328
L. Zaharia et al.
Researches on future expected impacts of climate changes on water availability
and extreme hydrological events in Romania were also carried out within the International Commission for the Protection of the Danube River (ICPDR). The researches
are based mainly on IPCC SRES scenarios A1B and A2 and on RCP scenarios, by
considering as future periods 2021–2050 and 2071–2100. According to [175], for the
entire Danube River basin, seasonal changes in runoff regime are expected in the 21st
century, concretized in the increase of the mean discharge in winter and decrease in
summer, with local differences. A decline in solid precipitation and consequently in
snow cover, together with an earlier snow melt, will lead to the alteration of the runoff
regime, by causing in the high parts of the watersheds draining the Carpathians, a
shift in peak runoff from early summer to spring.
In the Lower Danube River basin, the studies based on IPCC SRES scenarios
show an increase in flood frequency, but the possible changes in flood frequency and
magnitude remain uncertain. Flood events are projected to occur more frequently,
particularly in winter and spring. For small catchments, an increase in flash floods
due to more extreme weather events (torrential rainfall) is expected. Concerning the
drought and low flow events, they are likely to become more intense, longer and more
frequent. The frequency could increase especially for moderate and severe events.
These extreme events will be more severe in summer, due to less precipitation in this
season, whereas they will become less pronounced in winter [175].
The impacts of climate change on the flow regime of the Danube River and its
tributaries were investigated in [85] by using an ensemble of climate scenarios and
the SWIM hydrological model, for two future periods (2031–2060 and 2070–2100)
and the reference period 1971–2000. The simulations showed a possible increase in
river runoff for the winter and spring months (especially during January–March),
while a general decreasing trend is projected in summer runoff for the whole Danube
Basin and, additionally, in autumn runoff for the Middle and Lower Danube Basin.
The trends are more evident towards the end of the 21st century. At the entrance of
the Danube River to its delta (at Ceatal Izmail/Chilia g.s.), the projections based on
ENSEMBLES data under A1B SRES show, for the near future period 2031–2060 relative to the reference period, an increase (of 5–40%) in winter and early spring runoff
(from January to March). The flow peak specific for May is projected to decrease
slightly (up to −5%) and tends to appear earlier (in April). The projections also
indicate, in the Lower Danube River, a decrease (up to −20%) of discharges during
the warm season (May–October), aggravating the low flow period in late summer
and autumn (August–November). For the far future (2071–2100), the simulations
indicate increase in runoff for January–April, with rates similar to those projected
for the near future period. In the rest of the year, no clear changes were identified,
except for a decreasing trend in late summer [85].
L. Zaharia et al.
Researches on future expected impacts of climate changes on water availability
and extreme hydrological events in Romania were also carried out within the International Commission for the Protection of the Danube River (ICPDR). The researches
are based mainly on IPCC SRES scenarios A1B and A2 and on RCP scenarios, by
considering as future periods 2021–2050 and 2071–2100. According to [175], for the
entire Danube River basin, seasonal changes in runoff regime are expected in the 21st
century, concretized in the increase of the mean discharge in winter and decrease in
summer, with local differences. A decline in solid precipitation and consequently in
snow cover, together with an earlier snow melt, will lead to the alteration of the runoff
regime, by causing in the high parts of the watersheds draining the Carpathians, a
shift in peak runoff from early summer to spring.
In the Lower Danube River basin, the studies based on IPCC SRES scenarios
show an increase in flood frequency, but the possible changes in flood frequency and
magnitude remain uncertain. Flood events are projected to occur more frequently,
particularly in winter and spring. For small catchments, an increase in flash floods
due to more extreme weather events (torrential rainfall) is expected. Concerning the
drought and low flow events, they are likely to become more intense, longer and more
frequent. The frequency could increase especially for moderate and severe events.
These extreme events will be more severe in summer, due to less precipitation in this
season, whereas they will become less pronounced in winter [175].
The impacts of climate change on the flow regime of the Danube River and its
tributaries were investigated in [85] by using an ensemble of climate scenarios and
the SWIM hydrological model, for two future periods (2031–2060 and 2070–2100)
and the reference period 1971–2000. The simulations showed a possible increase in
river runoff for the winter and spring months (especially during January–March),
while a general decreasing trend is projected in summer runoff for the whole Danube
Basin and, additionally, in autumn runoff for the Middle and Lower Danube Basin.
The trends are more evident towards the end of the 21st century. At the entrance of
the Danube River to its delta (at Ceatal Izmail/Chilia g.s.), the projections based on
ENSEMBLES data under A1B SRES show, for the near future period 2031–2060 relative to the reference period, an increase (of 5–40%) in winter and early spring runoff
(from January to March). The flow peak specific for May is projected to decrease
slightly (up to −5%) and tends to appear earlier (in April). The projections also
indicate, in the Lower Danube River, a decrease (up to −20%) of discharges during
the warm season (May–October), aggravating the low flow period in late summer
and autumn (August–November). For the far future (2071–2100), the simulations
indicate increase in runoff for January–April, with rates similar to those projected
for the near future period. In the rest of the year, no clear changes were identified,
except for a decreasing trend in late summer [85].