Class 9 : Social Science (In English) – Lesson 13. Drainage n

EXPLANATION & SUMMARY

🗺️ 1. Meaning of Drainage
🌊 Drainage → network of rivers and streams draining an area.
🟢 Drainage basin → area drained by one river and its tributaries.
🟡 Water divide → upland separating two basins.
Example: Ambala → divide between Indus & Ganga basins.

🏞️ 2. Drainage Systems in India
Two major systems:
🔵 Arabian Sea Drainage → ~77% area.
🟢 Bay of Bengal Drainage → ~23% area.
Most rivers flow east into Bay of Bengal; few west into Arabian Sea.

🌊 3. The Himalayan Rivers
Features:
Perennial (snow + rain fed).
Long courses, deep valleys, heavy erosion, large basins.
Major systems:
🚩 (i) Indus River System
Origin: Manasarovar Lake, Tibet.
Flows through J&K → Pakistan → Arabian Sea.
Tributaries: Jhelum, Chenab, Ravi, Beas, Sutlej.
Indus Water Treaty (1960) → India uses 33% water.

🕉️ (ii) Ganga River System
Origin: Gangotri Glacier (Bhagirathi).
Alaknanda joins at Devprayag → Ganga.
Tributaries: Yamuna, Ghaghara, Gandak, Kosi (north); Chambal, Betwa, Son (south).
Distributaries in delta: Hooghly, Padma.
Largest delta → Sundarbans.

🕉️ (iii) Brahmaputra River System
Origin: Tibet (Tsangpo).
Enters India at Arunachal (Siang/Dihang).
Joins with Dibang, Lohit → Brahmaputra (Assam).
Known for floods, silt, braided channels.

🏞️ 4. The Peninsular Rivers
Features:
Older, shorter, seasonal.
Erode less, form shallow valleys.
Mostly east-flowing → Bay of Bengal.

🔵 (i) East-Flowing Rivers
🌊 Godavari: “Dakshin Ganga”, largest peninsular. Tributaries: Purna, Wardha, Manjira.
🌊 Mahanadi: Flows through Chhattisgarh, Odisha → Bay.
🌊 Krishna: Tributaries: Tungabhadra, Bhima, Musi.
🌊 Kaveri: Originates Karnataka; tributaries: Amravati, Bhavani.

🟢 (ii) West-Flowing Rivers
🌊 Narmada: Rift valley, flows into Arabian Sea. Waterfalls: Dhuandhar.
🌊 Tapi: Flows parallel to Narmada, also westward.
🌊 Small rivers: Mandovi, Zuari, Sharavathi.

🌍 5. Lakes in India
🟦 Types:
Tectonic (Wular).
Glacial (Dal, Bhimtal).
Lagoon (Chilika, Pulicat, Vembanad).
Man-made (Gobind Sagar).
🟢 Importance: regulate flow, hydropower, tourism, biodiversity.

🌧️ 6. Role of Rivers in Economy
🌊 Irrigation for agriculture.
⚡ Hydroelectric power.
🚢 Navigation and transport.
🏭 Industrial raw material, water supply.
🕌 Religious & cultural significance.

🌳 7. River Pollution & Challenges
⚠️ Dumping of untreated sewage, industrial effluents.
🛢️ Oil & chemical discharge.
🐠 Decline in aquatic life.
🛑 Encroachment on floodplains.
🚨 Examples: Pollution in Ganga, Yamuna.

🌱 8. Conservation Efforts
🟢 Ganga Action Plan (GAP).
🟢 National River Conservation Plan (NRCP).
🟢 Water harvesting & sustainable use.
🟢 Public awareness & eco-friendly tourism.

📝 Summary (~200 words)
India’s drainage system is shaped by two sets of rivers: the Himalayan and Peninsular. Himalayan rivers such as the Indus, Ganga, and Brahmaputra are perennial, long, and carry huge volumes of water and silt. They form fertile plains and large deltas. Peninsular rivers like the Godavari, Krishna, Mahanadi, and Kaveri are seasonal, flow eastward into the Bay of Bengal, and form smaller deltas, while the Narmada and Tapi flow west into the Arabian Sea.

