Drainage — Practice

Question 1

Distinguish between Himalayan and Peninsular rivers.

Accepted Answer

Step 1 — Flow regime.
  Himalayan: PERENNIAL (year-round) due to snowmelt + monsoon.
  Peninsular: SEASONAL (mainly during monsoon).

Step 2 — Catchment.
  Himalayan: VAST catchment areas.
  Peninsular: SMALLER catchment areas.

Step 3 — Sediment.
  Himalayan: HEAVY sediment (eroding Himalayas).
  Peninsular: LESS sediment (older, more stable terrain).

Step 4 — Course.
  Himalayan: LONG, winding (cross plains for hundreds of km).
  Peninsular: SHORTER, more direct.

Step 5 — Examples.
  Himalayan: Indus, Ganga, Brahmaputra.
  Peninsular: Godavari, Krishna, Kaveri, Narmada, Tapi, Mahanadi.

✦ Answer: Himalayan rivers are perennial (snowmelt + monsoon), with vast catchments, heavy sediment, long courses. Peninsular rivers are seasonal (rainfall only), with smaller catchments, less sediment, shorter courses. Examples: Ganga/Brahmaputra (Himalayan); Godavari/Krishna (Peninsular).

Question 2

Name the source and the longest tributary of the Indus river.

Accepted Answer

Step 1 — Source.
  The Indus originates near Mansarovar Lake in Tibet (Manasarovar region).

Step 2 — Longest tributary.
  Sutlej — flows from Tibet, joins the Indus in Pakistan. Approximately 1,400 km long.

✦ Answer: Source: near Mansarovar Lake in Tibet. Longest tributary: Sutlej.

Question 3

Name the largest Peninsular river of India.

Accepted Answer

Step 1 — Recall.
  The GODAVARI is the largest Peninsular river of India.

Step 2 — Details.
  Length: 1,465 km. Source: Western Ghats in Maharashtra. Drains into Bay of Bengal in Andhra Pradesh.
  Nicknamed 'Vridha Ganga' or 'Old Ganga' for its size and significance.

✦ Answer: Godavari (1,465 km). Also called Vridha Ganga / Old Ganga.

Question 4

Which is the largest freshwater lake in India? Where is it located?

Accepted Answer

Step 1 — Recall.
  Wular Lake is the largest natural freshwater lake in India.

Step 2 — Location.
  Jammu & Kashmir. Located in the Kashmir Valley, north of Srinagar.

Step 3 — Origin.
  Tectonic origin — formed by Himalayan plate movements.

✦ Answer: Wular Lake (Jammu & Kashmir). Largest natural freshwater lake in India. Tectonic origin.

Question 5

What is the Indus Water Treaty (1960) and what does it specify?

Accepted Answer

Step 1 — Date and parties.
  Signed in 1960 between India (Prime Minister Nehru) and Pakistan (Field Marshal Ayub Khan). Mediated by the World Bank.

Step 2 — Provisions.
  • INDIA gets full use of the EASTERN rivers: Ravi, Beas, Sutlej.
  • PAKISTAN gets full use of the WESTERN rivers: Indus, Jhelum, Chenab.
  • Both can use the other's rivers for limited non-consumptive purposes (hydroelectricity).

Step 3 — Significance.
  Despite multiple wars between India and Pakistan (1965, 1971, 1999), the Indus Water Treaty has continued to function. It's considered one of the most successful international water-sharing agreements in the world.

Step 4 — Modern concerns.
  Climate change and political tensions are creating new challenges. India has periodically threatened to revisit the treaty.

✦ Answer: The Indus Water Treaty (1960) between India and Pakistan, mediated by the World Bank, gave India full use of Ravi, Beas, Sutlej (eastern rivers) and Pakistan full use of Indus, Jhelum, Chenab (western rivers). It has functioned despite multiple wars — a notable success.

Question 6

Describe the Ganga river system from source to mouth.

Accepted Answer

Step 1 — Origin.
  Source: Gangotri Glacier in Uttarakhand, where it emerges as the BHAGIRATHI river.

Step 2 — Junction at Devprayag.
  At Devprayag (Uttarakhand), the Bhagirathi joins another stream — the ALAKNANDA (originating from another glacier). The combined river is called the GANGA from this point on.

