25 August, 2017

Class IX: Chapter 3 - Drainage

 Objectives and Goals:
1. Drainage.
2. Drainage Basin, Water Divide and Perennial.
3. The Drainage System of India.
4. The division of Indian rivers (i.e. The Himalayan Rivers and the Peninsular Rivers).
5. The Drainage Pattern (i.e. Dendritic, Trellis, Rectangular and Radial Patterns).
6. The Course of the River and features formed by river during it's course.
7. The Himalayan Rivers (i.e. The Indus River System, The Ganga River System and The Brahmaputra River System).
8. The Peninsular Rivers (i.e. The Narmada Basin, The Tapi Basin, The Godavari Basin, The Mahanadi Basin, The Krishna Basin and The Kaveri Basin).
9. The Lakes and its value to the mankind.
10. The Role of rivers in the economy.
11. The River Pollution and how we can protect our rivers.
12. The National River Conservation Plan (NRCP).

 Drainage Patterns:
Depending on the slope of land, underlying rock structure and climate of an area, the streams in a drainage basin form certain patters. Different types of drainage pattern are as follows:
1. Dendritic Drainage Pattern: When the river channel follows the slope of the terrain, it develops dendritic pattern. The stream and its tributaries resemble the branches of a tree. Hence, it is called dendritic pattern.
2. Trellis Drainage Pattern: When a river is joined by its tributaries at almost right angles, it develops a trellis pattern. Trellis pattern develops where hard and soft rocks exist parallel to each other.
3. Rectangular Drainage Pattern: When rocks are strongly joined, then rectangular pattern develops.
4. Radial Drainage Pattern: When the streams flow in different directions from a central peak or dome like structure, a radial pattern is developed.
It is important to note that a combination of different patterns may develop in the same drainage basin.

 

Course of a River:
1. Rivers are the most important agents of degradation.
2. Work of the river depends on two factors: -
(a) The volume of Water.
(b) Slope of river beds.
3. Common features formed by river while flowing through mountains: -
(a) 'I' & 'V' shaped valleys.
(b) Gorges or Canyons (deep valleys).
(c) Waterfalls, etc.
4. Common features formed by river while flowing through plains: -
(a) Meanders(curves & large bends or loops)
(b) Oxbow Lakes
(c) Flood Plains
(d) Levees (slightly raised river banks)
5. Common features formed by river when it reaches near the sea: -
(a) River breakup into various streams called 'distributaries'.
(b) Delta

 

 

The Drainage System of India
The drainage systems in India can be divided into two major groups:
1. The Himalayan Rivers 2. The Peninsular Rivers.

 

1. The Himalayan Rivers:
The Himalayan Rivers: Most of the Himalayan Rivers are perennial (i.e. they have water throughout the year).
River System: A river along with its tributaries forms a river system.
The three major Himalayan River Systems are:
1. The Indus River System
2. The Ganga River System
3. The Brahmaputra River System

 

The Indus River System:

  • The river Indus originates in Tibet; near Lake Mansarowar. It enters India in the Ladakh district of Jammu & Kashmir.
  • Zaskar, Nubra, Shyok and Hunza are the main tributaries which join the Indus in Kashmir region.
  • After flowing through Baltistan and Gilgit, the Indus emerges from the mountains at Attock.
  • Sutlej, Beas, Ravi, Chenab and Jhelum join together and enter the Indus near Mithankot in Pakistan.
  • After that, the Indus flows southwards and finally reaches the Arabian Sea, east of Karachi.
  • Indus is 2900 km long.
  • The Indus plain has a very gentle slope.
  • A little over one-third of the Indus basin is located in India; in the states of Jammu & Kashmir, Himachal Pradesh and Punjab. The rest of the portion is in Pakistan.