India also has diverse lakes — tectonic (Wular), glacial (Dal), lagoons (Chilika), and man-made (Gobind Sagar). These water bodies support irrigation, power, fisheries, and tourism. Rivers play a vital role in agriculture, industry, transport, and culture. However, river pollution, overuse, and ecological damage threaten sustainability. National programs like GAP and NRCP focus on cleaning and conserving rivers.
Thus, India’s drainage system is central to economic growth, ecology, and cultural heritage. Sustainable management is crucial for future generations.

⚡ Quick Recap (~100 words)
🗺️ Drainage = river network; water divide = separates basins.
🌊 Himalayan rivers → Indus, Ganga, Brahmaputra (perennial).
🏞️ Peninsular rivers → Godavari, Krishna, Mahanadi, Kaveri (east); Narmada, Tapi (west).
🟦 Lakes → tectonic, glacial, lagoons, man-made.
🌱 Importance → irrigation, power, transport, culture.
⚠️ Problems → pollution, floods, overuse.
🌍 Conservation → GAP, NRCP, awareness.
➡️ Drainage is the backbone of India’s agriculture, industry, and ecology.

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QUESTIONS FROM TEXTBOOK

🔵 Question 1. Choose the right answer from the four alternatives given below.
(i) In which of the following states is the Wular lake located?
(a) Rajasthan
(b) Uttar Pradesh
(c) Punjab
(d) Jammu and Kashmir
🟢 Answer: (d) Jammu and Kashmir

(ii) The river Narmada has its source at
(a) Satpura
(b) Brahmagiri
(c) Amarkantak
(d) Slopes of the Western Ghats
🟢 Answer: (c) Amarkantak

(iii) Which one of the following lakes is a salt water lake?
(a) Sambhar
(b) Dal
(c) Wular
(d) Gobind Sagar
🟢 Answer: (a) Sambhar

(iv) Which one of the following is the longest river of the Peninsular India?
(a) Narmada
(b) Krishna
(c) Godavari
(d) Mahanadi
🟢 Answer: (c) Godavari

(v) Which one amongst the following rivers flows through a rift valley?
(a) Mahanadi
(b) Tungabhadra
(c) Krishna
(d) Tapi
🟢 Answer: (d) Tapi

🔵 Question 2. Answer the following questions briefly.
(i) What is meant by a water divide? Give an example.
🟢 Answer:
🗺️ A water divide is a highland separating the drainage basins of two rivers.
🌄 Rainfall on one side flows to one river system, while the other side flows to another.
📍 Example: Ambala → divide between Indus and Ganga basins.

(ii) Which is the largest river basin in India?
🟢 Answer:
🌊 Ganga Basin is the largest in India.
🟢 Covers about 26% of land area.
👥 Supports 40% of India’s population.

(iii) Where do the rivers Indus and Ganga have their origin?
🟢 Answer:
🕉️ Indus → originates from Manasarovar Lake (Tibet).
🕉️ Ganga → originates from Gangotri Glacier (Bhagirathi stream).

(iv) Name the two headstreams of the Ganga. Where do they meet to form the Ganga?
🟢 Answer:
🏞️ Headstreams: Bhagirathi and Alaknanda.
📍 They meet at Devprayag (Uttarakhand).
🌊 From here, the river is called the Ganga.

(v) Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?
🟢 Answer:
🏔️ Tibetan course is cold and dry, with less erosion.
🌊 River carries little water and silt there.
🌍 After entering India (Assam), heavy rainfall → large volume + silt load.

(vi) Which two Peninsular rivers flow through troughs?
🟢 Answer:
🌊 Narmada and Tapi.
🏞️ Both flow in rift valleys between Vindhya and Satpura ranges.

