- Discolouration of water of the Periyar River, Kerala has continued unprecedently, thus raising concerns among environmentalists. Environmentalists allege that that discolouration was caused due to excess discharge of chemical wastes into the river by industries located on the banks.
- The Periyar River is the longest river in Kerala. It originates from Sivagiri Hills of Western Ghats and flows through the Periyar National Park and drains into the Periyar Lake.
- According to environmentalists, the discolouration is due to the poor quality of water as a result of eutrophication. Eutrophication is the enrichment of a lake or other water body with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both.
- Eutrophication occurs naturally in lake as they age through the geological time. However, human activities accelerate the rate and extent of eutrophication. Runoff from agriculture and development, pollution from septic systems and sewers, and other human-related activities increase the flux of both inorganic nutrients and organic substances into lakes or water bodies thus resulting in eutrophication.
- Excessive nutrients in water bodies result in algal bloom- rapid increase in the population of algae. Algal blooms limit light penetration, thus reducing growth and resulting in death of plants in littoral zones. Further when algae die and decay, it results in a foul smell and discolouration of water.
- Further, high rates of photosynthesis associated with eutrophication deplete dissolved inorganic carbon and raise pH to extreme levels in water bodies.
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