 

 The Ganga River System:

  • The river Ganga in its origin state is known as Bhagirathi. It is fed by the Gnagotri Glacier.
  • Bhagirathi is joined by Alaknanda at Devprayag in Uttarakhand.
  • Ganga emerges from the mountains on to the plains at Haridwar.
  • Yamuna, Ghaghara, Gandak and Kosi are the major tributaries of Ganga.
  • Yamuna originates from the Yamunotri Glacier in the Himalayas. It meets Ganga at Allahabad.
  • Ghaghara, Gandak and Kosi rise in the Nepal Himalaya.
  • Chambal, Betwa and Son are the major tributaries which come from the peninsular uplands.
  • After taking waters from various tributaries, Ganga flows towards east till Farakka (West Bengal).
  • The river bifurcates at Farakka. The Bhagirathi-Hooghly (a distributary) flows towards south to the Bay of Bengal.
  • The mainstream flows southwards into Bangladesh; where it is joined by the Brahmaputra. It is known as Meghna.
  • Finally, the Ganga and the Brahmaputra flow into the Bay of Bengal forming the Sunderban Delta.
  • The total length of river Ganga is 2500 km.
  • Ambala is located on the water divide between Indus and Ganga.
  • Length of plains from Ambala to Sundarban detla is around 1800 kms. But the slope is only 300 metres.
  • In this area river develops large meanders.

 The Brahmaputra River System:

  • The Brahmaputra rises in Tibet; east of Mansarowar lake.
  • River Brahmaputra is a little longer than the river Indus.
  • Most of the course of the Brahmaputra lies outside India, popularly known as Tsangpo . It flows eastwards parallel to the Himalayas.
  • After reaching Namcha Barwa, it takes a "U" turn (also known as Hair Pin turn) and enters India in Arunachal Pradesh through a gorge known as Dihang. In this region the river is known as Dihang.
  • It is joined by Dibang, Lohit, Kenula and many other tributaries and finally forms the Brahmaputra in Assam.
  • Majuli (in Assam) is the largest riverine island in the world. The island had a total area of 1,250 square kms.
  • Unlike other north Indian rivers the Brahmaputra gets huge deposits of silt on its bed. This results in rising of the river bed.
  • River Brahmaputra is known by different names in different regions: (Tsangpo in Tibet, Brahmaputra in India & Jamuna in Bangladesh).

 

THE PENINSULAR RIVER SYSTEM

  • Most of the Peninsular Rivers are seasonal because they depend on rainfall for water.
  • These rivers have shorter and shallower courses; compared to the Himalayan rivers.
  • Most of the major rivers of the Peninsula flow eastwards and drain into the Bay of Bengal Major rivers are The Mahanadi, The Godavari, The Krishna and The Kaveri.
  • These rivers make deltas at their mouths.
  • The Narmada and Tapi are the only long rivers, which flow westwards and make estuaries.
  • The drainage basins of the peninsular rivers are smaller in size.

The main differences between Delta and Estuary are as follows:

 

The Narmada Basin:

  • The Narmada rises in the Amarkantak hills (Maikal Range) in the Madhya Pradesh.
  • The river flows towards the west through rift valleys.
  • The Narmada basin covers parts of Madhya Pradesh and Gujarat.
  • All the tributaries of the Narmada are very short.
  • Most of the tributaries join the Narmada at right angles.
  • The river travels a distance of 1,312 km.
  • The major tributaries of the Narmada river are the Hallon River, Banjar River, Barna River and Tawa River.

 The Tapi Basin:

  • The Tapi rises in the Satpura ranges, in Betul district of Madhya Pradesh.
  • The basin of Tapi covers parts of Madhya Pradesh, Gujarat and Maharashtra.
  • The river flows towards the west through rift valleys parallel to river Narmada.
  • The river travels a distance of 724 km.
  • Tributaries of the Tapti River are the Mindhola River, Girna River, Panzara River, Waghur River, Bori River and Aner River.

 The Mahanadi Basin:

  • This river originates in the highlands of Chhattisgarh and drains into the Bay of Bengal.
  • It is about 860 km long.
  • The Mahanadi basin covers Maharashtra, Chhattisgarh, Jharkhand and Orissa.

