Rivers of West Bengal | WBCS Preparation: All Subjects - WBCS (West Bengal) PDF Download

Drainage systems

River systems, or drainage systems, refer to the arrangements created by the streams, rivers, and lakes within a specific drainage basin. Their formation is influenced by the topography of the terrain, the prevalence of hard or soft rocks in a region, and the slope of the land.

River system as a Introduction

• As the Ganges enters West Bengal near Rajmahal, it flows southeastward, splitting into two near Dhulian in Murshidabad district. One branch becomes the Padma in Bangladesh, while the other becomes the Bhagirathi River and Hooghly River, flowing southward through West Bengal. The Bhagirathi is the primary river in West Bengal, passing important cities before releasing into the Bay of Bengal near Sagar Island.
• Various rivers such as the Mayurakshi, Ajay, Damodar, Kangsabati, and Rupnarayan, originating in the Western plateau, join the Bhagirathi on its right bank. The Damodar, controlled by the Damodar Valley Project, is known as the sorrow of Bengal. Distributaries of the Padma River, like Bhairab, Jalangi, and Mathabhanga, enter West Bengal and join the Bhagirathi on its left bank. Silting caused by these rivers poses challenges to the Kolkata Port and leads to flooding during heavy rains.
• The Sunderbans region is characterized by numerous estuaries and streams, mainly distributaries of major rivers like Hoogly, Matla, Gosaba, and others. The Teesta, Torsa, Jaldhaka, Kaljani, Raidak, Sankosh, and Mahananda rivers in the northern hilly region, originating in the Himalayas, flow southward through various districts before entering Bangladesh.
• Most rivers in the region are snow-fed, making them perennial and prone to flooding during the rainy season. The region is composed of sand, gravel, and pebbles deposited by these rivers.

RIVER BASINS of  Rivers of West Bengal

The state is divided into three drainage basins under the Ganga, Brahmaputra, and Subarnarekha systems, each further divided into sub-basins with individual catchments. The area-wise distribution of the main basins includes the Brahmaputra Basin, Ganga Basin (including Sundarban Area), and Subarnarekha Basin.

Brahmaputra Basin Drainage System

The northern region of the state experiences high rainfall, particularly in the Sub-Himalayan regions of the northern districts. The Brahmaputra Basin covers an area of 11,860 sq.km, constituting approximately 14% of the state's geographical area. This basin includes numerous drainage channels that join main arteries such as the rivers Teesta, Torsa, Raidak, Mansai, and Jaldhaka. These rivers, originating in Bhutan/Sikkim, traverse the Terai region before reaching the plains of West Bengal and ultimately joining the Brahmaputra in Bangladesh. The Brahmaputra's tributaries include various rivers originating from the Himalayas in Bhutan/Sikkim.

BRIEF DESCRIPTION OF RIVERS UNDER BRAHMAPUTRA BASIN

SANKOSH
Originating in Bhutan, the river Sankosh is the easternmost tributary of the Brahmaputra river basin. It acts as the boundary between the states of West Bengal and Assam. Eventually, it merges with Raidak-II and ultimately flows into the Brahmaputra in Bangladesh under the name Gangadhar.

RAIDAK
Beginning at an altitude of 6400 m in Mt. Akungphu in Bhutan, the Raidak River divides into two channels, Raidak-I and Raidak-II, near the Indo-Bangladesh border at Bhutanghat. Raidak-I combines with the Torsa and Kaljani streams, while Raidak-II is joined by the Sankosh, finally emptying into the Brahmaputra in Bangladesh as the Gangadhar.

TORSA
With its source in the Chumbi Valley of southern Tibet at 7065 m, the Torsa River traverses Tibet, Bhutan, West Bengal, and Bangladesh. After splitting into Sil-Torsa and Char-Torsa below the Hasimara bridge, the two channels reunite at Patla Khowa forest. Passing by Coochbehar town, the river is joined by the Kaljani and Raidak-I before flowing into the Brahmaputra near Nageswari in Rangpur, Bangladesh.

JALDHAKA
Originating at Bitang Lake in Sikkim at an altitude of 4400 m, the Jaldhaka River flows through Sikkim, Bhutan, West Bengal, and Bangladesh. After merging with various streams and tributaries, including the Dharala, it ultimately joins the Brahmaputra in Bangladesh.

