1. Tick [√] the correct option.

a. Why is the Earth known as the ‘blue planet’? Choose the most appropriate reason.
i. The Earth’s atmosphere is filled with a layer of blue-coloured gas.
ii. Two-thirds of the Earth’s surface is covered in water.
iii. As Mars, next to the Earth, is known as the ‘red planet’, the Earth is called the ‘blue planet’.
iv. No colour other than blue is visible from space.

• Answer: (ii) Two-thirds of the Earth’s surface is covered in water. [√]

b. The distribution of water on the earth is shown in the given pie diagram. What is the percentage of saline water not fit for human consumption?
i. 97%
ii. 3%
iii. 2%
iv. 1%

• Answer: (i) 97% [√]

c. There are two statements marked as Assertion (A) and Reason (R). Read the statements and tick [√] the correct option.
Assertion (A): Most of the world’s largest deserts are in the subtropical regions.
Reason (R): The subtropical regions receive more precipitation than evaporation.
i. Both A and R are true, and R is the correct explanation of A.
ii. Both A and R are true, but R is not the correct explanation of A.
iii. A is true, but R is false.
iv. A is false, but R is true.

• Answer: (iii) A is true, but R is false. [√]
• Explanation: Deserts are found in subtropical regions because these areas experience high evaporation and very low precipitation, which is the opposite of what the Reason (R) states.

d. Read the clues below and identify the water conservation technique.

• It is a technique of supplying water in dry regions where the evaporation rate is very high.
• This technique helps plants to receive very little water at a time and hence, absorb the whole.
  i. Sprinkler irrigation
  ii. Contour bunding
  iii. Rainwater harvesting
  iv. Trickle irrigation
• Answer: (iv) Trickle irrigation [√]

e. Which of the following correctly defines the term ‘desalination’?
i. Removal of salt from seawater
ii. Recharging the underground water
iii. Avoiding wastage of water in domestic use
iv. Recycling of water from industrial waste and urban sewage by treating them, before releasing them into water bodies

Answer: (i) Removal of salt from seawater [√]

2. Answer the following questions in 10 to 20 words.

a. Why is ocean water not fit for human consumption?
Answer: Ocean water contains a high concentration of salt, which makes it saline. Our bodies cannot process this much salt.

b. Why are dams known as multipurpose river valley projects?

Answer: Dams are called multipurpose projects because they serve many needs at once, like irrigation, electricity generation, and flood control.

c. What do you mean by water scarcity?
Answer: Water scarcity means there is not enough safe, clean water available in a region to meet people’s daily needs.

d. How can we reduce water shortages in our immediate environment?
Answer: We can reduce water shortages by fixing leaks, using water-saving fixtures, and practicing rainwater harvesting.

Let Us Exercise

3. Answer the following questions in 50 to 70 words.

a. Water is our most precious resource. Justify the statement.

Answer: Water is our most precious resource because it is essential for all forms of life. Without water, no plant, animal, or human can survive. It is needed for drinking, growing food, and maintaining hygiene to prevent diseases. Unlike other resources, there is no substitute for water. Despite covering most of the Earth, the freshwater we can actually use is very limited, making its careful use extremely important for our future.

b. Explain any three causes of water scarcity.
Answer: Three main causes of water scarcity are:
1. Overuse and Mismanagement: As populations grow, we use more water for homes, farms, and industries, often wasting a lot of it.
2. Pollution: Factories and cities often dump untreated waste into rivers and lakes, making the water dirty and unsafe for use.
3. Unequal Distribution: Water is not spread evenly around the world. Some places get plenty of rain, while others, like deserts, are naturally dry and face constant scarcity.

c. Suggest any three measures of water conservation.
Answer: Three effective measures for conserving water are:
1. Rainwater Harvesting: Collecting rainwater from rooftops and storing it for later use recharges groundwater and provides water for daily chores.
2. Drip Irrigation: This method delivers water directly to the roots of plants in farms, reducing evaporation and saving a lot of water.
3. Fixing Leaks and Mindful Use: Repairing leaking taps and pipes, and turning off taps while brushing teeth can save thousands of litres of water every year.

d. How does the natural availability of water vary from place to place? Support your answer by providing suitable examples.
Answer: The natural availability of water varies greatly due to differences in climate and geography. For example, the state of Kerala in India receives very heavy rainfall, leading to abundant water resources. In contrast, a place like Rajasthan receives very little rain and is often dry, leading to water scarcity. Similarly, Canada has many freshwater lakes, while countries in the Middle East, like Saudi Arabia, have vast deserts with very few natural water sources.

4. Give reasons.

a. The total volume of water on the Earth is constant.
 Answer: The total volume of water is constant because of the continuous process of the water cycle. Water evaporates from oceans and land, forms clouds, and then falls back as rain or snow. It is constantly moving and changing form (solid, liquid, gas), but no water is created or destroyed; it is only recycled.

b. Only 1% of freshwater is available for human consumption.

Answer: Although 3% of Earth’s water is freshwater, most of it is locked away in glaciers and ice caps (about 2%). The remaining 1% is found in rivers, lakes, and underground sources, which is the portion we can easily access and use for our needs.

c. Water from industrial waste should be recycled before releasing into water bodies.
Answer: Water from industries contains harmful chemicals and toxins. If released directly into rivers or lakes, it poisons the water, killing fish and plants and making it unsafe for drinking or farming. Recycling this water by treating it removes the dangerous substances and protects our environment.

5. Think Ahead [HOTS]

a. Imagine walking two to three hours daily to get water from a water hole 12 km away from your home and back. How will this activity affect your life?

 Answer: This daily struggle would severely affect my life. I would have no time to go to school or do a proper job, keeping my family in poverty. The physical strain would lead to exhaustion and health problems. My family would also have very little water, making it hard to stay clean, leading to illnesses.

b. Apart from the one mentioned in the image, list four more effects of water scarcity.
 Answer: Four effects of water scarcity are:
1. Poor Health: Lack of clean water for drinking and hygiene causes diseases like cholera and diarrhea.
2. Hunger: Without enough water for irrigation, crops fail, leading to food shortages and famine.
3. Poverty: People, especially women and children, spend hours fetching water instead of working or studying.
4. Conflict: Different communities may fight over the limited available water resources.