Persistent flooding of an Indian lake calls for permanent remedies to be implemented
In the heart of Kerala, India, thousands of residents are battling against severe waterlogging due to the intrusion of seawater into Vembanad Lake, the country's longest lake. This ongoing issue, exacerbated by the phenomenon known as 'kallakkadal', has been a concern for decades.
First reported by the Indian Ocean Survey in 1973, and later adopted for scientific use after UNESCO's formal approval in 2012, kallakkadal refers to flooding during the pre-monsoon season caused by swelling waves originating in the Indian Ocean. These swell waves can reach heights of two to six metres, making them a formidable force against the lake's defences.
KV Thomas, a former head of the marine sciences division at the National Centre for Earth Science Studies, was the first to report the phenomenon of kallakkadal in 1984. However, experts find it hard to predict the arrival of these swell waves, making it challenging to prepare for their impact.
The current water level in Vembanad Lake has remained high since last December, longer than the supposed 'kallakkadal' season. This prolonged high water level, coupled with the disappearance of beaches, ocean currents, rising sea temperature, and thermal expansion of water in the Arabian Sea, are contributing to the rise in sea water levels in Vembanad Lake.
The lake, which covered an area of 365 square kilometres in 1900, has shrunk to 206.4 square kilometres. The average depth of Vembanad Lake has dropped from eight metres to less than three metres. This reduction in size and depth has significantly impacted the lake's ability to store water, with around 400 million cubic metres of silt having accumulated in the lake, reducing its water storage capacity from 2,678 cubic metres in 1930 to 385 cubic metres in 2020.
Residents like Raphel Abraham and Rajendran Thavanakkadavu have been forced to abandon their homes due to flooding. Abraham believes that temporary government shelter will worsen the situation due to a lack of adequate facilities.
Forecasting the coming of swell surge in the Indian Ocean is challenging, but implementing altimeter data assimilation on a regional wave forecasting system can improve the swell forecast. Researchers also suggest recreating natural beaches and constructing sand dunes as potential solutions to mitigate the damage caused by kallakkadal.
However, Sanjeevan believes that removing silt from the lake would lead to higher intrusion of sea water. This complex issue underscores the need for comprehensive and sustained efforts to address the challenges posed by kallakkadal and protect the residents of Vembanad Lake.
This article was originally published on SciDev.Net.
