Number of found documents: 10
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Sediments as a dynamic pool of phosphorus in a stratified reservoir
Borovec, Jakub; Hejzlar, Josef; Brzáková, Martina; Jan, J.
2004 - English
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. Za účelem odhadu rychlostí vybraných procesů cyklu fosforu byl v období březen 2003 až březen 2004 sledován ekosystém malé, dimiktické, hypertrofní nádrže Jordán. Rychlosti procesů byly odhadnuty z měření bilance fosforu, intensity sedimentace sestonu a rychlosti uvolňování fosforu ze sedimentů. Byl zjištěn posun sezónním průběhu koncentrací fosforu na přítoku a odtoku z nádrže způsobený dočasnou akumulací fosforu v hypolimniu nádrže a v sedimentech. V období letní stratifikace byla významná část fosforu dočasně zadržena na povrchu sedimentů ve formě sedimentovaného sestonu, později, během podzimního míchání, byla část fosforu uvolněna zpět do vodního sloupce díky „vypláchnutí” ze sedimentů nebo rychlým rozkladem organické hmoty. Keywords: phosphorus mass-balance; phosphorus release; reservoir management Available at various institutes of the ASCR
Sediments as a dynamic pool of phosphorus in a stratified reservoir

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. ...

Borovec, Jakub; Hejzlar, Josef; Brzáková, Martina; Jan, J.
Hydrobiologický ústav, 2004

Transport of phosphorus in the river network of a highland basin with mixed landuse (the Malše River, Czech Republic)
Turek, Jan; Hejzlar, Josef; Žaloudík, Jiří
2004 - English
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). V povodí o ploše 437 km2 byly v letech 1999–2003 analyzovány zdroje fosforu a byl sledován jeho transport říční sítí. Sledované povodí leží v jižních Čechách a jeho území tvoří zalesněné plochy, zemědělská a zastavěná půda. Koncentrace rozpuštěného fosforu se na měřených profilech pohybovaly okolo 0,015 mg/l pro toky lesních povodí, mezi 0,001 až 0,25 mg/l pro povodí s převahou zemědělské půdy a až 2 mg/l pro výtoky z čistíren odpadních vod (ČOV). Vysoké koncentrace nerozpuštěného fosforu (až /~0,6 mg/l ) byly zjištěny ve všech tocích (bez zjevné závislosti na využití území) za situací, kdy docházelo povrchovému odtoku z povodí. Koncentrace v odtocích ČOV dosahovaly za stejných podmínek až /~4 mg/l. Analýza toků fosforu odhalila významné zadržení fosforu v říční síti za rok, a to jak rozpuštěného P (26 až 41% všech zdrojů), tak nerozpuštěného P (27 až 61% všech zdrojů). Keywords: diffuse and point sources; phosphorus retention Available at various institutes of the ASCR
Transport of phosphorus in the river network of a highland basin with mixed landuse (the Malše River, Czech Republic)

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 ...

Turek, Jan; Hejzlar, Josef; Žaloudík, Jiří
Hydrobiologický ústav, 2004

Modelling of hydrodynamics and water quality in a dimictic reservoir - Jordán Reservoir, Czech Republic
Hejzlar, Josef; Jarošík, Jiří; Borovec, Jakub; Růžička, Martin
2004 - English
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. Dvojrozměrný dynamický model CE-QUAL-W2 byl použit pro simulaci kvality vody v malé, vysoce eutrofní nádrži s intenzivním koloběhem živin mezi vodním sloupcem a dnovými sedimenty. Model byl kalibrována a hodnocen pro čtyřleté, hydrologicky variabilní období a použit pro scénářovou simulační studii, ve které se analyzovaly vlivy vnějšího a vnitřního zatížení fosforem a dopady hloubky vypouštění na trofické podmínky a kvalitu vody. Nádržová hydrodynamika byla simulována s dobrou přesností během celého studovaného období ve všech fázích sezónního cyklu. Kvalitu vody a koloběh živin bylo možné zkalibrovat s uspokojivými výsledky pro jednotlivé roky, ale extrapolace modelu do podmínek s jiným zatížením živinami byla problematická. Navzdory této částečné limitaci byl model shledán vhodným pro hodnocení a predikci kvality vody v nádrži Jordán. Keywords: coupled hydrodynamics-water quality model; phytoplankton; nutrients Available at various institutes of the ASCR
Modelling of hydrodynamics and water quality in a dimictic reservoir - Jordán Reservoir, Czech Republic

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 ...

