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criterions were found for the rivers Imula and Iecava. The
validation of model was done for the next 10-years period -
from 1991 to 2000, except for the river gauging stations
Imula-Pilskalni and Iecava-Dupši which was closed in 1995.
We obtained lower statistical criterions comparing with
calibration period for studied gauging stations in this study:
the statistical efficiency R 2 varies from 0.77 to 0.44 and
correlation coefficient r – from 0.87 to 0.70. One of the
main reasons of difference between the simulated and
observed runoff values is the quality of precipitation and
vapour pressure deficit input data, and location of the
available meteorological stations characterising the spatial
and temporal distribution of precipitation in the studied
drainage area. Another explanation of the above mentioned
calibration differences could be a broad palufied flood plain,
a high percentage of wetlands in the sub-basins of the river
Salaca and a lack of the channel measurements at the outlet
of the lake Burtnieks. These reasons determine a specific
hydrological regime and additional riverbed measurements
for the better simulation of the hydrological processes within
the studied catchments.
After learning the results of many researches in Europe and
the Baltic region (Hisdal el al. 2006; Danker et al, 2007;
Bolle et al, 2008; etc.), we can conclude that in this study we
have identified similar tendencies of meteorological and
hydrological trends in projections of future climate changes.
Analysis of the climate change conditions metrological data
in the studied river basins show an average increase in the
annual atmospheric temperature by 3.8-4.1 o C for the HCA2
scenario and by 2.5-2.7 for the HCB2 scenario in the period
of 2071 to 2100 comparing to the control period of 1961-
1990. The most considerable temperature increase is
forecasted for the winter and autumn seasons: 4.1-4.9 o C
HCA2 and 3.0
o C HCBA2 respectively. Atmospheric
precipitation, at the same time, will increase by 11-12%
according to the HCA2 scenario and by 8-9% according to
the HCB2 scenario. The highest atmospheric precipitation
increase is registered in winter, but the major decrease – in
the summer and autumn seasons. Climate scenario data,
particularly the HCA2 scenario, allows forecasting the
eventual decrease of total annual river runoff by 15-20% in
the future. The highest increase in the river runoff is
registered in winter due to the increase of the mean
atmospheric temperature and precipitation, while the
decreased river runoff is forecasted for the second half of the
year, particularly in autumn. The mentioned changes in the
river runoff regimes can be explained by the higher
atmospheric temperatures and particularly increased total
evaporation as well as decreased amount of precipitation.
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Acknowledgements
This study was supported by the National Research
Program Climate change impact on water environment in
Latvia and data were provided by Latvian Environment,
Geology and Meteorology Agency and SIA
Meliorprojekts.