💧 Water Resources — Class 10

Water scarcity, dams, rainwater harvesting, and multi-purpose river valley projects

1. Water Scarcity

📖 The Water Crisis

Though 71% of Earth's surface is water, only 2.5% is freshwater and just 1% is accessible. India receives adequate rainfall, but faces water scarcity due to:

• Uneven distribution of rainfall (some areas flood, others are arid)

• Over-exploitation of groundwater for agriculture and industry

• Pollution of water bodies

• Growing population and increased demand

• Loss of traditional water harvesting systems

2. Multi-Purpose River Valley Projects (Dams)

📖 Benefits of Large Dams

Multi-purpose projects serve many functions simultaneously — Jawaharlal Nehru called them "temples of modern India."

Irrigation: Provide water to agricultural land throughout the year

Electricity generation: Hydroelectric power (clean, renewable)

Flood control: Regulate river flow during monsoons

Water supply: Drinking water to cities

Navigation: Helps river transport

Tourism: Reservoirs become recreational areas

⚡ Problems with Large Dams — Anti-Dam Movements

Despite benefits, large dams have serious drawbacks:

Displacement: Millions of people (mostly tribal and rural poor) displaced from reservoir areas

Ecological damage: Forest submergence, loss of biodiversity, altered river ecosystems

Inter-state conflicts: Disputes over river water sharing (Cauvery, Krishna, Narmada)

Sedimentation: Dams trap silt → rivers lose capacity → flood plains become less fertile

Narmada Bachao Andolan (NBA): Movement led by Medha Patkar and Baba Amte against the Sardar Sarovar Dam — highlighted displacement of 40,000 families

3. Major River Valley Projects in India

  • Bhakra-Nangal: On Sutlej River (Punjab-Himachal Pradesh border); one of India's largest dams; serves Punjab, Haryana, Rajasthan
  • Hirakud Dam: On Mahanadi River (Odisha); world's longest earthen dam (25.8 km)
  • Sardar Sarovar: On Narmada River (Gujarat); controversial due to displacement
  • Tungabhadra: On Tungabhadra River (Karnataka-Andhra Pradesh); irrigation in Deccan
  • Damodar Valley Project: Often called "sorrow of Bengal" (due to floods) → now controlled by dams

4. Rainwater Harvesting

📖 Traditional Water Conservation

India has a rich tradition of water harvesting — collecting and storing rainwater for future use:

  • Khadins / Johads (Rajasthan): Embankments to collect rainwater in arid areas; used for centuries in Thar Desert
  • Baolis / Vav (Gujarat, Rajasthan): Step-wells — ornate underground wells you descend into
  • Kulhs (Himachal Pradesh): Traditional irrigation channels diverted from hill streams
  • Surangams (Kerala, Karnataka): Underground tunnels to tap spring water in hillsides
  • Bamboo drip irrigation (Meghalaya): Bamboo pipes divert stream water to fields — an ancient, sustainable system
  • Rooftop rainwater harvesting: Modern revival — collecting roof runoff into storage tanks; now mandated in many Indian cities

💡 Rooftop Rainwater Harvesting in Tamil Nadu

Tamil Nadu was the first state to make rooftop rainwater harvesting mandatory for all buildings. Result: Groundwater levels improved significantly in Chennai within a few years. This shows how reviving traditional practices can solve modern water crises!

🔑 Important Facts

  • India has 4% of world's freshwater resources but 16% of world population
  • Bhakra Dam is India's highest gravity dam (225 m height)
  • Narmada Bachao Andolan led by Medha Patkar and Baba Amte
  • Groundwater provides 60% of India's irrigation water
  • India's annual rainfall: ~1200 mm average (extremely uneven distribution)
  • Rajasthan receives less than 150mm/year; Meghalaya receives over 11,000mm/year