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No end to discolouration of river Periyar in Kerala

Topics Covered:

  1. Conservation, environmental pollution and degradation, environmental impact assessment.


No end to discolouration of river Periyar in Kerala


What to study?

For Prelims and Mains: Eutrophication- causes, effects and measures for prevention.


Context: The Periyar River in Kerala has turned black near the Pathalam Regulator cum Bridge.



The discolouration of Periyar and fish kill has been a serious issue for last couple of years. Decrease in dissolved oxygen level has caused several fish-kills in the past few years.

Environmental activists have been protesting against the pollution of the river and demanding steps for its protection. For the record, the pollution of the river system had earlier led to violent protests in the region.


What is the reason for discolouration?

  • The discolouration was due to the poor quality of water as a result of eutrophication. When excessive nutrients reach the waterbody, it will lead to algal bloom. A few days later, algae will die and decay, resulting in a foul smell and discolouration of water.
  • Water in some reaches of the river system has been stagnant. Reduced water flow in the system has added to the deteriorating water quality.
  • Huge quantities of organic load in the form of sewage from nearby townships are regularly reaching the river system. Discharge of untreated effluents into the river from industrial units is also causing discolouration of water.


What needs to be done?

Areas near industrial units are to be regularly monitored. The river flow should not be restricted by closing the bund so that the natural pollutants will flow away from the water. Excessive discharge of pollutants from an unauthorized industrial unit functioning upstream must be controlled.


Sources: the hindu.