NCERT Questions & Answers + Important Extra Questions
NCERT Textbook Questions
Q1. Multiple Choice Questions
(i) Based on the information given below, classify each of the situations as a situation of water scarcity or water abundance:
(a) Region with 200 cm annual rainfall — Water abundance
(b) Region with high population density and high per capita water use — Water scarcity
(c) Region with polluted water bodies — Water scarcity (despite water being present, it is unusable)
(d) Region near a dam with adequate supply — Water abundance
(ii) Which one of the following statements is not a valid reason for the growing water scarcity?
(a) Growing population (b) Unequal access to water (c) Increasing number of industries is a valid reason, but in the NCERT context, the answer meant to be selected is the one that is least directly relevant. All options are valid reasons — this question tests understanding of relative importance.
Q2. Answer the following questions in about 30 words
(i) Explain how water becomes a renewable resource.
Ans. Water is a renewable resource because of the hydrological cycle — water evaporates from oceans/water bodies due to solar heat, forms clouds through condensation, and returns to the earth as precipitation (rain, snow). This cycle continuously replenishes freshwater supplies. However, overuse and pollution can make it scarce despite its renewable nature.
(ii) What is water scarcity and what are its main causes?
Answer
Water scarcity means shortage of adequate water for human needs. Main causes: (i) Growing population increases domestic and agricultural water demand. (ii) Unequal distribution — some areas receive heavy rainfall while others are arid. (iii) Over-exploitation of groundwater for irrigation (tube wells). (iv) Industrialisation — industries consume and pollute large quantities. (v) Urbanisation — growing cities need more water. (vi) Pollution of rivers and lakes makes water unusable.
(iii) Compare the advantages and disadvantages of multi-purpose river projects.
Ans.
Advantages: (i) Generate hydroelectricity (clean energy). (ii) Provide irrigation for agriculture. (iii) Enable flood control by regulating water flow. (iv) Supply drinking water to towns and cities. (v) Support inland navigation and fisheries. (vi) Provide recreation and tourism opportunities.
Disadvantages: (i) Displacement of local communities — large-scale submergence of settlements. (ii) Environmental damage — destruction of forests, loss of biodiversity, disruption of aquatic ecosystems. (iii) Sedimentation reduces reservoir capacity over time. (iv) Earthquakes can be triggered by the weight of reservoirs (reservoir-induced seismicity). (v) Inter-state disputes over sharing of river water. (vi) Waterlogging and salinity in command areas due to excessive canal irrigation. (vii) Benefits often favour the urban and industrial sectors at the expense of local communities.
Q3. Answer the following questions in about 120 words
(i) Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out.
Ans. In the semi-arid and arid regions of Rajasthan, rainwater harvesting has been practised for centuries due to the extreme scarcity of water. The main methods include:
(i) Rooftop rainwater harvesting: Rainwater from rooftops is collected through pipes and stored in underground tanks called tankas (cylindrical underground tanks lined with lime mortar). These tankas can store water for the entire dry season. Almost every household in Bikaner, Barmer, and Jaisalmer had tankas traditionally.
(ii) Khadins and Johads: These are earthen check dams that capture rainwater runoff. Khadins are long earthen embankments built across lower slopes of hills to collect surface runoff for agriculture. Johads are small earthen check dams that collect and store rainwater for recharging groundwater.
(iii) Nadi: Village ponds that collect rainwater during the monsoon. These are common in Jodhpur region.
(iv) Bawris (stepwells): Deep wells with steps leading down to the water level, found across Rajasthan.
The decline of traditional water harvesting systems due to modernisation (piped water, tube wells) has ironically worsened water scarcity. Today, there is a revival movement to restore and maintain these traditional systems alongside modern technology.
(ii) Describe how modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.
Ans. Modern adaptations of traditional methods are being widely adopted:
(i) Tamil Nadu: The first state to make rooftop rainwater harvesting compulsory for all buildings. Rainwater from roofs is channelled through pipes into recharge pits or underground sumps.
(ii) Shillong, Meghalaya: Despite receiving the highest rainfall in India, Shillong faces water shortage. Rooftop rainwater collection is common — nearly every household has its own system.
(iii) Gendathur village (Mysuru, Karnataka): People have installed rooftop water harvesting systems on 200 houses, saving them from dependence on tankers during summer. They now have adequate water for the entire year.
(iv) Bangalore: In suburban areas, over 800 apartment complexes have been encouraged to adopt rainwater harvesting to recharge depleted groundwater.
(v) Delhi: Several colonies and government buildings now have rainwater harvesting pits that channel rooftop runoff into the ground for recharging aquifers.
These modern adaptations combine the wisdom of traditional methods (capturing and storing rainwater at source) with modern materials and technology (PVC pipes, filter systems, motorised pumps, recharge wells).
Important Extra Questions
What is a dam? What are multi-purpose projects? Name some important dams of India.
Answer
A dam is a barrier built across a river to obstruct the flow of water and create a reservoir behind it. Dams can be small (check dams) or very large (like Bhakra Nangal).
A multi-purpose project is a large dam designed to serve several purposes simultaneously — irrigation, hydroelectric power generation, flood control, water supply, inland navigation, fisheries, and recreation. Jawaharlal Nehru called dams the "temples of modern India."
Important dams
(i) Bhakra Nangal Dam — Sutlej River (Punjab-Himachal Pradesh border)
(ii) Hirakud Dam — Mahanadi River (Odisha) — one of the longest dams in the world
(iii) Nagarjuna Sagar Dam — Krishna River (Telangana-Andhra Pradesh)
(iv) Sardar Sarovar Dam — Narmada River (Gujarat)
(v) Tehri Dam — Bhagirathi River (Uttarakhand) — India's tallest dam
(vi) Tungabhadra Dam — Tungabhadra River (Karnataka-Andhra Pradesh)
What is rainwater harvesting? Explain its importance.
Answer
Rainwater harvesting is the technique of collecting and storing rainwater for future use rather than allowing it to run off. It can be done at individual (rooftop) or community (watershed) level.
Importance: (i) Recharges groundwater — the most critical benefit in water-scarce regions. (ii) Reduces dependence on external water supply (tankers, canals). (iii) Prevents flooding by reducing surface runoff. (iv) Cost-effective — relatively cheap to set up and maintain. (v) Improves water quality — rainwater is relatively clean compared to surface water. (vi) Addresses water scarcity in areas with seasonal rainfall by storing water for dry months. (vii) In urban areas, it reduces the load on municipal water supply systems.
Why are inter-state water disputes common in India? Give examples.
Answer
Inter-state water disputes arise because rivers flow across state boundaries, and states in the upper and lower reaches have competing claims over the same water. Causes:
(i) India's rivers are shared resources with no single state having exclusive rights. (ii) Growing demand for irrigation and drinking water in all states. (iii) Construction of dams by upstream states reduces flow to downstream states. (iv) Lack of a comprehensive national water policy for equitable distribution.
Examples: (i) Cauvery water dispute between Karnataka and Tamil Nadu — Karnataka's dams (KRS) reduce flow to Tamil Nadu's delta agriculture. (ii) Krishna-Godavari dispute between Andhra Pradesh (now Telangana too), Maharashtra, and Karnataka. (iii) Sutlej-Yamuna Link (SYL) Canal dispute between Punjab and Haryana. (iv) Narmada dispute between Gujarat, Madhya Pradesh, Maharashtra, and Rajasthan (Sardar Sarovar). These disputes highlight the need for better water governance and cooperative federal mechanisms.