Class 10 Geo Ch 3 – Water Resources
NCERT CLASS 10 GEOGRAPHY • DETAILED SOLUTIONS • CHAPTER 3 • WATER RESOURCES

Water Resources

Detailed Explanations & Solutions

Short Answer Questions
Question 1
Explain how water becomes a renewable resource.
Water is a renewable resource because it is continuously recycled through the Hydrological Cycle:
  • Evaporation: Water from oceans and lakes evaporates into the atmosphere due to the sun’s heat.
  • Condensation: The water vapor cools down to form clouds.
  • Precipitation: Water falls back to earth as rain or snow.
  • Run-off: This water flows into rivers and eventually back into the oceans, completing the cycle. This process ensures that water is never permanently lost, though its form and location change.
[Image of hydrological cycle water cycle diagram]
Question 2
What is water scarcity and what are its main causes?
Water Scarcity refers to the shortage of water required to meet basic human needs. It is caused by:
  • Over-exploitation: Excessive pumping of groundwater for irrigation (agriculture) and industry leads to falling water tables.
  • Unequal Access: In many regions, water is available but is controlled by a few, leaving the poor without access.
  • Pollution: Even if water is available, it may be polluted by domestic and industrial waste, chemicals, and pesticides, making it hazardous for human use (Qualitative Scarcity).
  • Growing Population: A larger population means more demand for water for domestic use and food production.
Question 3
Compare the advantages and disadvantages of multi-purpose river projects (Dams).
Advantages:
Irrigation: They provide water for agriculture in dry regions.
Electricity: They generate hydroelectric power.
Control: They help in flood control and provide water supply for domestic and industrial use.
Recreation: Inland navigation and fish breeding.
Disadvantages:
Ecological Impact: They fragment rivers, blocking migration of aquatic life and submerging natural vegetation.
Displacement: Local people are displaced from their ancestral lands (e.g., Narmada Bachao Andolan).
Sedimentation: Excessive sedimentation at the bottom of the reservoir reduces the dam’s lifespan and deprives downstream plains of fertile silt.
Long Answer Questions
Question 1
Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out.
In the semi-arid and arid regions of Rajasthan (Bikaner, Phalodi, Barmer), almost all houses traditionally had underground tanks or ‘tankas’ for storing drinking water.
  • Structure: The tankas were as large as a big room (e.g., 6.1m deep, 4.27m long, and 2.44m wide). They were built inside the main house or the courtyard.
  • Connection: They were connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops would travel down the pipe and was stored in these underground tankas.
  • First Spell: The first spell of rain was usually not collected as it was used to clean the roof and the pipes. The subsequent spells were collected.
  • Palar Pani: This water, called ‘Palar Pani’, is considered the purest form of natural water. It was a reliable source of drinking water when all other sources dried up in summer.
  • Cooling: Many houses built rooms adjoining the tanka to keep the room cool in summer.
Question 2
Describe how modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.
While traditional methods declined with the arrival of canal water (like the Indira Gandhi Canal), modern adaptations are reviving these practices:
  • Rooftop Harvesting in Cities: In many states like Tamil Nadu, rooftop rainwater harvesting has been made legally compulsory for all buildings. Defaulters are punished. This helps recharge groundwater in urban areas.
  • Gendathur Village (Karnataka): In a backward village in Mysore, nearly 200 households have installed rooftop rainwater harvesting systems. The village has earned the distinction of being rich in rainwater. Each house collects about 50,000 liters annually.
  • Meghalaya: In Shillong, rooftop harvesting is common because despite high rainfall in the state (Cherrapunji/Mawsynram), the capital city faces acute water shortage. Nearly 15-25% of the total water requirement is met through rooftop harvesting.
  • Bamboo Drip Irrigation: In Meghalaya, a 200-year-old system of using bamboo pipes to transport water from springs to plantations is still used. It is efficient and eco-friendly.
Key Concepts & Map Work
Concept
Hydraulic Structures in Ancient India
India has a long history of water management:
  • 1st Century B.C.: Sringaverapura (near Allahabad) had a sophisticated water harvesting system channeling the flood water of the river Ganga.
  • Chandragupta Maurya: During his time, dams, lakes, and irrigation systems were extensively built.
  • Kalinga (Odisha) & Nagarjunakonda (Andhra Pradesh): Evidence of sophisticated irrigation works has been found in these regions.
  • 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 Iltutmish to supply water to the Siri Fort area.
Map Work
Important Dams (Locate and Label)
For the Board Exam, you must be able to locate these dams on the map of India:
  • Salal: Chenab River (Jammu & Kashmir)
  • Bhakra Nangal: Satluj River (Himachal Pradesh/Punjab)
  • Tehri: Bhagirathi River (Uttarakhand)
  • Rana Pratap Sagar: Chambal River (Rajasthan)
  • Sardar Sarovar: Narmada River (Gujarat)
  • Hirakud: Mahanadi River (Odisha) – *Longest Dam*
  • Nagarjuna Sagar: Krishna River (Telangana/Andhra Pradesh)
  • Tungabhadra: Tungabhadra River (Karnataka)
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