an aerial image of a city surrounding a lake park.
Lake Sembakkam in Chennai, India. © Ram Keshav

Our Priorities

Restoring Chennai’s Lake Sembakkam for water security and improved health

Putting wetlands to work for the local communities, biodiversity and the environment.

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Chennai, the largest city in India’s southern state of Tamil Nadu, is currently home to 474 wetland complexes that serve as the lifeline for its people, nature and wildlife. Sadly, over the last few decades, the majority of these wetlands have been degraded due to human encroachment, untreated sewage inlets, garbage dumping and the city’s rapid economic growth. While the city’s urban development improves the living standards for many, rampant urbanisation is negatively affecting its wetlands, lakes and rivers and depleting its limited water sources.

The Troubled Waters of Lake Sembakkam

Lake Sembakkam is among the 54 lakes that ultimately drain into the Pallikaranai Marshland, one of the most critical and fragile marshlands of Tamil Nadu. The Pallikaranai Marshland is among the last remaining natural wetlands of the city that contain several rare and threatened species and acts as a breeding ground for thousands of migratory birds such as the Wood Sandpiper, Comb Duck, Northern Shoveller, pintail ducks, cormorants, spoonbills, Spot-billed Pelicans and more.

Once spanning over 8,000 hectares, only 10% of the original wetland remains and is now protected from development. This freshwater marsh, until recently, worked as an effective natural system for groundwater recharge and as a flood reservoir during heavy rains. Lake Sembakkam, surrounded by residential developments, has degraded over time due to excessive silt accumulation, untreated sewage disposal, solid waste dumping and increased encroachment.

Putting Things Right

In 2018, we set out to restore Lake Sembakkam to achieve multiple benefits for the local communities living around its shores, its biodiversity and the environment as a whole. Restoration efforts also contribute towards improving the health of its surrounding interconnected lakes and in turn, the Pallikaranai Marshland. 

A graphic showing the water cycle of a wetland.
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

Setting Benchmarks to Secure Early Wins

To ensure Chennai’s future economic development does not further degrade its freshwater resources, The Nature Conservancy and our partners (Care Earth Trust and the Indian Institute of Technology, Madras) are working in Chennai to demonstrate science-based lake restoration efforts through our on-ground pilot project for Lake Sembakkam.

The project involves a close assessment of the environment, biodiversity and the communities living near the lake. Our work is ensuring broader integration and the application of freshwater conservation and restoration activities into country and state policies.

The project is addressing degradation causes such as excessive silt accumulation, infestation of invasive alien species of weeds, and pollution from wastewater and solid waste disposal.

Project Goals

  • Restoring a 100-acre urban wetland in Chennai
  • Improving the water storage capacity by nearly 40% 
  • Improving flood mitigation benefits
  • Improving water quality to meet wildlife and fisheries propagation standards prescribed by the Central Pollution Control Board, India. 
  • Establishing a nature-based wastewater treatment system at a large scale—seven million litres per day
  • Creating an eco-friendly landscape and a biodiversity habitat at the lake

We are undertaking a scientific study of the catchment area around the lake that forms the watershed of Lake Sembakkam. This will enable us to identify interventions to improve the hydrology and natural habitats of the entire watershed while addressing the environmental challenges faced by the lake.

Quote: Dr. Jayshree Vencatesan

The lake is now attracting more birds like the Spot-billed Pelican, cormorants and Painted Storks. The lake continues to attract Dabchicks (also called Little Grebes) and moorhens.

Managing Trustee, Care Earth Trust

Additionally, our initial restoration activities have measurably increased the water storage capacity of the lake by over 1,00,000m3 through silt removal and have offered flood mitigation benefits through the construction of embankments and flood regulator gates.

Notably, the project's three-pronged approach which involves science, community and government is crucial to having sustainable restoration outcomes. 

The renewed and restored banks of the lake looking clean and healthy with graphics showing people enjoying it as a recreational outdoor space.
The polluted banks of Lake Sembakkam before restoration work.
Lake Sembakkam before and after restoration Swipe right to see the banks of Lake Sembakkam before restoration work and swipe left to see how we plan for the banks to look after restoration work.

Communities as Custodians of Lake Sembakkam

The local communities living around and nearby Lake Sembakkam are its real custodians. They are playing an important role in nursing the lake back to health. The community members are equally essential to ensure the maintenance and upkeep of the lake once it is revived to good health. Without their support, restoration efforts will not have a lasting impact. To ensure sustainability, local communities have been engaged in the project right from the start.

They are involved in:

  • clean-up drives to remove solid waste.
  • conducting surveys to document the biodiversity around the lake.
  • assessing the water quality of the lake.
  • plantation drives to improve the natural habitat around the lake.

Such community involvement and activities have developed a sense of responsibility and ownership towards the lake among the community members. 

Continued Support and Future Opportunities for Lake Restoration

Our on-ground experience coupled with key stakeholder engagement and knowledge sharing will aid the development of best practice guidelines on wetland restoration. These guidelines will inform wetland restoration efforts and build the much-needed momentum to mainstream wetland restoration efforts among various stakeholders not only just across Chennai but also in India. 

Quote: Dr. Emmanuel Varghese

Most NGOs focus on quick implementation and maximum visibility, whereas TNC focuses on inclusiveness, economy and sustainability. Clearly, this is going to be a model for the region and the entire country.

Technical Expert - Nature based Solutions for Wastewater treatment

Our project will serve as a foundation for providing a tried and tested science-based wetland restoration plan that we aim to integrate into the efforts of the Chennai Government to improve the health of wetlands across Chennai.

We are excited to partner with International Business Machines (IBM) to device Internet of Things (IoT) based monitoring for Lake Sembakkam. This technology will help regularly monitor and measure the water quality and water level of the lake in real-time. Simply put, we will utilize a cloud-based platform and install sensors in the lake to track its health, giving us actionable insights for our future work. 


Lake Sembakkam Factsheet

Know more about how we are changing Chennai's water story and restoring Lake Sembakkam.

Blue Waters (4:03) A comeback story of the Lake Sembakkam and its biodiversity.

Contribute to the Chennai Challenge

To help us meet the needs of this ambitious initiative and in support of the Conservancy’s contribution towards Chennai’s long-term planning and action toward water security and climate change, a generous supporter has created the Chennai Challenge, a challenge grant of US $200,000 to help us raise additional support for our work in Chennai.  We need to raise US $600,000 to unlock the full potential of this wonderful gift. TNC is proud to recognize a new donor, the Guru Krupa Foundation, which has supported our work in Lake Sembakkam, and Grundfos, a corporate supporter of our work in Chennai. To contribute to the Chennai Challenge, please contact Nandita Mishra, Associate Director - Marketing & Development, India at


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