Drainage System of India — Practice Questions
UPSC Prelims-pattern practice questions on Indian rivers with explanations — Indus Waters Treaty, Brahmaputra, drainage patterns, west-flowing rivers.
Questions
These are original UPSC-pattern practice questions. Attempt each one before revealing the answer.
Under the Indus Waters Treaty, 1960, which of the following rivers were allocated to India as the “eastern rivers”?
Solution
The treaty gave the eastern rivers — Ravi, Beas and Satluj — to India and the western rivers — Indus, Jhelum and Chenab — to Pakistan, with India permitted specified limited uses of the western rivers (including run-of-the-river hydropower). Every other option mixes the two groups.
Answer: C
Consider the following statements:
- The Brahmaputra enters India in Arunachal Pradesh, where it is known as the Siang or Dihang.
- The Dibang and the Lohit join it in the Assam valley.
- The Teesta joins the Brahmaputra as a left-bank tributary inside Assam.
Which of the statements given above are correct?
Solution
Statements 1 and 2 are correct — the Tsangpo enters India as the Siang/Dihang and, after it is joined by the Dibang and Lohit, is called the Brahmaputra. Statement 3 is wrong — the Teesta joins the Brahmaputra on its right bank in Bangladesh.
Answer: A
Consider the following pairs:
| Drainage pattern | Example |
|---|---|
| 1. Radial | Amarkantak range |
| 2. Centripetal | Loktak Lake |
| 3. Trellis | Rivers of the Ganga plains |
How many of the pairs given above are correctly matched?
Solution
Pair 1 is correct — the Narmada, Son and Mahanadi radiate from Amarkantak. Pair 2 is correct — streams converge into Loktak Lake (Manipur). Pair 3 is wrong — the rivers of the Ganga plains form a dendritic pattern. So two pairs.
Answer: B
Which Peninsular river has the largest river system and is often called the “Dakshin Ganga”?
Solution
The Godavari rises in Nasik district of Maharashtra and flows about 1,465 km (NCERT) to the Bay of Bengal. It is the largest Peninsular river system. The Krishna is the next largest; the Mahanadi and Kaveri basins are smaller.
Answer: D
Which of the following rivers flow into the Arabian Sea?
- Sabarmati
- Mahi
- Penner
- Sharavati
Select the correct answer using the code given below.
Solution
The Sabarmati and Mahi drain into the Gulf of Khambhat; the Sharavati (Jog Falls) flows west from the Western Ghats. The Penner rises in Karnataka and flows east through Andhra Pradesh into the Bay of Bengal.
Answer: C
Mains
Inter-linking of rivers is presented as a solution to both floods and droughts. Critically examine its geographical, ecological and federal implications.
Solution
Introduction: The National Perspective Plan (1980) envisaged transferring water from surplus to deficit basins. The National Water Development Agency identified 30 links — 14 Himalayan and 16 Peninsular — and the Ken–Betwa link is the first to be taken up (foundation stone, December 2024).
Body — the case for:
- Spatial mismatch of water: surplus in the Brahmaputra and Ganga basins, deficit in western and peninsular India.
- Potential gains: irrigation for drought-prone regions such as Bundelkhand, flood moderation, drinking water, hydropower, inland navigation.
Body — the concerns:
- Geographical: the “surplus” of a basin is contested and varies with monsoon variability and climate change; lifting water across watersheds needs large amounts of energy.
- Ecological: submergence of forests (Ken–Betwa affects part of Panna Tiger Reserve); loss of environmental flows; reduced sediment reaching deltas, which causes delta erosion and salinity ingress.
- Social: displacement and rehabilitation.
- Federal and international: water is a State subject (Entry 17, List II), so consensus between States is hard; Himalayan links involve Nepal, Bhutan and Bangladesh.
- Economic: very high costs and long gestation.
Way forward: prioritise intra-basin solutions, watershed management, micro-irrigation and groundwater recharge; take up links one by one with independent ecological assessment, guaranteed e-flows and consent of affected States.
Conclusion: River linking can be one tool of water security, but it works only with careful basin science, ecological safeguards and cooperative federalism — not as a single engineering fix.