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

The status report presented above depicts that the water availability is less than
90L per head per day, a value much less than that ofa developed country. It may be noted
that per capita demand depends on season and way of life. A realistic estimate is 360L
percapita per day. According to Prof. Malin Falkenmark 100Uday (36.5 cubic meters per
year) is the minimum per capita water requirement to meet one's basic domestic needs.
(Falkenmark and Widestrand, 1992). In India, ofthe urban population 84.9% had access
to clean drinking water in 1993 as compared to 69% in 1985, but rural population figure
fell from 82 % in 1985 to 78.45 % in 1993 (State of India's Environment, Report
No.1995EE52, 1996). When Cochin catches up with the Western industrialized
democracies it will require ten times more water even if the population remains
unchanged (Figure 1.9). This fact itself is reason enough to turn to the natural water
bodies ofthe city. The Cochin back waters are fresh enough for at least some part ofthe
year and the study zeros upon these water bodies. Many ofthe major rivers ofthe world
finally reach the ocean through deltas, which have some of the characteristics of an
estuary. In many instances the flow in these rivers is so great that the dilution of the
ocean can be measured for miles out into the sea. Some plants have used the brackish
waters of the tidal basins as cooling tower make up, since the water is low enough in
dissolved solids to be concentrated by evaporation without severe scaling problems just as
fresh waters. One example is a chemical plant on the island ofTrinidad which uses water
from thebay side ofthe island as cooling tower make up (NALCO, 1979)
1.3 Estuaryand the urban situation
An estuary is a semi enclosed coastal body of water which has a free connection
with the open sea and within which the sea water is measurably diluted with fresh water
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