The Vembanad-kol wetland is a large complex aquatic ecosystem covering 2.5% of the geographical area of Kerala State. The wetland ecosystem includes a chain of lagoons from Kuttanad on the south to the kol wetlands of Thrissur on the north (refer map). The total area is about 1,51,250 hectares and is the largest brackish water wetland. It is spread over Kottayam, Ernakulam, Alleppy, Thrissur and Malapuram districts of Kerala. This wetland complex includes Vembanad Lake, Kuttanadu marshy areas and Kol wetlands. Ten rivers feed this wetland; they are Keecheri, Puzhakkal, Karuvannur, Chalakudy, Periyar, Muvattupuzha, Meenachil, Manimala, Pamba and Achancoil. All these rivers originate from the Western Ghats, flow westwards through the wetland system and join the Arabian Sea. The wetland is typically divided into two distinct segments, the freshwater dominant southern zone and the salt-water dominant northern zone. The wetland system receives about 21,100 mm3 of water annually, 17,740 mm3 during the monsoon and 3,360 mm3 during the dry period. The mean annual rainfall varies from 1,600 mm to 4,800 mm, the temperature ranges from 21 0C to 360C and the humidity ranges from 70 to 80 percentages. It was designated as a Ramsar site in November, 2002.
Importance of the Vembanad-Kol wetland
Research studies are being carried out by organizations such as Centre for Water Resources Developmentand Management, Centre for Environmental Studies, Kottayam, Kerala Agricultural University and Central Marine Fisheries Research Institute. Information on various ecological aspects is available for different parts of the wetland ecosystem. There are about 161 species of fish, 6 species of shrimps, 5 species of Palaemoneds, 3 species of crabs and bivalves in Vemband. Freshwater, euryhaline and true estuarine fish are available in this wetland. The common fish species are Mugil cephalus, M.parsia, M.macrolepis, Etroplus suratensis, Ambassis sps. Chanes sps., Sciaenides sps., Megalops sps., and Wallago sps. Both marine and fresh water molluscs are available (including prawns and clams). The common fresh water prawn is Macro branchium sps. Among the clam species the black clam (Villorita cyprinoids) is the most common. The common edible crab is Scylla serrata. This wetland supports threatened species such as spot billed pelican (Pelicanus philippensis), oriental darter (Anhinga melanogaster), watercock (Gallicrex cinerea) and blackbellied tern ( Sterna acuticauda ). It supports the third largest population of more than 20,000 waterfowls in India during the winter months. A total of 233 species of birds have been reported from Kol wetlands and the Vembanad supports a total of 185 species of birds. The soft organically rich sedimentary substratum of the inshore region is an ideal habitat of shrimps. The estuarine zone plays an important role in the life cycle of many shrimps caught and the entire Vembanad Kol act as nursery for important shrimps like Panaeus indicus, P. monodon, Metapenaeus dobsoni, M.monoceros, M.affinis, Macrobrachium rosenbergii and also serves as a habitat for variety of finfish, shellfish and a nursery of several species of aquatic life, and a transitional zone (ecotone) between sea and land.
Rare mangrove species such as Excoecaria agallocha, Bruguiera sexangula are found in this wetland. Mangrove vegetation is abundant at Kumarakom, Vypeen, Kannamali and Chettuva areas.
Socio-economic values of the wetland
The study carried out by the Kerala Agricultural University reveals that the Kol wetland, part of the Vembanad-Kol wetland complex, generates employment for about 12.49 lakhs man days in a single year (approximate profit = Rs. 17.30 crores). Retting and coir production is a major cottage industry in Vaikom area. Live clam collection is a major occupation of women and children in the area. The meat and shell have a good market and the meat is a part of the food habits of the poor people of the locality. About 50 tonnes of clam shells are exported daily to different markets, both inside and outside Kerala. The clamshells of this area are heavy and rich in calcium carbonate. 300-400 tonnes of giant fresh water prawns are harvested every year. But excess fishing is resulting in declining number of prawn and fishery catch, noticed since the 1970’s.
Threats to the wetland