Location: from the region
of Cochin south for about 75 km, Kerala
Area: 25,600 ha (formerly at least 100,000 ha)
Altitude: 0-5 m
Description of site: A chain of fresh to brackish
coastal lagoons and swamps, on average about 3-4 km wide, stretching for 96
km from the estuary of the Chalakaudi and Periyar rivers south along the coast
to Vembanad Lake and its surrounding floodplain. The northern portion of the
backwaters is called Varazuzah Lake. The backwaters occupy an alluvial plain
lying parallel to, and in between, the Indian Ocean and the Western Ghats.
The system of lagoons has two permanent openings to the sea: the northernmost
at Crangannore and the other at the city of Cochin. A third at Thollappally,
south of Aleppey, is open only during the southwest monsoon. The lagoons are
fed by a number of perennial rivers draining the southern Ghats, notably the
Chalakaudi, Periyar, Muvattupuza, Manimala, Pambiyar, and Achankovil rivers.
The Cochin backwaters constitute a vast estuarine system under monsoonal regime. The system is flushed by rains and freshwater run-off during the southwest monsoon from May to September. After the rainy season, an intrusion of seawater invades the estuary and, by the end of the inter-monsoon period, becomes perceptible up to 15 km or 20 km upstream. The surface water salinity ranges from almost freshwater conditions during the monsoon to about 34 ppt near the mouth of the backwaters during the dry season. The average tidal range at Cochin is about one metre.
Vembanad Lake, situated in the higher reaches of the backwaters (extending from Gagnanole in the north to Alleppy in the south), in Kottayam and Pathanamthitta districts, is the largest among the Kerala backwaters, covering some 7,94,00 ha together with the adjacent Kuttanad wetlands. The lake has shrunk considerably from its original size due to reclamation for agriculture. The rivers Achankoil, Pamba, Manimala, Meenachil, Moovattupuzha, and a branch of Periyar draining into the lake bring large quantities of silt. The water spread (minimum spread is 49,000 ha), salinity levels, and other water quality characteristics undergo diurnal and seasonal rhythmic changes affected by daily tides (entering through the mouth at Kochi) and monsoonal floods. The construction of a barrier across Vembanad at Thanneermukkam has altered the hydrology of the wetlands
Climatic conditions: Humid, tropical monsoon climate,
with an average annual rainfall of 3600 mm. Most of the rainfall occurs during
the southwest monsoon from May to September. There is a short, dry season
from December to March. Humidity is between 75% and 80%. Temperature ranges
from 18�C to 36'C
Principal vegetation: The whole of the backwater
area was originally occupied by mangrove swamps, with Rhizophora apiculata,
Derris heterophylla. Sonneratia albs, Acanthus ilicifolius. Acrostichum aureum,
and Cerbera manghas. Most of the mangroves have now been destroyed, and only
a few isolated pockets of stunted Rhizophora and Sonneratia remain. In the
Vembanad-Kuttanad complex, only remnants of mangroves, freshwater swamp vegetation,
and a few reed beds survive. A few pockets of original wet, evergreen forests
are preserved in temple lands as 'sacred groves'. Exotic water weeds, in particular,
Eichhornia and Salvinia have multiplied
Fauna: The fauna are diverse but inadequately catalogued.
These wetlands are known to be among the richest avifaunal habitats on the
west coast of India. Some 91 species of resident/ locally migratory, and 50
species of migratory birds have been observed in the area. Among the migratory
waterfowl are Indian reef heron, pintail, white-eyed pochard, teal (3 species),
marsh harrier, osprey, plover (2 species), sandpiper (4 species), shanks (2
species), snipe, gulls (4 species) and terns (6 species).
Common resident species include: little grebe, little cormorant,
darter, eastern grey heron, little bittern, pond heron, four species of egret,
lesser whistling teal, banded crake, palm swift, Malabarjungle babbler, and
Malay pipit. The fish fauna include Mugil cephalus, M.cunnesius, M.parsia,
M.macrolepis, Lates calcifer, Chanos chanos, Etroplus suratensis, Tachysurus
spp., and several other species. The estuarine crocodile (Crocodylus porosus)
once occurred throughout the backwaters but is now thought to be extinct in
Kerala
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