NCERT Solutions for Class 7 Science Chapter 16 – Water A Precious Resource

Ans : (a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T) 
(b) Water shortage is a problem faced only by people living in rural areas. (F) 
(c) Water from rivers is the only source for irrigation in the fields. (F) 
(d) Rain is the ultimate source of water. (F) 

Ans : Rain water and the water from water bodies on earth's surface pass through the soil by the process of infiltration. The infiltrated water then gets accumulated in the aquifer deep under the ground. There are some layers of impermeable rocks which prevent the water in the aquifer from seeping down further. In this way, the groundwater is recharged. 

Ans : If the people of the fifty houses use the ten tube wells, then the water required by them is drawn from the ground. If these tube wells are used for long time, then the ground water would be reduced and the water table would go down. 

Ans : To maintain a garden, water iS necessary. Therefore, to minimise the use of water, we can apply the drip irrigation meth0d. In this meth0d, water iS supplied directly to the base of the Plants using narrow pipes, thereby reducing the loss Of water. 

Ans : The factors responsible for the depletion Of water table are as follows: 
(i)increasing population 
As a result of increasing population, all the facilities such as houses, Shops, roads, Offices, pavements, etc. increase to fulfil the increasing demands. This, in turn, decreases the open area for seepage Of water into the ground. 
(ii)increasing industries 
Most of the stages of manufacturing processes in industries require water. If the number of industries increases, then the water required by them will also increase. Therefore, increase of industries contributes to the depletion of water table. 
(iii)Agricultural activities 
India is an agricultural country and agriculture is impossible without water. The water 
for agriculture is mainly utilised from groundwater, rain water and canal water. As there is no rainfall in many places, agriculture cannot be entirely depended on rain water. Also, canal water is available in a few places only. Therefore, ground water is the main source of water for agricultural activities and this causes depletion of water table.