Topic outline

    • Drainage

      Q36. Which river is known as Dihang?

      Ans. On reaching the Namcha Barwa (7757 m), Brahmaputra river takes a ‘U’ turn and enters India in Arunachal Pradesh through a gorge. Here, it is called the Dihang.


      Q37. How is Brahmaputra river different from other north Indian river?

      Ans. Unlike other north Indian rivers the Brahmaputra is marked by huge deposits of silt on its bed causing the river bed to rise. The river also shifts its channel frequently.


      Q38. Where are India's most of the freshwater lakes located and why?

      Ans. Most of the fresh water lakes are in the Himalayan region. They are of glacial origin. They formed when glaciers dug out a basin, which was later filled with snowmelt.


      Q39. List the factors on which the drainage patterns depend.

      Ans. The streams within a drainage basin form certain patterns, depending on the slope of land, underlying rock structure as well as the climatic conditions of the area.


      Q40. Why are Peninsular rivers seasonal in nature?

      Ans. A large number of the Peninsular rivers are seasonal, as their flow is dependent on rainfall. During the dry season, even the large rivers have reduced flow of water in their channels.


      Q41. From which place does Yamuna river originate?
      Mention the journey of river Yamuna.

      Ans. The river Yamuna rises from the Yamunotri Glacier in the Himalayas. It flows parallel to the Ganga and as a right bank tributary, meets the Ganga at Allahabad.


      Q42. Mention the composition of water on earth's surface.

      Ans. 71 per cent of the world’s surface is covered with water, but 97 per cent of that is salt water. Of the 3 per cent that is available as freshwater, three quarters of it is trapped as ice.


      Q43. Which tributaries join Ganga from peninsular uplands?
      What is the main feature of the tributaries of Ganga joining from the peninsula?

      Ans. The main tributaries, which come from the peninsular uplands, are the Chambal, the Betwa and the Son. These rise from semi arid areas, have shorter courses and do not carry much water in them.


      Q44. Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?

      Ans. In Tibet the river carries a smaller volume of water and less silt as it is a cold and a dry area. In India it passes through a region of high rainfall. Here the river carries a large volume of water and considerable amount of silt.


      Q45. Why are rivers considered to be the lifeline of human civilization?

      Ans. Rivers have been of fundamental importance throughout the human history. Water from the rivers is a basic natural resource, essential for various human activities. Therefore, the river banks have attracted settlers from ancient times. These settlements have now become big cities.


      Q46. How does river Ganga form large meanders?

      Ans. The plains from Ambala to the Sunderban stretch over nearly 1800 km, but the fall in its slope is hardly 300 metres. In other words, there is a fall of just one metre for every 6 km. Therefore, the river develops large meanders.


      Q47. What do Himalayan rivers do in their upper, middle and lower course?

      Ans. They perform intensive erosional activity in their upper courses and carry huge loads of silt and sand. In the middle and the lower courses, these rivers form meanders, oxbow lakes, and many other depositional features in their flood plains.

      Q48. Briefly discuss the Indus water treaty (1960).

      Ans. According to the regulations of the Indus Water Treaty (1960), India can use only 20 per cent of the total water carried by Indus river system. This water is used for irrigation in the Punjab, Haryana and the southern and western parts of Rajasthan.


      Q49. What is meant by a water divide? Give an example.

      Ans. Any elevated area, such as a mountain or an upland, separates two drainage basins. Such an upland is known as a water divide.

      Example: The main water divide in Peninsular India is formed by the Western Ghats, which runs from north to south close to the western coast.

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