CLASS 9 GEOGRAPHY CHAPTER 3 - DRAINAGE

 DRAINAGE

Drainage:The river system of an area is called drainage. The area drained by a single river system is called the drainage basin.

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:

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.

 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.

 Rectangular Drainage Pattern: When rocks are strongly joined, then rectangular pattern develops.

 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.

WORK OF A RIVER:

On the basis of the slope of the land over which a river flows, its course can be divided into three sections:

     I.    THE UPPER COURSE: river usually flows through mountainous regions. Volume of water is not much, but gradient being steep, the water flows swiftly. Its eroding and transporting powers are at the maximum. The river in this course develops typical landforms:

1.    Gorge or I-Shaped Valley: when a river flows through a mountainous region made up of herd rocks with little rainfall, most of the energy of the river is spent in down-cutting action, resulting in narrow valleys with almost vertical walls.

2.    V-Shaped Valley: when a river flows through a mountainous region made up of relatively soft rock and plenty of rainfall, the sides or the banks of the river erode easily and widen by the increase in volume of the river, resulting in V-shaped Valleys.

3.    Waterfalls: is steep descent of a river over a rocky edge, when the river falls down almost vertically from a sufficient height, it forms a waterfall.

   II.    THE MIDDLE COURSE: here the river enters the plain. As the gradient decreases, the flow of energy slows down and so does its energy. The volume of water increases considerably. As the slope of the course flattens, the river cuts less into its river bed. Instead, it widens its banks and its river bed, giving rise to U-shaped valleys. The main work of the rivers here is to transport sediments. Deposition also takes place. The river develops typical landforms:

1.    Alluvial Fans: as the river enters the plains its velocity declines and the river drops its load of sand and gravel. The course material like boulders, pebbles, and gravel is dropped near the base of the slope while the finer material is carried further. Such depositional features are called alluvial fans.

2.    Flood Plain: due to low gradient the downward erosion is reduced. More of the river’s energy is directed from side to side. As the river cuts away at one bank and then at the other, the valley widens. In this manner, flat valley covered with alluvium brought by the river, is created. This is a flood plain or an alluvial plain.

3.    Meanders: in the plain stretch of its course the downward erosion by the river is replaced by sideways or lateral erosion. Due to lateral erosion the bed of the stream becomes wider. Even a minor obstruction in its path makes the river changes its course and river flows making large curves called meanders.

4.    Ox-Bow Lakes: is produced when a meander forms almost a complete circle and the meandering river cuts across the narrow neck of land. When silt is deposited at the entrance to this backwater, an ox-bow lake is created.

5.    Braided River: when a river carries an enormous amount of load it is unable to carry it all the way to the mouth and the channel becomes clogged, causes the river to divide into many intertwining channels forming islands in the river channel.

 III.    THE LOWER COURSE: river is considerably slow, gradient is almost flat. River flows sluggishly due to the heavy load it carries. The main work of the river here is that of deposition, here the river develops typical landforms:

1.    Delta: a triangular piece of land that develops at the mouth of rivers by the deposition of sediments. The river has less energy to cut into land and it can no longer carry heavy load sediments. When the sediments are deposited in the river channel where the river meets the sea, a new land is formed-delta.

2.    Distributary: sediments build up along the river channel, it gets blocked and the river is forced to divide into branches called distributaries.

3.    Estuary: many rivers do not form deltas especially along rocky coasts. Instead they have a narrow, gradually widening bay at the mouth, cutting deep inland. Such a funnel-shaped opening at the mouth of a river is called an estuary.

4.    Levee: active deposition along the banks of an old river when it is flood. Each time this happens, the banks get higher and they are called natural levees.

Drainage System of India Himalayan The Indus The Ganga The Brahmaputra Peninsular Rivers flowing into Bay of Bengal                                          i.    Mahanadi                                         ii.    Godavari                                        iii.    Krishna                                        iv.    Kaveri Rivers flowing into the Arabian Sea                                          i.    Narmada                                         ii.    Tapi                                        iii.    Sabarmati                                        iv.    Mahi

River System: A river alongwith its tributaries forms a river system.

