Tuesday, March 28th, 2023 00:55:38

Why East Kolkata Wetlands need to be protected

Updated: September 22, 2017 12:58 pm

East Kolkata Wetlands that provides many ecosystem services needs to be preserved to meet the SDGs and to mitigate the effect of global warming.

Increasingly in both academic and social sectors, sustainable development goals (SDGs) are being quoted often and set as targets. Coming close on the heels of the marginal success of millennium development goals or MDGs with its target as 2015, SDGs were set by the United Nations to be fulfilled by 2030.

The SDGs are different from MDGs in that the goals are for all countries and not just for the rich countries to do for the poor. SDGs expect all countries to work towards a better future (Sachs 2012). Sachs 2012 feels that middle income emerging economies, such as Brazil, China, India, and others, will be crucial leaders in the implementation of the SDGs while they also deal with their own internal challenges of balancing growth and environmental sustainability.

Out of the 17 SDGs, the ones pertinent to my study were:

No. 6 (clean water and sanitation)

No. 11 (sustainable cities and communities)

No. 13 (climate action)

Goal 6: It calls for access to clean water and better sanitation facilities, protection of water-related ecosystems including wetlands, rivers, aquifers and lakes and for the promotion of international cooperation for water harvesting and wastewater treatment facilities.

Goal 11: It is about making human settlements inclusive, safe, resilient and sustainable and efforts to be made to protect the world‘s cultural and natural heritage which includes biodiversity and ecosystems. Today’s cities have overgrown their boundaries and are fast swallowing the surrounding rural areas and creating peri-urban areas where rural and urban characteristics coexist. This goal takes these emerging urban phenomena into considerations and seeks to strengthen national and regional planning for better governance as well. The overall aim of this goal is to make cities more resilient and adaptive to climate-induced changes.

Goal 13: This goal is for building resilience to adapt to climate-induced events in different countries. One way of doing this is by maintaining the natural safeguards like wetlands for sponging floods and forests to stop soil erosion. It puts further emphasis on goal no.11.

The ecological system crucial to achieving these three SDGs is the wetlands. What are wetlands? The International Union for the Conservation of Nature and Natural Resources (IUCN) standardised the meaning of the term wetlands at the Ramsar Convention as the “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters”.(Shine and de Klemm 1999).

A total of 2242 Ramsar sites covering 215,240,112 ha across the world have been identified for protection. This foresight to protect wetlands seems to have insured several countries against potential losses from extreme events. Despite commitments made at the convention, however, wetlands continue to shrink at an alarming rate and get lost to urban expansion.

What is East Kolkata Wetlands?

One of the wetlands which provides most of the ecosystem services as designated in the millennium assessment report about wetlands is the East Kolkata Westlands or EKW. EKW is the world’s largest resource recycling ecosystem which helps to treat around 600 million litres of sewage and wastewater daily. This sewage and wastewater are generated mainly by the city of Kolkata (Mukherjee 2016). Canals and creeks, both natural and man-made, constructed during the colonial times are used to bring sewage to flow through the wetlands.

Development of such a system to treat sewage has been possible because the city of Calcutta (now Kolkata) is located between the river Hooghly, a distributary of the Ganga on its west and numerous wetlands on its east. These wetlands are the inter-distributary marshes between the Hooghly and the now dead Bidyadhari river (declared dead in 1920), another distributary of the Ganga and the Brahmaputra delta (Chatterjee 1993). These water bodies, being the spill basin of the estuarine river Bidyadhari, were salty in nature and thus earned the name salt lakes (Chatterjee 1993). From the 1940s, the liquid sewage was decided to be taken through the wetlands for treating it before draining it into the sea through Kulti river, another distributary further east of the city. Before this, since the last decades of the 19th century, the locals had embanked these salt lakes and started saline water fishing. But the treated sewage water is sweet in nature since it is domestic sewage and thus the local fishers switched to sweet water fishes from the saline ones. This treated water is also used for paddy and vegetable cultivation. The wetlands, over a period of time, not only treated sewage of the city but also performed various ecosystem services which appealed to the locals who adapted to the wetlands.

Urban expansion and the changes

Urban expansion of Kolkata has resulted in the city’s eastward movement towards the wetlands which has consequently led to the usurpation of much of the wetlands over the years. The area of wetlands has shrunk considerably since the colonial times. Recognising the loss and destruction of valuable services provided by the wetlands, 12,500 acres of wetland area was brought under the protection of Ramsar Convention in the year 2002. Since then, the pace of changing the land use of wetlands may have reduced but the encroachments of wetlands continue in the form of expansion of a major arterial road, the metro railway or for elite residential complexes.

The map above shows the steady growth of the city of Kolkata from the 17th century into the wetlands.The city needed to grow and since it was bound on the west by the river, the only way to grow (apart from growing longitudinally) was towards marshy wetlands.

