WATER : A PRECIOUS RESOURCE

 NOTES 

The upper limit of groundwater is called water table. It represents the depth of water filled area at a given place. The water table rises and falls depending upon the amount of rainwater that seeps into the groundwater and how much groundwater is drawn out for irrigation and industry. The seeping down of rainwater into the groundwater is called infiltration. The groundwater thus gets recharged by this process.

At some places, the groundwater is stored between layers of hard rock below the water table. This is aquifer which contains the groundwater usable by tubewells and handpumps. These sources however, have limited sources of water and may get exhausted if used excessively.

Exercise Questions

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)

Solution:

a) True

b) False

c) False

d) False

2. Explain how groundwater is recharged.

Solution:

The rainwater and water from other sources such as rivers and ponds seep through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. The groundwater thus gets recharged by this process.

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

Solution:

If ten tube-wells in a lane of fifty houses are situated, the groundwater will get used for domestic purposes. This results in depletion of groundwater level and water table would go down.

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

Solution:

We can reduce the usage of water for gardening by adopting drip irrigation method. In this method, water will reach the roots of the plant drop by drop, which will reduce the wastage of water.

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

Solution:

Factors responsible for the depletion of the water table are as follows:

Increase in population; Increase in population leads to increased demand for water for domestic and drinking purpose. This reduces the water table.

Industrialisation: Industries need a lot of water for manufacturing purposes. This reduces the water table.

Agriculture: Agriculture requires a lot of water for growing crops; this results in 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 ________.

Solution:

(a) People obtain groundwater through tube wells and hand pumps.

(b) Three forms of water are ice, water and vapour.

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

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

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

(i) Rapid growth of industries

(ii) Increasing population

(iii) Heavy rainfall

(iv) Mismanagement of water resources

Solution:

The answer is (iii) Heavy rainfall

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.

Solution:

The answer is (iv) of the world remains constant.

9. Make a sketch showing groundwater and water table. Label it.

Solution: