Thursday, July 31, 2008

The Rivers

Life Sustaining Waters

The heavy seasonal rainfall from the South West Monsoon has sustained a large number of rivers flowing either to the east or to the west of the Western Ghats range which is the main watershed of the peninsular India.
The Western Ghats are remarkable for being the headwaters of all the major and many smaller rivers of the peninsula. The principal rivers originate and flow eastward, journeying across the peninsula for hundreds of kilometers to pour their waters finally into the Bay of Bengal. On the western face of the Sahyadri scarp, numerous indentations have been made by a large number of short, perennial, torrential west flowing rivers which traverse the short distance through the narrow west coastal plains before discharging into the Arabian Sea through narrow inlets and creeks. Several of these streams form remarkable waterfalls.

The duration of the wet season varies from about three months in the north to over nine months in the south. The rainfall ranges from 2,000 to 7,500 mm per annum in some places on the western, windward side but rapidly decreases on the eastern, leeward side to about <>

The source of Hiranyakeshi river - Amboli Ghat - Pic by Mohan Pai
The three major rivers that originate in the Western Ghats and flow to the east and traverse a great distances right across the peninsula are:-
1. The Godavari 2. The Krishna 3. The Kaveri
They are all mature, that is, they are so ancient that they have reached the base level of their erosion. Their valleys are wide and shallow, and they flow through flatlying alluvial tracts through which they meander at a sluggish rate, or through uplands and plateaus where their velocities are greater and into which they occasionally cut narrow defiles and gorges.

Vivid Rock formation - Sintheri Rocks, kaseri River, Uttara Kannada - Pic by Mohan Pai

There are other smaller streams that also originate in the Western Ghats and flow east to join the Bay of Bengal. These are Tambraparni (arises in the Agasthyamalai Hills) and Vaigai (originates in the Varushanad Hills).
River Sharavathy - tailrace

The Godavari
The Godavari arises in the Tryambak plateau near Nasik about 80 km from the shores of the Arabian Sea at an elevation of 1,067 m it meanders south-eastwards through fairly steep banks of lavas, and then, from its confluence with the Manjra through gneisses and Gondwana sediments until it arrives at its delta, traversing over 1,465 km it flows through Maharashtra, Madhya Pradesh and Andhra Pradesh.
It reaches Bay of Bengal through an extensive delta beyond Rajamundri in Andhra Pradesh where it divides into branches - western branch is called ���Vashistha Godavari��� and the eastern branch is called ���Gautami Godavari���. It projects about 35 km into the sea with a front of 120 km with many distributaries. Its northern part is made up of low-lying marshes extending into a 15 km long spit forming the Kakinada Bay.
Its main tributaries in the upper reaches, the Purna and Manjra, flow roughly parallel to the Godavari before draining into it. The Godavari has many tributaries such as the Purna, Manjra, the Pranhita (Penganga - Wardha), Indravati, the Sabari, Darna, Kadwa, Mula, Karanji, Madhurnala, Devanala, Hebbala. etc.

The Krishna

The Krishna is the second largest river in the peninsular India. It begins at an altitude of 1,360 m near Mahabaleshwar in Maharashtra 64 km away from the Arabian Sea.
It is augmented by several tributaries along its 1,400 km course, until it reaches Machilipatnam on the east coast of Andhra Pradesh. The delta area of the Krishna begins from Vijayawada and occupies an area of about 4,600 sq. km, and also extends about 35 km into the sea with a shoreline of about 120 km it has been progressing gradually to south due to vast amount of sediments brought and spread by the river and its distributaries.

Several rivulets and rivers arising in the Western Ghats go to form its tributaries - the Koyna, Varna, Panchganga, Doodhganga, Bhima, Musi, Paleru, Maneru, Ghataprabha, Malaprabha and Tungabhadra.
The Kaveri
The Kaveri is the third major river of the peninsula. It originates near Talakaveri at a height of 1,340 m in the Brahmagiri range of Kodagu district in Karnataka at the very edge of the Sahyadri range overlooking the Arabian Sea. As peninsular rivers go, this is a comparatively small river only about 800 km long.

