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The nature of highly permeable flowpaths in the Turonian aquifers in the eastern part of the Bohemian Cretaceous Basin
Starý, Jiří ; Bruthans, Jiří (advisor) ; Datel, Josef (referee) ; Tesař, Miroslav (referee)
The thesis deals with the study of highly permeable porosity and the potential for karstification in the area of the East Bohemian Cretaceous synclines, which are of great importance for water supply. The susceptibility of the rocks to karstification was studied by taking cores and determination of their calcite content and by leaching the cores in 10 % HCl and monitoring of rock disintegration after leaching. A scanning electron microscopy and elemental mapping by microprobe were used to understand the structure and composition of the rock. The nature of the inflow zones to the boreholes was studied by evaluating available well logging data, particularly acoustic well logging, inflow data to the boreholes and by leaching rock samples from cores taken from the depth intervals where inflows occurred. A total of 247 cores taken from both boreholes and surface outcrops were studied. Only 5 % of the samples from the Turonian B, Ca, Cb aquifers that disintegrate from more than 50 % after leaching will form karst conduits in tectonically intact rock. This representation is much lower than in the Jizera Formation in the western part of the Bohemian Cretaceous Basin. Only a small fraction of the samples disintegrate if calcite content is below 78 %, the majority show no or very little disintegration. Only...
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Temporal distribution of groundwater recharge, base flow and groundwater resources in selected areas of Czech Republic, focusing on quaternary fluvial terraces: comparison of different approaches
Šabatová, Kateřina ; Bruthans, Jiří (advisor) ; Nol, Ondřej (referee)
The aim of this thesis is to quantify temporal distribution of groundwater recharge, baseflow and groundwater storage, mainly in quaternary fluvial terraces in the Czech Republic by different approaches, compare the outputs and assess limitations of each of the methods. The methods used are saturated zone modeling using FEFLOW program, and soil-water deficit modeling to estimate recharge and consequently calculate groundwater storage and baseflow. For this purpose, a simple soil-water deficit model was developed and proved to give reasonable estimates of recharge, despite using only 3 optimization parameters. The model is designed for unconfined aquifers with slow runoff (hydraulic pulse propagation). Calibration of the models was performed by comparison of modelled water table to water table measurements by CHMI and others. One pumping test with observation well was performed to obtain storativity of aquifer, which suggested a semi-confined regime of the aquifer, explaining the difference between storativity obtained from pumping test and from modeling. Furthermore, baseflow estimates from DPV modeling were compared to baseflow obtained from hydrograph analysis, showing reasonable similarity.
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The effect of moisture on the surface strength of sandstone rock outcrops
Fraňková, Kateřina-Alexandra ; Weiss, Tomáš (advisor) ; Bruthans, Jiří (referee)
The aim of the thesis is to evaluate the influence of moisture on the tensile strength of sandstone rock outcrops and also to evaluate the possible influence of man on the erosion of sandstone rocks, especially by climbing activities, by means of a research study and specific examples from my own and non-own researches. Just a few studies have so far addressed the effect of moisture on the tensile strength of sandstone, and although the results of these studies generally suggest that the tensile strength of sandstone rock outcrops decreases with increasing moisture, there are differences depending on the specifics of the selected study areas. It would therefore be interesting to do a study that names and evaluates the possible aspects influencing this dependence. In my thesis I have evaluated studies carried out using different methodologies, which are described in a separate chapter. The results of the studies show that the tensile strength does indeed decrease with increasing moisture content, but the degree of decrease depends mainly on the mineralogical composition of the rock. The tensile strength of rocks with a high clay or organic content will decrease significantly more with increasing moisture than the tensile strength of rocks with a high quartz content. I have also reviewed several...