(vii) State some economic benefits of rivers and lakes.
🟢 Answer:
🌱 Provide irrigation for agriculture.
⚡ Hydroelectric power generation.
🚢 Inland navigation and transport.
🏭 Supply water to industries and cities.
🐟 Fisheries, recreation, tourism.

🔵 Question 3. Grouping of lakes
Below are given names of a few lakes of India. Group them under two categories – natural and created by human beings.
(a) Wular (b) Dal (c) Nainital (d) Bhimtal (e) Gobind Sagar (f) Loktak
(g) Barapani (h) Chilika (i) Sambhar (j) Rana Pratap Sagar
(k) Nizam Sagar (l) Pulicat (m) Nagarjuna Sagar (n) Hirakund

🟢 Answer:
🌊 Natural Lakes
Wular
Dal
Nainital
Bhimtal
Loktak
Barapani
Chilika
Sambhar
Pulicat

🏞️ Man-Made Lakes
Gobind Sagar
Rana Pratap Sagar
Nizam Sagar
Nagarjuna Sagar
Hirakund

🔵 Question 4. Discuss the significant difference between the Himalayan and the Peninsular rivers.
🟢 Answer:
🔵 Himalayan Rivers
🌊 Perennial (fed by snow + rain).
🏞️ Long, deep valleys.
🌱 Bring fertile alluvium → plains agriculture.
🟡 Large deltas (e.g., Sundarbans).
🟢 Peninsular Rivers
🌊 Seasonal (rain-fed).
🏞️ Short, shallow courses.
🌱 Less fertile alluvium.
🟡 Smaller deltas or estuaries.

🔵 Question 5. Compare the east flowing and the west flowing rivers of the Peninsular plateau.
🟢 Answer:
🔵 East-Flowing Rivers
🌊 Flow into Bay of Bengal.
🏞️ Form deltas (Godavari, Krishna, Kaveri, Mahanadi).
🟡 Longer courses, larger basins.
🟢 West-Flowing Rivers
🌊 Flow into Arabian Sea.
🏞️ Form estuaries (Narmada, Tapi, Mandovi).
🟡 Shorter courses, flow through rift valleys.

🔵 Question 6. Why are rivers important for the country’s economy?
🟢 Answer:
🌱 Irrigation for agriculture → food security.
⚡ Hydroelectricity for power supply.
🚢 Inland navigation + trade.
🏭 Industrial water supply.
🕌 Religious, cultural, tourism significance.
📦 Enable international trade via ports and deltas.

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OTHER IMPORTANT QUESTIONS FOR EXAMS

🌟 SECTION A — Multiple Choice Questions (1 mark each)
🔵 Q1. In which state is Wular Lake located?
(A) Rajasthan
(B) Uttar Pradesh
(C) Punjab
(D) Jammu & Kashmir
🟢 Answer: (D) Jammu & Kashmir

🔵 Q2. The river Narmada originates from:
(A) Satpura
(B) Brahmagiri
(C) Amarkantak
(D) Western Ghats
🟢 Answer: (C) Amarkantak

🔵 Q3. Which lake is a salt-water lake?
(A) Dal
(B) Wular
(C) Sambhar
(D) Gobind Sagar
🟢 Answer: (C) Sambhar

🔵 Q4. Longest river of Peninsular India is:
(A) Narmada
(B) Krishna
(C) Godavari
(D) Mahanadi
🟢 Answer: (C) Godavari

🔵 Q5. Which river flows through a rift valley?
(A) Mahanadi
(B) Tungabhadra
(C) Krishna
(D) Tapi
🟢 Answer: (D) Tapi

🔵 Q6. Which is the largest river basin in India?
(A) Ganga
(B) Indus
(C) Godavari
(D) Brahmaputra
🟢 Answer: (A) Ganga

🔵 Q7. Where does the Indus river originate?
(A) Gangotri Glacier
(B) Manasarovar Lake
(C) Amarkantak
(D) Satpura Hills
🟢 Answer: (B) Manasarovar Lake

