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

not effective during the dry months. Therefore, in the lean months, primary effect of
sea water intrusion is dilution ofphosphates followed by accumulation due to subdued
flushing. Thus the governing process is physical than chemical. It can safely be
assumed that pH and salinity levels should cross a threshold which could potentially
trigger salt water induced chemical reactions bringing about a shift in the chemical
environment comparable to the patterns spelt out in the introduction.
In water logged regions and in places where natural drainage is ineffective or
stalled, salinity will persist, irrespective of the season of the year. In the case of tidal
canals where the flux is not severely impeded, migration of salinity is essentially
seasonal and is decided by runoff and tidal impact. Urbanization confounds the
situation because of lightning floods and diminished residual flow. In the light of the
data obtained across the water year 2003-2004, the saline pendulum characteristic of
each canal of the city is spelt out in the pages to follow. Annual precipitation and its
distribution being invariable within reasonable margins, the tidal fingerprint and
human intervention alone are the deciding factors in the salt-water migration
phenomenon. The time frame given in the data below is subject to small variations
given the vagaries of monsoons. During the sampling year, for example, North East
Monsoon was comparatively very weak and sporadic. Though samples were collected
from the surface it has been pointed out by Mishra et al., (2003) from their studies
held in the coastal waters of Orissa, that phosphate and nitrate have a proclivity of
concentrate at the bottom
Perhaps the most important environmental problem that the water bodies of the
city are nagged by is deficiency of DO. With improved DO, the whole chemical
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