Water Resources

Three-fourths of the earth's surface is covered with water, but only a small proportion is fresh water fit for use. About 96.5% of the world's water is in the oceans, and only about 2.5% is fresh water, much of it locked in ice sheets and glaciers. India receives nearly 4% of the global precipitation, yet many regions face water scarcity. Scarcity results not only from low rainfall but from overuse, unequal access, a growing population, intensive irrigation, industrialisation, urbanisation and pollution. You will study multi-purpose river projects such as the Bhakra Nangal project on the Sutlej and the Hirakud project on the Mahanadi, which Jawaharlal Nehru called the 'temples of modern India'. The chapter discusses their benefits and problems, including displacement of people, the Narmada Bachao Andolan and inter-state water disputes. Finally, it describes traditional and modern rainwater harvesting systems: guls and kuls in the Western Himalayas, inundation channels in Bengal, khadins and johads and rooftop tankas in Rajasthan, bamboo drip irrigation in Meghalaya, and rooftop harvesting in Gendathur in Karnataka and in Tamil Nadu.

Detailed Worksheet: Water Resources Section A - Definitions (10 marks) 1. What is water scarcity? (2 marks) 2. What is a multi-purpose river project? Give two examples. (2 marks) 3. What are 'guls' and 'kuls'? (2 marks) 4. What is rooftop rainwater harvesting? (2 marks) 5. What is the Narmada Bachao Andolan? (2 marks) Section B - Calculations and Applications (15 marks) 6. A house has a flat roof of area 120 square metres in a town with annual rainfall of 500 mm. Calculate the volume of rainwater falling on the roof in cubic metres and in litres (1 cubic metre = 1,000 litres). If 80% can be collected, how much water is harvested? (3 marks) 7. A tanka in Rajasthan is a cylindrical tank of radius 2 m and depth 3 m. Calculate its capacity in cubic metres and litres (take pi = 3.14). For how many days could it supply a family using 150 litres per day? (3 marks) 8. In Gendathur village, Karnataka, about 200 households have installed rooftop systems, each harvesting about 50,000 litres a year (illustrative). Calculate the total water harvested in a year in litres and in cubic metres. (3 marks) 9. Of the world's water, about 96.5% is in oceans and 2.5% is fresh water. If about 70% of fresh water is in ice sheets and glaciers, calculate the percentage of the world's total water that is fresh water locked in ice. (3 marks) 10. A city of 20 lakh people needs 135 litres per person per day. Calculate the daily and annual requirement in crore litres (1 year = 365 days). If groundwater supplies 40% of it, calculate the daily groundwater use. (3 marks) Section C - Diagrams (10 marks) 11. Draw an outline map of India and mark the Bhakra Nangal, Hirakud, Sardar Sarovar, Tehri and Nagarjuna Sagar dams. (4 marks) 12. Draw a labelled diagram of a rooftop rainwater harvesting system with a tanka. (3 marks) 13. Draw a flowchart showing the benefits and problems of multi-purpose river projects. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. 'Water scarcity in most cases is caused by over-exploitation, excessive use and unequal access to water among different social groups.' Explain with examples. (5 marks) 15. Why are multi-purpose river projects facing increasing opposition? Discuss the social and environmental problems with examples of the Narmada Bachao Andolan and the Tehri Dam Andolan. (5 marks) 16. Why is rainwater harvesting important in India? Explain how traditional systems in different regions suit local geography, and how modern adaptations are reviving them. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Show the steps of all calculations with units. Draw maps and diagrams neatly with labels.