The water retention capacity of Vembanad Lake, the longest lake in the country, has diminished by 85 per cent in the last 120 years mainly because of massive encroachments and the destruction of the lake’s ecosystem, according to a study by Kerala University of Fisheries and Ocean Studies (Kufos).

The carrying capacity at Mean Sea Level (MSL) in the south and central sectors of the lake, spanning from Kuttanad to the Cochin Port area, has decreased by 85.63 per cent over the years. From a capacity of 2677.50 million cubic meters (MCM) of floodwater in 1930, it has reduced to 384.66 MCM in 2020, according to the five-year study conducted by a team of scientists under the leadership of VN Sanjeevan at the Centre for Aquatic Resources Management and Conservation at Kufos.

Furthermore, the lake, which covered an area of 365 sq km in 1900, has shrunk to 206.40 sq km today. The average depth in the south and central sectors has drastically reduced from 8-9 meters in 1930 to 1.8 meters (Thanneermukkom to Kuttanad - 78.82 per cent depth loss) and 2.87 meters (Thanneermukkom to Kochi Port - 66.34 per cent depth loss) respectively. The rapid loss in depth has been attributed to heavy siltation, with sediment-laden waters directly reaching the lake instead of flowing to the paddy fields, the study revealed.

T Pradeepkumar, Kufos vice-chancellor, emphasized the urgency of addressing the drastic degradation witnessed by Vembanad Lake over the past century. He said that the upcoming three-day International Fisheries Congress and Expo, scheduled to take place from January 12-14, will feature a dedicated session focusing on the degradation of the Lake ecosystem.

Unscrupulous filling of the wetland has also contributed to the lake losing area. The decline in fish species is alarming, with numbers dropping from 150-200 identified species in the 1950s to below 100 today. Iconic species like pearl spot, freshwater prawn, mullet, crab, anchovy, salmon, silver belly, sole fish, and shellfish are particularly affected by the accumulation of silt in the lake bed, causing a significant decrease in the fishery wealth of Kerala’s backwaters and impacting the livelihoods of thousands of fishermen.

The Vice Chancellor expressed the intention to leverage the International Fisheries Congress to draw international attention to the core issues of Vembanad Lake.

With a combination of regulatory measures, community engagement, and sustainable practices, he said, it is possible to reverse the degradation trends and secure the future of Vembanad Lake. Collaboration among international bodies, government agencies, local communities, and environmental organizations is deemed crucial for implementing and sustaining these measures to preserve the biodiversity and ecological integrity of Vembanad Lake for generations to come.

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