TEESTA
The formidable North Bengal river, Teesta, begins in the glaciers of North Sikkim at an altitude of 6400 m. Formed by the union of Lachen and Lachung streams at Chungthung in Sikkim, it serves as the boundary between West Bengal and Sikkim up to Mechi. Tributaries like the Great Rangit and Rammam also act as natural boundaries. The river eventually flows into the Brahmaputra in the Rangpur district of Bangladesh.

GANGA BASIN

• The sacred rivers Bhagirathi and Alakananda, originating from Himalayan glaciers at 7000 m, merge at Devprayag to form the Ganga. After entering the plains at Rishikesh in Uttaranchal, it flows through Uttaranchal and Uttar Pradesh, receiving the Yamuna's flow at Allahabad. The Ganga then becomes the boundary between Uttar Pradesh and Bihar before entering Bihar and subsequently West Bengal. After joining the Kosi, the river continues eastward in Bihar and then enters West Bengal, where it divides into two arms below Farakka. 
• The left arm, known as the Padma, flows eastward into Bangladesh, while the right arm, Bhagirathi, continues south through West Bengal. Beyond Nabadwip, the river is called Hooghly and ultimately meets the Bay of Bengal near Sagar Island. The Ganga Basin encompasses the central, southern, and southwestern parts of West Bengal, covering a total area of 74,732 sq.km within the state. The river's total length, measured along Bhagirathi and the Hooghly, is approximately 2575 km, with specific lengths in different states.

MAHANANDA

• The Mahananda River originates near Darjeeling town in the Darjeeling district, specifically from Ghoom. This river system is situated between latitude 25º15′ N to 26º15′ N and longitude 87º45′ E to 88º15′ E. It is bordered by the Himalayas to the north, ridges separating it from the Teesta river system to the east, the Ganga to the south, and the Kosi river system to the west. 
• The river divides into two channels at Barsoi in Bihar, with one branch, named Fulahar, flowing through Bihar, and the other, named Mahananda, flowing through West Bengal. The Mahananda river, fed by tributaries such as Nagar, Kalindri, Tangon, and Punarbhaba, eventually joins the Ganga from the North-Western side at Godogarighat, just downstream of where the Ganga leaves the boundary of West Bengal.

ATRAI-PUNARBHABA

• Several rivers, including Sahu, Neem, Talma, Chaoai, and Panga, originate in the highlands of Jalpaiguri district and converge to form a stream called Karotowa. This stream enters Bangladesh as Atrai, which then bifurcates into Dheepa and Atrai channels. The Atrai channel re-enters West Bengal in South Dinajpur district, covering a length of 40 km, before entering Bangladesh again and eventually joining the Brahmaputra. 
• The Dheepa channel takes a South-Western course, enters Gangarampur P.S. in South Dinajpur district, and becomes the Punarbhaba, flowing through Maldah district before entering Bangladesh. In Bangladesh, Punarbhaba meets the Mahananda river.

NAGAR-KULICK, GAMARI-CHIRAMATI, TANGON, KALINDRI

• Rivers such as Nagar, Kullick, Gamari, Chiramati, Tangon, and Kalindri flow through the districts of Malda and North Dinajpur. They often form boundaries between West Bengal and Bihar or West Bengal and Bangladesh. Nagar, originating in Bangladesh, flows along the West Bengal boundary, receiving a spill channel from Mahananda, and is joined by Kullick. 
• Gamari and Chiramati, two smaller rivers, unite in North Dinajpur before joining Mahananda. Tangon, a Mahananda tributary, originates in Bangladesh, flows through North Dinajpur and Malda, and meets Mahananda on the boundary of Malda and Bangladesh.

PAGLA-BANSLOI-BRAHMANI
Rivers like Pagla, Bansloi, and Brahmani originate in the Rajmahal hills in Bihar. After flowing across Birbhum district, they become tributaries of the river Bhagirathi.

JALANGI-BHAIRAB

• Jalangi originates from the right bank of the Padma in Murshidabad district, downstream of Farakka. It remains dry except during the rainy season when it receives water from the Padma. Jalangi eventually flows into the Hooghly near Nabadwip. 
• Bhairab starts from the Ganga in Lalbag P.S. of Murshidabad and, although mostly dry, receives water from the Padma during the rainy season.

