Evaluation of precipitation in the winter season in higher altitudes of the Bohemian Forest under changing environmental conditions

Precipitation during the winter season represents a very significant proportion of the yearly precipitation total in higher mountainous areas in the Czech Republic. This region generally has lower fluctuations in precipitation during the year than in the lowlands. In addition to the altitude, this is mainly due to the oceanic character of precipitation, especially in Bohemia, where there is an increase in precipitation before and during winter.  

The main objectives of the present contribution are to (i) describe the snow cover characteristics (snow depth and snow water equivalent) concerning the mid-latitude forested catchment; (ii) use the snow cover evaluation in the Bohemian Forest as an indicator of climatic and related changes; and (iii) introduce new techniques for a monitoring both snow depth and snow water equivalent.

The influence of the forest canopy (Picea Abies and Fagus Sylvatica) and altitude (ranging from 835 m a.s.l. to 1118 m a.s.l.) has been investigated for the time period from 2002 to 2021. Preliminary results proved that forest cover has a significant influence on the snow cover accumulation, reducing SWE by 50 % on average, compared to open sites. The elevation gradient concerning SWE ranged from 30 to 40 mm and from 5 to 20 mm per 100 m in open and forested sites, respectively. Its magnitude was found to be temporarily variable and positively related to the total seasonal snowfall amount.

The hydrological effects related to changes in the snowmelt regime were studied in a small forested basin Liz (0,99 km², 835 – 1074 m a.s.l.). The attention was paid to the streamflow generation during spring snowmelt, which is a dominant hydrological event in many seasonally snow-covered regions. The changes in snow cover amount and its variability at two mountainous stations in the Bohemian Forest (Churanov 1118 m n. m., 1962 - 2021 and Breznik 1137 m n. m., 1987 - 2021) were used as indicators of going along climate transition in the area. It was proved that the streamflow originating from the snowmelt starts earlier compare to the end of the 20th century.