The East Calcutta (Kolkota) Wetlands:

The city sewage treatment system of Kolkota, a city of 14 million

The East Calcutta Wetlands lie approximately between 22°25' to 22°40' latitude North and 88°20' to 88°35' longitude East, covering 37 mouzas (a mouza is the lowest revenue collection unit in West Bengal and may include one or more villages) within the police stations of Tiljala, Sonarpur, Kolkata Leather Complex (formerly Bhangor KLC), Purba Jadavpur, South Bidhan Nagar, and Rajarhat. The wetlands encompass an area of approximately 12,500 hectares. The East Calcutta Wetlands originally formed as a spill-over basin of the Bidyadhari River, and has now been converted into a vast derelict swamp with the cessation of tidal influx.

In the late 1920's, pisciculture (aquaculture), with the aid of gravity-fed sewage was introduced into the wetlands. Sewage-fed pisciculture is the major economic activity among the wise-use practices in the East Calcutta Wetlands, and involves 351 fish farms (locally known as bheris) within the designated conservation area. Besides these, there are many small homestead ponds that are utilized for pisciculture with the aid of sewage. Water availability, and more precisely sewage availability, forms the backbone of this unique ecosystem that provides food and a livelihood for a large number of people from the local population. The uniqueness of the East Calcutta Wetlands is that it is the world's largest waste water ecosystem created to sustain successive resource recovery practices in the form of pisciculture, agriculture, and vegetable farming on a garbage substrate.

All of the Kolkota city sewage, except that of the suburban areas, is distributed to the fish bheris through a network of channels (locally called khals) that are segregated as primary, secondary, and tertiary channels based on their functional features. The wise-use practices and resource recovery from the city sewage essentially depend on the twenty major sewage-carrying khals, which provide a way to make a living, as well as sustenance for the large suburban population located east of Kolkota. Smaller channels and a number of inlet channels bisect the wetlands and connect the various fish bheris, tanks, and agriculture fields. Regulator gates hold the key to the supply and availability of sewage to the entire area.

The resource recovery system of the East Calcutta Wetlands consists of three areas: sewage-fed bheris, the garbage farms, and the rice paddies. The sewage-fed bheris produce about 8,000 tonnes of fish annually. The garbage farms produce approximately 150 tonnes of fresh vegetables daily, while the rice paddies produce approximately 16,000 tonnes of rice annually. In addition to the obvious benefits of food production, the old solid waste dumping grounds have now been converted into cultivated land and effluent from the waste-water fed fisheries are spread on the land providing water and nutrients for the crops grown in these fields.

However, problems are increasingly undermining the functional capacity of these wetlands. Silt deposition in the canal-beds due to the low velocity sewage flow has caused partial choking of the Bidyadhari siphon at Lalkulthi by raising the bheri bed levels. This in turn has impacted the availability of sewage water at most of the fish farms. Non-functional regulator gates further aggravate the sustainability of the fish farms. Additional problems include:

Lack of a rational, need-based, equitable sewage distribution system;
Inadequate availability of sewage leading to conflict between the government / local bodies and the stakeholders;
Pollution load due to industrial wastes;
Lack of sewage water due to siltation / bed level rise of the fish ponds;
Lack of sewage water due to inefficiency in management practices;
High input costs;
Lack of government initiatives; and
Conflicts over tenurial rights (e.g., owner-worker conflicts).

Nevertheless, the East Calcutta Wetlands were designated as a Ramsar site in 2002 underscoring its importance as a wetland of international importance. As part of the exercise for the conservation and management of wetlands, the East Calcutta Wetlands (Conservation and Management) Act, 2006 was enacted by the Government of West Bengal and came into force on November 16, 2005. Subsequent to this the East Calcutta Wetlands Management Authority was constituted.

For more information, please go to http://www.wetlands.org/reports/ris/2IN013en.pdf.