394
outlets usually drain out the lake water for cultivation. The soil in and around the lake is laterite,
and the area surrounding it generally slopes
towards the lake. Paddy, sugarcane, etc., are generally farmed in the catchment and the drainage
basin, due to which the wetland often receives
nutritive substances of biological signifi cance
from the farm lands. Certain factors seem to contribute to the peculiar type of AM and phytoplankton found in this wetland, notably highly
irregular shoreline, so that there are a number of
bays which make greater contact of water with
land and also provide with increased areas of
shallow water for growth of rooted AM. The
depth of wetland ranges from 3.04 to 7.62 m, and
the waterbody is subjected to both SW and NE
monsoons. The region has a salubrious climate.
The air temperature usually varies from 21 to
28 °C. The water characteristics revealed variations of temperature 19.1–27.4 °C, pH 7.0–8.9,
DO 6.42–11.37 mg/l, saturation of DO 68.2–
132.7 %, TA 200–223 mg/l, ammoniacal nitrogen 0.284–0.516 mg/l, nitrous nitrogen traces to
0.03 mg/l, nitric nitrogen 0.12–1.60 mg/l, phosphate traces to 0.07 mg/l and silicate 3.4–7.0 mg/l.
Further, some of the AM are Hydrilla verticillata, Vallisneria spiralis, Potamogeton sp.,
Nymphaea sp., Scirpus sp., etc. Some of the
phytoplankton are Oscillatoria, Spirulina,
Cosmarium, Staurastrum, Navicula, Synedra,
Microcystis, etc. (Joyangoudar 1964 ).
20.3.8 Wetlands of Kerala
There are a large number of wetlands in Kerala.
They have peculiar ecological conditions being
in the coastal region. An account of some of the
wetlands in Kerala is given below:
These lie at 0–1 m MSL, between 10° 20′ and
10° 35′N and 76° 6′ and 76° 11′ E in the Trichur
District of Kerala. They have an area of 11,000 ha.
The climate is humid with an annual average
rainfall of 2,500 mm. The temperature varies
from 16 to 39 °C. The region is subjected to
ingress of salt water although steps are taken to
prevent this. The name Kole is derived from the
peculiar type of cultivation done in these wetlands during December to April. Natural vegetation includes mainly grasses and sedges. The
principal cultivated crop is paddy. Areca nut,
coconut and banana are grown on the slopes
around the paddy fi elds. Conversion of paddy
fi elds for construction purposes has been a threat
to these wetlands. Release of pesticides and trapping of birds are some of the other threats to these
wetlands. These wetlands serve as habitats for
different kinds of aquatic birds. Declaring the
wetland as a protected site is an important suggested conservation measure.
20.3.8.1 Vembanad Lake (Vembanad
Kayal or Vembanad Kol)
Vembanad Lake (Plate 20.70 , Fig. 20.18 ) lies at
(surface elevation) 0 (zero) m MSL, between 9°
35′ N and 76° 25′ E. It is one of the longest lakes
in India and is the largest lake in Kerala (area
200 km
2
). The principal infl ows of the lake are the
Achankovil, Manimala, Meenachil, Muvattupuzha,
Pamba and Periyar, while there are several canals
serving as outfl ows. The maximum length and
breadth of the lake are 96 km and 14 km, respectively. Some of the settlements around the lake are
Alleppey, Cochin, Cherthala, etc., and the lake is
bordered by Alappuzha (Alleppey), Kottayam and
Ernakulam districts. The port of Kochi (Cochin) is
located at the lake’s outlet to the Arabian Sea.
Alleppey, ‘Venice of the East’, has a large network
of canals that meander through the town.
Geography and Hydrography
A unique characteristic of the lake is the location
of the Thanneermukkom saltwater barrier. It is
the largest mud regulator in India. This barrier
essentially divides the lake into two parts: (a) one
part with brackish water perennially and (b) the
other part with freshwater fed by the rivers draining into the lake. This barrier has helped the
farmers in Kuttanad, where farming is done
below sea level. It has, however, created ecological problems, regarding the extensive spread of
water hyacinth in freshwater.
Signifi cance
Vembanad Kol is a Ramsar wetland. It is home to
more than 20,000 waterfowls in India, the third
largest of its population in India. It is also an
ideal habitat for shrimps.
