Surface salinity of Cochin backwater with reference to tide

In connection with the prawn studies of the Sub-station, routine observations on the surface salinity, temperature, oxygen etc., were conducted regularly in the Cochin backwater for the past few years. A paper on the plankton and its relationship with salinity of the Bunder canal at Narakkal connected with the backwater has been published (George, 1958). For this study, observations along the canal were made throughout during the high water. A doubt then arose whether it would give a true picture of the conditions of the canal by following only the high waters of each day since varying amounts of sea water might enter into the backwater and from there into the canal during the high water, bringing with it planktonic organisms and salinity conditions which are more marine than what had existed during the low water. Balakrishnan (1957) while studying the surface salinity of Ernakulam channel noticed a number of rapid fluctuations which were attributed, to a certain extent, to the influence of tide. The present work is an attempt to understand the amount of tidal influence, if any, on the salinity of the backwater, at the various heights of the tide and to see whether two different conditions, one during high and the other during low water, exist in the area