Siltation and periodic closure of the bar mouth due to the dynamic process of sediment transport has caused reduction of size and seasonal closure of the mouth of the lagoon. It has reduced fresh sea-water exchange and made the lagoon shallow and turbid. It is reported that average depth, in the early 20th century, has been reduced to less than in the lagoon. This has caused difficulties such as the bar mouth getting silted up and being closed during the summer season (June–July to Oct–Nov), and an increase in flood levels during the rainy season. The lagoon acts as a large evaporating basin when the bar is closed resulting in salinity levels remaining low or high subject to the flood discharge into the lagoon during the north east monsoon. Fluctuation of water levels in the lagoon (above or below the sea level) is affecting flora, fauna and fisheries; siltation has caused variation of the lagoon mouth resulting in reduction of tidal inflows and consequent decline in stocking of commercially important species of prawns and mullets. The flood plains reclamation in Arani River basin for industrial and residential purposes is also increasing lagoon maximum water level during the floods.