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

The design, according to Maxted et al (1997) of man made linear, dead end canals
dug deeperthan the estuary produces poor flushing and circulation, leading to poor water
quality, poor sediment quality, and a decimated biological community. A suggested
method for improvement of tidal water quality is to connect canals in a loop to natural
bodies of water (Baca, 1988). Marvin et al, (1990) recommends that canal excavations be
designed to maintain adequate oxygen levels by eliminating dead end canals and aligning
canals in such a direction as to receive maximum turbulent mixing from prevailing winds
and that canal depths not exceed the bordering bay, Maxted et al., (1997) suggested to
maintain certain channel shapes like low aspect ratio and rounded corners. Mitigation
techniques for the problem of low oxygen levels focus on knowing the system (i.e. its
nutrient load) use of aerators has been shown to be a short term approach to the problem
while a long term measure points toward circulation as a critical design feature. Other
options are a reduction ofsources ofcontaminants and introduction ofbuffer strips to act
as contaminant filters. It is, however, impossible to insulate the tidal canals from urban
and periurban influence as humanity has a seasoned tendency to gravitate towards
estuarine coastal belts.
The effectofurban discharges on the natural water bodies has lately provoked a great
deal of interest and concern. The effect of market effluent from the Oja-titun market,
Nigeria on the chemical quality ofthe Opa Reservoir was investigated between February
and November; 2000. Sharp seasonal variations were recorded for most variables.
Comparison of the reservoir water with international limitation standards for drinking
water showed that the quality ofthe reservoir water was very low and that treatment was
required to achieve minimum limitation standards, (Eludoyin et al., 2004). Water
represents a key element in the development ofHo Chi Minh City, Vietnam. The city is
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