Some aspects of the hydrographical conditions of the backwaters around Willingdon Island (Cochin)

Abstract

The Cochin backwaters which form more or less a northward extension of the Vembanad lake have all the characteristics of a typical estuary. On the southern side of the backwaters there is the influx of waters of the Pampa river and on the northern side, the Periyar. The channel to the west opening out into the Arabian Sea is the main area for the exchange between the sea and the estuary. These backwaters thus form a very interesting subject of study not only from the point of view of the seasonal variation in the various hydrographic parameters, but also this is an area where there is considerable scope for a theoretical study of magnitude of exchanges across the transition. The tidal exchanges across the channel are fairly high, as also the influx of freshwater. Apart from the influence of monsoon rains and the considerable amount of evaporation during hot months in this shallow environment, the influence of various types of phenomena in the Arabian Sea such as upwelling, sinking, coastal piling etc. is quite considerable and these result in certain characteristic variations in the hydrographical and associated conditions in this area. The present paper is an attempt to work out the main pattern of distribution of the various parameters—spatial as well as temporal and to indicate the mixing processes which make this area quite interesting not only to the hydrographer but to the biologist as well.