Climate change is one of the key factors influencing the quantity and quality of water resources in hydrologically sensitive regions. In order to downscale global climate simulations from horizontal resolutions of about 125-200 km to about 7 km, a double nesting strategy was chosen. The modelling approach was implemented with the Regional Climate Model CCLM (COSMOClimate Local Model) with a first nesting covering a central part of Europe and with a second nesting covering parts of Poland, Belarus, and the Ukraine. A control run-driven by global reanalysis data-was evaluated by comparing the model results with corresponding reference data. Longterm yearly and monthly mean differences of temperature and precipitation were statistically assessed. As reference data for the first nesting, the gridded CRU data set with a horizontal resolution of about 55 km was used. Station data of the NOAA and ECA databases were interpolated to provide an appropriate reference data set for the second nesting. Both nestings overestimated long-term yearly precipitation means. Seasonal evaluation of the first nesting showed positive precipitation biases for spring and winter months and negative biases in summer. Furthermore, differences in the spatial precipitation patterns occured, especially in the high mountain area of the Carpathians. The second nesting overestimated precipitation in spring and summer with smaller biases than in the first nesting. Long-term area means of temperature were properly reproduced. The first nesting showed an overestimation for all months with maximal deviations in summer and spring. In contrast, the second nesting was slightly too warm for summer and autumn and too cold for winter and spring.

The Influence of climate changes on the water balance in the Western Bug River basin-Kamianka Buzka. Quantitative indicators of water balance represent the ratio between the air and water components of the environment. Therefore, by analyzing the structure of water balance of the river basin, it is possible to estimate the local manifestations of the global climate change impact on the aquatic components. The main goal of this paper is to calculate and display water cycle process within the Western Bug River basin-city of Kamianka Buzka and to define its input-output elements. For this purpose the water balance equation of the catchment area was calculated monthly and yearly for climate normal and current periods and the general water balance equation was calculated for long-term (1961-2014) period. Meteorological components were determined as the weighted average for river basin, according to the observations at three meteorological stations. Compared to the climate normal period, the air temperature in the basin of the river Вug increased by 0.8°C, which led to an increase of both input and output parts of the water balance.

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