National Repository of Grey Literature 94 records found  beginprevious31 - 40nextend  jump to record: Search took 0.01 seconds. 
Report on the results of reduction the fish stock of the PEN and the subsequent stocking of predatory fish
Peterka, Jiří
The aim of the study was to reduce undesirable species of fish by electrofishing and then to stock predatory fish species in order to achieve a biomanipulative effect and maintain low total population density of fish. The report summarizes the work carried out and results achieved.
Revitalization of a Small Water Reservoir in the Níhov Cadastral Area
Matoušek, David ; Doležal, Petr (referee) ; Menšík, Pavel (advisor)
Thesis has main goal to introduce the topic of small water reservoirs as an important regional element, which has added value to creation and sustaining of ecological stability, improvement local microclimate, the quality of water in catchment area and groundwater supply. Thesis is divided into two parts. In the first theoretical part thesis describes the topic of small water reservoirs and the key factors affecting their environmental state and their self-cleaning abilities. In the second practical part are created conceptual design of revitalization to solve the unsuitable state of water reservoir in Níhov.
Quality of surface water in the Czech Republic and their treatability
Bedáňová, Jana ; Macsek, Tomáš (referee) ; Biela, Renata (advisor)
The thesis deals with the quality of surface water in the Czech Republic and the development of its quality in the streams and reservoirs. Issues related to wastewater discharge to the recipient (often without cleaning) and seepage from agricultural land. At the end, it deals with water quality indicators, their acquisition and assessment based on normative documents and their calculation on the basis of measured values.
The influence of agricultural activities on selected physical and chemical parameters of surface water
MIKEŠOVÁ, Aneta
The aim of this diploma thesis was a statistical evaluation of the impact of farming methods and the land cover on hydrochemical parameters of surface waters drainage patterns in Novohradské mountains and identify the possible impact of agriculture on the valuesof these parameters. The area for the evaluation is consist of lower and upper parts of the basin of Pasecký, Bedřichovský and Váčkový stream. Sampling sites include agriculturally cultivated land, but also forest ecosystems. The work is mainly focused on the following parameters: conductivity, nitrate nitrogen (N-NO3-), suspended solids (NL105) and phosphate phosphorus (P-PO43-), which are parameters causing eutrophication of water. The parameters changes were analysed for the years 2014 - 2017. Significant differences were observed in the all three streams in the water chemisms between upper and lower parts of the watersheds of conductivity and nitrate nitrogen (N-NO3-). The results confirmed that the farming has a significant influence on the water quality in the Pasecký, Bedřichovský and Váčkový stream although it is an extensive farming.
Phosphorus concentration in the Orlík and Slapy reservoirs: a result of socio-economic trends in the catchment and climate change
Hejzlar, Josef ; Jarošík, Jiří ; Kopáček, Jiří ; Vystavna, Yuliya
Based on existing phosphorus data series in the Slapy and Orlík reservoirs and their main tributaries, we reconstructed P inputs to the reservoirs from the catchment during 1961–2016 and compiled\nempirical models of P retention. P concentrations in both reservoirs increased from the 1960s to 1991 and then declined, with the Slapy Reservoir having a significantly increased year-on-year\nvariability. Trends in the increase and decrease of P reflected the socio-economic development in the Vltava river basin, in particular sewerage, wastewater discharges, fertilizer application, livestock,\nand fishpond fisheries. In the Slapy reservoir after 1991, the P concentrations increased during wet summers and created conditions for growth of phytoplankton, whereas in dry summers they\ndecreased to mesotrophy. Climatic and hydrological processes have now apparently begun to compete with a generally decreasing P pollution and support eutrophication despite the drop in P loads from the catchment.
Assessment of Czech water-bodies ecological potential based on fish community
BLABOLIL, Petr
Ongoing environmental changes and increasing pressure on freshwater habitat require that we understand the ecological quality of freshwater ecosystems across a wide range of habitat types. This Ph.D. thesis addresses the utility of fish as ecological indicators in heterogeneous reservoir ecosystems. In the first section, I develop suitable indices and calculate ecological potential in two case studies, one using common fish guilds and traits at a large continental scale and another using species-specific indicators for a country-specific dataset. In the second section, I compare the assessment of fish communities across a large geographical region and identify anthropogenic stressors with the highest impact on fish communities. In the third section, I discuss the issue of optimal gillnet sampling design for reliable fish indicator values to increase the utility of assessment methodologies and to reduce sampling effort and fish mortality required to obtain reliable data. In the fourth section, I compare estimates of fish recruitment based on different sampling methods and develop a novel statistical approach to analyse factors affecting fish recruitment. This work provides an initial step towards the improvement of ecological quality of freshwater reservoirs.
