Water: A Precious Resource

About 71 percent of the Earth's surface is covered with water, yet most of it is salty seawater. Only a tiny fraction of the total water is fresh water fit for human use; much of the rest is locked as ice in the polar caps and glaciers. Water exists as solid (ice and snow), liquid (rivers, lakes, groundwater) and gas (water vapour), and it keeps circulating through the water cycle by evaporation, condensation and precipitation. Rainwater seeping into the ground, called infiltration, fills the spaces between soil and rocks; the upper surface of this water is the water table, and water stored between layers of hard rock is an aquifer. The water table falls when we draw out more groundwater than is recharged, because of rising population, industries, agriculture, and less infiltration due to concrete surfaces and deforestation. Rainfall is also unevenly distributed across India. We can manage water better by rainwater harvesting, reviving traditional systems like bawris (stepwells), using drip irrigation, fixing leaking taps and reusing water. Every drop must be saved.

Detailed Worksheet: Water: A Precious Resource Section A - Definitions (10 marks) 1. What is the water table? (2 marks) 2. Define infiltration and aquifer. (2 marks) 3. What is groundwater? Name two ways it is drawn out. (2 marks) 4. What is rainwater harvesting? (2 marks) 5. What is drip irrigation? Why is it useful? (2 marks) Section B - Calculations and Applications (15 marks) 6. Name the three forms of water with one place where each is found on Earth. (3 marks) 7. Give three reasons for the depletion of the water table. (3 marks) 8. The United Nations recommends about 50 litres of water per person per day. A family of 4 uses 300 litres a day. (i) How much is the recommended amount for them? (ii) How much more are they using? (iii) Suggest two ways to cut down. (3 marks) 9. A leaking tap wastes one drop per second. If 20 drops make 1 mL, how much water is wasted in one day? Give your answer in litres. (3 marks) 10. A roof of area 100 square m receives 800 mm of rain in a year. Using volume = area x rainfall depth, find the volume of rainwater in cubic metres and litres (1 cubic m = 1000 litres). (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of the water cycle showing evaporation, condensation, precipitation, infiltration and groundwater. (4 marks) 12. Draw a labelled diagram showing the water table, aquifer, hand pump and the layers of soil and rock. (3 marks) 13. Draw a labelled diagram of a rooftop rainwater harvesting system. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Bawris were built in many parts of India, such as in Delhi and Rajasthan. (i) What is a bawri? (ii) Why were they built? (iii) Why did many fall into disuse? (iv) How can such traditional systems be revived? (v) Name one more traditional water harvesting method. (5 marks) 15. A city with many new buildings and paved roads found its wells drying up. (i) Why does paving reduce groundwater? (ii) What other reasons might cause wells to dry? (iii) Suggest two solutions. (iv) What can students do? (5 marks) 16. Bhujpur village in Kutch, a dry area, built check dams to collect rainwater. (i) Why are check dams useful? (ii) How did they help the water table? (iii) Why is community participation important? (iv) What lesson can other villages learn? (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Show units in calculations and label diagrams clearly.