Step 3 — Course through plains.
  The Ganga flows EAST through:
  • Uttarakhand → Uttar Pradesh → Bihar → Jharkhand → West Bengal.
  • Major cities along the Ganga: Haridwar, Allahabad/Prayagraj (junction with Yamuna), Varanasi, Patna, Kolkata.

Step 4 — Tributaries.
  Right bank (Peninsular): YAMUNA, Son, Damodar, Mahananda.
  Left bank (Himalayan): Ghaghara, Gandak, Kosi.
  All major tributaries are perennial.

Step 5 — Delta.
  Near Bangladesh border, the Ganga splits into two distributaries:
  • The MAIN GANGA flows into Bangladesh (where it's called the Padma).
  • The HOOGHLY (Bhagirathi-Hooghly) continues through West Bengal — past Kolkata — to the Bay of Bengal.
  Together with the Brahmaputra in Bangladesh, they form the SUNDARBANS DELTA — the largest delta in the world.

Step 6 — Length.
  ~2,510 km from Devprayag to mouth.

✦ Answer: Source: Bhagirathi from Gangotri Glacier (Uttarakhand) + Alaknanda meet at Devprayag → Ganga. Flows through UP, Bihar, West Bengal. Tributaries: Yamuna, Ghaghara, Gandak, Kosi, Son, Damodar. Splits at delta into Hooghly (to Kolkata) and main Ganga (to Bangladesh). Forms Sundarbans Delta — world's largest.

Question 7

Why does the Brahmaputra have a different name in each region it flows through?

Accepted Answer

Step 1 — Name changes across regions.
  • In TIBET, the river is called the TSANG PO.
  • In ARUNACHAL PRADESH (where it enters India), it's the DIHANG.
  • In ASSAM (where it widens into the plains), it's the BRAHMAPUTRA.
  • In BANGLADESH (where it joins the Ganga), it's the JAMUNA.

Step 2 — Why so many names.
  Each region's local language and culture had its own name for the river before modern atlases standardised things. The names reflect the river's:
  • Origin (Tsang Po = 'cleanser' or 'purifier' in Tibetan).
  • Course transition (Dihang refers to the Arunachal stretch).
  • Cultural significance (Brahmaputra means 'son of Brahma' — the Hindu creator god).
  • Different identity in Bangladesh (Jamuna is the name in Bengal).

Step 3 — Single river, many cultures.
  The Brahmaputra/Tsang Po/Dihang/Jamuna crosses three countries (China, India, Bangladesh) and many cultural-linguistic regions. Each names it differently — reflecting the river's significance to each culture.

✦ Answer: The Brahmaputra has different names in each region — Tsang Po (Tibet), Dihang (Arunachal), Brahmaputra (Assam), Jamuna (Bangladesh) — because each culture had its own local name before modern atlases standardised geography. Single river, many cultural identities.

Question 8

Why do most Peninsular rivers flow eastward, while the Narmada and Tapi flow westward?

Accepted Answer

Step 1 — General slope.
  The Peninsular Plateau slopes from west to east. The Western Ghats are higher (~ 1,000-2,500 m); the Eastern coast is at sea level. So MOST rivers naturally flow east — following the slope toward the Bay of Bengal.
  Examples: Mahanadi, Godavari, Krishna, Kaveri all flow east.

Step 2 — Exception: Narmada and Tapi.
  These two rivers flow WESTWARD through what are called RIFT VALLEYS — long, narrow troughs created by geological faulting (subsidence between parallel faults).
  • The Narmada flows between the Vindhyas (north) and Satpuras (south).
  • The Tapi flows just south of the Satpuras.

Step 3 — Why the rift valleys go west.
  During Earth's geological history, faulting in the Peninsular Plateau created these grabens (sunken blocks between fault lines). The faulting tilted the floor of these valleys WESTWARD, so rivers within them flow toward the Arabian Sea.

Step 4 — Implications.
  Narmada and Tapi:
  • Flow through narrow valleys with steep walls.
  • Don't form large deltas (because they flow into the Arabian Sea with no shallow continental shelf).
  • Their valleys are major north-south transport corridors.

Step 5 — Summary.
  General slope of the Peninsular Plateau → most rivers flow east. Geological faulting creates west-flowing exceptions (Narmada, Tapi).

✦ Answer: Most Peninsular rivers flow east because the Peninsular Plateau slopes from west (higher) to east (lower). The Narmada and Tapi are exceptions — they flow west through RIFT VALLEYS (subsiding blocks between geological faults) that tilt westward. Geological faulting creates these exceptional river courses.

