National Repository of Grey Literature 40 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Multi-criteria calibration of a hydrological model using runoff, snow water equivalent and groundwater level data
Hlavatý, Vojtěch ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
Multi-criteria calibration of a hydrological model (against multiple output variables simultaneously) has in previous research mostly resulted in satisfactory quality and reduced uncertainty in the simulations of all variables considered. However, its importance in the context of groundwater and low flows has rarely been studied. Therefore, a multi- criteria calibration using observed runoff, snow water equivalent and groundwater level data was performed in this study to determine if this approach leads to more accurate simulations, especially for low flows. The HBV hydrological model was calibrated using a genetic algorithm on the case of 14 mountain and sub-mountain basins in Czechia. The accuracy of different calibration variants was evaluated according to objective functions and hydrological signatures. The results show that multi-criteria calibration against the three mentioned variables is a good compromise for correct simulation of all these variables, where the value of objective function for each of them differs only slightly from a calibration more focused on it alone. Considering groundwater in the calibration further increases the simulated baseflow and its variability and refines the simulation of low flows, especially in summer, in terms of deficit volumes, minimum runoff and other...
Evapotranspiration of peat soils
Urbánková, Karolína ; Weiss, Tomáš (advisor) ; Šípek, Václav (referee)
The correct determination of evapotranspiration is critical for the calculation of the water balance. Although research on evapotranspiration in general is already quite advanced, peat soils are so specific that they may require their own unique approach. Hydrologists have a series of calculations and models to determine evapotranspiration, but these are not always sufficiently accurate, especially at higher temperatures. The aim of this thesis was to summarise the existing knowledge of evapotranspiration in peat soils and to determine whether the peat layer thickness has an effect on peat evaporation. The thesis presents a survey of methods for determining evapotranspiration that can be applied to peat soils. The laboratory experiment used a split container, one part of which contained peat and the other part had peat only in the top 7 cm, with quartz sand underneath. The two parts were joined at the bottom with gravel and thus permeable to water. The trend of water loss, soil water potential and soil moisture was monitored. Preliminary results show that peat strength has a clear effect on evaporation. Further research would, among other things, look for a specific height of the peat layer for which the underlying material would no longer have an effect. Key words: evapotranspiration, peat,...
Where and how much water do trees transport? Modelling the impact of spruce and beech stands on soil water fluxes during extreme climatic conditions
Zelíková, Nikol ; Šípek, Václav
Soil moisture links processes that influence the entire hydrological cycle and thus the availability of water resources. One important factor influencing these processes is the presence of vegetation. Research on the interactions between vegetation, its management and the processes affecting soil water fluxes is of particular importance in times of ongoing climate change and land cover changes. However, the complexity of these interactions, further influenced by differences between plant species, makes this research more difficult. Land cover change is also taking place in Czechia, specifically in the replacement of spruce monocultures by beech. Therefore, this study investigates the influence of two types of forest stands, spruce (Picea abies) and beech (Fagus sylvatica), on the soil water regime in the experimental Liz catchment in Bohemian Forest, Czechia. This was performed by (1) evaluating differences in soil moisture based on twenty years of measured data and (2) obtaining the two components of the soil water balance (transpiration and percolation) at two plots (beech and spruce) using a soil water balance model. Analysis of the long-term soil moisture data show slightly lower soil moisture values under the beech stands, which disappear when comparing the annual mean values. Differences are evident when evaluating average soil moisture data with depth, where the topmost layer of the soil profile at the spruce site has on average 6% higher soil water content than beech. At the start of the growing season the soil moisture was initially drier under spruce, due to its earlier start of transpiration. This difference was reduced over the season by the intensive transpiration of beech. The outputs of the balance model indicated a higher rate of actual evapotranspiration of beech and a higher rate of percolation of spruce every year. This effect was more pronounced over the dry years, whereas in years with sufficient rainfall the differences were minimal. Thus, the replacement of spruce trees by beech trees may affect the rate of groundwater recharge.
Time variabilty of soil hydraulic properties and their impact on soil moisture estimation
Šípek, Václav ; Vlček, Lukáš ; Tesař, Miroslav ; Zelíková, Nikol ; Hnilica, Jan
The study was focused on the temporal variability of saturated hydraulic conductivity in an experimental plot covered by spruce forest and investigated benefits of its incorporation into soil water balance model. The results showed that the higher saturated hydraulic conductivity (33.6-44.8 cm hr-1) was observed in summer period compared to lower values (13.2-22.3 cm hr-1) in the winter period. The use of seasonally variabile saturated hydraulic conductivity improved the efficiency of soil water balance model in terms of lower root mean square error between observed and simulated volumetric soil water content by 33.2 %. The Nash-Sutcliffe coefficient rose from 0.34 to 0.68.
Report on the hydroledological survey in the Černý Důl, Krkonoše Mts.
