137
fresh water reservoir; however, only 45% of it is
composed of fresh water (Table 4.9). This is also
a significant amount (10,530,000 km
3
) utilised in
increasing amount but a major part of it is also
unavailable (too deep) for humans. Ground ice
and permafrost can also be regarded unavailable
water. Moisture stored in soils is estimated to be
around 16,500 km
3
. Its preservation and the supply of the agricultural loss (irrigation) are very
important regarding food supply.
Humanity has utilised the most easily accessible surface waters in highest grade since early
times. The amount of water stored in riverbeds at
any one time hardly exceeds 2000 km
3
while that
stored in fresh water lakes is more significant
with 91,000 km
3
. Since river water is supplied
continuously via precipitation the society uses
this water mostly as drinking water (following
cleaning and disinfection), irrigation and industrial water. Apart from these, major rivers are
used for transport while most of them are suitable
for various sports especially large reservoirs. The
number and size of water reservoirs built for
energy production, drinking water storage and
irrigation are growing: more than half a million
engineered dams have been built on Earth so far
the joint water surface of which covers
258,570 km
2
(Downing et al. 2006). Their joint
effects are so sizeable that they even modify the
global water cycle. Kohli and Frenken (2015)
studying 14,200 dams estimated their evaporation for 346 km
3
/year; however, this could be
more than 800 km
3
when completely filled. They
also noted that the lack of data is too extensive to
estimate the evaporation of all reservoirs accurately. It seems likely, however, that the evaporation excess caused by all artificial lakes and
reservoirs exceeds 1000 km
3
/year globally
(Fig. 4.48). Evaporation of water reservoirs is
especially significant in tropical desert areas. For
example, the 5000 km
2
surface of the Nasser
Lake built on the Nile River evaporates around
10% of the discharge of the river. Although the
total amount of fresh water would be enough for
humans today, the uneven distribution of water
there are areas suffering from the lack of water
even today and the future seems to be even more
critical (c.f. Sect. 4.3.3).
Humanity influences the water cycle by draining swamps, cultivation (cultivation effects transpiration, different transpiration of commercial
plants, irrigation), forest clearing (evapotranspiration is modified), constructions (drainage and
evaporation
conditions
are
changed).
Consequences are rather regional today and cannot be detected in the global water cycle since the
effects on the global flux remain below 1000 km
3
/
year for the moment.
Water in the oceans is an almost inexhaustible
raw material source for humans (salts, chemical
elements); however, it cannot be used as drinking
water which is the most important for humans and
it cannot be used as irrigation water for agriculture
either or it can be used only after desalination.
Since this process requires a great amount of energy
desalinated seawater is used generally as drinking
water. Oceans are the means of material transport
as well providing also space for fishing, whale
hunting and have an important role in food supply
via fish and oyster breeding along the shoreline.
The influence of anthropogenic activities on
the water cycle of oceans is not known and their
quantification cannot be given. The evaporation
of the ocean surface could be modified only
slightly by various contaminants (like crude oil,
plastics) compared to the global scale. It is likely,
however, that evaporation increased as a result of
temperature rise caused by anthropogenic climate change exceeds significantly the decreasing
effects of contamination thus in the end anthropogenic activities cause increasing evaporation,
the extent of which is not known yet. In case the
warming of the climate remains permanent the
fluxes of the water cycle will increase: besides
greater global evaporation the total moisture content of the atmosphere and the quantity of annual
precipitation increase as well. The spatial distribution of the latter will be modified resulting in
much more extreme precipitation in certain climate regions of the Earth than today.
4.3.2 Contamination of Oceans
Population boom in the twentieth century,
increased consumption of people and technical
and technological development rapidly increasing production resulted in a rapid growth of waste
products and environmental pollution including
the pollution of the hydrosphere. Contamination
4.3 Changes in the Hydrosphere
fresh water reservoir; however, only 45% of it is
composed of fresh water (Table 4.9). This is also
a significant amount (10,530,000 km
3
) utilised in
increasing amount but a major part of it is also
unavailable (too deep) for humans. Ground ice
and permafrost can also be regarded unavailable
water. Moisture stored in soils is estimated to be
around 16,500 km
3
. Its preservation and the supply of the agricultural loss (irrigation) are very
important regarding food supply.
Humanity has utilised the most easily accessible surface waters in highest grade since early
times. The amount of water stored in riverbeds at
any one time hardly exceeds 2000 km
3
while that
stored in fresh water lakes is more significant
with 91,000 km
3
. Since river water is supplied
continuously via precipitation the society uses
this water mostly as drinking water (following
cleaning and disinfection), irrigation and industrial water. Apart from these, major rivers are
used for transport while most of them are suitable
for various sports especially large reservoirs. The
number and size of water reservoirs built for
energy production, drinking water storage and
irrigation are growing: more than half a million
engineered dams have been built on Earth so far
the joint water surface of which covers
258,570 km
2
(Downing et al. 2006). Their joint
effects are so sizeable that they even modify the
global water cycle. Kohli and Frenken (2015)
studying 14,200 dams estimated their evaporation for 346 km
3
/year; however, this could be
more than 800 km
3
when completely filled. They
also noted that the lack of data is too extensive to
estimate the evaporation of all reservoirs accurately. It seems likely, however, that the evaporation excess caused by all artificial lakes and
reservoirs exceeds 1000 km
3
/year globally
(Fig. 4.48). Evaporation of water reservoirs is
especially significant in tropical desert areas. For
example, the 5000 km
2
surface of the Nasser
Lake built on the Nile River evaporates around
10% of the discharge of the river. Although the
total amount of fresh water would be enough for
humans today, the uneven distribution of water
there are areas suffering from the lack of water
even today and the future seems to be even more
critical (c.f. Sect. 4.3.3).
Humanity influences the water cycle by draining swamps, cultivation (cultivation effects transpiration, different transpiration of commercial
plants, irrigation), forest clearing (evapotranspiration is modified), constructions (drainage and
evaporation
conditions
are
changed).
Consequences are rather regional today and cannot be detected in the global water cycle since the
effects on the global flux remain below 1000 km
3
/
year for the moment.
Water in the oceans is an almost inexhaustible
raw material source for humans (salts, chemical
elements); however, it cannot be used as drinking
water which is the most important for humans and
it cannot be used as irrigation water for agriculture
either or it can be used only after desalination.
Since this process requires a great amount of energy
desalinated seawater is used generally as drinking
water. Oceans are the means of material transport
as well providing also space for fishing, whale
hunting and have an important role in food supply
via fish and oyster breeding along the shoreline.
The influence of anthropogenic activities on
the water cycle of oceans is not known and their
quantification cannot be given. The evaporation
of the ocean surface could be modified only
slightly by various contaminants (like crude oil,
plastics) compared to the global scale. It is likely,
however, that evaporation increased as a result of
temperature rise caused by anthropogenic climate change exceeds significantly the decreasing
effects of contamination thus in the end anthropogenic activities cause increasing evaporation,
the extent of which is not known yet. In case the
warming of the climate remains permanent the
fluxes of the water cycle will increase: besides
greater global evaporation the total moisture content of the atmosphere and the quantity of annual
precipitation increase as well. The spatial distribution of the latter will be modified resulting in
much more extreme precipitation in certain climate regions of the Earth than today.
4.3.2 Contamination of Oceans
Population boom in the twentieth century,
increased consumption of people and technical
and technological development rapidly increasing production resulted in a rapid growth of waste
products and environmental pollution including
the pollution of the hydrosphere. Contamination
4.3 Changes in the Hydrosphere