 The Godavari Basin:

  • This is the longest Peninsular river.
  • This river is popularly known as "Dakshin Ganga".
  • Its drainage basin is also the largest among the peninsular river basins.
  • The Godavari is about 1500 km long.
  • It originates from the slopes of the Western Ghats in Nasik district of Maharashtra and drains into the Bay of Bengal.
  • The Godavari basin covers parts of Maharashtra, Madhya Pradesh, Orissa and Andhra Pradesh.
  • Purna, Wardha, Pranhita, Manjra, Waiganga and Penganga are the main tributaries of Godavari.

 The Krishna Basin:

  • The Krishna originates near Mahabaleshwar and drains into the Bay of Bengal.
  • It is about 1400 km long.
  • Tungbhadra, Koyana, Ghatprabha, Musi and Bhima are some of its tributaries.
  • The Krishna basin covers Maharashtra, Karnataka and Andhra Pradesh.

The Kaveri Basin:

  • The Kaveri originates in the Brahmagiri range of the Western Ghats and drains into the Bay of Bengal.
  • It is about 760 km long.
  • Amravati, Bhavani, Hemavati and Kabini are its main tributaries.
  • The Kaveri basin covers Karnataka, Kerala and Tamil Nadu. .

 Lakes:

  • A large water body which is surrounded by land is called a lake.
  • Most of the lakes are permanent, while some contain water only during the rainy season.
  • Lakes are formed by the action of glaciers and ice sheets, by wind, river action and by human activities.

Types of Lakes:
1. Ox-bow Lake: A lake formed when a meandering river is cut off from the mainstream. The shape of this lake resembles an ox-bow.
2. Lagoon: When the lake is formed by spits and bars in coastal areas, it is called a lagoon. Chilika lake, Pulicat lake, Kolleru lake, etc. are examples of lagoon.
3. Glacial Lake: A lake formed by melting of glacier is called a glacial lake. Most of the lakes in the Himalayan region are glacial lakes. Wular lake (Jammu & Kashmir) is the largest freshwater lake in India. It was formed by tectonic activity.
4. Man Made Lakes: These lakes are created by human activities. Gobind Sagar is a man-made reservoir situated in Bilaspur District, Himachal Pradesh.

Benefits of a Lake:
1. A lake helps in preventing flood by regulating the flow of river.
2. During dry seasons, a lake helps to maintain an even flow of the river.
3. Lakes can also be used for generating hydel power.
4. Tourism development.
5. Maintain aquatic ecosystem.

 Role of rivers in the economy:

  • Rivers have been the centre of human civilization since ancient times.
  • Even today, many big cities are situated on the bank of a river.
  • River water is used for irrigation, navigation, hydroelectricity, fisheries, etc.

 River Pollution:

  • The growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water.
  • As a result, more and more water is being drained out of the rivers reducing their volume.
  • On the other hand, 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.

 National River Conservation Plan (NRCP)

  • The National River Conservation Directorate (NRCD) in the Ministry of Environment, Forests and Climate Change is implementing the Centrally Sponsored Schemes of National River Conservation Plan (NRCP) for conservation of rivers, lakes and wetlands in the country.
  • The objective of the River Action Plans is to improve water quality of rivers through implementation of pollution abatement schemes in identified polluted stretches of rivers.
  • NPCA aims at conserving aquatic ecosystems (lakes and wetlands) through implementation of sustainable conservation plans, and governed with application of uniform policy and guidelines.

 Ganga Action Plan (GAP)

  • Ganga Action Plan (GAP) Phase-I was launched in the year 1985 to improve the water quality of river Ganga and was completed in March 2000.
  • Phase-II of the programme was approved in stages from 1993 onwards which included tributaries of the river Ganga namely, Yamuna, Gomti, Damodar and Mahananda.
  • Pollution abatement works undertaken include, interception and diversion of raw sewage, setting up of sewage treatment plants, creation of low cost sanitation facilities, setting up of electric/improved wood crematoria and river front development.
  • GAP Phase–II is currently under implementation.
  • An expenditure of Rs. 896.05 crore has been incurred so far on Ganga under GAP and sewage treatment capacity of 1064 mld (million litres per day) has been created.

 

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Comments

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