Attached to the right is the present day map of the metropolitan areas of Kolkata alongside the designated boundary of EKW and the Salt Lake Township. One can see the different canals which carry the sewage away from the city. In the 1960s, 1650 acres were reclaimed from the wetland area to accommodate millions of refugees who poured in from Bangladesh after independence. That was the beginning of wetland reclamation in an organised, large-scale way.  Since then, a series of real estate and commercial development have continued to encroach upon the wetland area.

Generally, ecosystem services occur naturally in wetlands but in EKW, there has always been a positive blend of human interventions and nature (Ghosh 2005, 60). This is because the natural water source to these water bodies was cut when river Bidyadhari dried up. Now it is the sewage water which is the source of water for them. The provisioning and regulating roles of EKW have blended perfectly and have been rightfully put to use.

Administratively the EKW is divided into varying units, locally called mauzas. I collected data from three of them–Kharki, Dhapa Manpur and Dhapa–out of which two are governed by the Kolkata municipal corporation while the third is run by its gram panchayat. The dominant sources of livelihood in Kharki are fishing and paddy cultivation while in Dhapa Manpur, it is fishing and Dhapa has vegetable farms. From all these three mauzas, however, men and women are forced to go out to the city for additional sources of income.

The ecosystem services of EKW

Water scarcity is perhaps the biggest worry of the present and future generations. Wastewater can be an alternative source of water for fish culture and crop cultivation. EKW has been using this unique system for almost a century now. The cleaning of the water is basically done by oxidation, radiation and biological breakdown of organic waste (Mukherjee 2006) and all this is done with the help of photosynthesis. The fish farms are kept very shallow to allow the rays of the sun to pass through them. Once the effluents settle, the water is channeled into the maturation ponds where fishes are grown. Maturation ponds also help in nutrient cycling (Chakraborty 2013).

The treated wastewater from the ponds is then used in the surrounding paddy and vegetable farms for irrigating the fields before it is finally drained into the Kulti river. According to one estimate, there is 8100 ha of wetland area, out of which 3900 ha is under fisheries. With an average production of 3.44 tons/ha per year, the total production in a year is estimated at 13000 tons (Mukherjee 2006). The fishes, paddy, and vegetables grown with sewage water are safe for human consumption as long as they are cooked properly. The fishes and the vegetables from EKW are sold in the nearby wholesale markets. But paddy is not grown in every mauzas and the ones in which it is grown is usually used for subsistence.

I observed during my fieldwork that the inhabitants of EKW depend on the wetlands for fuel. Cowdung cakes could be seen drying in Kharki mauza. Wood is collected by the residents of Kharki and Dhapa for cooking fuel. Kharki residents also collect thatching materials from their surroundings. These are the provisioning services available at EKW.

According to Chatterjee (1999), keeping in mind the latitude, temperature range, average annual rainfall, EKW (computed for 365 days on 3000 hectares of the wet surface) generates 248,291.25 tonnes of oxygen per year. However, this is quite dated literature and newer research on such dimensions would give more accurate information.

Apart from these, EKW acts as a retention basin in general. The tilt of the land is towards the east, so water inevitably flows towards the wetlands by gravity. But with urban growth, the wetlands on the east have been reclaimed, many have atrophied or converted into residential areas. This causes flooding in the city after a heavy downpour. The EM Bypass acts as a virtual dike cutting natural spill basin in the erstwhile salt lake swamps and stops the smooth flow of the storm water into the wetlands (Ghosh 1993).

Urban wetlands also act as the only source of water for domestic use for populated urban settlements. Bathing and washing clothes in local ponds are very common in Kolkata. Such water sources act as protection against fire hazards (Ghosh 1993).

Changing faces of wetlands

In the recent past, several fishers from the wetland area have converted their fish farms into amusement parks, water sports parks, boating and picnic spots. Visitors have a good time while the fishermen make some extra profits. Usually, such places function actively during winter months.

EKW came under the Ramsar Convention in 2002. Wise use of wetlands as defined by Ramsar in the case of EKW are quite a few. It provides direct employment for 70,750 men and women who maintain fishponds, catch fishes, grow paddy and vegetables (Mukherjee 2006, 106). Several stakeholder groups who receive payment-in-kind for work undertaken for fish farmers and laborers employed mainly in aquaculture can find employment on farms producing rice during the paddy season. These wetlands also supply affordable and fresh fish and vegetables to markets serving poor communities. The water resources, if managed properly, mitigate environmental degradation and reduce public health risks (Bunting et al. 2010).

The above-mentioned services provided by EKW to the city of Kolkata are thus both ecologically and economically very important. These wetlands, however, are treated by the city residents as dirty and a breeding ground for mosquitoes and attach no aesthetic value to them. Keeping in mind the SDGs and global warming, there is a strong need to acknowledge and appreciate the importance of these wetlands and work towards conserving them.


By Haimanti Pakrashi



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