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Page No 249:

Question A:

Solve the following crossword puzzle:
Figure

Across
1. The process of seeping of water into the ground
3. It is a type of irrigation

Down
2. The decrease in the water table due to overuse of groundwater
4. A method of conserving water

Answer:

Page No 249:

Question B.1:

Top level of water present under the ground is called
(a) groundwater
(b) water table
(c) aquifer
(d) all of these

Answer:

(b) water table

The top level of water present under the ground is called water table.

Page No 249:

Question B.2:

Water can be watered for conserving water by
(a) drip irrigation
(b) sprinkler irrigation
(c) both (a) and (b)
(d) none of these

Answer:

(c) Both (a) and (b)
Plants can be watered for conserving water by drip irrigation and sprinkler irrigation.

Page No 249:

Question B.3:

Water scarcity in plants causes
(a) wilting
(b) leaves dry up
(c) leaves droop
(d) all of these

Answer:

(d) all of these

Plants wilt, their leaves droop and, ultimately, they dry up if they are not watered for few days.

Page No 249:

Question B.4:

The percentage of ocean water on earth is
(a) 97%
(b) 3%
(c) 2%
(d) 0.6%

Answer:

(a) 97%
97% of the total water available on earth is in seas and oceans.

Page No 249:

Question B.5:

World water day is celebrated on
(a) 22nd Feb
(b) 22nd March
(c) 22nd April
(d) 22nd May

Answer:

(b) 22nd March
World Water Day is celebrated on 22nd March every year.

Page No 249:

Question B.6:

Which of the following is not a cause of depletion of water table?
(a) overpopulation
(b) industrialisation
(c) deforestation
(d) flood

Answer:

(d) Flood
Flood is not a cause of the depletion of water table.



Page No 250:

Question 1:

The physical and chemical properties of water mostly from the attraction that the atoms in water molecules have form one another. It is because of this strong attraction that the energy required to melt ice and boil liquid water is greater than might otherwise be predicted. Have you heard of this strong attraction? You must take the help of your teacher.

Answer:

Water consists of hydrogen and oxygen atoms. Oxygen atoms have a strong affinity for electrons. Because of this, it is slightly negatively charged. Hydrogen, being positively charged, gets attracted towards the oxygen atoms of the other molecules of water, forming intermolecular hydrogen bonds. Breaking of these strong hydrogen bonds requires huge amounts of energy. So the boiling point of water is higher than what is predicted.

Page No 250:

Question 2:

Why do we feel the need for conservation of water is more today in comparison to earlier days?

Answer:

The rapid growth in population has resulted in excess usage of water these days. Overpopulation has led to an increase in agricultural and industrial activities, both of which depend on water at all levels of productivity. Urbanisation and industrialisation have led to the destruction of forests, resulting in scarcity of rainfall, soil erosion and the depletion of water table. Hence, the need for conservation of water is more today in comparison to earlier days.

Page No 250:

Question 3:

Wells dug to get groundwater, often dry up after some time. Why?

Answer:

Following are the reasons for wells drying up.
(i) Over usage of water from the wells
(ii) Scarcity of rainfall, which is the main source of water for wells
(iii) Depletion of water table due to the excess extraction of water from the ground

Page No 250:

Question B.7:

Traditional way of collecting water is
(a) bawri
(b) tube well
(c) well
(d) tap

Answer:

(c) Well
Wells are the traditional ways to collect water.

Page No 250:

Question C:

Fill in the blanks:
1. In rural areas ............................. are the main source of water.
2. Underground water is also called ............................. .
3. The three forms of water are .............................,  ............................. and ............................. .
4. The top level of underground water is called ............................. .
5. ............................. can be done be increase the level of water table.

Answer:

1. In rural areas wells and hand pumps are the main source of water.
2. Underground water is also called aquifer.
3. The three forms of water are solid, liquid and gas.
4. The top level of underground water is called water table.
5. Infiltration can be done to increase the level of water table.

Page No 250:

Question D:


Match the items in Column A with the items in Column B:

Column A Column B
1. Rain (a) Reservoirs of water
2. Dams (b) Groundwater
3. Aquifer (c) Solid
4. Glaciers and ice caps (d) Main source of water
  (e) Vapour

Answer:

 Column A  Column B
1. Rain (d) Main source of water
2. Dams (a) Reservoirs of water
3. Aquifer (b) Groundwater
4. Glaciers and ice caps (c) Solid

Page No 250:

Question E:

Write True (T) of False (F) against the following statements in the given brackets:
1. Rain is the major source of water of agriculture in our country. ( )
2. Water harvesting should be encouraged to conserve water. ( )
3. Level of water table at a place remains same throughout the year. ( )
4. Land areas without trees help in better seepage of water. ( )
5. Groundwater is also called aquifer. ( )

Answer:

1. True

2. True

3. False
The level of water table varies according to the usage of water.

4. False
Land areas without trees cause soil erosion, which decreases the ability of holding water. Hence, there is less seepage of water.

5. True



Page No 251:

Question A.1:

Which is the most important source of water for farmers?

Answer:

Rainwater is the most important source of water for farmers.

Page No 251:

Question A.2:

In which forms does water exist on the earth?

Answer:

Water exists on Earth in three forms: solid, liquid and gas.

Page No 251:

Question A.3:

Why should we try to recharge bawris?

Answer:

Bawris are the main source of water in hilly areas and snow-studded areas. To avoid the acute shortage of water in the future, we should try to recharge the bawris.

Page No 251:

Question A.4:

What do you mean by the mean water table?

Answer:

Water table refers to the top level of underground water.

Page No 251:

Question A.5:

Name the main source of groundwater.

Answer:

Rainwater is the main source of groundwater.

