Rivers and Water Ways
The hilly region in the north comprising the district of Darjeeling is cut through by deep gorges ofthe Teesta which flows from north to south between mountainous banks rising two to three kilometres above the stream. The Teesta on debouching into the plains south of Darjeeling at Sevoke, flows in a mighty stream on straight line towards the south east until it pours its waters into the Brahamaputra in Bangladesh. Other rivers, smaller than the Teesta, rising in the Himalayas are Jaldhaka, the Torsha, the Sankosh and the Raidak. Of these the Torsha is the most turbulent. These rivers, carrying the back of the monsoon waters of the huge catchment area of the Himalayas. During the dry reason they are navigable in the plains below. The Mahananda rises from springs in the Dow Hills forest, below Darjeeling town falls in the spectacular cascade named Pagla-Jhora in to the sloping plains of southern Darjeeling district and fed by three other similar rivers the Mahanadi, the Balason, and the Machi runs a zig-zag course through Maldah district into the Padma in Bangladesh.
The central region is watered by the Mahananda as well as such rivers arising in the plains as the Tangan, the Punarbhava and the Atrai the former two combine their streams and flow into the Mahananda and the Atrai flows into the Padma in Bangladesh. The southern region is served by two river systems. One for plateau and the plains west of the Gangetic delta and the other for the Gangetic delta itself. In the former area, a number of rivers originating in the western plateau flow down in a south easterly direction and join the Bhagirathi, the main westerly channel of the Ganga moving down to the estuary of the Bay of Bengal. Of these the north most is the Mayurakshi, which is fed by tributaries Brahmani, Dwaraka, Bakreswar and Kopai. A little to the south the river Ajay rising in the hills of Bihar, flows down the plateau fringe, marking the boundary between Bankura nd Birbhum districts and joins the Bhagirathi at Katwa. Three other small streams Khari, Banka and Behula were one distributaries of Damodar, but are now meandering streams. The biggest river of the plateau fringe, the Damodar, also rising in the Bihar hills runs down in an easterly course until it takes a turn to the south and flows into the Hooghly river. Hooghly river is called as 'River of Sorrow'.
Further south is the Rupanarayan made up of two streams, Dwarakeswar and Silai or Silabati. It joins the Hooghly near the estuary at Haldia and its impressive width up to Kolaghat is due to the tidal action on estuary. Still farther south are the Kansabati or Kasai and the Subarnarekha, the latter rising in the Orissa hills and striking the boundary between the states of Orissa and West Bengal.
In the remainder of the southern region, the main channel of Ganga called Padma runs into Bangladesh where it joins to Brahmaputra and the two rivers runs into one of the broadest estuaries of the world and later meets Bay of Bengal below Noakhali in Bangladesh. The main body of the Ganga waters being carried by the Padma. The main channel with in a West Bengal is the Bhagirathi named in its lower reaches the Hooghly river by the British taking off at the head of Murshidabad district, the Bhagirathi flows southwards into a sea past the port city of Calcutta. Near the Sea-mouth it is joined by the Rupmarayan at Haldia. The other main channels the Bhairah and the Jalangai were mighty waterways on account of changes in the land level due to seismic factors and the deposition of heavy quantities of salt the Bhagirathi has been reduced to a spill channel. The silting of the main channel river itself has assumed such alarming proportions that steamship navigation up to the Port of Calcutta has been seriously hampered by rise and spread of Sand banks. An effort have to resuscitate its flow has been made in the shape of the Farakka Barrage project which has completed in 1974.
The channels near the bay mouth are broad and comparatively free from silt deposits. Tidal bores coming up from the sea on full-moon days during late monsoon and in autumn sometimes rise to a height of over six metres at the estuary, to about three metres in-land at Calcutta.
The other main channels in tidal basin are the Manganga or Baratola, the Saptamukhi, the Thakuran, the Malta, the Gaushaba and the Raimangal which skirts the boundary between West Bengal and Bangladesh in the extreme south. All the channels are safe and pleasant during fair weather months for navigation by country boat and streamers, affording as they do a unique view of the majestic Sunderbans.