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
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.