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Periyar River

Why is it in News?

Periyar River has witnessed extensive discoloration of its water due to eutrophication.

About Periyar River:

  • Periyar (means big) is a perennial river of Kerala that originates from Sivagiri Hills of the Western Ghats.
  • It is 2nd largest river of Kerala that flows through Periyar National Park and finally drains into the Arabian Sea.
  • Periyar River is the backbone to the economy of Kerala as its water is used for agriculture, drinking purposes etc. and so it is referred to as the ‘Lifeline of Kerala’.
  • The largest hydroelectricity project - Idukki Hydro Project - is built on this river.

Tributaries of Periyar River:

Its major tributaries are - Muthirapuzha River, Mullayar River, Cheruthoni River, Perinjankutti River and Edamala River.

Causes of Discoloration of Water of Periyar River:

  • Reduced water flow to the river led to the stagnant streams of water in few pockets leading to algal boom.
  • Discharge of pollutants from industries and sewage from households.
  • The main cause for discoloration is ‘Eutrophication’.


  • Eutrophication is the process through which lakes, streams, or bays become overloaded with nutrient-rich water.
  • When this occurs, large blooms of algae and aquatic plants occur, fed by the excess nitrogen and phosphorus.
  • When the algae dies, microorganisms in the water begin feeding on the remains as part of the decomposition process and consequently use up the available oxygen in the water.
  • This leaves little oxygen for fish and other aquatic animals, resulting in the suffocation of aquatic life which finally leads to death of the water body itself.

Sources of Nutrients to the Water Body:

  • Sources of excess nutrients to these systems include agricultural runoff, overuse of synthetic fertilizers, septic tank or sewage leaks, and erosion etc.

Source: Down to Earth, Livemint, IE