Hejzlar, Josef; Jarošík, Jiří; Borovec, Jakub; Růžička, Martin
Hydrobiologický ústav, 2004

The diet of larval and juvenile pikeperch (.i.Stizostedion lucioperca./i.)(L.)), comparative study of fishponds and a reservoir
Peterka, Jiří; Matěna, Josef; Lipka, J.
2002 - English
Diet of larval and juvenile pikeperch (.i.S. lucioperca./i.) reared in ponds was investigated and compared with the diet of pikeperch from a reservoir. Numbers of rotifers were found low in the diet of pikeperch larvae in fishponds and they were soonreplaced by nauplii of cyclopoid copepods. .i.Daphnia./i. spp. were consumed from the onset of exogenous feeding. Another smaller cladoceran .i.Bosmina./i. longirostris did not contribute to the diet significantly. In the reservoir, rotifers were not found in the diet of pikeperch larvae. Dominant food items were nauplii and 1st copepodite instar of .i.Eudiaptomus gracilis./i. and .i.Cyclops./i. spp. .i.Daphnia galeata./i. and to a lesser extent .i.Diaphanosoma brachyurum./i. appeared in the pikeperch diet at a length of about 10 mm. A shift towards larger prey, especially .i.Leptodora kindtii./i., could be recognised in pikeperch at a length of 20 mm. Growth of pikeperch was found faster in nursing ponds than in the reservoir. Keywords: diet composition; food selection; growth; růst Available at various institutes of the ASCR
The diet of larval and juvenile pikeperch (.i.Stizostedion lucioperca./i.)(L.)), comparative study of fishponds and a reservoir

Diet of larval and juvenile pikeperch (.i.S. lucioperca./i.) reared in ponds was investigated and compared with the diet of pikeperch from a reservoir. Numbers of rotifers were found low in the diet ...

Peterka, Jiří; Matěna, Josef; Lipka, J.
Hydrobiologický ústav, 2002

Eutrophication trends in the Vltava catchment area, Czech Republic
Hejzlar, Josef; Vyhnálek, V.; Kopáček, Jiří; Procházková, Lidmila; Komárková, Jaroslava
2000 - English
Long-term trends in phosphorus and phytoplankton concentrations were studied in Slapy Reserv.,as a representative of most reservoirs with medium flushing rate in the Czech Rep. Phosphorus and chlorophyll a concentrations increased from the 1950s to the middle 1990s as a consequence of an increase of phosphorus use and release into surface waters by human population. The decrease in phosphorus and chlorophyll a concentrations during the last decade can be interpreted as a beginning of a long-term recovery of Slapy Reservoir resulting from the decrease in P-loading into the surface waters by human population. Further possibility how to reduce phosphorus input to the surface waters is especially P removal from municipal waste waters. After higher reduction of phosphorus from waste waters, accomplishable especially by the entire elimination of P from detergents and by technologies of enhanced P removal in waste water treatment facilities,the trophic status of Slapy Reserv. lower than in the 1950s can be expected. Keywords: povrchové vody; čištění odpadních vod Available at various institutes of the ASCR
Eutrophication trends in the Vltava catchment area, Czech Republic

Long-term trends in phosphorus and phytoplankton concentrations were studied in Slapy Reserv.,as a representative of most reservoirs with medium flushing rate in the Czech Rep. Phosphorus and ...

Hejzlar, Josef; Vyhnálek, V.; Kopáček, Jiří; Procházková, Lidmila; Komárková, Jaroslava
Hydrobiologický ústav, 2000

Modelling the sedimentation of inflow particulate matter in the longitudinal profile of a stratified reservoir
Hocking, G. C.; Hejzlar, Josef; Borovec, Jakub
1999 - English
Keywords: hmota; sedimentace Available at various institutes of the ASCR
Modelling the sedimentation of inflow particulate matter in the longitudinal profile of a stratified reservoir

Hocking, G. C.; Hejzlar, Josef; Borovec, Jakub
Hydrobiologický ústav, 1999

Effect of biomanipulation on the structuring of the planktonic food web and water treatability by coagulation
Hejzlar, Josef; Dolejš, P.; Komárková, Jaroslava; Seďa, Jaromír; Šimek, Karel; Vyhnálek, Vojtěch
1997 - English
Keywords: voda; potrava Available at various institutes of the ASCR
Effect of biomanipulation on the structuring of the planktonic food web and water treatability by coagulation

Hejzlar, Josef; Dolejš, P.; Komárková, Jaroslava; Seďa, Jaromír; Šimek, Karel; Vyhnálek, Vojtěch
Hydrobiologický ústav, 1997

Sources and transport of phosphorus in the Vltava River watershed (Czech Republic)
Hejzlar, Josef; Vyhnálek, Vojtěch; Kopáček, Jiří; Duras, J.
1995 - English
Keywords: republika; fosfor Available at various institutes of the ASCR
Sources and transport of phosphorus in the Vltava River watershed (Czech Republic)

Hejzlar, Josef; Vyhnálek, Vojtěch; Kopáček, Jiří; Duras, J.
Hydrobiologický ústav, 1995

Mountain lakes as sensors of air pollution - importance of monitoring water ecosystems in mountain regions
Straškrábová, Viera
1995 - English
Keywords: znečištění vzduchu; jezera Available at various institutes of the ASCR
Mountain lakes as sensors of air pollution - importance of monitoring water ecosystems in mountain regions

Straškrábová, Viera
Hydrobiologický ústav, 1995

Limnological research of acidified lakes in Czech part of the Šumava Mountains: trophic status and dominance of microbial food webs
Vrba, Jaroslav; Kopáček, Jiří; Straškrábová, Viera; Hejzlar, Josef; Šimek, Karel
English
Available at various institutes of the ASCR
Limnological research of acidified lakes in Czech part of the Šumava Mountains: trophic status and dominance of microbial food webs

Vrba, Jaroslav; Kopáček, Jiří; Straškrábová, Viera; Hejzlar, Josef; Šimek, Karel
Hydrobiologický ústav

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