77
6.2.6 Lakes in Hungary: Lake
Balaton
Lake Balaton (47° N and 18° E; altitude 104 m;
lake area 596 km
2
; volume 1.8 km
3 ; catchment
area 5,178 km
2 ; maximum depth 11 m; average
depth 3.3 m) is situated in Hungary. It provides a
well-studied example of an extensive, shallow
lake in the temperate zone. It is a long lake
having a length of 77 km and a mean width of
9 km. It is supposed to have been formed about
18,000 years ago as the ice retreated from central
Europe. The principal infl ow is the Zaia River,
while the main outfl ow is the Sio Canal which
fl ows into the river Danube.
The lake water is alkaline (pH 8.5). The calcium
content is quite high. As the algae give off CO 2
during respiration, calcium carbonate precipitates out and fl akes of it fl oat on the water. The
water temperature ranges from 0 to 30 °C.
People are said to be living around this lake since
millennia. Today, it is a tourist resort. The lake had
been a victim of eutrophication since the beginning
of twentieth century due to increased use of fertilisers by the growing human population. There have
been increased pollution loads in the inlets also.
These changes have led to changes in the lake communities since last few years.
About 100 km
2 of the lake is only about 1.5 m
deep. Hence, littoral conditions prevail over a
large proportion of the lake area. Littoral zone
frequently supports a much wider variety of
species than the open limnetic zone. Thus, it is
reasonable to expect a better quantity and diversity
of invertebrates in this shallow swamp-fringed
lake. This makes the lake an ideal habitat for a
rich diversity of birds such as waders and herons.
The reeds also provide support for nesting, roosting, breeding, etc.
Forty-seven species of fi sh have been recorded
from Lake Balaton. These include the pike perch
( Stizostedion lucioperca ) . However, the bream
( Abramis berma ) accounts for major bulk (70–
80 %) of the annual yield.
6.2.6.1 Neusiedlersee
This shallow lake is situated on the AustroHungarian border. It is known as Neusiedlersee
in Austria and as Lake Fertő in Hungary.
Neusiedlersee (47° 50′ N, 16° 50′ E; altitude
113 m; lake area 300 km
2 ; lake volume 200–
250 km
3
; max. depth 1.8 m; mean depth 1.3 m)
has enormous reed beds, which form c 50 % of
the lake. The River Wulka is the principal infl ow.
There is no outfl ow. The lake has an important
fi shery, but it is signifi cant for bird population.
The water is highly turbid due to constant churning of the sediments. The lake water also contains
much amount of organic phosphate throughout
the year to support quite a rich phytoplankton
population. One of the largest invertebrates to
depend upon the reeds is a moth, reed leopard
( Phragmataecia castaneae ) whose caterpillars
are stem borers. The reed beds are dominated by
the common reed ( Phragmites australis ), which
is one of the most widespread reeds in Europe.
6.2.7 Lakes in Norway
Lakes of true Arctic and Antarctic proximity contain fl ora and fauna which had to tolerate diffi cult
conditions of cold and prolonged darkness. So, it
is hardly surprising that they are relatively few in
number. The behaviour of ice and snow is the
chief determinant of physical conditions in such
lakes for the survival of the biota.
6.2.7.1 Ovre Heimdalsvatn
It is a small mountain lake in Norway. It lies on
the eastern slopes of Jotunheimen Mountains in
Norway (latitude 61° 25′ N at an altitude of
1,090 m above MSL). It is situated just below the
upper limit (1,200 m) of the mountain; and as
such, trees are quite abundant around the lake.
