63
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_6, © Springer India 2013
6.1
Lakes of Tropical Latitudes
Tropical lakes generally have moderate depth,
except those at high altitudes which are usually
frozen. They generally have one period of mixing in a year.
6.1.1 Lake Nabugabo
It is a small lake adjacent to Lake Victoria. It was
separated from Lake Victoria by a sand bar
which is said to be 3,700 years old. Similarity
exists between the fi sh species of Lake Victoria
and Lake Nabugabo.
6.1.2 Lake Victoria
Lake Victoria has an area of approx. 75,000 km
2 .
It has a long indented shoreline of varied structure. Much of it is swampy and it is surrounded
by gently undulating landscape of low relief.
The lake was supposed to have been formed
when the western edge of the Eastern Rift and
the eastern edge of the Western Rift were gradually pushed upwards as the rifts were formed.
The land between them had perhaps bent to
form the basin in which the lake now lies. This
upwarping possibly interrupted the passage of
rivers to the west which were previously fl owing from the east to the west and draining into
the Western Rift. This had resulted in the fl ow
of the rivers and the eastward fl owing Katonga
and Kafu rivers now drain into Lake Victoria.
Both these now arise from swampy watershed.
The Kagera River is now the biggest infl ow into
Lake Victoria. Possibly, it had also undergone
reversal in its fl ow during the same period
(approx. 2,500 years ago). It seems that the
level of the lake was much higher during the
ancient period as compared to the present. It
appears that rising of the lake levels by >2 m
during the early 1960s resulted in inundation of
large areas of land. This was, perhaps, caused
due to increased rainfall on the lake itself rather
than further movement of the earth’s crust. It
may be noted here that an enormous lake like
Victoria is sure to infl uence the local weather
and the catchment.
The immense saucer-shaped basin has a
maximum depth of 80 m. It contains a complex
of organisms of best-known component. They
are zoologically important and interesting
being food for the local people. More than 350
species of fi sh have been identifi ed from Lake
Victoria. Most of them are endemic to the lake
and belong to the family Cichlidae. Most of
these fi sh species are believed to have evolved
from ancestors that lived in the rivers which
crossed the present basin. The evolution of the
diverse variety of fi sh in Lake Victoria is
believed to have been encouraged by fl uctuation in water levels at the time of its formation.
It is presumed that there might have been several smaller lakes in the present basin during
the dry periods, within which isolated groups of
fi sh evolved as new species. When there was
6
Lakes of the World
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_6, © Springer India 2013
6.1
Lakes of Tropical Latitudes
Tropical lakes generally have moderate depth,
except those at high altitudes which are usually
frozen. They generally have one period of mixing in a year.
6.1.1 Lake Nabugabo
It is a small lake adjacent to Lake Victoria. It was
separated from Lake Victoria by a sand bar
which is said to be 3,700 years old. Similarity
exists between the fi sh species of Lake Victoria
and Lake Nabugabo.
6.1.2 Lake Victoria
Lake Victoria has an area of approx. 75,000 km
2 .
It has a long indented shoreline of varied structure. Much of it is swampy and it is surrounded
by gently undulating landscape of low relief.
The lake was supposed to have been formed
when the western edge of the Eastern Rift and
the eastern edge of the Western Rift were gradually pushed upwards as the rifts were formed.
The land between them had perhaps bent to
form the basin in which the lake now lies. This
upwarping possibly interrupted the passage of
rivers to the west which were previously fl owing from the east to the west and draining into
the Western Rift. This had resulted in the fl ow
of the rivers and the eastward fl owing Katonga
and Kafu rivers now drain into Lake Victoria.
Both these now arise from swampy watershed.
The Kagera River is now the biggest infl ow into
Lake Victoria. Possibly, it had also undergone
reversal in its fl ow during the same period
(approx. 2,500 years ago). It seems that the
level of the lake was much higher during the
ancient period as compared to the present. It
appears that rising of the lake levels by >2 m
during the early 1960s resulted in inundation of
large areas of land. This was, perhaps, caused
due to increased rainfall on the lake itself rather
than further movement of the earth’s crust. It
may be noted here that an enormous lake like
Victoria is sure to infl uence the local weather
and the catchment.
The immense saucer-shaped basin has a
maximum depth of 80 m. It contains a complex
of organisms of best-known component. They
are zoologically important and interesting
being food for the local people. More than 350
species of fi sh have been identifi ed from Lake
Victoria. Most of them are endemic to the lake
and belong to the family Cichlidae. Most of
these fi sh species are believed to have evolved
from ancestors that lived in the rivers which
crossed the present basin. The evolution of the
diverse variety of fi sh in Lake Victoria is
believed to have been encouraged by fl uctuation in water levels at the time of its formation.
It is presumed that there might have been several smaller lakes in the present basin during
the dry periods, within which isolated groups of
fi sh evolved as new species. When there was
6
Lakes of the World