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Tracer tests with fluorescent dyes with respect to those tracing experiments where arrival of dye to water supply systems is expected and Tracer test in Chýnov Karst
Koutník, Jakub ; Bruthans, Jiří (advisor) ; Kůrková, Iva (referee)
The thesis is dedicated to fluorescein tracer tests, especially those where the tracer ends in drinking water. The review part of the thesis describes the usage and characteristics of sodium fluorescein (uranine) and other fluorescent tracers in tracing tests. Special attention is given to the toxicity of fluorescent tracers and to the legislation limiting their use in the Czechia and abroad. The practical part of the work is to perform a fluorescein tracer test from Chýnov Cave to the Rutice Spring on distance 1260 m away. The tracer test has confirmed that the Rutice Spring is the only karst spring where water flows from Chýnov Cave. The results differ from previous tracer tests made on the same flowpath in 1962, 1965 and 1966. While previous studies have concluded that the mean tracer transit time is in the order of tens to hundreds of hours, this tracer test has shown that the mean tracer transit time is in the order of hundreds of days. This work has thus provided completely new knowledge about water flow in the Chýnov karst.
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Hydrogeological character of selected hardrock environments and groundwater recharge in populated areas
Krupař, Josef ; Bruthans, Jiří (advisor) ; Slavík, Martin (referee)
The purpose of this thesis is to adress the hydrogeology of hard-rock environment and groundwater recharge in urban areas. The theoretical part describes hydrogeology character of granite and ophiolite rock environment with emphasis on features such as transmissivity, storativity and hydraulic conductivity that corresponds to the fissuring of the rock environment. It is clear that fault tectonics is the most important factor that influence the hydraulic conductivity. Storativity, on the other hand, is most affected by fissured systems. Ophiolites are a more significant water supply aquifer than granites in terms of storativity. This thesis also describes groundwater recharge in urban areas and not only from precipitation but also through surface water reservoirs, leaks from pipeline network and by import of water from surrounding watershed. Practical part compares values of precipitation from 2013 to 2022 from four ČHMU stations. It compares PET (Potential evapotranspiration), API (antecendant precipitation index) values and their difference. Subsequently, in the practical part, the normalized relative groundwater recharge from the measured values of the well level is compared with the flow rate at all monitored locations and it is evaluated whether the time course of the recharge according to the...
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Residual Contamination of Soils with Artificial Radionuclides Sr-90 and Cs-137
Kadlecová, Tereza ; Sedlářová, Barbora (advisor) ; Bruthans, Jiří (referee)
The review part of this bachelor thesis deals with sources of artificial radionuclides strontium- 90 and caesium-137, which are released into the environment mainly due to nuclear weapons tests and nuclear accidents. The most extensive contamination of the Czech Republic was caused by the Chernobyl accident in 1986. The transport of strontium-90 and caesium-137 through the environment is summarised, with emphasis on soil. In the experimental part of the work, the residual contamination of arable and meadow soil with these radionuclides was evaluated in the Veltrusy locality in relation to hydropedological properties. This site was chosen in connection with the project "Innovative methods for the detection of ultra-low concentrations of radionuclides to assess the vulnerability of drinking water sources in the event of a nuclear accident", which was carried out within the T. G. Masaryk Water Research Institute. It was found that contamination varies depending on land use, such as cultivated and uncultivated land. Strontium-90 was not measurable at either site, whereas caesium-137 was detectable at both of them. Most of the caesium-137 in the grassland soil was measured in the near-surface layer of the soil, whereas in the arable soil it was evenly distributed throughout the profile. The mobility of...
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Character of groundwater flow in highly permeable sediments of Bohemian Cretaceous Basin
Kůrková, Iva ; Bruthans, Jiří (advisor) ; Datel, Josef (referee) ; Tesař, Miroslav (referee)
The study focuses on water flow in sandstones and sandy limestones of the so-called facies transition in the western part of the Bohemian Cretaceous Basin. The area between Turnov, Milovice, Úštěk and Doksy is a part of most important aquifer in the Czech Republic, in terms of water supply. However, there are considerable discrepancies in hydrogeological concepts regarding groundwater flow in this area. The prevailing opinion is that quartz sandstones form the main aquifer, although largest springs are partly located outside the area of their occurrence. The aim of the work is therefore to determine which rocks are the source of the large springs and where diffused seepage predominate. Furthermore, to characterize the possibility of rock karstification, to describe the character of the channels and the flow in them, and at the same time to compare it with the flow in the adjacent porous environment in selected areas. Thermometry (winter profiling of temperature and conductivity along watercourses) was carried out in order to distinguish areas with large springs, diffused seepage and stream segments without any drainage. The karst potential of rocks was determined using calcimetry and adopted leaching tests. To determine flow velocity in karst channels and to characterize the channels, a series of...
