Eco India: Is Chennai sacrificing its ecological security for drinking water?

Chennai, the coastal capital of Tamil Nadu in South India, has a complicated relationship with its waters. While its streets flood every monsoon, summers leave the city scrambling for every drop. The city supplies about 800 million litres of drinking water every day, according to government data. But its demand has already exceeded 1,100 million litres. In 2023, the state went on to propose a solution. Transform 5,000 acres of backwaters in the south of the city into a giant freshwater tank. With a budget of more than 300 crore rupees, the aim of the Marmalin project was to create a coastal reservoir that captures floodwaters to help solve the drinking water crisis. But the project has faced strong opposition from scientists and local communities alike. Located nearly 40 kilometres south of Chennai, the Nemmeli-Kovalam backwaters, also known as the Great Salt Lake, sits between two very different worlds. To its west runs the rapidly expanding Oamar Corridor. To its east, coastal fishing villages. The old Mahabalipuram Road, or the Oamar, serves as the premier IT corridor in the city. But it was built over the parts of once-past Pallikaranai marshlands. During the rains, the high-rises here are often surrounded by floodwaters. Meanwhile, along the east, the shorelines of Kovalam and Nemmeli seem to be slowly disappearing, putting generations of fishing communities at risk. So, what happens when this already fragile landscape is turned into a water tank? When a wetland is closed off and turned into a tank, it loses one of its fundamental roles – to absorb floodwaters and slowly release them back to sea. Which potentially means destroying nature's own flood control system. Raju, with the community-led research platform, Chennai Wetland Collective, says this pattern is all too familiar. He watched the neighbouring Pallikaranai marshlands, once the city's largest natural sponge, disappear to make way for high-rises. The government now wants to transform this floodplain into a giant, controlled basin. Thus, such a reservoir would have to contend with both monsoon floods from the land and tidal surges from the sea. In the buzzing fishing village of Kovalam, the Great Salt Lake isn't just an ecological buffer, it's a lifeline. This, however, is not just Kovalam's story. Fishers and tribals from over 15 neighbouring villages fish in these backwaters. They too had recently joined the protest against the Marmalin project. The message was clear – don't try and fix a problem by creating a bigger one. Govindan, an artisan fisher, has worked these waters all his life. He says that the water started changing within days of construction for the project. Marine biologist Dr. T.D. Babu is one of the scientists who has submitted a petition against the project. Today, he takes us to the heart of a mangrove habitat to explain the interconnectedness between marine life and uninterrupted waters. Which connects to the Bay of Bengal in the north at Muthukadu and south at Kokilamedu. Both estuarine ecosystems have a natural mangrove habitat. You can see lots of crabs and other crustaceans and fishes coming in. This estuarine ecosystem is not like riverine marine ecosystem. It is flooded with backwater runoff to the sea and that is how these flourishes because of the freshwater inflow. Closing off these backwaters, Dr. Babu warns, could destroy the mangroves. These are the breeding and feeding grounds for young migratory fish and other marine species. But beyond marine biology, this landscape is also the city's crucial line of defense against tidal surges. So this act like a suspension. It absorbs the waves, the catastrophic waves protecting the neighboring landscapes. And if it is blocked, then the waves will start take in a different course and it will have an adverse impact on either side of the estuarine ecosystem and it will be having a devastating impact of the landscapes on either side. And again, it will accelerate in general. It will accelerate the erosion on either side. Pradeep Elangovan, a geologist, has been working with coastal landscapes for over seven years. He tells us that his biggest reason to oppose the project was the fact that the government hadn't conducted any geotechnical surveys before sanctioning it. Just a few kilometers away, the quiet backwaters give way to the roar of the Nemmeli desalination plant, one of Chennai's largest facilities that turns seawater into drinking water. For fishers here, these plants have already changed the way they live. 46-year-old Ruban tells us how concentrated salt water flowing out from these plants has already affected their sea catch, as it has affected their seasonal beach seining. For Chennai, desalination plants and coastal reservoirs may seem like technological fixes to a growing water crisis. But scientists say that anchoring these megaprojects directly into vulnerable coastal ecosystems could prove disastrous. In other words, Chennai may need to return to its traditional wisdom of working with the lay of the land, instead of bulldozing over it. This means protecting its wetlands, marshlands and lakes. As the first stones of the 34-kilometer bund get laid, the fate of Marmalen project remains tied up in a battle of perceptions between a government that sees a vacant basin for storage and a community that continues to fight for a vital, living lung of the city.