Talakaveri, the source of river Kaveri, Kodagu - Pic by Mohan Pai
It flows mainly through the Dharwarian crystalline rocks during its passage through the Eastern Ghats and the Tamil Nadu uplands where its gradient is quite gentle. The river cuts across the strike of the country rocks and appears to be an ancient river whose meandering course has been superimposed on a topography which has become youthful as a result of recent uplift.
A dam has been constructed near Mysore - Krishnaraj Sagar where it meets Hemavati and Laxmantirtha rivers. After 25 km from Srirangapatna, Kabini and Suvarnavati rivers meet with it. The river creates waterfalls at Sivanasamudram (101 m high) and then enters a long picturesque gorge.
River Kaveri at Srirangapatna - Pic by Mohan Pai

On the border of Karnataka and Tamil Nadu it meets with Simsa and Akrawati rivers. In Tamil Nadu it flows in easterly direction but from Hogenkal waterfall, it flows in south direction. It cuts through the Eastern Ghats and emerges from the hills at the Stanley Reservoir formed by the Mettur Dam. At 45 km from Mettur it meets its main tributary - the Bhavani and when it enters Tiruchirapalli district it meets with Noyil and Amravati.
Here it is the widest of whole of its path and hence called ���Akhand Kaveri���. After Tiruchirapalli it divides into two branches. The delta starts from below the island of Srirangam in the river, where it issues its largest deltaic channel, the Coleroon and joins the Bay of Bengal at Poompuhar. The southern branch is called Kaveri and joins the Bay of Bengal at Tranquebar.
The Kaveri delta is quadrilateral in shape covering about 8,000 sq. km area; it consists of several terraces which indicate that it was subject to uplift and erosion at various periods of its formation. It has an almost straight front of about 130 km along the Bay of Bengal and on the south it takes an almost right angle turn towards the west at point Calimere from where it faces the Palk Bay for another 60 km.
The major tributaries of the Kaveri which arise in the Western Ghats are : The Hemavathi, Harangi, Kabini, Lakshmantirtha, Moyar and Bhavani.
Tambraparni
The river Tambraparni originates on the eastern slopes of the Western Ghats near Agasthyamalai in Tirunelveli district at an altitude of 2,000 m.
The Tambraparni basin is situated between latitudes 8021��� and 9013 ���N. Vanatheertham waterfalls (40 m) is located close to the origin of the main river. Among the many tributaries which join it are: Peyar, Ullar, Karaiar, Pambar, Servalar, Manimuthar, Gadana, Pachaiyar and Chittar. The river Tambraparni after the confluence of Chittar, travels another 53 km and enters the Gulf of Mannar near Palayakayal.

Vaigai
The river Vaigai arises in the Varushanad Hills of the Western Ghats and initially flows north-east through Kambam and Varashunad valleys and then flows eastward into the Vaigai Reservoir at Narasingapuram. Near Sholavandan it bends south east, passing Madurai town on its course to its mouth on the Palk Strait which separates the south-east coast of India from Sri Lanka. The total length of the river is 250 km.
The West-flowing rivers
The western side of the Sahyadris is characterised by a very large number of short perennial/non-perennial torrential west-flowing rivers.
From Gujarat to Kerala these short, swift west-flowing rivers plunge over the precipitous escarpments to discharge their waters into the Arabian Sea. As they plunge towards the coastal strip they often pass through deep gorges creating spectacular waterfalls, some with a drop of over 200 m when the rivers encounter geological faults.
Magod Falls - River Bedthi plunges in two steps -Uttara Kannada - Pic by Mohan Pai

Among them may be mentioned the Bedthi Falls (137 m) also known as Magod Falls, Jog Falls (253 m), Chalakudi Falls (56 m) and several falls ranging in height from 20 to 300 m on the Anaimalai - Palni - Elaimalai hill chain.
The west side rivers which flow into the Arabian Sea do not form deltas, but only estuaries, which are channels where the fresh water of the rivers mix with the tidal sea waters. The possible reason why deltas are not formed is that they flow through hard rocks and therefore unable to form distributaries through the coast. The coast had been advancing seawards during historical times in these parts as is proved by the fact that Surat - now an inland town - was a port on the sea only a few centuries ago.
The west side streams are too numerous to be listed. Kerala alone has 44 west-flowing streams.

Periyar River, Kerala - Pic by Mohan Pai
The main west-flowing rivers of the Western Ghats are listed below :
Gujarat : Purna, Auranga, Par
Maharashtra : Surya, Vaitarna, Damanganga, Ulhas,
Savitri, Vashisthi, Gad, Kajavi, Kodavali
Goa : Mandovi(Mahadayi), Zuari, Tiracol, Chapora, Talpona
Karnataka : Kali, Gangavali (Bedthi), Aganashini, Sharavathy, Kollur-Chakra-Gangoli, Sita, Mulki, Gurupur, Netravathi
Kerala : Chaliar, Bharatpuzha, Periyar, Pamba

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