Question 9

Why is the Ganga heavily polluted, and what is being done about it?

Accepted Answer

Step 1 — Sources of Ganga pollution.

(a) SEWAGE: Most major cities along the Ganga (Kanpur, Allahabad, Varanasi, Patna, Kolkata) discharge largely untreated sewage. ~80% of pollution comes from domestic sewage.

(b) INDUSTRIAL EFFLUENTS: Kanpur leather tanneries (chromium pollution), paper mills, distilleries, chemical factories all discharge waste.

(c) AGRICULTURAL RUNOFF: Fertilisers and pesticides from intensive agriculture in the Ganga plains.

(d) RELIGIOUS OFFERINGS: Flowers, ash, plastic items, idol immersion (especially during Durga Puja) contribute to pollution.

(e) SOLID WASTE: Plastic, dead animals, garbage dumped into the river.

Step 2 — Current state.
  Several stretches of the Ganga have:
  • Bacterial contamination far exceeding safe levels (faecal coliform).
  • Dissolved oxygen too low for most aquatic life.
  • Heavy metal contamination (especially Kanpur stretch).
  • Visible garbage and plastic.

Step 3 — Government response.

(a) NAMAMI GANGE programme (2014 onwards):
  • Multi-billion rupee mission to clean the Ganga.
  • Sewage treatment plant (STP) construction.
  • Industrial pollution control.
  • Public awareness campaigns.
  • Solid waste management.

(b) National Mission for Clean Ganga (NMCG):
  • Coordinates all Ganga clean-up.
  • Special legal status to the Ganga (under the Environment Protection Act).

(c) Earlier programmes:
  • Ganga Action Plan (1985 — Rajiv Gandhi).
  • Ganga Action Plan Phase 2 (1993).
  • National River Conservation Plan (NRCP).

Step 4 — Results.
  Mixed. Some stretches have improved (Allahabad area). Others (Kanpur, Varanasi) remain heavily polluted. Coordinated multi-state effort is difficult; political will varies; population pressure continues to grow.

Step 5 — What needs more work.
  • Universal sewage treatment.
  • Industrial pollution enforcement.
  • Behavioural change (religious practices).
  • Long-term governance.

✦ Answer: The Ganga is polluted by sewage (80%), industrial effluents (tanneries, paper mills, chemicals), agricultural runoff, religious offerings, and solid waste. The Namami Gange programme (2014) is a multi-billion rupee national effort to clean the river — including sewage treatment plants, industrial pollution control, and awareness campaigns. Results have been mixed; some stretches have improved while others remain heavily polluted.

Question 10

Compare Wular Lake, Chilika Lake, and Sambhar Lake.

Accepted Answer

Step 1 — Wular Lake.
  • Location: J&K, north of Srinagar.
  • Type: FRESHWATER, TECTONIC origin (formed by Himalayan plate movements).
  • Status: Largest natural freshwater lake in India.
  • Use: Fishing, water supply for Srinagar.

Step 2 — Chilika Lake.
  • Location: Odisha (eastern coast).
  • Type: BRACKISH (mixed freshwater + saltwater) — connected to Bay of Bengal.
  • Status: Largest brackish-water lake in ASIA.
  • Use: Major fishing area; bird sanctuary; Ramsar wetland site.
  • Famous for: dolphins, migratory birds (flamingos, pelicans).

Step 3 — Sambhar Lake.
  • Location: Rajasthan (north India, near Jaipur).
  • Type: SALT-WATER (inland salt lake).
  • Status: Largest inland salt-water lake in India.
  • Use: Salt production (~ 196,000 tonnes per year).
  • Endorheic basin: water has no outlet to the sea, so salt accumulates.

Step 4 — Comparison summary.

| Lake | Type | Status | Use |
  |------|------|--------|-----|
  | Wular | Freshwater (tectonic) | Largest freshwater in India | Fishing, water |
  | Chilika | Brackish | Largest in Asia (brackish) | Fishing, bird sanctuary |
  | Sambhar | Saltwater (inland) | Largest inland salt | Salt production |

✦ Answer: Wular Lake (J&K) is the largest natural freshwater lake in India, of tectonic origin. Chilika Lake (Odisha) is the largest brackish-water lake in Asia, connected to the Bay of Bengal. Sambhar Lake (Rajasthan) is the largest inland salt-water lake in India, used for salt production.

