154
Po River in Italy transports vast amounts of plant
nutrients, mainly nitrate of agricultural origin
and this causes significant concerns in the
Adriatic Sea because algae proliferated.
Pollution in this case comes mostly from the
agricultural lands in the Po Valley.
Natural sediment transport of the Chinese
Yellow River (Huang He) is also enormous intensified by agricultural works in the drainage basin
that increase soil erosion. Added to this are the
sewage of almost 350 million people and the
occasional small discharge of the river caused by
the overuse of its water. Agriculture uses the
water in highest ratio as irrigated land was
increased by 7.3 million ha in the drainage basin
(Fu et al. 2007). As a result, the water of the great
river becomes extremely polluted now and then,
and it is also frequent that it cannot reach the sea
at all. In the 1990s the river could not reach the
sea on 100–200 days annually.
The discharge and water regime of rivers are
determined fundamentally by climatic conditions, therefore, climate change could alter substantially by water system properties as well.
With global warming and drying in many areas
water systems are threatened in regions that are
found currently in semi-arid environments. For
example, in Southern Europe fiumara type small
streams completely dry out during the summer.
This process is going to be intensified and even
greater rivers will dry out for increasingly long
periods of time each year and the region will be
desertificated. Such changes could be expected in
the water systems of China and in SE Asia as
well.
Greatest changes, however, may occur in the
water system of the Amazonas where drying climate is further enhanced by intense deforestation. As a result the currently highest discharge in
the world could be reduced to a fraction of the
current values.
Life in the intensely warming water of the rivers with decreasing discharge grows poor and the
water could be contaminated more easily due to
the small discharge. This latter process strongly
depends on changes in the population of the
given drainage basin and also on the treatment of
the produced sewage. Nevertheless decreasing
surface water supply limits the amount of exploitable groundwater as well thus the carrying capacity of the land also decreases. Water supply of
inhabitants in several regions of the Earth is
threatened seriously; however, we will get back
to this issue when climate change is discussed
(Sect. 4.5).
4.3.3.2 Groundwater
Subsurface waters are mosaic regarding both
quantity and quality in the upper layers of the
crust depending on the geological conditions.
Their availability for humans is very variable.
Global review of aquifer systems was made
possible by the hydrogeological mapping of the
countries. The project WHYMAP was carried out
with
support
from
the
International
Hydrogeological Map (IAH), the UNESCO and
the Commission for the Geological Map of the
World (CGMW) (Margat 2007).
Figure 4.55 shows the large aquifers in the
world. First order aquifer systems are classified
here whose extents range between 100,000 and
2,000,000 km
2
or more. Their total area is 35 million km
2
.
Richey et al. (2015) studied the 37 largest
aquifer systems to understand the relationship
between water resources and water use. The
study was performed for the time period between
2003 and 2013. The ratio between water use and
water resources was called renewable groundwater stress (RGS):
RGS = use availability.
/
The study used the GRACE (Gravity Recovery
and Climate Experiment Satellite Mission)
methods.
When stress types were identified the natural
discharge (Delta D) and recharge (Delta R) of the
aquifer were considered. The relationship of the
two factors (Delta R—Delta D) was defined as
capture. Stress takes place in water systems
where water extraction exceeds capture thus storage loss occurs. Discharge could exceed recharge
for natural reasons (e.g. dry climate) as well.
Most severe conditions occur if water extraction
also increases. Four characteristic stress regimes
are defined:
4 Changes on Earth as a Result of Interaction Between the Society and Nature
Po River in Italy transports vast amounts of plant
nutrients, mainly nitrate of agricultural origin
and this causes significant concerns in the
Adriatic Sea because algae proliferated.
Pollution in this case comes mostly from the
agricultural lands in the Po Valley.
Natural sediment transport of the Chinese
Yellow River (Huang He) is also enormous intensified by agricultural works in the drainage basin
that increase soil erosion. Added to this are the
sewage of almost 350 million people and the
occasional small discharge of the river caused by
the overuse of its water. Agriculture uses the
water in highest ratio as irrigated land was
increased by 7.3 million ha in the drainage basin
(Fu et al. 2007). As a result, the water of the great
river becomes extremely polluted now and then,
and it is also frequent that it cannot reach the sea
at all. In the 1990s the river could not reach the
sea on 100–200 days annually.
The discharge and water regime of rivers are
determined fundamentally by climatic conditions, therefore, climate change could alter substantially by water system properties as well.
With global warming and drying in many areas
water systems are threatened in regions that are
found currently in semi-arid environments. For
example, in Southern Europe fiumara type small
streams completely dry out during the summer.
This process is going to be intensified and even
greater rivers will dry out for increasingly long
periods of time each year and the region will be
desertificated. Such changes could be expected in
the water systems of China and in SE Asia as
well.
Greatest changes, however, may occur in the
water system of the Amazonas where drying climate is further enhanced by intense deforestation. As a result the currently highest discharge in
the world could be reduced to a fraction of the
current values.
Life in the intensely warming water of the rivers with decreasing discharge grows poor and the
water could be contaminated more easily due to
the small discharge. This latter process strongly
depends on changes in the population of the
given drainage basin and also on the treatment of
the produced sewage. Nevertheless decreasing
surface water supply limits the amount of exploitable groundwater as well thus the carrying capacity of the land also decreases. Water supply of
inhabitants in several regions of the Earth is
threatened seriously; however, we will get back
to this issue when climate change is discussed
(Sect. 4.5).
4.3.3.2 Groundwater
Subsurface waters are mosaic regarding both
quantity and quality in the upper layers of the
crust depending on the geological conditions.
Their availability for humans is very variable.
Global review of aquifer systems was made
possible by the hydrogeological mapping of the
countries. The project WHYMAP was carried out
with
support
from
the
International
Hydrogeological Map (IAH), the UNESCO and
the Commission for the Geological Map of the
World (CGMW) (Margat 2007).
Figure 4.55 shows the large aquifers in the
world. First order aquifer systems are classified
here whose extents range between 100,000 and
2,000,000 km
2
or more. Their total area is 35 million km
2
.
Richey et al. (2015) studied the 37 largest
aquifer systems to understand the relationship
between water resources and water use. The
study was performed for the time period between
2003 and 2013. The ratio between water use and
water resources was called renewable groundwater stress (RGS):
RGS = use availability.
/
The study used the GRACE (Gravity Recovery
and Climate Experiment Satellite Mission)
methods.
When stress types were identified the natural
discharge (Delta D) and recharge (Delta R) of the
aquifer were considered. The relationship of the
two factors (Delta R—Delta D) was defined as
capture. Stress takes place in water systems
where water extraction exceeds capture thus storage loss occurs. Discharge could exceed recharge
for natural reasons (e.g. dry climate) as well.
Most severe conditions occur if water extraction
also increases. Four characteristic stress regimes
are defined:
4 Changes on Earth as a Result of Interaction Between the Society and Nature