Water Resources – Important Questions & Answers

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(i) Explain how water becomes a renewable resource.

Answer:

• Water is a renewable resource because it is naturally replenished through the hydrological cycle.
• In this cycle:
  • Water from oceans, rivers, and lakes evaporates due to the Sun’s heat.
  • This water vapour condenses into clouds and falls back as precipitation (rain, snow, hail).
  • Precipitation replenishes surface water (rivers, lakes) and groundwater.
• As long as we use it sustainably, water availability can be maintained for future generations.
• However, over-exploitation and pollution can make renewable water resources scarce.

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(ii) What is water scarcity and what are its main causes?

Answer:

• Definition: Water scarcity is the situation when the demand for water exceeds its available supply, either in terms of quantity or quality.
• Main Causes:
  1. Over-exploitation – Excessive withdrawal of water for agriculture, industry, and domestic use.
  2. Uneven Distribution – Rainfall and river systems are not evenly spread across India.
  3. Pollution – Industrial discharge, sewage, and agricultural chemicals make water unsafe.
  4. Growing Population – More people increase the demand for drinking water and food (irrigation).
  5. Urbanisation – Expanding cities require more water for housing, sanitation, and industries.

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(iii) Compare the advantages and disadvantages of multi-purpose river projects.

Answer:

Advantages	Disadvantages
Provides irrigation for agriculture	Displacement of large numbers of people
Generates hydroelectric power (renewable energy)	Submerges forests and affects biodiversity
Supplies drinking water to urban and rural areas	Can cause waterlogging and salinity
Helps in flood control by regulating river flow	Changes natural river flow and aquatic ecosystems
Supports inland navigation and fisheries	May lead to inter-state disputes over water sharing
Promotes tourism and recreation	High construction and maintenance costs

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(iv) Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out.

Answer:

• Rajasthan is a desert state with low rainfall and high evaporation.
• People have developed traditional techniques to store rainwater:
  1. Kunds and Tankas – Underground circular or rectangular tanks with a sloping catchment area to collect rainwater; covered to prevent evaporation.
  2. Johads – Small earthen check dams that collect rainwater and recharge groundwater.
  3. Rooftop Rainwater Collection – Rainwater from sloping roofs is diverted into storage tanks.
• Example: In districts like Jaisalmer and Barmer, families store enough rainwater in underground tanks to last through the dry season.
• These methods ensure survival in a region with scarce and unpredictable rainfall.

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(v) Describe how modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.

Answer:

• Modern adaptations build upon traditional wisdom but use improved materials and designs.
• Examples:
  1. Rooftop Rainwater Harvesting – Common in urban areas; water collected from roofs is stored in tanks or directed to recharge pits.
  2. Percolation Pits and Recharge Wells – Modern equivalents of traditional percolation ponds to replenish groundwater.
  3. Revival of Traditional Tanks and Ponds – Old structures like Eris, Kunds, and Johads are repaired and linked with piped systems.
  4. Government Policies – Many states (e.g., Tamil Nadu) have made rooftop rainwater harvesting compulsory for buildings.
  5. Community Participation – Local groups manage and maintain small dams, check dams, and tanks, ensuring equitable water distribution.
• This combination of old and new ensures sustainability, cost-effectiveness, and local adaptability in water management.

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