CHENNAI: A group of scientists, ecologists and conservation experts has urged Chief Minister MK Stalin to withdraw the proposed Mamallan reservoir project, warning it could cause irreversible damage to the Kovalam-Nemmeli backwater ecosystem.
In a letter, the signatories, including contributors to national and global climate assessments, said scientific evidence shows the project would harm one of Tamil Nadu’s important coastal wetlands.
The experts stressed the Kovalam-Nemmeli backwaters function as a tidal marsh ecotone hydrologically connected to the Bay of Bengal through the Kovalam and Kokilamedu inlets, and are not an inland freshwater depression. Restricting tidal flow, they warned, would alter salinity, temperature and circulation patterns, ultimately limiting marine biodiversity.
They noted the southern stretch near Mamallapuram remains ecologically healthy due to continued tidal inflow, while parts of the Nemmeli stretch already show early signs of degradation because of partial blockage by roads and bunds.
According to the petition, the wetland supports seagrass patches, mudflats used by migratory waders, and brackish habitats essential for juvenile fish and shrimp. Converting the system into a freshwater reservoir could destroy these functions within a single season.
The group also flagged hydrological risks, pointing out the Environmental Impact Assessment itself attributes flooding in western villages to drainage bottlenecks along Old Mahabalipuram Road and the Kelambakkam-Kovalam Link Road. The proposed reservoir, they said, does not address these choke points and could create a rigid basin vulnerable to overtopping during cyclones.
Calling for an alternative approach, the signatories urged the government to instead declare the area a protected lagoonal wetland, ‘Mamallan Lagoon’, and pursue restoration based on scientific and community knowledge.
The appeal was endorsed by over 20 experts, including Nityanand Jayaraman, Asad Rahmani, Romulus Whitaker and Ravi Chellam.