open file - Viru Peipsi

Changes in Water
Level and Storage in
Lakes
Water level Decrease the flooded
areas surround of lakes
during the higher water
period
Storage of lakes Increase of total and
active storage of lakes
during winter period
Possible decrease the
level in the end of
summer under the
optimal level
Conclusions
In general, all climate change scenarios for Estonia forecast mild winters, a
decrease in snow cover and an increase in the duration of dry periods in mid–
summer. The predicted global warming will cause more changes in the water
balance elements in the cold period than in the warm season. Modelled
annual runoff and its seasonal variability in study area are not very sensitive
to climate change. The main results of the study are following:
• Periodical fluctuations of water level and river runoff. Long time
series of annual precipitation has a significant periodicity of 25–35
years in Estonia during more than a century. It causes long-term
fluctuations in hydrological regime and alternation of wet and dry
periods also in the future.
• Increase in annual runoff. Due to the climate change, annual runoff
will increase by 20–40 % in the average, for the year 2100, but
modelled river runoff show a great spatial variation.
• Significant increase in winter runoff. During mild winters, duration of
snow and ice cover should decrease, winter weather should be
changed more unstable, freezing and melting periods should
alternate.
• Decrease of spring runoff maximum and its shift earlier. Mild winters
cause faster melting of snow and earlier beginning of spring
hydrological season. Frequent melting periods in winter prevent big
accumulation of snow. The mean maximum runoff should move
from April to March.
• Increase of river runoff in autumn. This is directly caused by
significant increase of autumn precipitation predicted by both of the
GCMs. In East-Estonia autumn maximum runoff would not exceed
maximum runoff in spring.
• Lengthening of the period of minimum runoff in summer. Due to
faster melting of snow, decreasing and moving earlier of runoff
maximum in spring, dry period should begin earlier. Minimum runoff
period when rivers receive the majority of water from groundwater,