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Frequency and trend analysis of rain-on-snow events at selected meteorological stations in the Czech Rebublic
Kakalejčík, Matej ; Jeníček, Michal (advisor) ; Blahušiaková, Andrea (referee)
Rain-on-snow events represent a natural hydro-meteorological phenomenon and their occurrence is often associated with floods. Due to the climate change occurrence, rain-on snow events are also changing. The main goal of diploma thesis is to define spatial and temporal occurrence of rain-on-snow events at 16 selected meteorological stations in the Czech Republic between the years 1966-2012. Spatial occurrence of rain-on-snow events is expressed by number of events per meteorological station. Final number of events varies widely even between the stations with similar altitude. Stations with the highest frequency of rain-on-snow events are located in Jizerské hory between 675 and 780 m a.s.l. Temporal occurrence of rain- on-snow events is expressed by number of events per year and month respectively. Time series of rain-on-snow events were analysed by statistical trends to gain information about changes in occurrence over time. Most of the stations proved no statistically significant trend. There was a trend detected only at four out of 16 stations. Three meteorological stations showed a rising trend, whereas one station signalled a decreasing trend. More complex results were produced by the trend analysis of monthly time series of rain-on snow events. Nine stations yielded at least one month with a...
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Modelling the impact of seasonal snowpack on summer low flows in mountain catchments
Nedělčev, Ondřej ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
This thesis analyses the impacts of winter snowpack and subsequent spring and summer liquid precipitation on low flows in the warm season. Meltwater is an important source of groundwater recharge. From groundwater storage streams are donated during summer months. Snow accumulation during cold season is reduced and snowmelt occurs earlier, which is a result of climate change and leads to lower groundwater recharge rates. That is the reason why change in snow cover dynamics affects summer low flows. Main goals of this thesis are to analyse how snow cover affects low flows I warm season and to compare it with impact of spring and summer precipitation. A conceptual runoff model HBV-light has been used to simulate the snow water equivalent (SWE) and streamflow from three mountain catchments. The integrated multi-variable model calibration procedure was used to calibrate the model. The model was used to simulate the snow and streamflow from 1981 to 2014. Besides the mentioned simulation, two hypothetical scenarios have been performed. These two scenarios accounted for reduced spring and summer liquid precipitation. In the first scenario, precipitation after maximum annual SWE was reduced to 75% of the real measured precipitation. In the second scenario, precipitation was reduced to 50% of the real...
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Local scale variability of new snow depth
Valdhansová, Klára ; Jeníček, Michal (advisor) ; Matějka, Ondřej (referee)
Vegetation has an important effect on the catchment water balance, especially due to its influence on snow acccumulation and snow melt. The aim of this bachelor thesis is to evaluate how the canopy structure influences the new snow depth variability, while emphasis is put on the interception process. The snow depth data obtained by field measurements in the Ptačí brook experimental catchment in the Šumava Mountains were analysed using the Natural Neighbor interpolation method and regression analysis. The thesis is focused on evaluating the new snow depth variability in relation to differences in the canopy structure described by the Leaf Area Index. The measurements were carried out in four study plots covered with healthy forest, disturbed forest affeted by the bark beetle, open area and mixed area, which consists of all three types. The results showed, that average snow depth is by 45% lower in healthy forest and by 18% lower in disturbed forest compared to open area. The variability of new snow depth was largest in plot with mixed vegetation during maximum snow accumulation. On the contrary, the snow depth variability was lowest in open area. key words: interception, snow depth, Leaf Area Index, linear regression
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Local scale snow accumulation and ablation variability using high spatial resolution data
Cuřín, Vojtěch ; Jeníček, Michal (advisor) ; Minařík, Robert (referee)
The focus of this bachelor's thesis is snow depth variability at local scale and modern methods of snow depth measurement with high accuracy, precision and resolution. The main goal is to provide an overview of current research in this area, give comparison of the most widely used methods and outline their most appropriate fields of application. A part of this work is also dedicated to an evaluation of snow distribution over a study area in Filipohuťský creek basin in Šumava (Bohemian Forest) and to an assessment of the impact of selected variables on snow depth variability using multiple linear regression models. This is done using manual snow depth measurement data and local digital surface model with high resolution. Multiple linear regression models capture the snow depth variability more precisely than models based on ordinary kriging, nevertheless the regression coefficients of selected predictors are too inconsistent to confirm their effect. Key words: snow depth, photogrammetry, laser scanning, multiple linear regression
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Calculation of melt factors in a forest with different structure and in an open area in a small mountain catchment
Hotový, Ondřej ; Jeníček, Michal (advisor) ; Matějka, Ondřej (referee)
This bachelor thesis focuses on the development of snowpack in connection with effects of different physical-geographical factors, especially with the strong influence of vegetation on components of energy balance of the snowpack, including rainfall and runoff regimes of the area. The main aim of this thesis is to investigate the differences in snowmelt characteristics in an open area, under healthy coniferous forest and under forest infected by the bark beetle (Ips typographus). The snow depth and snow water equivalent data were obtained by field measurements at selected study sites in the experimental basin of Ptačí Brook in the Šumava Mountains during winter 2015/2016. The data were evaluated by simple conceptual method based on degree-day approach (temperature index), which examines the relationship between the snowmelt rate and air temperature. According to vegetation, degree-day factors were defined for each type of area as 1.71 mm řC-1 d-1 for healthy coniferous forest, 2.07 mm řC-1 d- 1 in forest infected by the bark beetle and 2.68 mm řC-1 d-1 in an open area. A simple model is a part of the thesis. It predicts the development of snow water equivalents using melt factors and it was used to evaluate the snow storages during snowmelt in study sites. Furthermore, it showed, that the most...
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Influence of winter snow conditions on minimum discharges in the warm season in mountain catchments in the Czech Republic
Součková, Markéta ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
As a result of climate change, the snowfall amounts may be reduced and hence the snow accumulation, which recharges the groundwater in spring. Groundwater significantly influences summer low flows and its deficiency may negatively affect the streamflow and reduce the water supply in snow- dominated regions. This thesis aimes to describe the influence of changes in snow water equivalent on the inter-annual variability of minimal discharges in warm season (April to September) in eleven mountain catchments of the Czech Republic. The aimes were to determine 1) the duration of snow effects on the minimum discharges after the snowmelt onset, 2) the effect of inter-annual changes of snow water equivalent on minimal discharges in the warm season and 3) the date of the summer lowflows and the trend of its shift within the year. The results are based on hydrological and climatological station data collected by Czech Hydrometeorological Institute between the years 1980 and 2014. Snow affected the summer low flows until June and in exceptional cases even until July in higher elevation catchments. The most significant change was recorded in Úpa catchment, which belongs to higher elevation catchments, the 10 % decrease of maximum snow water equivalent caused reductions in minimal discharge by 8.8 % and 6.8 % in...
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