🔵 Q8. The two headstreams of Ganga meet at:
(A) Haridwar
(B) Allahabad
(C) Devprayag
(D) Rishikesh
🟢 Answer: (C) Devprayag

🔵 Q9. Which is the longest tributary of the Ganga?
(A) Yamuna
(B) Son
(C) Gandak
(D) Ghaghara
🟢 Answer: (A) Yamuna

🔵 Q10. The Brahmaputra enters India in:
(A) Arunachal Pradesh
(B) Sikkim
(C) Assam
(D) Meghalaya
🟢 Answer: (A) Arunachal Pradesh

🔵 Q11. Which Peninsular river is called “Dakshin Ganga”?
(A) Krishna
(B) Godavari
(C) Mahanadi
(D) Kaveri
🟢 Answer: (B) Godavari

🔵 Q12. Chilika Lake is located in:
(A) Kerala
(B) Odisha
(C) Tamil Nadu
(D) Andhra Pradesh
🟢 Answer: (B) Odisha

🔵 Q13. Which river forms the Sundarbans delta?
(A) Yamuna
(B) Brahmaputra
(C) Ganga
(D) Mahanadi
🟢 Answer: (C) Ganga (with Brahmaputra)

🔵 Q14. Dal Lake is a:
(A) Lagoon
(B) Glacial Lake
(C) Tectonic Lake
(D) Salt Lake
🟢 Answer: (B) Glacial Lake

🔵 Q15. Which Peninsular river flows westward into the Arabian Sea?
(A) Godavari
(B) Krishna
(C) Mahanadi
(D) Narmada
🟢 Answer: (D) Narmada

🔵 Q16. Wular Lake was formed due to:
(A) Glacier action
(B) Tectonic activity
(C) River meandering
(D) Volcanic eruption
🟢 Answer: (B) Tectonic activity

🔵 Q17. Which is the largest lagoon in India?
(A) Vembanad
(B) Pulicat
(C) Chilika
(D) Loktak
🟢 Answer: (C) Chilika

🔵 Q18. Which river is known for frequent floods in Assam?
(A) Ganga
(B) Brahmaputra
(C) Subansiri
(D) Dhansiri
🟢 Answer: (B) Brahmaputra

🔵 Q19. Which river is known as the “Sorrow of Bihar”?
(A) Gandak
(B) Ghaghara
(C) Kosi
(D) Son
🟢 Answer: (C) Kosi


🌟 SECTION B — Very Short Answer (2 marks each)
🔵 Q20. What is meant by a water divide? Give an example.
🟢 Answer:
🗺️ A water divide is an upland separating two river basins.
📍 Example: Ambala → divides Indus and Ganga basins.

🔵 Q21. Which is the largest river basin in India?
🟢 Answer:
🌊 Ganga Basin.
🟢 Covers ~26% of land area and supports ~40% population.

🔵 Q22. Where do the Indus and Ganga originate?
🟢 Answer:
🕉️ Indus → Manasarovar Lake, Tibet.
🕉️ Ganga → Gangotri Glacier (Bhagirathi stream).

🔵 Q23. Name the two headstreams of the Ganga. Where do they meet?
🟢 Answer:
🏞️ Headstreams: Bhagirathi and Alaknanda.
📍 Meet at Devprayag (Uttarakhand).

🌟 SECTION C — Short Answer (3 marks each)
🔵 Q24. Why does the Brahmaputra in Tibet carry less silt despite its long course?
🟢 Answer:
🏔️ Tibet → dry and cold region.
🌊 Little rainfall, less erosion.
🌍 In Assam, heavy rainfall increases silt and floods.

🔵 Q25. Which two Peninsular rivers flow through troughs? Explain.
🟢 Answer:
🌊 Narmada and Tapi.
🏞️ Flow westward in rift valleys between Vindhya and Satpura ranges.
🚢 Form estuaries in the Arabian Sea.

