Distribution and seasonal variation of temperature and salinity in Cochin Backwaters

Abstract

Hydrological conditions of Cochin Backwaters are greatly influenced by seawater intrusion and influx of river water as shown by the distribution of temperature and salinity at surface and bottom. The time series curves of temperature and salinity at 18 stations in the estuary reveal that the northern parts of the estuary are subjected to higher salinity wedging and oscillatory movement with vertical temperature exchange than the southern parts where mass movement of water-body with considerable mixing is observed. Marked variations of temperatures which are more pronounced on northern parts of the estuary occur during the transitional period of seasons. Comparatively higher temperatures are observed in the southern parts. The premonsoon period (February-May) indicates no salinity stratification whereas with the onset of monsoon (June) rapid buildup of stratification is observed. The Thannirmukham bund plays a decisive role during all seasons by maintaining the southern parts well mixed at uniform salinity. The barmouth region acts as a barrier in modifying the 2 arms of the estuary to the above mentioned hydrological conditions.