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Sedimenty jako dynamická zásoba fosforu ve stratifikované nádrži
Borovec, Jakub ; Hejzlar, Josef ; Brzáková, Martina ; Jan, J.
The ecosystem of the small, dimictic, and hypertrophic reservoir (Jordan Reservoir, Czech Republic) was studied from March 2001 till March 2004 to evaluate rates at selected pathways in the P-cycle. The rates were inferred from measurement of P mass-balance, sedimentation of seston, and P-release from sediments. A shift between seasonal changes of inflow and outflow P concentrations caused by P accumulation in the hypolimnion and the sediments was demonstrated. An important amount of P was temporally retained at the sediment surface during the summer stratification but a part of it was released back to water during the autumnal mixing, due to pore water „flushing out” and fast organic matter decomposition.
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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.
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Phosphorus in aquatic ecosystems - forms, determination, cycling
Hejzlar, Josef ; Borovec, Jakub
Ecological importance of phosphorus in the aquatic environment is analysed. Starting with characterising the phosphorus chemistry and properties of its compounds in water and organisms, the paper gives an overview of external and internal sources of P for aquatic ecosystems, explains main principles of cycling within the water column and between the water column and bottom sediments and discusses relations between phosphorus concentrations and eutrophication.
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Transport fosforu v říční síti podhorského povodí se smíšeným využitím uzemí (povodí Malše, ČR)
Turek, Jan ; Hejzlar, Josef ; Žaloudík, Jiří
Phosphorus sources and transport in the river network were evaluated for a medium size (437 km2), upland catchment with mixed land use (forests, farmland, urban) located in South Bohemia during 1999-2003. Dissolved P concentrations in streams in completely forested catchments, farmland catchments, and municipal wastewater treatment plant (WTP) effluents were /~0.015, <0.01 to 0.25, and up to 2 mg/l, respectively. High particulate P concentrations (up to 0.6 mg/l) occurred in all streams during surface runoff events, irrespective to land use, and even higher in WTP effluents (up to /~4 mg/1). Analysis of P fluxes in the river network showed a significant annual retention of both dissolved P (26 to 41% of all sources) and particulate P (27 to 67% of all sources).
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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.
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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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Possibilities to decrease of the phosphorus concentrations in wateshed and reservoir
Borovec, Jakub ; Hejzlar, Josef ; Maršálek, Blahoslav
P concentrations in the outflow from the watershed result from the group of factors including geology, climate, vegetation cover, morphology of streams and others. Selection of the watershed restoration strategy and its optimalisation depends on the regional, but the common idea for management of both watershed and reservoir should be the recovery to natural processes of nutrient retention together with the idea of sustainable development of the landscape. For the reservoirs, it is always lucrative to precede their overloading by phosphorus. Thinking about the decrease of P in the reservoir, the only possibility is to remove the sediments as the final deposition pool in the P-cycle. In case of the decrease of P in the water column, i.e. available for algae, another procedures of reservoir management can be used.
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