The river Elbe basin with a catchment area of approximately 150,000 km
2 is
located in Central Europe (Czech Republic, Germany, Austria and Poland). Especially in the mountainous upper parts of the Czech Republic a number of large
reservoirs are concentrated. These reservoirs are used to regulate the streamflow in
the rivers Vltava/Moldau and Labe/Elbe, and to promote navigation and other water
uses. As an example for the different quantities simulated by SWIM (natural
discharge) and successive by WBalMo Elbe (managed streamflow) the flow at
gauge Hrensko is displayed in the Fig. 3.4. The results are presented for the years
2010–2050, where 2010 stands for the time period 2008–2012 and so on. Since
100 realisations are used, 500 values (5 years * 100 realisations) are available for
the statistical analysis for each time step of the respective time period.
Especially for dry periods in summer a decline of the natural low flows is
simulated, e.g. “min” of natural discharges. The minimum managed streamflow
in summer months is higher compared to the natural discharge, due to low flow
augmentation by reservoirs and discharges from wastewater treatment plants etc.
However, for mean conditions the differences between natural discharge and
managed streamflow are rather small. During periods of high flows the managed
streamflow is lower compared to the natural discharge, because water is used to
refill the reservoirs. Overall the extremes caused by natural conditions are buffered
by water resources management.
From Fig. 3.4 also the potential of water resources management to counterbalance effects of climate change and land use change on streamflow and water
availability can be estimated. Not considered here are possibilities of adapting
water management to changing conditions.
3.3.4 Climate Change Impacts on Glaciers
Glaciers are considered as key indicators for the early detection of global greenhouse gas related warming trends (IPCC 2007). Moreover, glaciers itself have
considerable impact on the runoff regimes of rivers with glaciated areas within
their catchments. Basic requirement for the formation and persistence of glaciers is
the accumulation of snow which is not entirely melted in the following summer and
remains as firn till the next winter. The firn of several years compacts to ice and
finally starts to flow following gravity. In Central Europe, glaciers are located in the
Alps as well the Caucasus with a total ice covered area of 3,778 km
2 (Zemp
et al. 2008; WGMS and NSIDC 1989, updated 2012). Since their last maximum
during the little ice age in the middle of the nineteenth century, most glaciers in
these areas are shrinking.
In the twentieth century, annual temperature increased by 1.3
C for the alpine
region (Auer et al. 2007). Additionally, winters in the alpine areas became drier in
the last 25 years and therefore reduced the amount of snow accumulation (Zemp
et al. 2008). Both processes have negative effect on the existing glaciers.
3 Effects of Climate Change on the Hydrological Cycle in Central and Eastern Europe
39
2 is
located in Central Europe (Czech Republic, Germany, Austria and Poland). Especially in the mountainous upper parts of the Czech Republic a number of large
reservoirs are concentrated. These reservoirs are used to regulate the streamflow in
the rivers Vltava/Moldau and Labe/Elbe, and to promote navigation and other water
uses. As an example for the different quantities simulated by SWIM (natural
discharge) and successive by WBalMo Elbe (managed streamflow) the flow at
gauge Hrensko is displayed in the Fig. 3.4. The results are presented for the years
2010–2050, where 2010 stands for the time period 2008–2012 and so on. Since
100 realisations are used, 500 values (5 years * 100 realisations) are available for
the statistical analysis for each time step of the respective time period.
Especially for dry periods in summer a decline of the natural low flows is
simulated, e.g. “min” of natural discharges. The minimum managed streamflow
in summer months is higher compared to the natural discharge, due to low flow
augmentation by reservoirs and discharges from wastewater treatment plants etc.
However, for mean conditions the differences between natural discharge and
managed streamflow are rather small. During periods of high flows the managed
streamflow is lower compared to the natural discharge, because water is used to
refill the reservoirs. Overall the extremes caused by natural conditions are buffered
by water resources management.
From Fig. 3.4 also the potential of water resources management to counterbalance effects of climate change and land use change on streamflow and water
availability can be estimated. Not considered here are possibilities of adapting
water management to changing conditions.
3.3.4 Climate Change Impacts on Glaciers
Glaciers are considered as key indicators for the early detection of global greenhouse gas related warming trends (IPCC 2007). Moreover, glaciers itself have
considerable impact on the runoff regimes of rivers with glaciated areas within
their catchments. Basic requirement for the formation and persistence of glaciers is
the accumulation of snow which is not entirely melted in the following summer and
remains as firn till the next winter. The firn of several years compacts to ice and
finally starts to flow following gravity. In Central Europe, glaciers are located in the
Alps as well the Caucasus with a total ice covered area of 3,778 km
2 (Zemp
et al. 2008; WGMS and NSIDC 1989, updated 2012). Since their last maximum
during the little ice age in the middle of the nineteenth century, most glaciers in
these areas are shrinking.
In the twentieth century, annual temperature increased by 1.3
C for the alpine
region (Auer et al. 2007). Additionally, winters in the alpine areas became drier in
the last 25 years and therefore reduced the amount of snow accumulation (Zemp
et al. 2008). Both processes have negative effect on the existing glaciers.
3 Effects of Climate Change on the Hydrological Cycle in Central and Eastern Europe
39