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Polluted River - Shanmugam IAS academy in coimbatore
Polluted River


What’s in news?

The Central Pollution Control Board (CPCB) has identified 60 pollution river stretches based on Biochemical Oxygen Demand (BOD) in different northeastern states.

Key data’s:

  • A study published by Delhi-based Centre for Science and Environment (CSE) has revealed this.
  • CPCB has identified over 350 polluted river stretches across India and the number continues to grow. Unscientific coal mining has turned water in many river stretches highly acidic and polluted.
  • Polluted river stretches in the northeastern states are  Bharalu, Basistha, Kolong, Boko and Kopili in Assam; Wahumkhrah, Umshyrpi, Waikhyrwi, Rawaka, Kmai-um, Um-Mynkseh, Umpai, Mynkseh and Sarbang in Meghalaya; Nambul and Kongba in Manipur; Chite in Mizioram; Dhansiri in Nagaland and Gumti in Tripura.
  • While Arunachal Pradesh and Sikkim have comparatively clean water and pollution in Manipur, Mizoram and Tripura are localised near the urban areas, many stretches of Assam, Meghalaya and Nagaland are highly polluted due to unscientific coal mining.


  • The discharge of industrial and mining effluent and dumping of waste has been identified as the major causes of pollution of these stretches, which are mostly located near towns and cities.
  • The report further said that more than 60% of the country’s sewage is released into the streams and rivers untreated. Consequently, half of the rivers in the country is now polluted with the Ganga, Sabarmati, and Yamuna being the most polluted.


  • India stands a poor 120th among 122 countries on the Water Quality Index based on the availability of clean and sufficient water.
  • The 2018 Niti Aayog report on composite water management index shows that nearly 70 percent freshwater in the country is contaminated and more than 600 million people face high to the extreme water crisis.
  • The report further said that the northeast, which boasts of nearly 30% of the country’s water resources besides a low population density, it faces acute water shortage in many parts.

Biochemical Oxygen Demand (BOD):

  • The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand (BOD).
  • The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically.
  • Clean water would have BOD value of less than 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more.

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