The Pallikaranai Marshland—once a sprawling 5,000-hectare ecosystem—is now a fraction of its original size. Its slow death has drawn attention over the years, most notably during the devastating floods of 2015, which sparked public outrage over the unchecked encroachment of lake beds and rivulets feeding into the marsh.
What emerged from that disaster was a deeper understanding of the marsh not as a solitary swamp, but as part of a vast and interconnected hydrological system: the Pallikaranai Watershed Complex.
Mapping the watershed
Chennai’s water systems are typically classified by its major rivers—the Cooum, Adyar, and Kosasthalaiyar. But when viewed through the lens of how water drains into the sea, the city is split into four drainage basins: Adyar, Cooum, Kosasthalaiyar, and Kovalam. The Pallikaranai Marshland forms a critical component of the Kovalam Basin.
“Water from Chengalpattu and other southern highlands drains into lakes like Perungudi, Velachery, Narayanapuram, and Sembakkam,” explained B. M. Benisha, a Chennai-based eco-activist, pointing to a detailed map. “These lakes are interconnected, allowing water to flow downstream into the marsh and eventually into the Bay of Bengal.”
Each lake in the system acts as a step in a staircase—passing water along to the next, ensuring gradual percolation and safe drainage during heavy rains. At the heart of this system is Pallikaranai, nature’s own sponge.
The Marsh as a Sponge
Often obscured by thick grasses and reeds, the Pallikaranai Marshland is deceptively vital. It absorbs floodwater from upstream lakes, filters it, and slowly recharges the groundwater table. At the same time, it offers a buffer during monsoons—slowing the surge of water and preventing inundation of nearby areas.
But this finely tuned system is now breaking down.
Encroachment and Decline
A Digital Global Positioning Survey (DGPS) by the Tamil Nadu government—conducted under orders from the National Green Tribunal (NGT)—revealed that nearly 38% of the marsh has been encroached upon by a range of entities, including the Greater Chennai Corporation (GCC), Indian Railways, Electronics Corporation of Tamil Nadu (ELCOT), and the Perungudi Dumpyard. What remains is approximately 1,247 hectares—less than a quarter of its former expanse.
Historical records compiled by environmental groups like Aram Thinai reveal a sharp decline. In the 1980s, the marsh spread across over 5,000 hectares. Similarly, Velachery Lake has shrunk by over 70% between 1980 and 2015. Areas that once formed part of the tank are now home to the Velachery MRTS station and the busy Velachery 100 Feet Road.
Kannappan, a former fisherman and long-time Velachery resident, remembers the past vividly. “The water used to taste as sweet as coconut water,” he said. “Now, it reeks. Sewage from nearby neighbourhoods is dumped directly into the lake. Nobody eats fish from here anymore—we know better.”
Slow Progress on Conservation
To mitigate damage, the state has undertaken a few initiatives: wetland notifications, fencing, and sporadic cleanup drives. But these efforts remain piecemeal. Three years after the marsh was designated a Ramsar site of international importance, the Tamil Nadu State Wetland Authority has yet to share boundary and survey details with the Chennai Metropolitan Development Authority (CMDA). The lack of coordination has delayed CMDA’s compliance with NGT directives.
“The government is treating this like a checklist item, not a living system,” said Karthik, co-founder of Aram Thinai. “We’re wasting precious time trying to undo what’s already been concretised. Our focus should now be on preserving what little remains.”
What Now?
Environmentalists argue that it’s time to move beyond blame and towards urgent action. “We’re not going to get back the lost hectares,” said Benisha. “But if we act decisively by marking clear boundaries, enforcing sewage controls, and reconnecting the broken lake chains, we can still save this system.”
But the glaring truth today is evidently the fact that as Chennai faces rising temperatures, erratic monsoons, and groundwater depletion, the Pallikaranai Marshland stands as both a warning and a lifeline.
