JAC Board Class 9th Social Science Notes Geography Chapter 3 Drainage
→ Introduction
- The term drainage describes the river system of an area.
- The area drained by a single river system is called a Drainage Basin.
→ Drainage System in India
- The Indian rivers are divided into two major groups : (i) The Himalayan rivers, and (ii) The Peninsular rivers.
→ The Himalayan Rivers
- Most of the Himalayan rivers are perennial, which means they have water throughout the year.
- These rivers receive water from rain as well as from melted snow from the lofty mountains.
- The Indus, the Ganga and the Brahmaputra are major Himalayan rivers.
- These rivers are long and joined by many large and important tributaries.
- They have cut through the mountains, making Gorges.
- The Himalayan rivers have long courses from their source to the sea.
- These rivers perform intensive erosion activity in their upper course and carry huge loads of silt and sand.
- These rivers form meanders, ox-bow lakes and other depositional features during their middle and lower courses in the floodplains.
- These rivers have well-developed deltas.
→ The Indus River System
- The Indus river rises from China (Tibet) near Mansarovar lake. It flows westwards and enters India in the Ladakh region.
- It has a total length of 2900 km and it is one of the longest rivers of the world.
- Several tributaries like the Zaskar, Nubra, Shyok and Hunza join it in the Kashmir region. The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock.
- The Sutlej, Beas, Ravi, Chenab and Jhelum join together the Indus near Mithankot in Pakistan.
- The Indus flows southwards till it reaches the Arabian Sea, east of Karachi Port in Pakistan.
- As per the Indus Water Treaty signed between India and Pakistan in 1960, India can utilise only 20 percent of water carried by the Indus River system. Punjab,Haryana and southern and western parts of Rajasthan use this water for irrigation.
→ The Ganga River System
- This river system starts as the Bhagirathi from the Gangotri glacier in Uttarakhand. It is joined by the Alaknanda river at Devprayag to form the Ganga. Its length is over 2500 km.
- At Haridwar, the Ganga emerges from the mountains on to the plains. Its major tributaries are Yamuna, Ghaghara, Gandak and Kosi.
- The river Yamuna rises from the Yamunotri glacier in the Himalayas. It flows parallel to the Ganga as a right bank tributary. It meets the Ganga at Allahabad (Uttar Pradesh).
- The Ganga’s main tributaries which come from the peninsular uplands are Chambal, Betwa and Son.
- The Ganga flows eastwards till Farakka in West Bengal. Here, it divides into two branches and forms a distributary known as the Bhagirathi-Hooghly which flows into the Bay of Bengal.
- The main stream of the Ganga flows into Bangladesh where it is joined by the Brahmaputra coming from Assam to form the Meghna. It flows into the Bay of Bengal forming the Sunderban delta.
- The Namami Gange Programme, an integrated conservation mission was approved as a ‘flagship programme’ by the Government of India in June, 2014.
- The objective of this programme is the effective reduction of pollution, conservation and rejuvenation of the national river Ganga.
→ The Brahmaputra River System
- The Brahmaputra rises in Tibet, East of Mansarovar lake.
- It is slightly longer than the Indus and most of its course lies outside India.
- It is joined by many tributaries like Dihang, Lohit, etc. to form the Brahmaputra in Assam.
- It carries very little silt and water from Tibet as it is a cold and dry area.
- In Assam, it carries a large amount of water and silt because Assam is a high rainfall area.
- It has a braided channel in Assam, forming many riverine islands. Majuli Island the world’s largest riverine Island is formed by it.
- Brahmaputra overflows its banks during the monsoon every year, causing severe floods in Assam and Bangladesh.
→ The Peninsular Rivers
- The peninsular rivers are seasonal rivers as their flow is dependent on rainfall.
- These rivers have shorter and shallower courses as compared to the Himalayan rivers.
- Most peninsular rivers originate in the Western Ghats and flow towards the Bay of Bengal.
- The major rivers of the peninsular region are the Godavari, the Mahanadi, the Krishna and the Kaveri. They flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths.
- The Tapi and the Narmada are the only two long rivers which flow westwards and make estuaries. The drainage basins of the peninsular rivers are comparatively smaller in size.
