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Sediment oxygen demand in Jordan reservoir
Borovec, Jakub ; Hendl, Ondřej
Sediment oxygen demand was described in Jordan reservoir during the year. Sediment from the inflow part of the reservoir had SOD20 value was lower comparing to the ones from the dam part. By the peak of summer season the dam part sediments have consumed the oxygen three times faster that the infow sediments. The influence of freshly settled seston was shown. Remove of the upper most layer of the sediment – fresh seston – caused the decrease of 47% of the SOD value the dam part sediments. Sediment oxygen demand differed both among localities and during the year in dependence on temperature.
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New methods for sediment description – how to their "metabolism"
Jan, Jiří ; Borovec, Jakub
Volume of reservoir sediments is usually small comparing to volume of water, but there are i) important place of nutrient recycling of water ecosystems and, ii) there are a dynamic part of the ecosystem. Large number of tightly coupled processes in the sediments is dependent on seasonal development and changes of physical, chemical and biological conditions (temperature, DO concentration, microbial activity, current conditions, amount and quality of settling material). Modern methods for nutrient balance in sediments, rates of release/uptake of nutrients and pore-water profiles were shown.
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Evaluation of sediment importance for phosphorus internal load
Borovec, Jakub ; Hejzlar, Josef
Eutrophication still belongs to the serious problems waiting for solution. Phosphorus is the nutrient most often limiting the primary producers. It is well known, the improvement of water quality can be, after successful decrease of external P load, retarded by P-release from sediments. It is also necessary to realize, that the decrease of external P-load to the demanding level cannot be due to technical, political or economical reasons always possible. Measures increasing P-retention in sediments are often employed in such conditions. Many cases are known when the level of the water quality improvement remained far behind the expectations. Technical problems, still unknown mechanisms or insufficient screening followed by inadequate solution might be the reasons for the failures. The aim of this paper is to show simple decision-support system for exclusion of improper solutions and increase of the effectiveness of activities made before the rehabilitation measures realization.
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Complex assessment of the fish assemblage of the Želivka reservoir, the biggest water supply reservoir in the ČR, in years 2004 and 2005
Prchalová, Marie ; Kubečka, Jan ; Jůza, Tomáš ; Říha, Milan ; Jarolím, Oldřich ; Tušer, Michal ; Peterka, Jiří ; Vašek, Mojmír
In the summer 2004 and 2005, the complex assessment of the fish assemblage of the Želivka reservoir (1432 ha) was carried out by gillnetting, adult and fry seining, adult and fry pelagic trawls and hydroacoustic sampling. Detailed picture of the fish assemblage was composed from every fishing gear from every depth strata of the open water as well as from the littoral zone. During two-years survey, 40.168 fish of 19 species and one hybrid were captured. The fish assemblage was dominated by cyprinid species in both years – bleak prevailed in the open water together with roach and bream; perch was abundant in the littoral zone. The assemblage of the Želivka reservoir was found to be in the stable cyprinid phase. The average abundance was 1.700 ind/ha and average biomass was 110 kg/ha. In the fish spatial distribution, the general gradients could be found – higher abundance and number of species in the tributary area and in the epilimnion and littoral.
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