20 Wetlands of India
outlets usually drain out the lake water for cultivation. The soil in and around the lake is laterite,
and the area surrounding it generally slopes
towards the lake. Paddy, sugarcane, etc., are generally farmed in the catchment and the drainage
basin, due to which the wetland often receives
nutritive substances of biological signifi cance
from the farm lands. Certain factors seem to contribute to the peculiar type of AM and phytoplankton found in this wetland, notably highly
irregular shoreline, so that there are a number of
bays which make greater contact of water with
land and also provide with increased areas of
shallow water for growth of rooted AM. The
depth of wetland ranges from 3.04 to 7.62 m, and
the waterbody is subjected to both SW and NE
monsoons. The region has a salubrious climate.
The air temperature usually varies from 21 to
28 °C. The water characteristics revealed variations of temperature 19.1–27.4 °C, pH 7.0–8.9,
DO 6.42–11.37 mg/l, saturation of DO 68.2–
132.7 %, TA 200–223 mg/l, ammoniacal nitrogen 0.284–0.516 mg/l, nitrous nitrogen traces to
0.03 mg/l, nitric nitrogen 0.12–1.60 mg/l, phosphate traces to 0.07 mg/l and silicate 3.4–7.0 mg/l.
Further, some of the AM are Hydrilla verticillata, Vallisneria spiralis, Potamogeton sp.,
Nymphaea sp., Scirpus sp., etc. Some of the
phytoplankton are Oscillatoria, Spirulina,
Cosmarium, Staurastrum, Navicula, Synedra,
Microcystis, etc. (Joyangoudar 1964 ).
20.3.8 Wetlands of Kerala
There are a large number of wetlands in Kerala.
They have peculiar ecological conditions being
in the coastal region. An account of some of the
wetlands in Kerala is given below:
These lie at 0–1 m MSL, between 10° 20′ and
10° 35′N and 76° 6′ and 76° 11′ E in the Trichur
District of Kerala. They have an area of 11,000 ha.
The climate is humid with an annual average
rainfall of 2,500 mm. The temperature varies
from 16 to 39 °C. The region is subjected to
ingress of salt water although steps are taken to
prevent this. The name Kole is derived from the
peculiar type of cultivation done in these wetlands during December to April. Natural vegetation includes mainly grasses and sedges. The
principal cultivated crop is paddy. Areca nut,
coconut and banana are grown on the slopes
around the paddy fi elds. Conversion of paddy
fi elds for construction purposes has been a threat
to these wetlands. Release of pesticides and trapping of birds are some of the other threats to these
wetlands. These wetlands serve as habitats for
different kinds of aquatic birds. Declaring the
wetland as a protected site is an important suggested conservation measure.
20.3.8.1 Vembanad Lake (Vembanad
Kayal or Vembanad Kol)
Vembanad Lake (Plate 20.70 , Fig. 20.18 ) lies at
(surface elevation) 0 (zero) m MSL, between 9°
35′ N and 76° 25′ E. It is one of the longest lakes
in India and is the largest lake in Kerala (area
200 km
2
). The principal infl ows of the lake are the
Achankovil, Manimala, Meenachil, Muvattupuzha,
Pamba and Periyar, while there are several canals
serving as outfl ows. The maximum length and
breadth of the lake are 96 km and 14 km, respectively. Some of the settlements around the lake are
Alleppey, Cochin, Cherthala, etc., and the lake is
bordered by Alappuzha (Alleppey), Kottayam and
Ernakulam districts. The port of Kochi (Cochin) is
located at the lake’s outlet to the Arabian Sea.
Alleppey, ‘Venice of the East’, has a large network
of canals that meander through the town.
Geography and Hydrography
A unique characteristic of the lake is the location
of the Thanneermukkom saltwater barrier. It is
the largest mud regulator in India. This barrier
essentially divides the lake into two parts: (a) one
part with brackish water perennially and (b) the
other part with freshwater fed by the rivers draining into the lake. This barrier has helped the
farmers in Kuttanad, where farming is done
below sea level. It has, however, created ecological problems, regarding the extensive spread of
water hyacinth in freshwater.
Signifi cance
Vembanad Kol is a Ramsar wetland. It is home to
more than 20,000 waterfowls in India, the third
largest of its population in India. It is also an
ideal habitat for shrimps.
20 Wetlands of India