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Moisture regime in near sub-surface of porous rocks: measurement and visualization
Weiss, Tomáš ; Bruthans, Jiří (advisor) ; Migoň, Piotr (referee) ; Kumar, Navneet (referee)
Moisture regime in near sub-surface of porous rocks: measurement and visualization Doctoral thesis Tomáš Weiss Charles University, Faculty of Science Abstract The near-subsurface of porous rocks plays a critical role in hydrological, physical, and chemical interactions between the atmosphere and the lithosphere. Hydrologically, the area can be conceptually divided into two zones: the dry surface layer and a deeper zone with capillary water, separated by the so-called evaporation front between the zones. Since salts tend to crystallize at the evaporation front, knowledge of its depth is important for understanding weathering processes. However, measuring the depth of the front is difficult, as differences in water content above and below the front are too low to measure by most methods. This thesis presents new methods for studying the evaporation front and tests them in a variety of lithologies and climates. Na-fluorescein dye was used for visualization of the front either as a direct application to the material in the form of solution or powder or as a part of a moisture probe on which the dye dissolves in the capillary zone. This moisture probe (named uranine- probe) was successfully tested and used in a range of porous rock types, from sandstone and limestone to rhyolite, building materials, and soil;...
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Measurement and modelling of the seepage between river and fluvial sediments
Bašus, Jan ; Bruthans, Jiří (advisor) ; Pastuszek, František (referee)
EN This diploma thesis deals with the measurement of seepage between the river and fluvial sediments using seepage meters. Although this is not a new method, it has never been widely used to measure seepage in our country. The Morava River and its side channels (Malá Voda and Mlýnský potok) in the Litovelské Pomoraví region were chosen as the test location for this measurement. In this locality, conflict of interests between groundwater extraction and the protection of the of floodplain forests habitat has been ongoing for a long time. Data of the seepage intensity would be very helpful for the overall understanding of the groundwater flow and influence of water from rivers in this territory. The work also includes a numerical model of groundwater flow, which was used to verify the measured seepage values. Due to the overall complexity of the geological structure and groundwater flow, the model includes a wide area around the site of interest. In addition to the scope of the work, two more control measurement campaigns were carried out to verify the overall functionality of the devices. First of them took place on the Morava River near Kojetín, on the occasion of a pumping test carried out as part of the VUV TGM project. The bottom of the river is at a depth of 3.5 m below the surface, the aim of...
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Influence of the stress field on weathering and erosion of sandstone landforms
Řihošek, Jaroslav ; Bruthans, Jiří (advisor) ; Mikuláš, Radek (referee) ; Válek, Jan (referee)
The influence of mechanical stress on weathering and erosion has been overlooked in works focused on sandstone landforms formation, although stress has been shown to be a key factor in the formation of a number of different sandstone landforms recently. The main goal of the doctoral thesis is to understand the relationship between mechanical stress and weathering or erosion in the formation and development of sandstone landforms. The influence of mechanical stress on the mode of weathering and the rate of disintegration of the material forming historical monuments in Petra, Jordan was investigated on the site and on samples in laboratory. A negative exponential dependence has been proven between the speed of salt weathering and the magnitude of uniaxial compression of Petra sandstone samples. The role of mechanical stress as a mechanism controlling the formation and development of the shape of sandstone forms was further studied in rock overhangs, sandstone arcades and rock gates in the Czech Republic and the USA. The doctoral thesis presents and verifies a method using Střeleč sandstone as a natural analogue in physical models simulating weathering and erosion of cemented sandstone. These physical models usually take the form of a reduced initial shape of a sandstone object created in situ from...
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