Lichens and eutrophication
Jadrná, Iva ; Svoboda, David (advisor) ; Malíček, Jiří (referee)
Eutrophication is a process of organic nutrients enrichment in an ecosystem, especially nitrogen and phosphorus. This bachelor thesis is dealing with the influence of eutrophication on lichens, especially with the effect of nitrogen compounds in the air and the effect of the combination of nitrogen compounds with phosphorus on epiphytic lichens. Eutrophication is defined and information is provided on changes in abundance and diversity of lichen cover. The mechanisms of eutrophication tolerance in lichens are also described. Key words: lichens, epiphytes, eutrophication, ammonia, ammonium ions, nitrogen oxides, phosphorus
Forest vegetation in Eastern Elbe Basin in the mid-20th century and today
Pospíšková, Marie ; Hédl, Radim (advisor) ; Novák, Jan (referee)
This thesis describes the shift in vegetation of broadleaf forests in eastern part of the Elbe River Basin between 1958-1968 and 2011-2013. It emphasizes the understorey vegetation. From lowland woodlands in other temperate regions in Europe and North America changes towards eutrophic and mesophytic vegetation are documented, specifically driven by changes in forest management and by atmospheric depositions; in some localities the game impact can be also important. The data were obtained by sampling 190 typological semi-permanent plots, which were precisely located - in 43% the original soil pit was found. The vegetation on study sites shifted towards nutrient-demanding, shade- adapted species, it was partly ruderalized. These changes can be seen on the level of species and communities as well as on phytosociological level. Increase of soil pH and moisture was discovered using Ellenberg indicator values. The number of seedlings and cover of shrubs also increased significantly. Homogenization of sites was significant as well although total number of species and alpha- diversity remained unchanged. These changes are probably caused by changes in forest management and by atmospheric depositions of nitrogen. On subset of plots in game-preserves the vegetation also demonstrated eutrophication but no increase in...
Analysis of high concentrations of total phosphorus incidence in small agricultural subcatchments
DUŠEK, Jiří
This thesis focuses on analysis of the peak values of phosphorus concentration in small agriculturally used subcatchments. The cycle of phosphorus in nature, in water and issue of the eutrophication is described in this thesis as well as basic characteristics of three monitored subcatchments. The concentration of phosphorus, flow rate and precipitation was measured in these three monitored subcatchments. Peak values of phosphorus concentration and possible impact of rainfall-runoff occurrences on these peak values are as well analyzed in this thesis. This research uses statistical methods. The final part of this thesis assesses the impact of rainfall-runoff occurrences on the peak values of phosphorus concentration. Other possible factors which could cause these peak values are also discussed.
Vliv antropogenní činnosti na znečištění vybraných vodních nádrží v povodí Jordánu.
ŠÍMOVÁ, Barbora
The master thesis deals with influence of system of water reservois and farming on suface water quality in catchment Košín stream in the Tabor region. There were investigated effect on suface water quality of several watercourses flowing through farmland with markedly different land cover, farming, size of catchment area and different water reservoirs. The fundamental hydrochemical parameters such as content of nutrient, inorganic and organic carbon and undissolved substances were monitored. The water samples were collected from permanent sampling points during the growing season. The investigated compounds were determined in the laboratory by titration, gravimetry and spectrophotometry. Mean, median, interquartile range were determined within the basic descriptive statistics and the data were statistically processed by nonparametric tests. Results showed particularly significant influence of the littoral vegetation and wide strips of tree vegetation as an effective filter, which prevent pollution of surface water by nutrient runoff. In some cases, the land cover was reflected positive impact of vegetation on reducing contamination of the water above the level specified by legislation, therefore vegetation is great importance in the fight pollution of waterways. From the obtained data it is obvious that influence of anthropogenic pollution on surface water is very important, but appropriate land cover can minimalize this impact.

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