NCERT Class 9 Solutions: Drainage (Contemporary India-I) Chapter 3– Part 5
Q-2. Answer the following questions briefly
(i) Name the two head-streams of the Ganga. Where do they meet to form Ganga?
Answer: Two headstreams of the Ganga are Alaknanda and Bhagirathi and they meet at Deva Prayag.
(ii) Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?
Answer: The Brahmaputra River is known as Tsangpo in Tibet.
It has very little volume of water in Tibet and that’s way it has very little silt in this region. It passes through rocky region, additionally the less water causes less erosion.
When it enters in India it passes through heavy rainfall region and gains volume. The rain fed water contains the eroded silt, and the large volume of water is able to carry the larger amount of silt.
(iii) Which two peninsular rivers flow through trough?
Answer: Peninsular Rivers receive water from rainfall.
The two major west flowing peninsular rivers are the Narmada and the Tapi.
This exceptional behavior is because these rivers didn’t form valleys and instead they flow through faults (linear rift, rift valley, trough) created due to the bending of the northern peninsula during the formation process of Himalayas.
If they flowed in their own valleys they would have followed the natural slope and would move east.
(iv) State some economic benefits of rivers and lakes.
Economic benefits from rivers and lakes are as follow:
Rivers and lakes feed our cities, agriculture (irrigation) and industries which form the back-bone of any economy.
Rivers can be used for generating hydroelectricity powering homes, industries, offices and pumps.
A lake can be made into a good tourist attraction.
Since earlier times rivers are the centre of human civilization. Even now a days many big cities are located along the banks of rivers.
Rivers and lakes are also used for navigation, hydroelectricity, fisheries, etc.