A view of the lake Sembakkam in Chennai, showcasing its vast expanse and development all around.
Lake Sembakkam A view of the lake Sembakkam in Chennai, showcasing its vast expanse and development all around. © TNC-India

Stories in India

Changing Chennai’s Water Story By Restoring Its Wetlands

More than 85% of the wetlands in Chennai have been lost over the last three decades.

The last remaining natural wetland of Chennai—Pallikaranai—is easy to miss amid the urban spread of roads and buildings all around. The mere 10% that’s left is vaguely reminiscent of the 6,000 hectares that this wetland once covered in the 1960s. Pallikaranai represents the story of more than 90% of Chennai’s wetlands, which have been degraded or lost due to rapid and unplanned urbanisation. This is impacting the quality of life of its residents as they grapple with issues of water security, as well as the city’s environment and urban biodiversity. This degradation has compromised Chennai’s resilience against storms, floods and drought, as its wetlands can no longer absorb excess water during floods, nor provide adequate surface and groundwater during droughts.

In the aftermath of the 2015 floods that devastated the city, the Corporation of Chennai prioritised the restoration of 200 wetlands as part of its Smart Cities Initiative and disaster mitigation plans. We are working with partners—Care Earth Trust and the Indian Institute of Technology (Madras)—to support this effort by demonstrating a science-based wetland restoration plan that can be replicated across the city. Our aim is to bring together diverse stakeholders—NGOs, research institutions, corporates and citizens—and work collectively to transform Chennai into a city of thriving lakes.

A wetland is any land area that can hold surface water and support aquatic flora and fauna. In urban spaces, wetlands occur as lakes, ponds, marshlands, and swamps.
The Wonder of Wetlands A wetland is any land area that can hold surface water and support aquatic flora and fauna. In urban spaces, wetlands occur as lakes, ponds, marshlands, and swamps. © TNC

Restoring Sembakkam Lake

We are piloting our restoration efforts on Sembakkam lake, one of the 54 lakes that drain into the Pallikaranai wetland. This 100 acre lake is surrounded by residential colonies and has degraded over time due to excessive silt accumulation, untreated sewage disposal, solid waste dumping and illegal encroachment. Restoring this lake will have multiple benefits for the communities living around and the environment. It will also contribute towards improving the health of its surrounding interconnected lakes and, in turn, the Pallikaranai wetland.

“What’s unique about our approach is that we are undertaking a scientific study of roughly 12 sq km area around Sembakkam which forms the watershed of this lake," says Alpana Jain, Manager of our Cities Programme and lead for this project. "This will enable us to identify interventions that improve the hydrology and natural habitats of the entire watershed, along with addressing environmental challenges faced by the lake.”

Under the leadership of IIT Madras, we will understand the water quality, groundwater levels, soil composition and depth, sources of siltation and sewage, and blockages in inlet and outlet channels connecting Sembakkam to other lakes. Along with the standard interventions such as removing silt, weeds and cleaning up solid waste from the area, we will also address critical issues of sewage discharge through natural treatment methods such as constructed wetlands and floating islands integrated with DEWATS system. A strong focus will be to find solutions together with the local authorities by presenting scientific data about the impact of sewage discharge on the lake’s health. Further, we will re-establish connectivity between Sembakkam and surrounding lakes which together flow into the Pallikaranai wetland by unblocking inlet and outlet channels, thereby improving the hydrology of the entire region.

Engaging communities for long-term impact

The local communities living around Sembakkam lake are its real custodians who can play an important role in ensuring maintenance of the lake once it is revived to good health. Without their support, these restoration efforts will not have a lasting impact.

“We are regularly engaging with community members to encourage participation in restoration from the start," says Nisha Priya, Project Manager, who is overseeing project implementation on the ground. "We aim to involve them in clean-up drives to remove solid waste, conduct surveys to document the biodiversity around the lake, undertake health assessment of the lake to measure water quality and participate in plantation drives to improve the natural habitat around the lake. We want to inculcate a sense of responsibility among the community towards their lake and experience the ecosystem services it provides towards their well-being.”

We are regularly engaging with community members to encourage participation in restoration from the start.

Project Manager

Catalysing impact at scale

Our long-term vision is to catalyse science-based wetland restoration efforts across the city, so its wetlands can provide ecosystem services for people and nature. To this end, we are creating a knowledge network to gather experiences on wetland restoration efforts from diverse stakeholders.

We will use this information, along with our own experience at Sembakkam lake to create a set of wetland restoration best practice guidelines. We aim to present this to the Corporation of Chennai as a tried and tested wetland restoration model that can inform their efforts across the city.