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Social Sciences: Class 10 (Part 1) — Chapter 3: Water Resources

3.1 Introduction to Water Resources

Water is a vital natural resource. While $\frac{3}{4}$ of the Earth's surface is covered with water, only a small proportion of it accounts for freshwater that can be put to use.

3.2 Water Scarcity and the Need for Water Conservation and Management

Water scarcity is not only associated with low rainfall or drought-prone regions but is increasingly caused by over-exploitation, excessive use, and unequal access to water among different social groups.

3.2.1 Causes of Water Scarcity

  • Growing Population: A large population requires more water for domestic use and to expand irrigated areas for dry-season agriculture to produce more food.
  • Intensive Industrialisation and Urbanisation: Post-independent India witnessed rapid industrialisation. Industries are heavy users of water and require power, much of which comes from hydroelectric power.
  • Urban Lifestyles: Multiplying urban centres with dense populations have their own groundwater pumping devices, leading to the depletion of fragile water resources.
  • Water Pollution: Even where water is sufficiently available, it may be polluted by domestic and industrial wastes, chemicals, pesticides, and fertilisers, making it hazardous for human use.

3.2.2 Government Initiatives

  • Jal Jeevan Mission (JJM): Aims to enable every rural household to get an assured supply of potable piped water at a service level of $55\text{ litres}$ per capita per day regularly on a long-term basis.
  • Atal Bhujal Yojana (Atal Jal): Implemented in water-stressed Gram Panchayats across seven states to bring behavioural changes in the community towards conservation and smart water management.
3.3 Multi-Purpose River Projects and Integrated Water Resources Management

Historically, India has a rich tradition of constructing sophisticated hydraulic structures like dams, reservoirs, lakes, embankments, and canals for irrigation.

3.3.1 Hydraulic Structures in Ancient India

  • 1st Century B.C.: Sringaverapura near Allahabad had a sophisticated water harvesting system channelling the floodwater of the river Ganga.
  • Chandragupta Maurya's Reign: Dams, lakes, and irrigation systems were extensively built.
  • Sophisticated Irrigation Works: Found in Kalinga (Odisha), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka), and Kolhapur (Maharashtra).
  • 11th Century: Bhopal Lake, one of the largest artificial lakes of its time, was built.
  • 14th Century: The tank in Hauz Khas, Delhi, was constructed by Allauddin Khilji for supplying water to the Siri Fort area.

3.3.2 What is a Dam?

A dam is a barrier across flowing water that obstructs, directs, or retards the flow, often creating a reservoir, lake, or impoundment.

  • Dams are classified according to structure, intended purpose, or height (e.g., timber dams, embankment dams, masonry dams; low, medium, or high dams).
  • Dams are referred to as multi-purpose projects because they integrate multiple uses of impounded water, such as irrigation, electricity generation, domestic and industrial water supply, flood control, recreation, inland navigation, and fish breeding.
  • Examples include the Bhakra-Nangal project in the Sutluj-Beas basin and the Hirakud project in the Mahanadi basin.
  • Jawaharlal Nehru proudly proclaimed dams as the "temples of modern India" as they would integrate agricultural development with rapid industrialisation.

3.3.3 Scrutiny, Opposition, and Ecological Impacts

  • Altered River Flow: Regulating and damming rivers affects their natural flow, causing poor sediment flow and excessive sedimentation at the bottom of the reservoir, leading to rockier stream beds and poorer habitats for aquatic life.
  • Migration Barriers: Dams fragment rivers, making it difficult for aquatic fauna to migrate, especially for spawning.
  • Submergence of Land: Reservoirs submerge existing vegetation and soil, leading to decomposition over time.
  • Failure in Flood Control: Ironically, big dams have often triggered floods due to sedimentation in the reservoir during excessive rainfall, causing extensive soil erosion and land degradation.
  • Social Displacement: Multi-purpose projects often cause large-scale displacement of local communities, depriving them of their land and livelihoods.
  • Ecological Consequences: Irrigation has changed cropping patterns, leading to water-intensive commercial crops and causing ecological issues like salinisation of the soil.
  • Inter-State Disputes: Disputes arise over sharing water resources and costs, such as the Krishna-Godavari dispute regarding water diversion at Koyna by Maharashtra.
3.4 Rainwater Harvesting

Given the disadvantages and opposition to multi-purpose projects, rainwater harvesting emerged as a viable socio-economic and environmental alternative.

3.4.1 Traditional Rainwater Harvesting Methods

  • Guls / Kuls: Diversion channels built in hill and mountainous regions of the Western Himalayas for agriculture.
  • Rooftop Rainwater Harvesting: Commonly practised to store drinking water, particularly in Rajasthan.
  • Inundation Channels: Developed in the floodplains of Bengal to irrigate fields.
  • Khadins and Johads: Rain-fed storage structures in arid and semi-arid regions (like Jaisalmer and other parts of Rajasthan) that allowed water to stand and moisten the soil.
  • Tankas: Underground tanks built inside houses or courtyards in semi-arid regions of Rajasthan (Bikaner, Phalodi, Barmer) to store drinking water, locally called palar pani. A tank in Phalodi was measured at $6.1\text{ m} \times 4.27\text{ m} \times 2.44\text{ m}$.

3.4.2 Modern Adaptations and Case Studies

  • Shillong, Meghalaya: Despite receiving high rainfall, Shillong faces acute water shortage; nearly $15\text{--}25\text{ percent}$ of household water needs are met via rooftop rainwater harvesting.
  • Gendathur, Karnataka: A remote village in Mysuru where nearly 200 households have installed rooftop rainwater harvesting systems, earning the rare distinction of being rich in rainwater.
  • Tamil Nadu: The first state in India to make rooftop rainwater harvesting structures compulsory for all houses, with legal provisions to punish defaulters.
  • Bamboo Drip Irrigation System: A $200\text{-year-old}$ system in Meghalaya where stream and spring water is tapped using bamboo pipes, reducing water flow to $20\text{--}80\text{ drops}$ per minute at the plant site.