Pressure gauge experiments in India
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Date
2004Author
Joseph, A.
Desa, E.
Vijaykumar, K.
Desa, E.S.
Desai, R.G.P.
Prabhudesai, S.P.
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Pressure measurements made in differing turbid water bodies and turbulent clear-water bodies have led to the inference that the effective mean-depth in situ density value, Row eff, of these water bodies is less than the corresponding bulk density. The value of Row eff is also less than the density of the same turbid water after removal of suspended sediment. It was found that the use of bulk density to estimate tidal elevation yielded an under-estimation of tidal range. While the under-estimation was up to approx. 7% of the tidal range in the Hugli estuary, West Bengal, India, it was close to zero in the clear calm waters of the Zuari estuary, Goa, India. The under-estimation observed at many other sites was within these two extremes. The percentage under-estimation of tidal range was in agreement with the percentage reduction in the density of water at these sites compared to the corresponding bulk density. The under-estimation could be corrected with the use of the Row eff parameter. The effective mean density directly estimated by the use of a dual pressure gauge system was in close agreement with the density of water samples measured using a precision densitometer. Good quality sea level measurements can be obtained from pressure gauges by the use of the Row eff parameter obtained from dual pressure gauge systems. When single pressure gauge systems are deployed, the mean Row eff parameter can be derived with a lesser accuracy by a procedure of periodic in situ calibration using a fine-resolution tide-staff. The use of Row eff will marginally improve the accuracy of water level measurements also from clear-water estuaries where mean-depth water density undergoes marginal changes with differing phases of the tide and significant changes with seasons, but will result in more significant improvements at sites where suspended sediment is high.
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