Advantages of Multi-Purpose Projects
- Irrigation: Provide water for agriculture throughout the year
- Electricity: Generate cheap hydroelectric power (renewable energy)
- Flood Control: Store excess water and release gradually
- Water Supply: Domestic and industrial water needs
- Navigation: Enable inland water transport
- Employment: Create jobs during construction and operation
- Recreation: Tourism and recreation facilities
- Fisheries: Reservoirs support fish breeding
- Drought Prevention: Stored water helps during dry periods
Disadvantages and Criticism of Dams
Environmental Problems
| Problem | Description |
|---|---|
| Deforestation | Large forest areas submerged under reservoirs |
| Loss of Biodiversity | Destruction of habitats, loss of flora and fauna |
| Sedimentation | Silt accumulates in reservoir, reducing capacity over time |
| River Fragmentation | Natural flow of river disrupted, affecting aquatic life |
| Induced Earthquakes | Weight of water can trigger seismic activity (e.g., Koyna earthquake, 1967) |
| Waterlogging and Salinity | Over-irrigation causes soil degradation |
Social Problems
- Displacement: Millions of people (especially tribals) displaced from their homes
- Loss of Livelihood: Farmers, fishermen lose their traditional occupations
- Inadequate Compensation: Rehabilitation often incomplete or delayed
- Inter-state Disputes: Conflicts over sharing of water (e.g., Kaveri, Krishna)
- Unequal Benefits: Benefits often go to urban areas, not local communities
Case Study - Narmada Bachao Andolan: Led by Medha Patkar, this movement opposed the Sardar Sarovar Dam, highlighting displacement of tribal communities without proper rehabilitation. The movement raised important questions about development vs. displacement.
Criticism by Jawaharlal Nehru (Later Years)
Even Jawaharlal Nehru, who initially called dams "Temples of Modern India," later criticized them:
"I have been thinking about the river valley projects... the tendency to build higher and higher dams, and the tendency to imagine that all of a sudden we will create something wonderful... I think we have had a disease which I call 'gigantism'."
Rainwater Harvesting
Rainwater Harvesting: Technique of collecting and storing rainwater for future use.
Methods of Rainwater Harvesting
| Method | Description | Application |
|---|---|---|
| Rooftop Rainwater Harvesting | Rainwater from rooftops collected through pipes into storage tanks | Urban areas, individual buildings |
| Recharge Pits | Pits dug to allow rainwater to percolate into ground and recharge aquifers | Areas with declining groundwater |
| Recharge Wells | Bore wells used to inject rainwater directly into aquifer | Urban and semi-urban areas |
| Check Dams (Gully Plugs) | Small barriers to hold rainwater and allow percolation | Hilly and rural areas |
| Percolation Tanks | Artificial tanks to collect water and recharge groundwater | Agricultural areas |
Benefits of Rainwater Harvesting
- Increases groundwater recharge
- Reduces urban flooding
- Improves water quality (rainwater is soft and pure)
- Reduces dependence on external water supply
- Cost-effective and sustainable
- Prevents soil erosion
Tamil Nadu Example: Tamil Nadu is the first state in India to make rooftop rainwater harvesting compulsory for all buildings. This has significantly improved groundwater levels in Chennai and other cities.
Traditional Water Harvesting Systems
India has a rich tradition of water conservation. Different regions developed unique systems based on local geography and climate:
| Region/State | Traditional System | Description |
|---|---|---|
| Rajasthan (Phalodi-Barmer) | Khadins | Agricultural fields enclosed by earthen embankments to collect rainwater |
| Rajasthan (Bikaner) | Tankas | Underground tanks to store drinking water; found under houses |
| Rajasthan | Nadis | Village ponds to collect rainwater |
| Rajasthan | Johads | Earthen check dams to hold rainwater |
| Maharashtra | Bandharas, Tals | Small dams and reservoirs |
| MP & UP | Bundhis | Small embankments to store water |
| Bihar | Ahars, Pynes | Ahars (reservoirs) connected by Pynes (channels) |
| Tamil Nadu | Eris (Tanks) | Traditional irrigation tanks |
| Karnataka | Kattas | Stone and mud barriers across streams |
| Kerala | Surangams | Horizontal wells or tunnels to tap underground water |
| Himachal Pradesh | Kuls | Irrigation channels from glacier melt |
| J&K (Ladakh) | Zings | Tanks to store water from melting snow |
| Meghalaya | Bamboo Drip Irrigation | 200-year-old system using bamboo pipes; 18-20 liters water irrigates one hectare |
Memory Trick for Rajasthan: "KTNJ" = Khadins, Tankas, Nadis, Johads
Case Study: Rooftop Rainwater Harvesting in Shillong
Shillong (Meghalaya) has a long tradition of rooftop rainwater harvesting. Nearly every house collects rainwater from rooftops using pipes into tanks. This practice developed because:
- High rainfall but difficult terrain
- Groundwater is not easily accessible
- Rivers are far from settlements on hilltops
Case Study: Tankas in Rajasthan
Tankas (from Sanskrit 'Tanka' meaning underground tank) are found in Bikaner, Phalodi, and Barmer. Features:
- Underground cylindrical tanks lined with fine cement (lime)
- Collect rainwater from rooftops through pipes
- Main source of drinking water; water kept cool and pure
- Now declining due to piped water supply (Indira Gandhi Canal)