The drainage systems in India can be divided into two major groups, viz. the Himalayan Rivers and the Peninsular Rivers.

1. The Himalayan Rivers: Most of the Himalayan Rivers are perennial, i.e. they have water throughout the year.

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 headwaters of Ganga are called Bhagirathi. It is fed by the Gnagotri Glacier. It is joined by Alaknanda at Devprayag in Uttarakhand.

Ganga emerges from the mountains on to the plains at Haridwar.

Yamuna, Ghaghra, Gandak and Kosi are the major tributaries of Ganga. Yamuna originates from the Yamunotri Glacier in the Himalayas. It meets Ganga at Allahabad.

Gaghra, 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 Meghan; further downstream.

Finally, the Ganga and the Brahmaputra flow into the Bay of Bengal forming the Sunderban Delta. The total length of Ganga is 2500 km.

The Brahmaputra River System:

The Brahmaputra rises in Tibet; east of Mansarowar lake. It is a little longer than the Indus. Most of the course of the Brahmaputra lies outside India. It flows eastwards parallel to the Himalayas.

After reaching Namcha Barwa, it enters India in Arunachal Pradesh through a gorge. It is known as Dihang in this region. It is joined by Dibang, Lohit, Kenula and many other tribuatries and finally forms the Brahmaputra in Assam.

Unlike other north Indian rivers the Brahmaputra gets huge deposits of silt on its bed. This results in rising of the river bed. It also shifts its channel frequently.

2. The Peninsular Rivers: 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. 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.

1: The East Flowing Rivers:

The Godavari Basin: This is the longest Peninsular river. 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 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 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 Kavery basin covers Karnataka, Kerala and Tamil Nadu.

       Other East Flowing Rivers: the Damoder, Brahmani, Baitarni, And Subarnrekha, Panniyar, Penneru, Vagai are some rivers which flow eastward.

2: The West Flowing Rivers: West flowing rivers of the peninsula India are fewer and smaller as compared to east flowing rivers, narmada and Tapi are two major rivers.

The Narmada Basin: The Narmada rises in the Amarkantak hills in the Madhya Pradesh. 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 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.

Other West Flowing River: 

    The Sabarmati: Originates in hills of Mewar in the Aravalli range, drains into Gulf of Khambat

    The Mahi: rises in Vindhya and empties into Gulf of Khambat

    The Luni: originates in Aravalli and flows in the south-west direction/only stream that drains through the arid Thar Desert. Sukri is an important tributary. It flows for 482km, before it is finally lost in the marshy ground of the Rann of Kutch.

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.

1. Fresh Water Lakes: most are in the Himalayan region, glacial region. Thed erosive process of glacier can create U-Shaped valleys and the irregular surface of glaciated lowland in which water can accumulate. The Dal Lake, Bhimtal, Nainital, Loktak, Barapani are fresh water lakes in India.
2. Lakes of Tectonic Origin: folding and faulting produce hollows in the earth’s crust, may contain salty or fresh water. Wular Lake in J&K is a result of tectonic activity.
3. Saltwater Lakes: any lake with no natural drainage outlet or either as a surface stream or as a sustained subsurface flow will become saline. The sambhar in Rajasthan is used for producing salt. Lake Chilika in Orissa is a salted lake.
4. Manmade Lakes or Artificial Lake: in order to harness water for generation of hydel power to provide irrigation water to crops and to provide drinking water to urban places a number of lakes have been constructed. Govind Sagar & Govind Ballabh Pant Sagar are the two most important Man-made lakes of India.
5. 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.
6. 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.
7. 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.
8. Wular lake (Jammu & Kashmir) is the largest freshwater lake in India. It was formed by tectonic activity.
9. Benefits of a Lake: A lake helps in preventing flood by regulating the flow of river. During dry seasons, a lake helps to maintain an even flow of the river. Lakes can also be used for generating hydel power.

