Salinity Intrusion and Seasonal Water Quality Variations in the Tidal ...

or even equal to that of the sea water. By mid-May, salinity stoops to
brackish water level and yet it undergoes swift transformation in tune with
local weather. In any case, water is very saline from December to late
April. The effect of tides on polluted fresh water is more pronounced in
West Cochin in winter. Here the canal waters are severely denatured by
huge doses of municipal waste and fish processing wastes. Even if the
waste loads are brought down to an innocuous minimum, the water will not
be ofany economic significance because ofthe sharp fluctuations in salinity
in response to rains and close proximity to sea water. Hardness is mostly
from marine cations. And temporary hardness from bicarbonates is much
less than permanent hardness
3.2.8 From late May to mid October, the Poorni puzha and the associated lesser
canals are endowed with fresh water. From late October salinity begins to
build up and crosses 6000 mg/L level by mid January and reaches a
maximum in late April. Water is again fresh by late May. Highest
chloride-level was recorded at Venkiteswara School site and Iron Bridge
site. Temporary hardness does not alter significantly whereas total hardness
does as it closely follows chloride.
3.2.9 The tidal impact fails to reach out to the northern extremity of
Karanakkodam thod. The tail end of the canal on VIP Road flanking the
International Stadium is free of salinity throughout the water year. But
from the confluence of Adimury thod, the canal is progressively saline by
late September and remains so until after early March. So from mid April
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