ICHAMATI-CHURNI

• The Mathabhanga river begins at the mouth of the Jalangi of Padma and, while not significant in Nadia district, bifurcates into two streams - Churni and Ichamati. 
• Churni and Ichamati flow through the districts in a south-east direction, with Ichamati receiving some supply from the Padma and relying on tidal flows for sustenance.

BHAGIRATHI-HOOGHLY

• The Ganga Brahmaputra Meghna river system is one of the world's largest, with the Ganga originating in the Himalayas and draining a vast area. Near Farakka, it divides into two channels, Bhagirathi-Hooghly and Padma. Bhagirathi-Hooghly flows through West Bengal and drains into the Bay of Bengal, while Padma crosses into Bangladesh, joining the Brahmaputra at Goalundo. 
• Bhagirathi divides Murshidabad district and, after receiving right bank tributaries like Bagmari-Pagla, Mayurakshi, and Ajoy, becomes Hooghly. The river, formerly the main course of the Ganga, now serves as the main drainage artery for southern districts.

MAYURAKSHI-BABLA

• Mayurakshi originates in the Santhal Parganas highlands and is the primary river of Birbhum district. It gives rise to spill channels like Manikornika, Kana Mor, and Gambhira, which ultimately flow into Hijal Beel in Murshidabad. 
• From Hijal Beel, the Babla river emerges, eventually draining into the Bhagirathi. The flood level in Hijal Beel is influenced by the Bhagirathi's level.

AJOY
Ajoy originates near Deoghar in Jharkhand and has principal tributaries like Hinghlow, Kunoor, Pathro, and Jayanti.

DAMODAR
Damodar originates in the Palamau hills and bifurcates at Beguahana, with one channel passing through Mundeswari and discharging into Rupnarayan, and the other, Amta channel, carrying high flood discharge and outfalling into the Hooghly.

DWARAKESWAR-SILABATI-RUPNARAYAN

• Dwarakeswar originates from the high lands of Purulia district.
• River Ganddheswari rising from Bankura district meets Dwarakeswar near Bankura town receiving water from streams like Arkasha, Berai, enters Hooghly district and meets Silabati to form Rupnarayan. Silabati also originates in Purulia district.
• It traverses through the district of Midnapore.
• The river receives water of Joypanda and meets with Dwarakeswar to form Rupnarayan. Rupnarayan is a combination of number of streams.
• The tidal reach below confluence of Dwarakeswar and Silabati is known as Rupnarayan.
• It outfalls into Hooghly after receiving mainflow of Damodar through Mundeswari and branch of Kangsabati.
• The river is tidal throughout its entire course.

KANGSABATI-KALIAGHAI-HALDI

• Kangsabati originates in Purulia and is joined by Kumari in Bankura. It later bifurcates into Old Cossye/Palaspai Khal, flowing into Rupnarayan, and New Cossye. Kaliaghai, originating from Jhargram, joins New Cossye to form Haldi, which ultimately falls into the Hooghly. 
• The lower part of Haldi is prone to overbank spills and drainage issues during the monsoon.

RASULPUR
Rasulpur is formed by Bagda, Sarpai, and Madhakhali streams, serving as the main river in Contai Sub-Division of Midnapore district. It drains Dwarakeswar, Silabati, and a significant portion of Kangsabati rivers, causing flooding in Dubda and Contai areas before falling into the Hooghly.

TIDAL RIVERS OF SOUTHERN WEST BENGAL

• Apart from the rivers described earlier within the Ganga and the Brahmaputra river systems, there is a group of rivers in Southern part of the State which falls in the deltaic zone.
• These rivers mostly lie in the deltaic zone to the east of the Hooghly river popularly known as Sundarbans and form an intricate network with a number of criss-cross inter connecting channels, thus dividing the land spill channels of Ganga, then upland supply running dry, during winter months. But gradually their off-takes from Ganga have deteriorated and in some cases being cut-off from the river.
• Now these rivers drain off whatsoever fresh discharge comes from country sides, thus ultimately draining into Bay of Bengal through one or other of the principal estuaries in the area which are, starting from Hooghly river successively the Bartala of Muriganga or channel creek, Saptamukhi, Matla, Gosaba, Hariabhanga, Raimongal etc.
• The Tolly’s Nullah or the Adi Ganga, as it is sometimes called is a small but important tidal creek draining into the Hooghly from the left in the vicinity of the city of Kolkata.