Greens Flag Mamallan Reservoir Project, Call to Halt It
The petition also underlined significant hydrological risks
CHENNAI: A group of leading scientists and environmentalists has petitioned Chief Minister M.K. Stalin to withdraw the proposed Mamallan reservoir project in the Kovalam–Nemmeli backwater system, warning that it could cause irreversible ecological damage to one of Tamil Nadu’s most vital coastal wetlands.
In a detailed representation submitted to the Chief Minister, the signatories — including ecologists, hydrologists, ornithologists and marine social scientists — urged the government to protect the Kovalam–Nemmeli wetland on East Coast Road and, instead, declare it a protected lagoon ecosystem.
They emphasised that the backwaters are not an inland freshwater depression but a tidal-marsh ecotone, hydrologically connected to the Bay of Bengal through the Kovalam and Kokilimedu inlets.
Quoting the state’s own publications, including the Wetlands Report Card and a Department of Environment booklet on lagoon ecosystems, the petition said lagoons and brackish wetlands depend on tidal exchange. Restricting tidal flow, it noted, drastically alters salinity balance, water temperature and circulation, limiting marine biodiversity. Brackish wetlands are among Tamil Nadu’s richest habitats, supporting fish nurseries, shellfish beds and migratory birds.
The scientists pointed out that lagoons such as Pulicat, Muthupet and Kaliveli are recognised as critical ecosystems that sustain fisheries, benthic invertebrates and coastal protection. The Kovalam–Nemmeli wetland mirrors these functions, with field observations showing seagrass patches, mudflats supporting migratory waders, and brackish habitats essential for juvenile fish and shrimp.
They warned that converting this ecotone into a freshwater reservoir would destroy these ecological functions within a single season and permanently alter species composition. The southern stretch near Mamallapuram remains ecologically vibrant precisely because tidal inflow continues, while the Nemmeli stretch has already shown early signs of lagoonal degradation due to partial obstruction by roads and bunds.
The petition also underlined significant hydrological risks. It cited the project’s environmental impact assessment (EIA), which acknowledges that flooding in western villages is linked to inadequate drainage on Old Mahabalipuram Road and the Kelambakkam–Kovalam Link Road that restrict floodwater egress through the estuary. The reservoir proposal, the scientists said, does not address these choke points.
Instead, constructing 4.5-metre bunds inside a tidal floodplain will eliminate natural flood buffers, create a rigid basin prone to overtopping during cyclones, and undermine the lagoon’s natural ability to dissipate storm energy. Such an approach, they argued, runs counter to climate-resilient design principles and Tamil Nadu’s own documented understanding of lagoon dynamics.
The signatories — including noted conservationists, academics and members of national wildlife bodies — appealed to the Chief Minister to halt the Mamallan project and initiate a science-based restoration plan that respects tidal connectivity and incorporates the experiential knowledge of local fishing communities.
They said declaring the area a protected ‘Mamallan lagoon’ would preserve biodiversity, strengthen fisheries-based livelihoods, enhance coastal resilience and uphold Tamil Nadu’s legacy of working with water rather than against it.
