NCERT Book Class 7 Science Water A Precious Resource

16 Water: A Precious Resource 

Jal Hai, To Kal Hai”

“If you have water, you can think of the future”

You are perhaps aware that 22 March is celebrated as the world water day! A school celebrated ‘water day’ and invited posters from the children of your age group. Some of the posters presented on that day are shown in Fig. 16.1. What is the message you get from these posters? Write your observations in your notebook and discuss them in the class.

Have you ever felt a shortage of water at home or at school? Your parents or teachers must very often be advising you not to waste water. No wonder we celebrate water day every year to attract the attention of everybody towards the importance of conserving water.

The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day. This amount is about two and a half buckets of water per person per day. Is your family getting at least this much of water? If yes, you should consider yourself fortunate because millions of people in our country do not get enough water. What about your friends and their families? Share your experience with them. In some places there is an acute shortage of water. Taps running dry, long queues for water (Fig. 16.2), fights, marches and protests for demand of water have become a common sight, especially during summers. Some of the newspaper clippings shown in Fig. 16.3 clearly indicate this message. Is it not true that we face acute shortage of water?

16.1 HOW MUCH WATER IS AVAILABLE

Look at the picture of the earth taken from space. Why does it appear blue? Surely, you can guess! You are aware that about 71% of the earth’s surface is covered with water. Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere. However, most of this water is not fit for human consumption. The water that is fit for use is freshwater. Perform the following activity to estimate roughly the relative amount of water available in some of these sources.

Exercises

1. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)

(b) Water shortage is a problem faced only by people living in rural areas. (T/F)

(c) Water from rivers is the only source for irrigation in the fields. (T/F)

(d) Rain is the ultimate source of water. (T/F)

2. Explain how groundwater is recharged?

3. There are ten tubewells in a lane of fifty houses. What could be the long term impact on the water table?

4. You have been asked to maintain a garden. How will you minimise the use of water?

5. Explain the factors responsible for the depletion of water table.

6. Fill in the blanks with the appropriate answers:

(a) People obtain groundwater through________ and ________.

(b) Three forms of water are ________, ________ and ________.

(c) The water bearing layer of the earth is ________.

(d) The process of water seepage into the ground is called ________.

7. Which one of the following is not responsbile for water shortage?

(i) Rapid growth of industries

(ii) Increasing population

(iii) Heavy rainfall

(iv) Mismanagement of water resources

8. Choose the correct option. The total water

(i) in the lakes and rivers of the world remains constant.

(ii) under the ground remains constant.

(iii) in the seas and oceans of the world remains constant.

(iv) of the world remains constant

Please refer to attached file for NCERT Class 7 Science Water-A Precious Resource