The lake has an area of only 0.75 km
2 but the
catchment area is approx. 26.3 km
2 which rises to
an altitude of c 1,843 m. The lake has a maximum
depth of only 13 m. Hence, the water is well
mixed with only occasional brief stratifi cation
during the ice-free period from early June to midOctober. During winter, the air temperature may
dip to −30 °C and the lake is covered by a layer of
ice (70–90 cm thick) plus a blanket of snow up to
1 m deep. The water level under the ice is maintained by groundwater supplies and its renewal
6.2 Lakes of Temperate Region
6.2.6 Lakes in Hungary: Lake
Balaton
Lake Balaton (47° N and 18° E; altitude 104 m;
lake area 596 km
2
; volume 1.8 km
3 ; catchment
area 5,178 km
2 ; maximum depth 11 m; average
depth 3.3 m) is situated in Hungary. It provides a
well-studied example of an extensive, shallow
lake in the temperate zone. It is a long lake
having a length of 77 km and a mean width of
9 km. It is supposed to have been formed about
18,000 years ago as the ice retreated from central
Europe. The principal infl ow is the Zaia River,
while the main outfl ow is the Sio Canal which
fl ows into the river Danube.
The lake water is alkaline (pH 8.5). The calcium
content is quite high. As the algae give off CO 2
during respiration, calcium carbonate precipitates out and fl akes of it fl oat on the water. The
water temperature ranges from 0 to 30 °C.
People are said to be living around this lake since
millennia. Today, it is a tourist resort. The lake had
been a victim of eutrophication since the beginning
of twentieth century due to increased use of fertilisers by the growing human population. There have
been increased pollution loads in the inlets also.
These changes have led to changes in the lake communities since last few years.
About 100 km
2 of the lake is only about 1.5 m
deep. Hence, littoral conditions prevail over a
large proportion of the lake area. Littoral zone
frequently supports a much wider variety of
species than the open limnetic zone. Thus, it is
reasonable to expect a better quantity and diversity
of invertebrates in this shallow swamp-fringed
lake. This makes the lake an ideal habitat for a
rich diversity of birds such as waders and herons.
The reeds also provide support for nesting, roosting, breeding, etc.
Forty-seven species of fi sh have been recorded
from Lake Balaton. These include the pike perch
( Stizostedion lucioperca ) . However, the bream
( Abramis berma ) accounts for major bulk (70–
80 %) of the annual yield.
6.2.6.1 Neusiedlersee
This shallow lake is situated on the AustroHungarian border. It is known as Neusiedlersee
in Austria and as Lake Fertő in Hungary.
Neusiedlersee (47° 50′ N, 16° 50′ E; altitude
113 m; lake area 300 km
2 ; lake volume 200–
250 km
3
; max. depth 1.8 m; mean depth 1.3 m)
has enormous reed beds, which form c 50 % of
the lake. The River Wulka is the principal infl ow.
There is no outfl ow. The lake has an important
fi shery, but it is signifi cant for bird population.
The water is highly turbid due to constant churning of the sediments. The lake water also contains
much amount of organic phosphate throughout
the year to support quite a rich phytoplankton
population. One of the largest invertebrates to
depend upon the reeds is a moth, reed leopard
( Phragmataecia castaneae ) whose caterpillars
are stem borers. The reed beds are dominated by
the common reed ( Phragmites australis ), which
is one of the most widespread reeds in Europe.
6.2.7 Lakes in Norway
Lakes of true Arctic and Antarctic proximity contain fl ora and fauna which had to tolerate diffi cult
conditions of cold and prolonged darkness. So, it
is hardly surprising that they are relatively few in
number. The behaviour of ice and snow is the
chief determinant of physical conditions in such
lakes for the survival of the biota.
6.2.7.1 Ovre Heimdalsvatn
It is a small mountain lake in Norway. It lies on
the eastern slopes of Jotunheimen Mountains in
Norway (latitude 61° 25′ N at an altitude of
1,090 m above MSL). It is situated just below the
upper limit (1,200 m) of the mountain; and as
such, trees are quite abundant around the lake.
The lake has an area of only 0.75 km
2 but the
catchment area is approx. 26.3 km
2 which rises to
an altitude of c 1,843 m. The lake has a maximum
depth of only 13 m. Hence, the water is well
mixed with only occasional brief stratifi cation
during the ice-free period from early June to midOctober. During winter, the air temperature may
dip to −30 °C and the lake is covered by a layer of
ice (70–90 cm thick) plus a blanket of snow up to
1 m deep. The water level under the ice is maintained by groundwater supplies and its renewal
6.2 Lakes of Temperate Region