MCQs for Practice
1. What percentage of Earth's water is freshwater?
a) 1% b) 2.5% c) 4% d) 10%
Answer: b) 2.5%
2. Who called dams "Temples of Modern India"?
a) Mahatma Gandhi b) Jawaharlal Nehru c) Sardar Patel d) B.R. Ambedkar
Answer: b) Jawaharlal Nehru
3. Which is the highest dam in India?
a) Bhakra Nangal b) Hirakud c) Tehri d) Sardar Sarovar
Answer: c) Tehri Dam (260.5m)
4. Which is the longest dam in India?
a) Bhakra Nangal b) Hirakud c) Tehri d) Nagarjuna Sagar
Answer: b) Hirakud Dam (4.8 km)
5. Sardar Sarovar Dam is built on which river?
a) Ganga b) Krishna c) Narmada d) Godavari
Answer: c) Narmada
6. 'Tankas' are traditional water harvesting structures found in:
a) Tamil Nadu b) Kerala c) Rajasthan d) Bihar
Answer: c) Rajasthan
7. Which state made rooftop rainwater harvesting compulsory first?
a) Kerala b) Tamil Nadu c) Karnataka d) Gujarat
Answer: b) Tamil Nadu
8. Narmada Bachao Andolan was led by:
a) Sunderlal Bahuguna b) Medha Patkar c) Arundhati Roy d) Anna Hazare
Answer: b) Medha Patkar
9. 'Bamboo Drip Irrigation' is practiced in:
a) Rajasthan b) Gujarat c) Meghalaya d) Himachal Pradesh
Answer: c) Meghalaya
10. Bhakra Nangal Dam is built on which river?
a) Beas b) Ravi c) Sutlej d) Chenab
Answer: c) Sutlej
Important Questions for Board Exam
1 Mark Questions
- What percentage of Earth's water is freshwater?
- Which is the highest dam in India?
- What are 'Tankas'?
- Which state first made rainwater harvesting compulsory?
- Name the river on which Hirakud Dam is built.
Short Answer Questions (2-3 Marks)
- What are the main causes of water scarcity in India?
- What is rainwater harvesting? Mention two methods.
- Why did Jawaharlal Nehru call dams "Temples of Modern India"?
- What are the environmental problems associated with dams?
- Describe any two traditional water harvesting methods of Rajasthan.
Long Answer Questions (5 Marks)
- Explain the advantages and disadvantages of multi-purpose river projects.
- Describe the various traditional water harvesting methods in India.
- What is water scarcity? Explain its causes and suggest solutions.
- Describe any five major dams of India with their rivers and special features.
- Why is rainwater harvesting important? Explain different methods of rainwater harvesting.
Quick Revision Points
- Freshwater: Only 2.5% of Earth's water; only ~1% usable
- India's share: 4% of world's water, 4% of global precipitation
- "Temples of Modern India": Jawaharlal Nehru (for dams)
- Tehri Dam: Highest (260.5m), on Bhagirathi, Uttarakhand
- Hirakud Dam: Longest (4.8 km), on Mahanadi, Odisha
- Bhakra Nangal: Highest gravity dam, on Sutlej
- Narmada Bachao Andolan: Led by Medha Patkar
- Tamil Nadu: First state with compulsory rainwater harvesting
- Rajasthan traditional systems: Khadins, Tankas, Nadis, Johads
- Meghalaya: Bamboo Drip Irrigation (200 years old)
📚 More Geography Chapters:
Chapter 1: Resources and Development | Chapter 2: Forest and Wildlife | Chapter 4: Agriculture
MARWARI MISSION 100
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