422
Its maximum and mean depths are 36 m and
11.3 m, respectively. The local meteorological
factors appear to have only limited infl uence on
the physico-chemical aspects of the reservoir.
The reservoir has gradually sloping sides, mostly
fl ats. The main catchment area of the reservoir,
the Nilgiri Hills, is characterised by charnockites
associated with garnetiferous granulites. The soil
in the plains is lateritic throughout, red in colour,
sometimes loamy, but more often sandy or gravelly admixed with quartz. This soil is only approx.
17″ deep, the basic rock being gneiss. The slopes
of the hills and catchment are mostly in reserved
forests; cultivated lands and plantations are negligible. The temperature range of surface water
was 23.8–29.4 °C, while that of bottom water
was 23.2–28.1 °C; pH varied from 7.1 to 8.7;
maximum DO saturation was 96 % in the surface
water; FCO 2 ranged from 0.3 to 3.30 mg/l; bicarbonate content varied from 18.3 to 100.4 mg/l;
chloride varied generally from 10.0 to 22.0 mg/l;
silicate ranged from 2.0 to 10.0 mg/l; and electrical conductivity (TSS) was 65.0 mhos/cm. The
thermal features of the reservoir are approximately uniform (Srinivasan 1964a ).
20.3.16 Amaravathi Reservoir in TN
This reservoir, lying between 10° 35′ N and 77°
15′ E, was formed by impounding some streams
at Kallapuram village in Tamil Nadu. The main
stream, Amaravathi, originates near Munnar in
the Western Ghats at 1,575 m MSL and runs
through thick forests. It is joined by other streams,
like Chinnar, Pambar and Tenar, and then enters
the plains about 4.8 km above dam site, where a
steep fall (‘Thoovanam’ falls) occurs. The rivers
drain about 324 square mile of mountainous
region. The impounded water irrigates c 47,000
acres of crops downstream. The area, volume,
maximum depth and average depth of the reservoir at FSL are 931 ha, 4,047.41 million ft
3 , 35 m
and 13.7 m, respectively. The volume and shore
developments are 1.1 and 2.3, respectively. The
lake has a volume of 2.2 million ft
3 at DSL. The
basic rock type of the substratum is biotite granite gneiss and schistose gneiss. Small pegmatites
cut across this rock. These are hard, coarse,
crystalline, metamorphic rocks and highly resistive. Water is relatively cold because of infl ow
from higher reaches. Water characteristics reveal
temperature 23.8–28.8 °C, average pH of 8.2
with stratifi cation as a regular feature, DO 1.6–
8.8 mg/l, FCO 2 generally absent, with occasional
hypolimnial accumulation during summer, presence of phenolphthalein alkalinity when FCO 2 is
very low or absent, methyl orange alkalinity also
generally low, total hardness 30–50 mg/l and
electrical conductivity 38–60 μ mho. The phytoplankton is represented generally by cyanophytes, diatoms, etc. Further, there is usually a
permanent occurrence of Microcystis aeruginosa. A peculiar feature of this reservoir is that
despite the primary edaphic factor being unproductive, the secondary morphometric factor also
being similar, the chemistry of water also indicating oligotrophic conditions and the fl ushing
being too much, plankton development and primary production are usually good. This is generally followed by good growth of fi shes (Srinivasan
1964b ).
20.3.17 Some Wetlands in Kanchipuram
District of TN
These wetlands lie between 12.30° and 13.00° N
and 79.60° and 80.30° E in the southern region of
Chennai in TN. Some of the copepods in these
wetlands are Mesocyclops hyalinus, M. leuckarti,
Tropocyclops prasinus, etc.
20.3.18 Studies on the Ecology
of a Freshwater Pond
Community in TN
A FW pond, lying between 79° 5 ′E and 18° 8′ N
and at 146 m MSL (approx.), is situated at
Chepauk in Chennai, Tamil Nadu. The pond is
oval in shape with steep banks on the northern
side. It had an area of 8.094 ha, 3/4 of which is
shallow with an average depth of 1.2 m, while the
mean depth of the pond is 1.8 m. There are a
number of trees on the shore, notably Ficus
religiosa . The northern shore has a gentle slope
with an inlet for water. The air temperature varied
20 Wetlands of India
Its maximum and mean depths are 36 m and
11.3 m, respectively. The local meteorological
factors appear to have only limited infl uence on
the physico-chemical aspects of the reservoir.
