National Repository of Grey Literature 8 records found  Search took 0.01 seconds. 
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.
The influence of nutrient loading, meteorological and hydrological conditions and operating manipulations on phytoplankton in the water suply reservoir Římov.
Hejzlar, Josef ; Jarošík, Jiří ; Nedoma, Jiří ; Seďa, Jaromír ; Znachor, Petr
Analysis of data collected during long-term and complex limnologic monitoring of the Římov reservoir in the period 1983 – 2015, which depict the development of physico-chemical conditions, hydrology and hydrodynamics of the reservoir with links to biological data on phytoplankton, zooplankton etc. showed that the concentration and species composition of phytoplankton depend on the supply and availability of nutrients, but are also influenced by climatic and hydrological conditions and water management operation of the reservoir.\n
Modelling the hydrodynamics and water quality of the Vltava river reservoir cascade
Růžička, Martin ; Hejzlar, Josef ; Jarošík, Jiří
Mathematical modelling is an efficient tool for evaluation of impacts of human activities and environmental changes on water quality in rivers and reservoirs. This contribution describes simulations of water quality in the Vltava River reservoir system, namely cascade of reservoirs Hněvkovice, Orlík, Kamýk, Slapy, Štěchovice, and Vrané. The two-dimensional water quality model CE-QUAL-W2 was used for this task over years 2000 to 2003. Sensitivity analysis, calibration, and evaluation of the model were done. The model gave good results in particular for hydrodynamics, water temperature, and conservative constituents because of good quality of available hydrological and meteorological input data. The accuracy of results was strongly depended on the quality of input data and sampling frequency. Minor problems occurred in water quality simulations based on monthly input data in periods with fluctuating discharges.
Water quality simulation in reservoir system
Růžička, Martin ; Hejzlar, Josef ; Jarošík, Jiří
Aim of the paper is to describe state of art and to show the problem solution methodology on example of reservoir system located in the Vltava watershed.
Modelování hydrodynamiky a kvality vody v dimiktické nádrži – nádrž Jordán, Česká republika
Hejzlar, Josef ; Jarošík, Jiří ; Borovec, Jakub ; Růžička, Martin
The two-dimensional, dynamic model CE-QUAL-W2 was used to model water quality of a small, highly eutrophic reservoir with intensive nutrient cycling between the water column and bottom sediment. The model was calibrated and evaluated for a 4-year, hydrologically variable period and used in a scenario simulation study to analyse effects of the changing external and internal phosphorus loading and depth of outflow to trophic conditions and water quality. The reservoir hydrodynamics were simulated with good precision in all parts of the seasonal cycle and during the whole period. Water quality and nutrient cycling could be calibrated and simulated with satisfactory results for individual years, however, an extrapolation of model to conditions with different nutrient loading was problematic. It spite of this partial limitation, the model was found appropriate for water quality evaluation and prediction in Jordan Reservoir.
Restoration of aquatic ecosystem and water quality in the drinking-water reservoir Římov after the flood in 2002
Hejzlar, Josef ; Kaštovská, Klára ; Seďa, Jaromír ; Znachor, Petr ; Jarošík, Jiří ; Haider, Z.
The extreme flood event in the catchment of the Malše River in August 2002 markedly changed hydrodynamics of Římov Reservoir (loss of thermal stratification; water residence time dropped from months to single days) and caused problems in water treatment due to a long-lasting increase in concentrations of dissolved organic matter. However, biota of the aquatic ecosystem was influences relatively little. Although large proportions of phytoplankton and zooplankton biomasses were flushed out of the reservoirs the originally dominant species re-established in their original size of biomass within less than one month. The fish community was influenced almost negligibly except for a temporal enrichment by species from streams and fishponds. These results evidence that the reservoir ecosystem is very stable towards fluctuations of hydrologic conditions.
Model analysis of effects of hydrodynamics and nutrient loading to water-quality in a dimictic reservoir (Jordán)
Jarošík, Jiří ; Hejzlar, Josef ; Borovec, Jakub ; Růžička, Martin
The dynamic, two-dimensional model CE-QUAL-W2 was used to simulate recovery conditions in the eutrophic Jordan Reservoir. The aims were: (i) to calibrate the model and discuss differences between simulated and measured data; (ii) to use the calibrated model to determine the effects of external and internal phosphorus load and the depth of outlet on trophic conditions. After calibration the model reproduced thermal stratification, oxygen regime and concentrations of NO3-N with sufficient precision. Simulation of PO4-P was less exact. The results of mathematical simulation showed that (i) the required mesotrophic level cannot be accomplished without a significant decrease in inflow concentration of total phosphorus; (ii) the internal load of phosphorus is small and become insignificant after decrease of external load; and (iii) the use of bottom outlet is a potentially efficient method to partly decrease trophic level of Jordan Reservoir.

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