336
L. Zaharia et al.
floods cannot be recorded in the same years, but the interannual distribution of flows
can be extremely uneven.
From the total of 38 low flow periods identified during 1961–2012, 63% (24)
occurred in winter, 21% (8) in the autumn, 13% (5) in spring and just one case
during summer (in July). Monthly, the maximum frequency of the low flow periods
is specific in February. On the contrary, in April, May and June, when the snowmelt
has an important role in the surface runoff, there were not prolonged intervals with
flows below Q 95% .
10.5.3 Projected Hydrological Responses to Climate Changes
For Valea Cerbului River catchment the emission scenarios predict a rise in the air
temperature of 1.3 °C (the mean value indicated by the emission scenarios used).
Compared to the reference period (1961–2000), the scenarios show temperature
growths for all seasons, with maximum values in autumn and minimum values in
spring. The analysis conducted at the monthly level, reveals upward, significant
trends for A2 and A1B scenarios for the future period 2001–2065.
The trends indicated by the simulated precipitation data are not as clear as those
of the air temperatures: annually, a slightly descending trend and a higher variability
are expected; seasonally, the simulated precipitation shows more important decrease
during autumn (from 6.8 to 10.7% depending on the scenario).
The hydrological model used establishes the type of each precipitation event,
liquid or solid, by threshold transition temperatures, set in the model optimization
stage. Likewise, it can determine the precipitation values and types dissociated for
different zones of altitudes, in this case: the zone above 1750 m amsl, the zone
between 1250 and 1750 m amsl and the low part, with less than 1250 m amsl. The
simulation using the scenarios data as climatic input highlights the diminution of
the mean annual snowfall by 5–11% by 2065, relative to the reference period. On
the contrary, the projected liquid precipitation slowly increases on the chosen time
horizon.
For the winter months, the estimated snowfall is much lower than the simulations
for the reference period. Notable differences are estimated for the middle and lower
zones of the catchment, namely with approximately 15% less snowfall, but 18–40%
more rainfall, as average between the three scenarios (Fig. 10.13a). During spring
and summer, projected changes in the precipitation’s form have the same tendency:
less snow (4% in the spring, 35% in the summer) and more rain (11% in the spring,
just 1% in the summer) than during the reference period (as average between the
scenarios, for the whole basin). For the autumn, the scenarios show the diminution
of precipitation in general, but a strong diminution of snowfall: with 24% in average
and over 30% in the middle and lower part of the catchment (Fig. 10.13a). The shift
between solid and liquid precipitation during winter and spring entails a significant
L. Zaharia et al.
floods cannot be recorded in the same years, but the interannual distribution of flows
can be extremely uneven.
From the total of 38 low flow periods identified during 1961–2012, 63% (24)
occurred in winter, 21% (8) in the autumn, 13% (5) in spring and just one case
during summer (in July). Monthly, the maximum frequency of the low flow periods
is specific in February. On the contrary, in April, May and June, when the snowmelt
has an important role in the surface runoff, there were not prolonged intervals with
flows below Q 95% .
10.5.3 Projected Hydrological Responses to Climate Changes
For Valea Cerbului River catchment the emission scenarios predict a rise in the air
temperature of 1.3 °C (the mean value indicated by the emission scenarios used).
Compared to the reference period (1961–2000), the scenarios show temperature
growths for all seasons, with maximum values in autumn and minimum values in
spring. The analysis conducted at the monthly level, reveals upward, significant
trends for A2 and A1B scenarios for the future period 2001–2065.
The trends indicated by the simulated precipitation data are not as clear as those
of the air temperatures: annually, a slightly descending trend and a higher variability
are expected; seasonally, the simulated precipitation shows more important decrease
during autumn (from 6.8 to 10.7% depending on the scenario).
The hydrological model used establishes the type of each precipitation event,
liquid or solid, by threshold transition temperatures, set in the model optimization
stage. Likewise, it can determine the precipitation values and types dissociated for
different zones of altitudes, in this case: the zone above 1750 m amsl, the zone
between 1250 and 1750 m amsl and the low part, with less than 1250 m amsl. The
simulation using the scenarios data as climatic input highlights the diminution of
the mean annual snowfall by 5–11% by 2065, relative to the reference period. On
the contrary, the projected liquid precipitation slowly increases on the chosen time
horizon.
For the winter months, the estimated snowfall is much lower than the simulations
for the reference period. Notable differences are estimated for the middle and lower
zones of the catchment, namely with approximately 15% less snowfall, but 18–40%
more rainfall, as average between the three scenarios (Fig. 10.13a). During spring
and summer, projected changes in the precipitation’s form have the same tendency:
less snow (4% in the spring, 35% in the summer) and more rain (11% in the spring,
just 1% in the summer) than during the reference period (as average between the
scenarios, for the whole basin). For the autumn, the scenarios show the diminution
of precipitation in general, but a strong diminution of snowfall: with 24% in average
and over 30% in the middle and lower part of the catchment (Fig. 10.13a). The shift
between solid and liquid precipitation during winter and spring entails a significant