The reservoir has gradually sloping sides, mostly
fl ats. The main catchment area of the reservoir,
the Nilgiri Hills, is characterised by charnockites
associated with garnetiferous granulites. The soil
in the plains is lateritic throughout, red in colour,
sometimes loamy, but more often sandy or gravelly admixed with quartz. This soil is only approx.
17″ deep, the basic rock being gneiss. The slopes
of the hills and catchment are mostly in reserved
forests; cultivated lands and plantations are negligible. The temperature range of surface water
was 23.8–29.4 °C, while that of bottom water
was 23.2–28.1 °C; pH varied from 7.1 to 8.7;
maximum DO saturation was 96 % in the surface
water; FCO 2 ranged from 0.3 to 3.30 mg/l; bicarbonate content varied from 18.3 to 100.4 mg/l;
chloride varied generally from 10.0 to 22.0 mg/l;
silicate ranged from 2.0 to 10.0 mg/l; and electrical conductivity (TSS) was 65.0 mhos/cm. The
thermal features of the reservoir are approximately uniform (Srinivasan 1964a ).
20.3.16 Amaravathi Reservoir in TN
This reservoir, lying between 10° 35′ N and 77°
15′ E, was formed by impounding some streams
at Kallapuram village in Tamil Nadu. The main
stream, Amaravathi, originates near Munnar in
the Western Ghats at 1,575 m MSL and runs
through thick forests. It is joined by other streams,
like Chinnar, Pambar and Tenar, and then enters
the plains about 4.8 km above dam site, where a
steep fall (‘Thoovanam’ falls) occurs. The rivers
drain about 324 square mile of mountainous
region. The impounded water irrigates c 47,000
acres of crops downstream. The area, volume,
maximum depth and average depth of the reservoir at FSL are 931 ha, 4,047.41 million ft
3 , 35 m
and 13.7 m, respectively. The volume and shore
developments are 1.1 and 2.3, respectively. The
lake has a volume of 2.2 million ft
3 at DSL. The
basic rock type of the substratum is biotite granite gneiss and schistose gneiss. Small pegmatites
cut across this rock. These are hard, coarse,
crystalline, metamorphic rocks and highly resistive. Water is relatively cold because of infl ow
from higher reaches. Water characteristics reveal
temperature 23.8–28.8 °C, average pH of 8.2
with stratifi cation as a regular feature, DO 1.6–
8.8 mg/l, FCO 2 generally absent, with occasional
hypolimnial accumulation during summer, presence of phenolphthalein alkalinity when FCO 2 is
very low or absent, methyl orange alkalinity also
generally low, total hardness 30–50 mg/l and
electrical conductivity 38–60 μ mho. The phytoplankton is represented generally by cyanophytes, diatoms, etc. Further, there is usually a
permanent occurrence of Microcystis aeruginosa. A peculiar feature of this reservoir is that
despite the primary edaphic factor being unproductive, the secondary morphometric factor also
being similar, the chemistry of water also indicating oligotrophic conditions and the fl ushing
being too much, plankton development and primary production are usually good. This is generally followed by good growth of fi shes (Srinivasan
1964b ).
20.3.17 Some Wetlands in Kanchipuram
District of TN
These wetlands lie between 12.30° and 13.00° N
and 79.60° and 80.30° E in the southern region of
Chennai in TN. Some of the copepods in these
wetlands are Mesocyclops hyalinus, M. leuckarti,
Tropocyclops prasinus, etc.
20.3.18 Studies on the Ecology
of a Freshwater Pond
Community in TN
A FW pond, lying between 79° 5 ′E and 18° 8′ N
and at 146 m MSL (approx.), is situated at
Chepauk in Chennai, Tamil Nadu. The pond is
oval in shape with steep banks on the northern
side. It had an area of 8.094 ha, 3/4 of which is
shallow with an average depth of 1.2 m, while the
mean depth of the pond is 1.8 m. There are a
number of trees on the shore, notably Ficus
religiosa . The northern shore has a gentle slope
with an inlet for water. The air temperature varied
20 Wetlands of India