Page No 251:

Question A.6:

Write two ways of water conservation.

Answer:

Water can be conserved in the following ways:
(i) Rain water harvesting
(ii) Recycling of water in industries to use it for irrigation

Page No 251:

Question A.7:

Give two reasons for water scarcity.

Answer:

Following are two of the reasons for water scarcity:
(i) Increase in population
(ii) Increase in urbanisation and industrialisation

Page No 251:

Question B.1:

What are the ill effects of water scarcity on plants?

Answer:

The ill effects of water scarcity on plants are as follows:
(i) Plants wilt and their leaves droop and they dry up if they are not watered for a few days.
(ii) If water is scarce, germination does not take place in plants.
(iii) It affects the quantity as well as the quality of the crops.

Page No 251:

Question B.2:

Why is groundwater clean and safe to drink?

Answer:

Groundwater is clean and safe to drink because it passes through several layers of soil. These layers act as natural filters that remove the impurities in the water.

Page No 251:

Question B.3:

What are the reasons for lowering of water table in your area?

Answer:

The reasons for lowering of water table are as follows:
(i) Overpopulation, which results in the excess usage and wastage of water
(ii) Increased industrial activities, which require excess amount of water at all the levels
(iii) Scarcity of rainfall due to deforestation and urbanisation

Page No 251:

Question B.4:

State four causes of scarcity of water in India?

Answer:

In India, scarcity of water mainly occurs due to the following reasons:
(i) Overpopulation
(ii) Deforestation due to industrialisation and urbanisation
(iii) Following unscientific irrigation practices that result in huge wastage of water
(iv) Water pollution

Page No 251:

Question B.5:

What do you mean by drip irrigation?

Answer:

Drip irrigation is one of the irrigation practices followed in order to prevent wastage of water. In this method, water is allowed to fall drop by drop at the roots of the plants. By this method, plants get sufficient water and wastage of water by flooding the field is also prevented.

Page No 251:

Question B.6:

What is infiltration?

Answer:

Infiltration is the process of seeping of water into the ground. Rainwater and water from rivers, lakes and other resources seep through the soil. This water flows through several layers of soil and reaches the hard rocks underneath. This forms the underground water.

Page No 251:

Question B.7:

How do the people get water in villages?

Answer:

Groundwater is the main source of water for people living in rural areas. Water from groundwater resources such as wells and hand pumps are used for domestic purposes. In the absence of groundwater, people have to travel long distances to fetch water from nearby lakes or ponds.

Page No 251:

Question C.1:

What is the effect of water scarcity on the life of people?

Answer:

Scarcity of water has an adverse effect on  people, which may be listed as follows:
(i) It would be very difficult to find water for the essential day to day activities.
(ii) People have to travel long distances to fetch water or pay a high price for buying water.
(iii) This leads to poor sanitation, which may cause epidemic diseases.
(iv) The agricultural activities and also production in industries get affected due to the lack of water. As a result, crop productivity, animal productivity and industrial productivity decrease.

Page No 251:

Question C.2:

List six methods used in water conservation.

Answer:

The methods by which water can be conserved are as follows:
(i) We have to be very cautious while using water. Care has to be taken to avoid wastage and misuse of water.
(ii) Water recycling should be encouraged in industries so that recycled water can be utilised for irrigation.
(iii) Following scientific methods of irrigation like drip irrigation or sprinkler irrigation provides sufficient amount of water; hence, it reduces wastage of water.
(iv) Constructing dams and bunds across the rivers which will help recharge the water table.
(v) Growing more trees will help in the replenishment of groundwater.
(vi) We must encouraging rain water harvesting to conserve rainwater as well as to recharge groundwater.

Page No 251:

Question C.3:

How do people get water supply to meet their domestic needs?

Answer:

People get water supply by the following ways:
(i) In cities and towns, water is supplied to homes through a network of pipes, which are drawn from the nearby lakes or rivers by the Municipal Water Distribution System.
(ii) In the areas where there is a shortage of groundwater, water tankers supply water.
(iii) Groundwater is the main source of water in rural areas. Groundwater sources such as wells and hand pumps provide water for domestic use. Apart from this, nearby lakes and rivers also serve as major sources of water.
(iv) Sometimes, water for irrigation is supplied through the canals from the reservoirs present in the dams that are constructed across the rivers.
(v) In hilly areas and snow-studded regions, bawris serve as the source of water.
(vi) Rainwater, which is the most important source of water, fills up the water bodies, thereby providing water for domestic use.

Page No 251:

Question C.4:

Make a diagram showing aquifer and water table and label them.

Answer:



The diagram showing an aquifer and water table with the labels.

http://maps.unomaha.edu/maher/GEOL1010/lecture7/drawdownUSGS.jpg

Page No 251:

Question C.5:

What is rainwater harvesting? How does it help to solve the water problem?

Answer:

Collecting rainwater for use in the future by storing it in storage reservoirs is called rainwater harvesting. When rainwater falls on the ground, it runs down into lakes, rivers, ponds, seas and oceans. Some of it also evaporates into the air. Thus, precious rainwater is lost. To stop this loss of water, rainwater is collected and stored for future use. By doing so, rainwater will be conserved. When rainwater seeps into the ground, the water table is replenished.

Page No 251:

Question C.6:

How do agricultural activities causes a depletion of water table?

Answer:

Agriculture mainly depends on rainfall. Rainfall is variant and unpredictable. The increase in population demands agriculture to produce more food. Irrigation, an important part in agriculture, requires rainfall. When there is scarcity of rainfall, farmers rely on groundwater resources to meet their needs of irrigation. Thus, excess groundwater is used in irrigation, which causes a depletion in the water table.



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