161
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_7, © Springer India 2013
7.1
The Hydrological Cycle and
the Water Balance of Lakes
The distribution of water on the earth’s surface
is considered in studying the hydrological
cycle and the water balance of lakes because it
affects the distribution of lakes and the variation in their volume.
7.1.1 The Hydrological Cycle
The planet Mercury perhaps does not have any
known atmosphere among the four terrestrial
planets. On the other hand, Venus possibly has
a dry and dusty atmosphere, in which CO 2 is
the only identifi able constituent. Mars is supposed to have a little water vapour in equilibrium with ice, rather than liquid. Hence, it
cannot be said to have a hydrosphere. Only the
earth, perhaps, is gifted with abundance of
liquid water. Large quantities of ice are, possibly, present in major planets. But their whole
chemistry is quite different from that of the
terrestrial planets.
The most reasonable explanation of the presence of water on the earth is, perhaps, that the
planet was put together from relatively cold
pieces of matter, the water initially being incorporated as ice. Urey ( 1952 ) provided, by far, the
richest and convincing explanation of the chemistry of the formation of the planets. He believed
that they were formed due to aggregation of small
particles. Mercury was, perhaps, too close to the
sun to receive any water. Venus and earth, perhaps, received water in the form of ice particles
which tended to melt and became sticky. This,
most probably, had provided favourable condition for aggregation.
Notwithstanding the above, the water content
of the major part of the lithosphere of earth is
quite unknown, although it forms the great mantle of ultrabasic rock. Considering the mass of
the earth as 4.0 × 10
7 Gg without the metallic
core, Kulp ( 1951 ) concluded that the water content of the earth, as a whole, is about 2.5 × 10
5 Gg.
The water contents of the ocean and of the
atmosphere are well known. Plausible fi gures
could be derived for ice caps and other glaciated
regions (Hess 1933 ). On the other hand, the
total quantity of inland waters is relatively
small. The total area of lakes in the world is
about 2,500,000 km
2 , according to Penck
( 1894 ). This estimate was supported by Halbfass
( 1933 , 1934 ), who also quoted another estimate
of 1,700,000 km
2 . Out of this total area,
438,000 km
2 is contributed by the Caspian Sea
and 62,000 km
2 by the Aral Sea. Further, an area
of about 590,000 km
2 is contributed by the lakes
of the glaciated regions of Europe (160,000 km
2 )
and North America (430,000 km
2 ), according to
Wagner ( 1922 ). Halbfass ( 1933 , 1934 ) considers the mean depth of inland waters to be 10 m,
while Kalle ( 1945 ) assumes 100 m as the mean
depth of lakes and rivers, which appears to be
too big.
7
Lake Hydrology
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_7, © Springer India 2013
7.1
The Hydrological Cycle and
the Water Balance of Lakes
The distribution of water on the earth’s surface
is considered in studying the hydrological
cycle and the water balance of lakes because it
affects the distribution of lakes and the variation in their volume.
7.1.1 The Hydrological Cycle
The planet Mercury perhaps does not have any
known atmosphere among the four terrestrial
planets. On the other hand, Venus possibly has
a dry and dusty atmosphere, in which CO 2 is
the only identifi able constituent. Mars is supposed to have a little water vapour in equilibrium with ice, rather than liquid. Hence, it
cannot be said to have a hydrosphere. Only the
earth, perhaps, is gifted with abundance of
liquid water. Large quantities of ice are, possibly, present in major planets. But their whole
chemistry is quite different from that of the
terrestrial planets.
The most reasonable explanation of the presence of water on the earth is, perhaps, that the
planet was put together from relatively cold
pieces of matter, the water initially being incorporated as ice. Urey ( 1952 ) provided, by far, the
richest and convincing explanation of the chemistry of the formation of the planets. He believed
that they were formed due to aggregation of small
particles. Mercury was, perhaps, too close to the
sun to receive any water. Venus and earth, perhaps, received water in the form of ice particles
which tended to melt and became sticky. This,
most probably, had provided favourable condition for aggregation.
Notwithstanding the above, the water content
of the major part of the lithosphere of earth is
quite unknown, although it forms the great mantle of ultrabasic rock. Considering the mass of
the earth as 4.0 × 10
7 Gg without the metallic
core, Kulp ( 1951 ) concluded that the water content of the earth, as a whole, is about 2.5 × 10
5 Gg.
The water contents of the ocean and of the
atmosphere are well known. Plausible fi gures
could be derived for ice caps and other glaciated
regions (Hess 1933 ). On the other hand, the
total quantity of inland waters is relatively
small. The total area of lakes in the world is
about 2,500,000 km
2 , according to Penck
( 1894 ). This estimate was supported by Halbfass
( 1933 , 1934 ), who also quoted another estimate
of 1,700,000 km
2 . Out of this total area,
438,000 km
2 is contributed by the Caspian Sea
and 62,000 km
2 by the Aral Sea. Further, an area
of about 590,000 km
2 is contributed by the lakes
of the glaciated regions of Europe (160,000 km
2 )
and North America (430,000 km
2 ), according to
Wagner ( 1922 ). Halbfass ( 1933 , 1934 ) considers the mean depth of inland waters to be 10 m,
while Kalle ( 1945 ) assumes 100 m as the mean
depth of lakes and rivers, which appears to be
too big.
7
Lake Hydrology