Šípek, Václav ; Vlček, Lukáš ; Zelíková, Nikol
The report documents results of hydropedological survey in the Černý Důl, Krkonoše Mts. Two experimental sites were selected based on the requirements of National Park Krkonoše with the aim to determine the effect of bark beetle outbreak on the soil water regime. The report contains description of soil hydraulic properties at two plots (healthy and impacted forest) for several soil horizons which will serve as a basis for hydropedological model.\n
Changes in groundwater recharge and base flow in mountain catchments in Czechia due to changes in snow storages
Kožíšek, Matěj ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
Changes in groundwater recharge and base flow in mountain catchments in Czechia due to changes in snow storages The diploma thesis deals with the topic of replenishing groundwater reserves due to the melting of snow cover. The main motivation is the importance of the topic for understanding the changes in the hydrological regime caused by decreasing snow cover and small number of research papers on this topic. The aim of the work is to find the relationships between changes in snow cover and groundwater recharge and runoff parameters in the warm part of the year. The main part of the thesis is work with the HBV model. The parameters of underground water reserves and the size of the basic runoff are modeled using climate data and snow water value data from selected mountain basins of the Czech Republic. The Mann-Kendall test and Theil- Sen linear trend is used to evaluate trends in data. The relationships between individual parameters, expressed by Spearmann correlation tests are also examined. The impact of climate change and the associated increase in air temperature was reflected in all runoff and groundwater parameters. Trends were observed at the annual and especially the monthly level. The impact of climate change and the associated increase in air temperature (0.24 to 0.4 řC/decade) was...
Analysis of precipitation regime in Šumava Mountains
Šípek, Václav ; Zelíková, Nikol
The analysis is focused on the description of precipitation regime in the Šumava National Park in comparison with other mountain ranges in the Czech Republic. The period of interest comprised the years 2001-2019. The daily and monthly precipitation amounts were compared to the reference period covering the years of 1971-2000.
Modelling of runoff changes due to forest disturbances in the Šumava catchments
Švejdová, Klára ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
Runoff conditions in river basins are heavily influenced by vegetation cover. Changes in the vegetation linked to forest disturbances significantly affect the water balance of the river basin. These changes can be effectively quantified using hydrological models. Therefore, this thesis aims to describe water balance change in forests disturbed by bark beetles and storms. Three model experiments were simulated using the HBV precipitation-runoff model for Roklanský potok, Ptačí potok and Rokytka catchments in Šumava, Czechia. All these catchments underwent significant forest damage after recent disturbance. First experiment used the split sample test method. Calibration was performed separately for the period before and after disturbance, and then simulated for the whole period. The resulting simulated runoffs notably differ from one to the other, which may be caused not only by deforestation, but also by the effects of climate and the characteristics of individual catchments, which also affect their runoff response. The second model experiment was based on changes in vegetation-dependent parameters (melt factor and snowfall correction factor) and analysis of their effect on the simulated runoff. The results did not reveal significant changes in the monitored runoff characteristics. However, this is...
Modelling runoff processes in experimental Bystřice River catchmet in the Krušné Mountains
Hasa, Martin ; Jeníček, Michal (advisor) ; Šípek, Václav (referee)
This work deals with the modelling of runoff processes in the experimental Bystřice river catchment in the Krušné Mountains. Rainfall-runoff model WaSiM (Topmodel version) was used for this purpose.Objective of this study was modelling snow accumulation and snowmelt in winter periods 2009/2010 and 2010/2011. Sensitivity analysis of TOPMODEL parameters was performed using Monte Carlo and GLUE methodology. Wasim was calibrated manually for 25 and 250 m grid scales and daily timestep. Results of simulations in both spatial scales different spatial scales differed significantly. Better performance of modelling in finer scale wasn't proved in validation of the model. Results of the simulations pointed out uncertainty in model calibration. Rasters of modeled snow water equivalent were also analyzed in selected days representing periods of snow accumulation and snowmelt. The goal was to examine the functioning of used snow model (combination of temperature index method and energy balance method) within the WaSiM frame. Finer scale raster proved to be practical for this purpose It was found that the spatial heterogeneity in the distribution of snow is determined by evapotranspiration and also by effect of radiation correction (in the case of rainfall).Influence of interception and vegetation effects on...
Optimization of digital river network and its impact on catchment water management
Hošek, Zdeněk ; Matoušková, Milada (advisor) ; Šípek, Václav (referee)
Digital river network dataset is an important source of information in any aspect of water management decision making. It is also a base for modelling or scientific research in many different fields. Development of the dataset in the Czech Republic had been fragmented in a past and as a result three different datasets have been developed that cover the whole of the state's territory. The datasets contain different geometries, different and often conflicting attributes and serve different purposes. Today the time has come that water management decision makers have realised that the situation is no longer sustainable and make effort to merge the datasets into one. The task brings in several technical issues and a potential for severe legal consequences. The aim of this study is to develop a methodological approach to merging the existing datasets into one. This methodological approach to decision which of the conflicting or different attributes should be adopted is based on assumption that the existing datasets will be merged into one consisting the best of all. Comparison of features in the existing dataset will inevitably lead to many conflicts when it will be necessary to decide which of the considered features should be adopted to the resulting dataset. The study considers the main purposes which...

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2 Šípek, Vojtěch
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