, 2 and 3 only
B. 1, 3 and 4 only
C. 2 and 4 only
D. 1, 2, 3 and 4

Answer: D

Explanation

• Statement 1 — Correct: Koshi is a left-bank tributary of the Ganga.
• Statement 2 — Correct: Arun, Sun Koshi and Tamor are the principal rivers that form the Saptakoshi system.
• Statement 3 — Correct: The Koshi crosses into Bihar, India, after flowing through Nepal.
• Statement 4 — Correct: Its enormous sediment load promotes channel shifting and contributes significantly to flooding in Bihar.