River Environments of North Bengal

The rivers of North Bengal are perennial and generally carry rain and snow water from the upland hilly region that flow to the downstream plains. This natural flow of the rivers of mountainous origin with a more or less stable state of equilibrium is considered as natural waterways. But the flows of such natural waterways are interrupted by the gradual reduction of carrying capacity that accommodates the river discharge from the upland areas due to human encroachment of the part of the riversides and floodplains. Apart from the reduction of the accommodation capability, the increase of rainfall including the snow-melt water for current issues like global warming due to climate change causes huge discharge into the rivers of North Bengal by which the state of equilibrium is not maintained. Destruction of riverside forests and conversion of forest lands into tea estates, agricultural lands, human habitation etc. is another problem that is accelerating soil erosion and spilling over the banks resulting in flooding. Changing river courses into new fluvial inlets sometimes causes avulsion of rivers where the main river channel becomes abandoned. Concrete bridges for roadways including railway bridges over the rivers contract the river course, a narrow one for its natural flow that sometimes causes flooding in the area. Apart from these, there are several towns and municipalities along the banks of rivers in North Bengal that discharge sewage from municipalities. The sewage along with wastewater enters the river water causing it unusable even for outdoor bathing. For this reason, Paharpur to Siliguri is the polluted stretch of Teesta in 2018 and along Sevoke during 2022 in the category of Priority-V as demarcated by the Central Pollution Control Board.