Learning Objectives
- Understand the importance and scarcity of water resources
- Learn about multi-purpose river valley projects and their advantages/disadvantages
- Study rainwater harvesting and water conservation methods
- Understand hydraulic structures in ancient India
Key Concepts
Water Scarcity
Water covers 71% of the Earth's surface but only 2.5% is freshwater, and most of it is locked in ice caps and glaciers. Only about 1% of freshwater is available for human use. India receives nearly 4% of global precipitation but has a growing water crisis.
Causes of water scarcity: Rapid population growth, unequal access, over-exploitation of groundwater, industrialisation, urbanisation, pollution of water bodies, and seasonal/regional variations in water availability. Agriculture uses about 89% of water in India.
Water scarcity is not just about absolute quantity but also about access — even in water-abundant areas, some communities may face scarcity due to unequal distribution and contamination.
Multi-Purpose River Valley Projects
Dams are hydraulic structures built across rivers to regulate flow. Multi-purpose projects serve irrigation, hydroelectric power, flood control, water supply, navigation, and recreation. Jawaharlal Nehru called dams the "temples of modern India".
Major Multi-Purpose Projects:
Bhakra Nangal: On River Sutlej (Himachal Pradesh-Punjab border). One of the highest gravity dams in the world.
Damodar Valley Corporation (DVC): On River Damodar (Jharkhand-West Bengal). Modelled on the Tennessee Valley Authority (TVA) of the USA.
Hirakud Dam: On River Mahanadi (Odisha). One of the longest dams in the world.
Nagarjuna Sagar: On River Krishna (Telangana-Andhra Pradesh).
Sardar Sarovar: On River Narmada (Gujarat). Controversial due to displacement of tribal communities — the Narmada Bachao Andolan (Save Narmada Movement) led by Medha Patkar opposed the project.
Advantages of dams: Irrigation, hydroelectricity, flood control, water supply, recreation, inland navigation.
Disadvantages: Displacement of local communities, submergence of forests and farmland, sedimentation, fragmentation of river ecosystems, induced seismicity, unequal distribution of benefits — upstream areas submerged while downstream areas get benefits.
Rainwater Harvesting
Rainwater harvesting is the collection and storage of rainwater for later use. In India, several traditional methods exist:
Rooftop harvesting: Collecting rainwater from rooftops and directing it to storage tanks or recharge pits.
Traditional systems: In Rajasthan — khadins, johads, tankas (underground tanks). In hilly areas — guls and kuls (diversion channels). In Bengal — inundation channels. In Tamil Nadu — eris (tanks). In Kerala — surangams. In Meghalaya — bamboo drip irrigation.
Tamil Nadu is the first state in India to make rooftop rainwater harvesting mandatory for all buildings.
Ancient Hydraulic Structures
India has a rich history of water management. In the first century BCE, Sringaverapura near Allahabad had sophisticated water harvesting systems. Bhopal Lake (11th century) was one of the largest artificial lakes. Hauz Khas in Delhi was built by Iltutmish for the residents of Siri Fort.
Summary
Water is a scarce resource despite covering much of the Earth's surface. India faces growing water scarcity due to population growth, pollution, and over-exploitation. Multi-purpose dams provide irrigation and power but cause displacement and ecological damage. Rainwater harvesting — both modern rooftop systems and traditional methods like tankas, johads, and eris — offers sustainable solutions. India has a rich tradition of hydraulic engineering that modern water management can learn from.
Important Terms
- Water Scarcity
- Insufficient availability of water to meet the demands of a region
- Multi-Purpose Project
- Dam serving irrigation, power generation, flood control, and other uses simultaneously
- Rainwater Harvesting
- Collection and storage of rainwater for future use
- Narmada Bachao Andolan
- Movement led by Medha Patkar opposing the Sardar Sarovar Dam
- Tanka
- Traditional underground rainwater storage tank in Rajasthan
- Bamboo Drip Irrigation
- Traditional water management system in Meghalaya using bamboo pipes
Quick Revision
- Only about 1% of Earth's freshwater is available for human use
- Agriculture uses 89% of India's water
- Nehru called dams "temples of modern India"
- Bhakra Nangal (Sutlej), Hirakud (Mahanadi), Nagarjuna Sagar (Krishna)
- Narmada Bachao Andolan opposed Sardar Sarovar Dam
- Tamil Nadu: first state to make rooftop rainwater harvesting mandatory
- Traditional systems: tankas, johads (Rajasthan), eris (Tamil Nadu), guls/kuls (hills)
Practice Tips
- Mark major dams and rivers on a map of India — very important for board exams
- Compare advantages and disadvantages of multi-purpose projects in a table
- Know traditional rainwater harvesting methods by region