ROLE OF RIVERS IN THE ECONOMY:

1. Development of Civilization:  rivers have played role in the development of civilizations. Most of the ancient civilizations like Indus-Valley, Aztec, etc. developed around river. Rivers have been of fundamental importance throughout the human history. The banks of the rivers have witnessed great cultural and economic progress since ancient times. Water is a basic natural resource, essential for human, agricultural and industrial activities.
2. Rivers and their associated alluvial soils provide the most productive agricultural lands of the country. The Ganga- Brahmaputra basins have been formed by the two great rivers. Agriculture is dependant on the vagaries of the monsoon, irrigation from rivers has been the backbone of the development of Indian agriculture.
3. Settlement: their valleys contain dense and concentrated settlements most of the large cities are located on rivers. They provide us with essential water supply but also receive, dilute and transport waste from settlement.
4. Industrial Development: has flourished along rivers and many industrial processes rely on water as a raw material, coolant and for the generation of hydroelectricity.
5. Means of Transportation: primary channels of inland transportation, directly in the form of navigable waterways, indirectly through their valleys, where roads and railway lines and other routes are built.
6. Recreation, tourist promotion and fishing are also being developed along the water fronts.

RIVER POLLUTION:

1. 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.
2. 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 cleaning capacity of the river.
3. Increasing urbanization and industrialization is responsible for the increase in the pollution level of many important rivers.

Fresh water from the rivers is essential for our livelihood. So to take care of the rivers is the duty of each and every citizen. A proper understanding of our river synthesis is crucial for our well being.

NATIONAL RIVER CONSERVATION PLAN (NRCP):

The activities of GAP phase I, initiated in 1985, were declared closed on 31st March 2000. The steering committee of the NRC authority reviewed the progress of the GAP and necessary correction on the basis of lessons learned and experiences gained from Gap Phase I. These have been applied on the major polluted rivers of the country under the NRCP. The GAP Phase II has been merged in with the NRCP. The expanded NRCP now covers 152 towns located along 27 interstate rivers in 16 rivers. Under this action plan, pollution abatement works are being taken in 57 towns. A total of 215 schemes of pollution abatement have been sanctioned. So far, 69 schemes have been completed under this action plan. A million litre of sewage is targeted to be intercepted, diverted & treated.

MULTIPURPOSE PROJECTS:

1. Generation of Power (Electricity): These multi-power projects are main source of power generation. They provide us neat, pollution free and economical energy.
2. Flood Control:control floods as they store water, many overflowing rivers are controlled.
3. Irrigation: many canals have been taken out to irrigate fields during dry season.

A comparative Study: Himalayan Rivers: originate from lofty ranges of the Himalaya large basins and catchment area Form deep I-shaped valleys called Gorges. Perennial, water flows throughout the year. are in a youthful age rivers form meanders and often shift their courses Form big deltas at their mouth.

Peninsular Rivers: originate in the peninsular plateau small basins and catchment areas Flow in comparatively shallow valleys. seasonal rivers as they are rain-fed, water flows mostly in rainy season mature rivers flow more or less straight course and do not form meanders Form smaller deltas, and estuaries.

East flowing Rivers	West flowing Rivers
1. The Mahanadi, the Godavari, the Krishna, the Cauvery are the main east flowing rivers of Peninsular India. 2. These rivers drain in the Bay of Bengal. 3. These rivers make deltas at their mouth. 4. These rivers have a developed, large tributary system. 5. These river flow not through very deep canals.	1. The Narmada and the Tapi are the main west flowing rivers of Peninsular India. 2.  These rivers drain in the Arabian sea. 3. These rivers enter the sea through estuaries. 4. These rivers are devoid of a developed tributary system. Their tributaries are quite small in size. 5. These rivers flow in troughs.

Delta - A more or less triangular and level tract of alluvium formed at the mouth of a river entering a relatively quite body of a river. e.g. Sunderban delta.

 Distributary - A channel which branches of from the main river and carries away a part of its water.