1 Summary Geography Class 38 ## DISCUSSION ON THE UPSC 2023 PRELIMS PAPER (5:16 PM) ## DISCUSSION ON THE PREVIOUS CLASS (5:44 PM) ## DRAINAGE SYSTEM OF INDIA (5:49 PM) - The drainage system of India is mainly divided into Himalayan rivers and Peninsular rivers. - **Evolution of Himalayan Drainage System(5:55 PM)** - Widely accepted theory regarding the evolution of Himalayan drainage proposes the existence of a single river all along the entire stretch of Himalayas to the south of Shivaliks flowing from East to West called Indobrahma or Shivalik River. - It drained into the Gulf of Sindh. - The earlier drainage system was disturbed by three main events: - (a) Higher upliftment of the western Himalayas. - (b) Rising of Potwar plateau and Delhi ridge. - (c) Downthursting of Malda gap or Garo-Rajmahal gap. - This divided the entire river into Indus and its tributaries, Ganga and its tributaries, and the Brahmaputra and its tributaries. - **Peninsular Drainage System (6:08 PM)** - The peninsular drainage system is influenced by three major events: - (a) Submergence of the western side of the western ghats which disturbed the earlier symmetrical pattern of peninsular drainage and shortened the west-flowing rivers. - (b) Upliftment of the Himalayas which caused the northern part of the Vindhyas to tilt more towards the north and also the deepening of the rift valley of Narmada and Tapi. - (c) Slight tilting of the peninsular block from northwest to southeast direction, causing the slope towards the Bay of Bengal drainage. - **Difference between Himalayan and Peninsular Drainage (6:26 PM)** - | | | | --- | --- | | **Himalayan Drainage** | **Peninsular Drainage** | | The source of the drainage is glaciers. | The source of the drainage is rainfall. | | The Himalayan drainage is perennial. | The Peninsular Rivers are seasonal. | | The Himalayan rivers are dominated by the youth stage. | The Peninsular rivers are dominated by mature and old stages. | | They form V-shaped valleys. | They formed U-shaped valleys. | | They have high meandering. (High meandering due to high sediments and flowing through plain regions.) | These have low meandering. (Low meandering due to lower sediments and flowing through plateau region.) | | These have larger river basins and a catchment area. | These have smaller river basins and a catchment area. | | The deltas of the Himalayan rivers are very large. | The deltas present are small. Some rivers just have estuaries. | | Himalayan rivers are more navigable in the plains. | These are less navigable. | | The Himalayan drainage has many antecedent rivers. | In Peninsular drainage, there are only consequent rivers. | | The drainage pattern is mainly dendritic. | The drainage pattern is mainly rectangular or trellis. | - Examples of antecedent rivers are Indus, Brahmaputra, Sutlej, Ghagra, Gandak, and Kosi. Ganga and Yamuna are the consequent rivers. ## DRAINAGE PATTERNS (7:06 PM) - The flow characteristic of a river is called a drainage pattern. - (a) ==Dendritic Pattern== - It appears like the branches of a tree or a leaf. - This is characterized by the lack of structural control. - This is found in the Himalayan rivers. For example, the Ganga drainage pattern. - (b) ==Rectangular Pattern== - The river takes sharp turns. - It is found in the plateau regions with high structural control. - This is found in the case of the peninsular rivers. For example, the River Mahanadi, Godavari, Cauvery, etc. follows this drainage pattern. - (c) ==Trellis pattern== - The main river flows in the rift valley and tributaries join at the right angle. - This is possible when the river flows in the rift valley. For example, the Narmada and Tapi Rivers follow this drainage pattern. - (d) ==Radial Pattern== - In this, the different rivers originate from the raised platform or mountain and flow in various directions. - For example, from Amarkantak we have the Narmada, Son, and Hasdeo rivers originate. - (e)==Parallel Drainage== - The rivers flow parallel to each other and drain directly into the sea. - For example, West flowing rivers of the western ghats. ## MAPPING OF THE RIVERS (7:28 PM) - (a) ==Indus River System== - Indus flows through three countries namely China, Pakistan, and India. - It originates near Mansarovar Lake. - The right bank tributaries are Shyok, Gilgit, and Kabul. - The left bank tributaries are Jhelum, Chenab, Sutlej, Ravi, and Beas. - Nubra is the tributary of River Shyok. It comes from the Siachen glacier. - (b) ==Jhelum== - Jhelum originates from Verinag. - It flows through the Jhelum River valley called Kashmir Valley. - It passes through Wular Lake. It is the largest freshwater lake in India. - Jhelum River meanders while it is flowing through Kashmir. It is the only river that meanders in the youth stage. - In Pakistan, Jhelum merges with Chenab. - (c) ==Chenab== - It originates near Bara Lacha La. - Chenab formed after the confluence of the Chandra and Bhaga rivers. - Chandra originates from the Chandra tal. - Bhaga originates from the Suraj tal. - Barashigri glacier feeds the Chander tal. - (d) ==Ravi== - It originates from the Kullu Hills. - In ancient times it was called the Parushni River. - It forms the natural boundary between India and Pakistan along the northern part of Punjab. - (e) ==Beas== - It originates from the Rohtang. - It lies completely inside India. - It merges with Sutlej in Punjab. - (f) ==Sutlej== - It originates from Lake Rakas. Its water is salty. - Sutlej and Beas merge in Harikke. ## THE TOPIC FOR THE NEXT CLASS: DRAINAGE SYSTEM OF INDIA (CONTINUED)