- The important basins of peninsular rivers are as follows:
→ The Narmada Basin
- The Narmada rises in the Amarkantak Hills of Madhya Pradesh.
- It flows towards the west in a rift valley formed due to a geological fault.
→ The Tapi Basin
- The Tapi rises in the Satpura ranges in Betul district of Madhya Pradesh.
→ The Godavari Basin
- The river Godavari rises from the slopes of the Western Ghats in Nasik distrir Maharashtra.
- It is the longest river (about 1500 km) having the largest drainage basin and the largest delta among all peninsular rivers.
- It is also known as the Dakshin Ganga because of its length and the area it covers.
→ The Mahanadi Basin
- The Mahanadi rises in the highlands of Chhattisgarh and flows through Odisha to reach the Bay of Bengal.
→ The Krishna Basin
- The Krishna river rises from the Western Ghats near Mahabaleshwar.
- It flows into the Bay of Bengal before forming a large delta. Its length is about 1400 – km.
→ The Kaveri Basin
- The Kaveri river rises in the Brahmagiri range of the Western Ghats and reaches the Bay of Bengal, South of Cuddalore in Tamil Nadu.
- The length of this river is about 760 km. Its main tributaries are the Amravati, Bhavani, Hemavati and Kabini.
- The river Kaveri makes the second biggest waterfall in India known as Sivasamudram.
→ Lakes
- Lakes are useful to human beings in many ways. They are popular tourist destinations and are also used for sporting activities like boating, swimming, water sports, etc.
- India has many lakes. These include both permanent as well as seasonal lakes.
- Most of the freshwater lakes are in the Himalayan region. They are of glacial origin.
- Lakes help to regulate the flow of rivers. During heavy rainfall, they prevent flooding and during the dry season they provide water to rivers.
→ Role of Rivers in the Economy.
- Rivers have played an important role throughout human history. Water from the rivers is a basic natural resource, essential for various human activities.
- They provide water for irrigation, facility for navigation, fisheries and also provide water for domestic use like washing, cooking, drinking, etc.
- They also help to generate hyderoelectric power.
→ River Pollution
- Today, pollution in rivers has become a major problem because of growing domestic, municipal, industrial and agricultural activities.
- A heavy load of untreated sewage and industrial effluents are emptied into the rivers.
- This affects not only the quality of water, but also the self-cleansing capacity of the river.
- To tackle this problem, government has launched several plans like the National River Conservation Plan.
- National River Conservation Plan (NRCP) aims to improve the water quality of the rivers.
→ Drainage: A system of flowing water from the higher level to the lower level.
→ Stream: A stream is a small water body with surface water flowing within the bed and bank of the channel. It exists by itself and joins with other streams tc form a large river.
→ Basin: An area of land surrounding a large river or a lake or a sea from which water and streams run down into it.
→ Water divide: Any elevated area such as a mountain or an upland that separates two drainage basins is known as a water divide.
→ Perennial rivers: Rivers having water throughout the year.
→ Gorge: A Gorge is a narrow valley with steep, rocky sides located between hills or mountains.
→ Meanders: A meander is a winding curve or bend in a river. Meanders are the result of both erosional and depositional processes.
→ Catchment Area: An area drained by a major river and its tributaries.
→ Ox-bow lake: An oxbow lake is a u-shaped lake thet forms when a wide meander of a river is cut off, creating a free-standing body of water.
→ Delta: Delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water body.
→ Tributary and Distributary: A small river that flows into a large river is called a tributary, while a river that originates from a main river is called a distributary.
→ River System: A river alongwith its tributaries is called a river system.
→ Lake: A body of water, lying on a hollow on the Earth’s surface and being entirely surrounded by land is known as lake.
→ Estuary: An Estuary is a partially enclosed body of brackish water with one or more rivers or streams flowing into it and with a free connection to the open sea.
→ Fault: A fault is a fracture in a rock where there has been movement and displacement.
→ Rift Valley: A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geological rift or fault.
→ Braided Channel: A drainage channel in which bars and spits have been deposited to form islands around which the river flows.
→ Lagoon: An area of calm seawater that is separated from the ocean by reefs or sandbars.