Question 11

Describe the role of rivers in the Indian economy and culture.

Accepted Answer

Step 1 — Agriculture.
  Rivers underpin ~70% of India's agriculture:
  • Direct irrigation from rivers and canals.
  • Groundwater recharge — about 90% of irrigated land uses groundwater that's recharged by rivers and rainfall.
  • Riverine alluvial soils (Northern Plains, deltas) are India's most fertile.
  • Rice cultivation: heavily dependent on river water (Ganga Plain, eastern coast deltas).
  • Wheat cultivation: irrigated by canals from rivers (Punjab, Haryana).
  • Cotton: relies on Krishna, Godavari, Tapi systems.

Step 2 — Water supply.
  Major cities are on rivers:
  • Delhi on the Yamuna.
  • Mumbai on Mithi and other minor rivers.
  • Kolkata on the Hooghly.
  • Chennai partly on the Cooum.
  • Hyderabad on the Musi.
  • Bangalore on the Vrishabhavathi.
  Rivers provide drinking water, industrial water, and municipal supply.

Step 3 — Hydroelectricity.
  Major hydroelectric projects:
  • Bhakra-Nangal (Sutlej, 1948-63): India's largest concrete gravity dam.
  • Tehri (Bhagirathi, 2006): one of world's tallest dams.
  • Sardar Sarovar (Narmada, 1980-2017): controversial mega-dam.
  • Hirakud (Mahanadi, 1957): one of world's longest dams.
  • Nagarjuna Sagar (Krishna).
  • Idukki (Periyar): Kerala's major hydro project.
  Hydroelectricity is ~12% of India's installed capacity but provides peaking power.

Step 4 — Industry.
  Heavy industry concentrated where water + minerals + power are available:
  • Iron and steel: Jamshedpur (Subarnarekha), Durgapur (Damodar).
  • Paper mills: along the Cauvery, Krishna.
  • Textile mills: depend on water for processing.
  Water-intensive industries are often located near rivers.

Step 5 — Transportation.
  Historically major:
  • The Ganga, Hooghly, Brahmaputra were the highways of pre-colonial trade.
  • Modern: National Waterway 1 (Allahabad-Haldia) on the Ganga.
  • Other waterways being developed for cargo transport.
  • Less important now than road and rail, but expanding.

Step 6 — Tourism.
  Religious pilgrimage:
  • Haridwar, Rishikesh on the Ganga.
  • Varanasi on the Ganga.
  • Pushkar on Pushkar Lake.
  • Allahabad/Prayagraj at the Sangam (Ganga + Yamuna + mythical Saraswati).
  Heritage tourism along the rivers.
  Adventure tourism: rafting in Himalayan rivers (Ganges, Indus, Zanskar).

Step 7 — Culture and religion.
  • Ganga is considered SACRED by Hindus — bathing in it cleanses sins. Death rituals (ashes scattered in Ganga) believed to bring moksha.
  • Yamuna also sacred — associated with Lord Krishna.
  • Kaveri sacred to many Tamilians.
  • Kumbh Mela: largest religious gathering in the world (held at Allahabad/Prayagraj, Haridwar, Nashik, Ujjain on a 12-year cycle).
  • Chhath Puja: major festival for Surya Worship, held on rivers (especially Bihar, UP).
  • Diwali, Durga Puja: idol immersion in rivers.

Step 8 — Cultural identity.
  Many Indian languages, cultures, and identities are tied to rivers:
  • Bengali culture closely tied to the Ganga and the Hooghly.
  • Punjabi culture: 'land of five rivers' (Pancha + Aap = five waters).
  • Telugu culture: along the Godavari and Krishna.
  • Tamil culture: along the Kaveri.

Step 9 — Modern challenges.
  • Pollution threatens all these uses.
  • Inter-state disputes (Kaveri, Krishna, Mahanadi, Periyar).
  • Climate change (glacial retreat, monsoon variability).
  • Groundwater depletion.
  • Damming controversies (Sardar Sarovar protests).

✦ Answer: India's rivers are economic infrastructure (agriculture, water supply, hydroelectricity, industry, transport, tourism) AND cultural-religious infrastructure (sacred Ganga, Yamuna, Kaveri; pilgrimages, festivals, identity). The economy and culture both depend on rivers — making their pollution, depletion, and inter-state disputes major national issues. India's water future is one of its central 21st-century challenges.

Practice — Drainage

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