🔵 Q26. State three economic benefits of rivers and lakes.
🟢 Answer:
🌱 Provide irrigation for crops.
⚡ Hydropower generation.
🛶 Navigation, tourism, fisheries.

🔵 Q27. Give three points of difference between Himalayan and Peninsular rivers.
🟢 Answer:
🌊 Himalayan → Perennial; Peninsular → Seasonal.
🏞️ Himalayan → Long, deep valleys; Peninsular → Short, shallow courses.
🌱 Himalayan → Form large deltas; Peninsular → Estuaries/smaller deltas.

🔵 Q28. Compare east-flowing and west-flowing rivers of Peninsular India.
🟢 Answer:
🟦 East-flowing → Bay of Bengal, form deltas (Godavari, Krishna, Kaveri).
🟩 West-flowing → Arabian Sea, form estuaries (Narmada, Tapi).
🌍 East → longer courses; West → shorter, rift valleys.

🌟 SECTION D — Long Answer (5 marks each)
🔵 Q29. Discuss the significance of rivers for the economy.
🟢 Answer:
🌱 Irrigation → agricultural productivity.
⚡ Hydroelectricity → renewable power.
🚢 Navigation + inland trade.
🏭 Supply water to industries, cities.
🕌 Cultural, tourism importance.

🔵 Q30. Why are rivers considered lifelines of human civilisation?
🟢 Answer:
🏞️ Provide fertile alluvium for farming.
⚡ Energy source (hydropower).
🚢 Enable connectivity and commerce.
🐟 Support biodiversity and fisheries.
🌍 Basis of settlements and culture.

🔵 Q31. Write a short note on lakes of India.
🟢 Answer:
🟦 Types: Tectonic (Wular), Glacial (Dal, Bhimtal), Lagoon (Chilika, Pulicat), Man-made (Gobind Sagar).
🌱 Uses: irrigation, power, fisheries, recreation.
🌍 Balance ecosystem and regulate river flow.

🔵 Q32. Explain how rivers are being polluted. Suggest measures to conserve them.
🟢 Answer:
⚠️ Pollution → untreated sewage, industrial waste, chemical discharge, religious dumping.
🛑 Overuse → water scarcity, decline in aquatic life.
✅ Measures → GAP/NRCP projects, awareness, wastewater treatment, eco-friendly tourism.

🌟 SECTION E — Case/Source-Based (4 marks each)
🔵 Q33. Case: A farmer in Assam faces floods due to Brahmaputra.
(i) Which river system causes it? (1)
(ii) Why are floods frequent? (1)
(iii) Suggest two solutions. (2)
🟢 Answer:
(i) 🌊 Brahmaputra system.
(ii) 🌧️ Heavy monsoon rains + silt deposition.
(iii) ✅ Embankments, afforestation.

🔵 Q34. Case: A student visits Sambhar Lake.
(i) Which type of lake is it? (1)
(ii) Where is it located? (1)
(iii) State two uses. (2)
🟢 Answer:
(i) 🟡 Salt-water lake.
(ii) 📍 Rajasthan.
(iii) ⚡ Salt production, tourism.

🔵 Q35. Source: A news article highlights the “Sorrow of Bihar”.
(i) Which river is referred to? (1)
(ii) Why is it called so? (1)
(iii) Suggest two control measures. (2)
🟢 Answer:
(i) 🌊 Kosi.
(ii) 🌧️ Recurrent floods damaging life and property.
(iii) ✅ Flood forecasting, embankment strengthening.

🌟 SECTION F — Map/Skill (5 marks)
🔵 Q36. On an outline map of India, locate and label:
🟢 Answer:
📍 Wular Lake
📍 Chilika Lake
📍 Godavari River
📍 Narmada River

🔵 Q37. For visually impaired candidates: Name four important lakes of India.
🟢 Answer:
🌊 Wular (J&K)
🌊 Chilika (Odisha)
🌊 Pulicat (Andhra Pradesh–Tamil Nadu)
🌊 Dal (J&K)

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