Facts that Matter | Extra Documents & Tests for Class 9 PDF Download

• The river system of an area is called drainage. Small streams flowing from different directions come together to form the main river, which ultimately drains into a large water body such as a lake or a sea or an ocean. The area drained by a single river system is called a drainage basin.
• Any elevated area that separates two drainage basins is known as a water divide.
• The Indian rivers are divided into two major groups – the Himalayan rivers and the Peninsular rivers.
  –    Most of the Himalayan rivers are perennial. They have long courses from their source to the sea.
  –    A large number of the Peninsular rivers are seasonal. They have shorter and shallower courses as compared to their Himalayan counterparts.
• The Himalayan rivers are comprised of the Indus, the Ganga and the Brahmaputra. Since these rivers are long and are joined by many large tributaries they form river systems.
  (i)    The Indus River System: With a total length of 2900 km, the Indus is one of the longest rivers of the world. It originates from a peak nearby Mansarovar lake in Kailash range of Greater Himalayas.
  (ii)    The Ganga River System: The Ganga originates from Gangotri situated in the glacier of Bhagirathi. At the spot of origin till its meeting with Alaknanda in Devprayag, she is called ‘Bhagirathi’. At Haridwar, the Ganga emerges from the mountains on to the plains. The Yamuna, the Ghaghara, the Gandak and the Kosi are its major tributaries.
  (iii)    The Brahmaputra River System: The Brahmaputra originates from Tibet. It flows parallel to the Himalayan mountains in Tibet. It flows eastwards parallel to the Himalayas. It takes U-turn at Namcha Barwa and enters India in Arunachal Pradesh. Here, it is called the Dihang and it is joined by the Dibang, the Lohit and many other tributaries to form the Brahmaputra in Assam.
• The Peninsular rivers are the Mahanadi, the Godavari, the Krishna, the Kaveri, the Narmada and the Tapi. The first four rivers flow eastward while the remaining two flows westward.
  (i)    The Mahanadi rises in the highlands of Chhattisgarh. It flows through Odisha to reach the Bay of Bengal. The length of the river is about 860 km.
  (ii)    The Godavari is the largest Peninsular river. It rises from the slopes of the Western Ghats in the Nasik district of Maharashtra. Its length is about 1500 km. It drains into the Bay of Bengal.
  (iii)    The Krishna rises from a spring near Mahabaleshwar. It flows for about 1400 km and reaches the Bay of Bengal.
  (iv)    The Kaveri rises in the Brahmagiri range of the Western Ghats and it reaches the Bay of Bengal in south of Cuddalore, in Tamil Nadu. The total length of this river is about 760 km.
  (v)    The Narmada rises in the Amarkantak hills in Madhya Pradesh. It flows towards west in a rift valley formed due to faulting. On its way to the sea, the Narmada creates many picturesque locations.
  (vi)    The Tapi rises in the Satpura ranges, in the Betul district of Madhya Pradesh.
• There are many lakes in India. These differ from each other in the size, and other characteristics. Most lakes are permanent; some contain water only during the rainy season.
• The Sambhar lake in Rajasthan is a salt water lake.
• The Wular lake in Jammu & Kashmir is the largest freshwater lake in India. The Dal lake, Bhimtal, Nainital, Loktak and Barapani are other fresh water lakes.
• Apart from natural lakes, the damming of the rivers for the generation of hydel power has also led to the formation of lakes such as Guru Gobind Sagar (Bhakra Nangal Project).
• Lakes and rivers are of great value to human beings. Water from the rivers is a basic natural resource, essential for various human activities. But growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water. The pollution level of many rivers has been rising.

Words that Matter

•     Drainage: The river system of an area.
•     Drainage basin: The area drained by a single river system.
•     Water divide: An elevated area, such as a mountain or an upland, that separates two drainage basins from each other.
•     Perennial rivers: Rivers which have water throughout the year.
•     Drainage patterns: The streams within a drainage basin form certain patterns.
•    Dendritic patterns: This pattern develops where the river channel follows the slope of the terrain. The stream with its tributaries resembles the branches of a tree, thus named dendritic.
• Trellis pattern: A river joined by its tributaries, at approximately right angles, develops such type of pattern.
• Rectangular pattern: This pattern develops on a strongly jointed rocky terrain.
• Radial pattern: This pattern develops when streams flow in different directions from a central peak or dome-like structure.
• River system: A river along with its tributaries.
• Delta: An area of land, shaped like a triangle, where a river has split into several smaller rivers before entering the sea.
• Shikaras: House boats found in the valley of Kashmir.
• Meandering river: The course of a river that does not follow a straight line.
• Ox-bow lakes: A meandering river across a flood plain forms cut offs that later develop into ox-bow lakes.
• Lagoon: A lake of salt water that is separated from the sea by an area of rock or sand.