Water Resources Class 10: Notes and Important Questions

Water Resources is chapter 3 of the Class 10 Geography book, Contemporary India-II. It explains why a renewable resource like water can still run short, how multi-purpose river projects work and why they face opposition, and how traditional and modern rainwater harvesting can help. This guide follows the chapter in order and ends with model answers and common mistakes.

CBSE 2026-27: the whole chapter is in the board exam, inside the Geography section worth "17+3 map pointing" marks (chapters 1 to 7; Lifelines of National Economy is tested only through map pointing). For map work, the syllabus asks you to locate and label eight dams: Salal, Bhakra Nangal, Tehri, Rana Pratap Sagar, Sardar Sarovar, Hirakud, Nagarjuna Sagar and Tungabhadra. See our CBSE Class 10 syllabus 2026-27 guide for the full marks split.

Water as a renewable resource

Three-fourths of the earth's surface is covered with water, but only a small share is freshwater we can use. Freshwater comes mainly from surface runoff and groundwater, which are renewed and recharged through the hydrological cycle. That cycle keeps water renewable.

Even so, the chapter asks why it is predicted that by 2025 nearly two billion people will live in absolute water scarcity.

Why water scarcity happens

Low rainfall is only part of the story. In most cases, scarcity comes from:

• Over-exploitation: a large population needs more water for homes and food. Irrigation expands for dry-season farming, and private wells and tube-wells lower groundwater levels, affecting food security.
• Unequal access to water among different social groups.
• Industrialisation and urbanisation: industries use a lot of water and hydroelectric power; growing cities pump their own groundwater.
• Poor water quality: waste, chemicals, pesticides and fertilisers can make available water hazardous.

Water quality and government programmes

Atal Jal covers Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Uttar Pradesh. A key aim is to change community attitudes from consumption to conservation.

Hydraulic structures in ancient India

• 1st century BC: Sringaverapura near Allahabad channelled the flood water of the Ganga.
• Chandragupta Maurya's time: dams, lakes and irrigation systems were built widely.
• 11th century: Bhopal Lake, one of the largest artificial lakes of its time.
• 13th–14th century: the Hauz Khas tank in Delhi, built by Alauddin Khalji to supply the Siri Fort area.

Multi-purpose river projects

A dam is a barrier across flowing water that obstructs, directs or slows the flow, often creating a reservoir. Dams are classified by structure and materials (timber, embankment or masonry) and by height (low, medium height or high).

A multi-purpose project uses stored water for several needs at once: irrigation, electricity, domestic and industrial water supply, flood control, recreation, inland navigation and fish breeding. Jawaharlal Nehru called dams the "temples of modern India" because they would link agriculture and the village economy with rapid industrialisation.

Examples:

• Bhakra-Nangal (Sutlej-Beas basin): hydel power and irrigation.
• Hirakud (Mahanadi basin): water conservation with flood control.
• Sardar Sarovar on the Narmada in Gujarat: covers Maharashtra, Madhya Pradesh, Gujarat and Rajasthan, and is meant to supply drought-prone and desert areas.

Problems with large dams

• They disturb natural river flow, causing too much sedimentation in the reservoir, rockier stream beds and poorer aquatic habitats.
• They fragment rivers, so fish find it hard to migrate, especially to spawn.
• Reservoirs submerge vegetation and soil, which decompose.
• Some flood-control dams have triggered floods because of sedimentation, and flood plains lose fertile silt.
• They have been linked to induced earthquakes, water-borne diseases and pests.
• Irrigation shifted farmers to water-intensive commercial crops, causing salinisation of soil.

Inter-state disputes: the Krishna-Godavari dispute arose when Karnataka and Andhra Pradesh objected to Maharashtra diverting more water at Koyna for a multi-purpose project, which would reduce downstream flow in their states.

Rainwater harvesting

Many see rainwater harvesting as a viable alternative, both socio-economically and environmentally.

Tankas: rain from sloping roofs flows down a pipe into an underground tank. The first spell is not collected because it cleans the roof and pipes. This stored rainwater, palar pani, is considered the purest natural water. The practice is declining in western Rajasthan because of the perennial Indira Gandhi Canal, though some families keep tankas as they dislike the taste of tap water.

Shillong faces water shortage even though Cherrapunjee and Mawsynram, about 55 km away, get the highest rainfall in the world.

Gendathur (Mysuru, Karnataka): nearly 200 households harvest rooftop rain. With 1,000 mm of rainfall, 80% collection efficiency and about 10 fillings, each house can collect about 50,000 litres a year.

Tamil Nadu is the first state to make rooftop rainwater harvesting compulsory for all houses, with legal provisions to punish defaulters.

Bamboo drip irrigation in Meghalaya is about 200 years old. About 18–20 litres of water enter the pipes and reduce to 20–80 drops per minute at the plant.

Remember this

• JJM target: 55 litres per person per day.
• "Temples of modern India": Nehru, about dams.
• Hirakud: Mahanadi. Bhakra-Nangal: Sutlej-Beas. Sardar Sarovar: Narmada.
• Palar pani = stored rainwater in Rajasthan.
• First state to make rooftop harvesting compulsory: Tamil Nadu.

Important questions with answers

1. Why is water called a renewable resource? (1 mark) It is continually renewed and recharged through the hydrological cycle.

2. Who called dams the "temples of modern India", and why? (1 mark) Jawaharlal Nehru, because dams would link agricultural development with rapid industrialisation.

3. Give three reasons for water scarcity in India. (3 marks) A large population needs more water for homes and food, so groundwater is over-used for irrigation. Industries and growing cities put heavy pressure on freshwater. Pollution from waste, chemicals and fertilisers makes available water unsafe.

4. What is a multi-purpose river project? Give one example. (3 marks) A project that uses a river's stored water for several purposes, such as irrigation, electricity, water supply, flood control, recreation and fish breeding. The Bhakra-Nangal project in the Sutlej-Beas basin gives both hydel power and irrigation.

5. Why have large dams faced opposition? (5 marks) They disturb natural river flow, causing sedimentation and poor habitats. They fragment rivers and block fish migration. Reservoirs submerge vegetation and soil. Some flood-control dams have caused floods, and flood plains lose fertile silt. They have been linked to earthquakes, water-borne diseases and salinisation of soil. Large projects also displace people and cause loss of livelihood.

6. Explain the tanka system of Rajasthan. (3 marks) Houses in Bikaner, Phalodi and Barmer had underground tanks connected to sloping roofs by pipes. The first rain was let go to clean the roof; later rain was stored as palar pani for the dry months.

7. What caused the Krishna-Godavari dispute? (3 marks) Karnataka and Andhra Pradesh objected to Maharashtra diverting more water at Koyna for a multi-purpose project, as it would reduce downstream flow and harm their agriculture and industry.

Common mistakes to avoid

• Saying water scarcity happens only in low-rainfall areas. Over-use, unequal access and pollution cause it too.
• Mixing up khadins (Jaisalmer) and johads (other parts of Rajasthan) with tankas.
• Placing Hirakud on the Godavari. It is on the Mahanadi.
• Forgetting that Tamil Nadu, not Karnataka, made rooftop harvesting compulsory.

To revise the dams map and check your answers, study this chapter with Joy.