Abstract

Dynamics of Cochin estuary, Kerala

There are many estuaries located along the Western Coastal Plain, among which the Cochin estuary, located in the state of Kerala, is considered a highly complex system.The complexity arises from two factors. The first complexity is related to the geomorphology of the estuary. The estuary has a lake with two very narrow opening to the sea and rivers discharging freshwater at several locations. The Cochin estuary consists of a labyrinth of lakes and canals covering an area of 157 km 2 extending from Azheekodu in the north to Thannirmukham Bund in the south. The estuary receives freshwater discharge from rivers like Periyar, Muvattupuzha, Meenachil, Achankovil, Pampa and Manimala. The river discharge is highly seasonal due to the monsoon climate experienced in the region. The consequence of these seasonal variations can be seen in all the estuarine variables, including  its salinity. As a result, the estuaries along the coast of India are often referred to as monsoonal estuaries (Vijith et al., 2009). The seasonality forces the estuaries to be highly unsteady, which forms the second complexity. The city of Kochi has a fast-growing population, that is above six lakhs, and rapid developmental activities are taking place in and around it. Discharge of untreated industrial and household waste in massive amounts poses
severe water quality issues, including bacterias like E. Coli. Another issue is related to water hyacinths and decay, which decreases the amount of  dissolved oxygen in the water. Saltwater intrusion to inland areas is another problem that will lead to drinking water shortage and affect agricultural productivity. Regular monitoring of the estuary is a viable solution to address these problems. Therefore, a better knowledge of its dynamics is  crucial for sustainably monitoring its health. As the estuary undergoes enormous changes spatially and temporally induced by natural and  anthropogenic factors, a model of the estuary will be a valuable contribution to address issues that may arise in the future.