Protecting the kidneys of Kolkata – the East Kolkata Wetlands

A real estate boom is tightening its grip on the East Kolkata Wetlands, a unique waste processing ecosystem. Cooperation and coproduction, not conflict are needed to save them.
Fishermen use wastewater of Kolkata to rear fish (Image Source: India Water Portal) Fishermen use wastewater of Kolkata to rear fish (Image Source: India Water Portal)

 The East Kolkata Wetlands (EKW) are a truly unique ecosystem, presenting a very different sight from the normal urban landscape in India.

What is so unique and different about them, and how have they survived the aggressive growth of Kolkata city? The credit goes to Dr. Dhrubajyoti Ghosh, an engineer-ecologist, who studied this neglected part of the city and came across an incredible finding - that the EKW function as kidneys for the city, efficiently converting harmful matter from the sewage generated by the city, into useful by products that can be used to generate food for its residents! 

This natural wetland, spread over 12,500 hectares on the eastern side of the city of Kolkata is now recognised as a Ramsar site and is known to be one of the largest wastewater fed aquaculture systems in the world, providing fishing opportunities for locals and supporting paddy and vegetable cultivation in small plots in and around the wetland.

However, the growing needs of the urban population and a real estate development boom are now threatening to gobble up these ecosystems, that have helped the city survive for so long. A report, 'From conflict to co production: A multi stakeholder analysis' published by the Forum for Policy Dialogue on Water Conflicts in India  provides an overview of the history of the East Kolkata Wetlands, their present status and what can be done to save them from further deterioration.

How do these kidneys function?

The city of Kolkata generates an estimated 750 mililitres of sewage every day. This wastewater is converted into food and used in fisheries and agriculture across the sprawling 12,500 hectares of wetland area. The process through which the waste gets converted into food is unique. The wastewater from the city is led by underground sewers to pumping stations in the eastern limit of the city and then pumped into open channels.

This sewage is then drawn by the local fishery owners into the fish ponds or bheris directly from the tributary wastewater canals. Bheris are a unique feature of the Kolkata wetlands, and are shallow fishponds fed by naturally treated wastewater rich in algae, which allows for low-cost fish cultivation.

Organic waste gets loaded in the bheris at the rate of 20 to 70 kg per hectare per day. It is allowed to stay in the sun and these sewage filled fishery ponds act as solar reactors.

The heat generated by the sun is adequate for photosynthesis to take place and helps in the growth of a dense plankton population in the bheri, which in turn grows on the organic matter in the wastewater. This high growing plankton serves as food for the fish population who thrive on this nutrient rich plankton. The fish play a two fold role – they maintain the balance of the plankton population in the pond and convert the available nutrients in the wastewater into readily consumable form (fish) for humans.

Organic pollution in the wastewater is thus reduced by 80 percent and the coliform bacteria in the wastewater is reduced by 99.9 percent in these ponds. Channels drain out the effluents and slurry from the treated wastewater, that is then used to grow rice and vegetables. Around a quarter of the city’s fish and vegetables are grown from the bheris. Not only do the wetlands help in providing cheap food and vegetables for the city, but also support the livelihoods of about 1,18,000 people. 

Current state of sewage fed fisheries in Kolkata

The majority of the fisheries in the East Kolkata Wetlands area are under private ownership. Though there are a few fishermen’s cooperatives, most of these are run informally. There are only two state-owned fisheries run by the State Fisheries Development Corporation in the East Kolkata Wetlands area. Seventy two percent of the sewage-fed fisheries in the East Kolkata Wetlands area are under private ownership, 27 per cent under Fishermen’s Cooperatives and 1 per cent State-owned.

Current threats to EKW fisheries in Kolkata

Today, the EKW wetlands and their fisheries are facing a number of institutional and governance challenges, besides the growing and most visible threat of urbanisation.

Survival of the cooperatives and fisherfolk is under threat

Corporatisation has been found to threaten the very survival of informal fishing cooperatives, as the fisheries department has now started the tender route of awarding licences. Sewage-fed fishing is unique not only India but also the whole world, and there is always the danger of the fisherfolk being pushed out of their occupations.

Decline in quality and quantity of sewage is a growing problem in EKW

Low amounts of sewage have negatively affected fish production and supply, as well as the well-being of the community that nurtures the fish. Poor governance also plays a part, and the lack of interest and poor management on the part of the Kolkata Municipal Corporation has also led to this problem, as it fails to ensure adequate sewage supply to the wetlands. 

No attention has been paid to sewage quality over the years. This has affected the availability of traditional fish varieties like the jiyol, which are gradually disappearing. The use of supplements and artificial fish feeds like jhilli are also increasing affecting the quality of fish. New fish varieties like Monosex Tilapia and Vietnam Koi are also increasingly being introducted, that grow more aggressively and are resilient to the change in sewage quality. They are thus fast replacing traditional varieties of fish. This, however is mainly in government-run fisheries.

Urban perceptions of fish quality

Many city residents believes that the fish from the bheris is of poor quality, as the wastewater pumped into the ponds goes through no pre-treatment or filtering. However, recent findings confirm that the traditional pretreatment and filtering processes that occur when sewage water passes through waste stabilisation ponds greatly help in making the water completely free from harmful agents.

Water hyacinths not only play a major role in removing metal toxins from sewage water, but they also serve as fish covers to arrest contamination when fish is carried by carriers.

Poor maintenance of fish ponds and sewage network

De-siltation of the fish ponds along with re-excavation of the canal distribution network is often ignored, leading to a decrease in the capacity of the bheris.

Threat from real estate developers looms large

While attempts were made earlier by private enterprises with support from the government to covert the wetlands into urban infrastructure, the NGO People United for Better Living in Calcutta (PUBLIC) went to court and won a verdict in favour of the wetland . This land mark judgment gained prominence all over the country, setting the tone for many other similar cases.

However, its relevance has gradually diminished as the local panchayat functionaries continue to be ill informed about the judgement. Even the Ramsar recognition has not helped in preventing the land mafia who have slowly and silently continued to build illegally.

Lack of support to the informal cooperatives and a lack of clarity on the part of the government regarding inter-departmental cooperation on the issue of conserving these wetlands has further made the wetlands vulnerable to land mafia.

Even more disturbing has been the amendment to the East Kolkata Wetlands (Conservation and Management) Act 2006, which now empowers the ministers to be at the top of East Kolkata Wetlands Management Authority by appropriating power, and can grant permission to build if they consider it appropriate.

The report argues that a more qualitative assessment of the ground realities of these wetlands is needed to help in their conservation. Thus there is a need for more research on:


•    Institutional practices in the management of sewage-fed fisheries and their changes over the years and the gaps
•    Challenges in the governance of the East Kolkata Wetlands
•    Status of wise use in East Kolkata Wetlands 

While the governance and institutional problems can be solved, the elements of external conflict look much stronger and the threat of real estate is more serious, lurking around for a chance to tighten its grip. Thus, no element of arbitrariness should be allowed to decide the future of the East Kolkata Wetlands, warns the report.

A copy of the report can be accessed here

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