- The term “drainage” describes the river system of an area.
- The area drained by a single river system is called a “drainage basin” or river basin.
- Any higher ground, such as mountain or upland separates two adjoining drainage basins. Such upland is known as a water divide or a watershed.
- Depending upon the relief, geological structure and climatic conditions of the area, the streams form different patterns.
- Drainage of an area is concerned with the study of main rivers and their tributaries with respect to their size, number, direction of flow, drainage basin, slope of the valley.
- A drainage system refers to the origin and development of stream through time.
- Drainage pattern means spatial arrangement and form of drainage system in terms of different rock types, geological structure, climatic conditions and denudational history.
1. Trellis Pattern: in this system the tributaries can be seen meeting the main stream at right angles. This exists where hard and soft rocks exist parallel to each other.
2. Dendritic Patterns (Tree shaped pattern): is the most common and widespread pattern to be found on the earth’s surface. In this pattern, the tributaries come from all directions to meet the main river. Like the branches of a tree the small streams meet larger streams and the larger streams meet the much larger streams, in the end they meet the river. This develops where the river channel follows the slope of the terrain.
3. Parallel Drainage Patterns: comprises numerous rivers which are parallel to each other and follow the regional slope. This pattern is developed on uniformly sloping areas such as coastal plains.
4. Radial Drainage Pattern/Centrifugal Pattern: develops where streams flow in different directions from a central peak or dome like structure. Streams which diverge from a central higher point in all directions.
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:
On the Basis of origin, two broad drainage systems of India are generally recognized:
Drainage System of India
The Himalayan Rivers & The Peninsular Rivers.
I: The Himalayan Rivers:
· Long courses and Perform erosion and depositional work
1. The Indus Drainage System:
· Comprises of Indus River and its five main tributaries: Chenab, Beas, Sutlej, Ravi, Jhelum
· Forms a system of five main rivers after which the state of Punjab is named. They join the Indus at Mithankot in Pakistan.
· Indus and its tributaries bring a large volume of water and sediments which make their doabs enormously rich and productive lands.
· Originates from the glaciers of the Kailash range in western Tibet near Mansarovar Lake.
· Flows west and northwestwards and enters India in J&K. Pierces through Kailash Range forming a Gorge. Several tributaries , the Zaskar, Nubra , Shyok & Hunza join it in Kashmir region
· Flows through Ladakh, Baltistan and Gilgit till finally emerge out of the hills at Attock. Here the river is joined by river Kabul from Afghanistan. The Indus flows southwards across Pakistan to reach Arabian Sea east of Karachi.
· With a length of 2900km, is one of the largest rivers of the world.
· Sharing of water is regulated by the Indus water treaty signed by India and Pakistan.
2. The Ganga Drainage System:
- River system includes Ganga and its tributaries like the Yamuna, Gomti, Gaghara, Gandak, Ramganga, Mahaganga, Kosi Etc. All originate from the Himalayas.
The Ganga: rises in the Garhwal Himalayas in Uttarkhand-altitude 6000mt. The headwaters of the Ganga called the “Bhagirathi” is fed by the Gangotri Glacier and joined by the Alaknanda at Devaprayag in Uttarkhand. At Haridwar the Ganga emerges from the mountains on to the plains. The total length is 2525km. Beyond Farakka, it flows south eastward into Bangladesh where it is known as Padma. This is the northern most point of the Ganga Delta. It bifurcates here: the Bhagirathi-Hooghly flows southwards through thr detaic plains to the Bay of Bengal. The mainstream- Padma joins the Brahmaputra which is known Meghna. The delta formed by the ganga and the Brahmaputra is known as the Sunderbans.
The Yamuna: the largest and most important right bank tributary of the Ganga, meets the Ganga at Allahabad. Originates from the Yamunotri glacier on the Bandurpunch Peak in Garhwal. After cutting a deep gorge across the lesser himlayas, it flows towards the south-west and enters the Ganga plain near Tajewala.
3. The Brahmaputra Drainage System:
- Rises in Tibet east of Mansarowar lake close to the sources of the Indus and the Sutlej
- Originates from the Chemayungdung glacier in the Kailash range.
- Length of 2900km-largest rivers of the world.
- Passes through Tibet, India and Bangladesh.
- In Tibet it is called-Tsangpo, flows here as a sluggish and navigable river through a wide valley.
- Towards the end of its journey in Tibet it takes a southward turn near Namchabarwa and enters AP as Dihang River.
- The Brahmaputra has a braided channel for most of its passage through Assam and forms many riverine islands.
- Its tributaries discharges enormous quantities of water & silt, river causes disastrous floods during monsoons.
- It is marked by huge deposits of silt on its bed causing the river bed to rise.
- The river also shifts its channel frequently.
- Majuli is the largest riverine island in the world.
- Traversing round the stairs of Garo Hills, the Brahmaputra bends southwards and enters Bangladesh near dhubri.
