The ecological importance of the Kolleru Lake, another Ramsar site of India is focused in this issue. Kolleru lake serves as a habitat for various resident and migratory birds, besides sustaining fishing, agriculture and related occupations of the people dependent on it for their livelihood. The lake has a variety of habitats ranging from coastal freshwater lagoons to seasonal freshwater marsh. It has been designated as a Ramsar Site in November 2002.
Kolleru is one of the largest natural fresh water lakes situated in the state of Andhra Pradesh. It was considered as ‘Jaladurga’ by the ancient kings. It is situated between the two major river basins of Godavari and Krishna and functions as a natural flood balancing reservoir between the two deltas. The total area of the lake is 90,100 hectares. The water spread area of the lake extends over 900 square kilometre. The depth of the lake varies from 1metre to 1.5 metre. Geologically, the origin of the lake is recent; the formation due to excessive siltation of the Krishna and Godavari rivers forming a lagoon separated from the sea. The lake collects its water from a number of rivulets, canals and streams. The main source is Budameru, Thammileru, Ramuleru and Gunderu. The catchment area of the lake is around 4,700 sq.km. The only outlet of the lake is the ‘Upputeru’ river, which is connected to the Bay of Bengal. The lake bed is made up of heavy silt and clay.
The entire area of the lake comprises of vast plains interspersed with pools of water with a few tree species such as Borassus flabellifer, Acacia nilotica and Azadirachta indica, etc.
The vegetation of the upland area is mostly scrub jungle and the common species are Acacia arabica, Acacia leucophloea, Tamarindus indicus, Thespesia populnea, Barringtonia acutangula, Pongamia glabra, Azadirachta indica, Wrightia tinctoria, Mimosa hamata and Borassus flabellifer.
The shrubs and herbs are of typical coastal vegetation. The entire vegetation of this area can be classified into aquatic and terrestrial vegetation. The lake is covered by littoral vegetation, predominantly of hydrophytes. The aquatic vegetation includes species such as Nymphaeae nouchali, Nyphoides indicum, Ottelia alismoides, Nechamandra alternifolia, Limnophila indica, Vallisneria spiralis, Blyxa octandra, Ipomaea aquatica, Scirpus articulatus, Paspalidium germinatum, Typha angustata and Phragmites karka. It shows variation in different spots with emergent, submerged and free floating aquatic macrophytes such as Ipomea aquatica, Aponogeton crispum, Limnophilla indica, Chara species and Utricularia species. Rare plants such as Excoecaria agallocha and Bruguiera sexangulata are also found in this wetland.
The lake supports a number of animal species; zooplankton, including 16 species of rotifera,one Conchostraca, 29 Cladocera, 18 Calanodia, 15 Cyclopodia and 20 Harpacticodia ; 11 species of molluscs , 63 species of fishes, 12 species of prawns and 188 species of birds. The lake supports more than 50,000 waterfowl which includes a variety of resident and migratory birds including the vulnerable species like grey pelican (Pelecanus philippensis). The migratory birds include gargeney teals, pintails, mallards, flamingoes, adjutant storks etc., and they visit the lake from October to March every year. Major fishes found in the lake include murrels, catfishes, carps and Indian climbing pearch.
Social & Cultral Values
The combination of culture and capture fisheries are practiced in the area. Kolletikota, situated in the middle of the lake has a temple of the local deity. Every year thousands of people visit the temple on a particular day during the annual ‘Jatara’. The place can be accessed only by boat and has religious importance.
Present Status of the lake
The lake has been turning into a wetland, and in large parts, into land-mass over the years. This natural process is disliked by human economic activity, which depends on the fresh water of this vast area. Partly due to the legal status accorded to culture fishing and agricultural activity within and around the lake spread in the last fifty years and partly due to the demand for freshwater fish besides paddy from the Kolleru, the ecological conservation of this area has become more a human than an aesthetic need.
Lack of regulation of the seaward flow of the Kolleru waters during monsoon which is progressively increasing the high - flood line, is causing major food problems in the surrounding cities of Eluru and Gudivada, besides submerging second - crop paddy lands and fishtanks.
There is sewage inflow from the towns of Eluru and Gudivada and industrial effluents, pesticides and fertilizers from the delta region.
There are about 50 villages in and around the lake and the total population is about 2.5 lakhs. The socio-economic condition of the people is quite disturbing.
“Saving Asia’s Threatened birds: a guide for government and civil society”, Birdlife International, Cambridge, UK., 2003.
Chatrath, K.J.S., “Wetlands of India” Ashish Publishing House, New Delhi, 1992.