- In Bangladesh it is known as Jamuna.
- At goalundo, the Jamuna joins the Ganga.
- The united stream of the Jamuna and the ganga is known as padma.
- The combination is known as Meghna.
- The meghna forms a very broad estuary before entering Bay of Bengal.
II: THE PENINSULAR RIVERS:
- All rivers of the peninsula are in the mature stage.
- Flow through wide valleys
- Except narmada and tapi which drain in the Arabian Sea, the other major streams drain into bay of Bengal.
- Two major directions of flow: the east flowing rivers and west flowing rivers.
1: The East Flowing Rivers:
a. The Mahanadi:
· rise in the highlands of Chattisgrah
· flows through Orissa to reach bay of Bengal, length is 860km.
· Mahanadi delta covers an area of about 9500sq.m. and 150km broad.
· The drainage basin is shared by Maharashtra, chattisgarh, jharkand and orsissa.
b. The Godavari:
· Largest peninsular river- Rises from slopes of Western Ghats in the Nashik Distt. Originates from the Trimbak plateau of the North Sahayadri near Nasik.
· Referred to Vriddha Ganga or Dakshin Ganga, Length is1500 kms. Drains into BoBengal
· Drainage basin is the largest of the peninsular rivers, 115832sq.km. About 50% of the basin lies in maharshtra, it covers MP, Orissa, and AP.
· Its principal tributaries include the Pravara, Purna, Manjra, Penganga, Wainganga, Wardha, Pranhita, Indravati, Maner, saberi. Among them the manjra, Penganga and wainganga are the largest.
c. The Krishna:
· Second largest east flowing river 1400 km long, Rises near Mahabaleshwar in the WG.
· The river has been dammed near Sri Sailem to form the Nagarjuna Sagar reservoir.
· The Bhima & the Tunghabadra are the imp. Tributaries including Koyana, ghatprabha, Musi.
· The Krishna forms a large delta which spreads across 4600sq.mt. with a shoreline.
· Its drainage is shared by Maharashtra, Karnataka, and Andhra Pradesh.
d. The Kaveri:
· The most sacred river of S.India, Source lies at Talakaveri on the Brahmagiri range in WG.
· Flows eastward, length is 800km, empty itself into BoBengal.
· River is unique as the upper part receives rainfall during summer from the southwest monsoons and the lower part receives rainfall in winter from the north east monsoon.
· Makes the 2nd biggest waterfall called Jog falls.
· It is a Perennial river. Main tributaries are Amravati, Bhavani, Hemavati, and Kabini.
· Its basin drains parts of Karnataka, Kerala and Tamil Nadu.
e. 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.
a. The Narmada Basin:
- Originates from amarkantak in MP, flows through a rift valley between the Vidhyan range on the north and satpura on its south.
- Length is 1078km, form Dhuan dhar falls at Jabalpur.
- Flows through narrow valleys confined by precipitious hills, does not permit large tributaries.
- Forms an estuary on entering Gulf of Khambat,several islands in the estuary of Narmada, aliabet being the largest. Flows into Arabian Sea.
- River originates from the sacred tank of Multai on the Satpura plateau.
- Second largest west flowing river of the peninsular region.
- It meets the Purna River near the western extremity of the Gawilgarh hills.
- Flows in a rift valley parallel to Narmada but is shorter in length.
- Tapti forms an estuary before falling into the gulf of khambat
Other West Flowing River:
c. The Sabarmati: Originates in hills of Mewar in the Aravalli range, drains into Gulf of Khambat
d.The Mahi: rises in Vindhya and empties into Gulf of Khambat
e. 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.
INLAND DRAINAGE: Inland drainage is formed by rivers with no outlet to any water body.
· They disappear into the soil-as the soil is porous or less water or evaporation.
· Large parts of rajasthan desert & parts of Aksai Chin in Ladakh have inland drainage.
· The Ghaghar is a river of inland drainage, a seasonal stream which rises on the lower slopes of the Himalayas and forms the boundary between Haryana & Punjab. The Tangei, Markanda, Saraswati, and the Chaitanya are the most important tributary of this river.
LAKE: is a depression filled with water & is entirely surrounded by land. India has comparatively few natural lakes. The three types of lakes found in India are:
- 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.
- 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.
- 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.
- 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.
ROLE OF RIVERS IN THE ECONOMY:
- 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.
- 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.
- 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.
- Industrial Development: has flourished along rivers and many industrial processes rely on water as a raw material, coolant and for the generation of hydroelectricity.
- 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.
- Recreation, tourist promotion and fishing are also being developed along the water fronts.
- 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.
- 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.
- 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.
- Generation of Power (Electricity): These multi-power projects are main source of power generation. They provide us neat, pollution free and economical energy.
- Flood Control:control floods as they store water, many overflowing rivers are controlled.
- Irrigation: many canals have been taken out to irrigate fields during dry season.
A comparative Study: