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An analysis of the hierarchy of importance of point and diffuse phosphorus sources in the Lomnice River catchment for the eutrophication of Orlík Reservoir
Hejzlar, Josef ; Polívka, Josef ; Žaloudík, Jiří
P sources in the Lomnice River catchment were analysed in two ways: (i) with a balance method of comparing P fluxes at monitored profiles on streams against the sums of partial P sources within their catchments that was reduced by P retention in the stream network and (ii) with the SIMCAT model of the Environmental Agency UK. Both methods appointed as the main source of high concentrations of total P (i.e., mean and 90% percentile of 0,28 and 0,45 mg/l, respectively, at the mouth of the Lomnice River to Orlík Reservoir in 2004-2008) municipal wastewater discharges and intensive fish pond production (55 and 25 % of P sources in the catchment, respectively) while the exports from agricultural and forested areas were 15 and 3 %, respectively. Scenario calculations by both methods indicated that the level of P concentration in the Lomnice River without eutrophication impacts on the reservoir cannot be achieved without measures both in the purification of wastewaters and fisheries.
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Phosphorus – the main cause of currently unfavourable state of eutrophication and water quality in Orlík Reservoir
Hejzlar, Josef ; Matěna, Josef ; Šimek, Karel ; Turek, Jan ; Znachor, Petr ; Žaloudík, Jiří ; Rohlík, V. ; Langhansová, M.
Inflow concentration and water retention time are major controlling factors for in-lake P concentration and consecutively development of water blooms and eutrophication. Orlík Reservoir has been hypertrophic in its inflow arms and eutrophic at the dam. For avoiding cyanobacteria blooms it is needed to decrease P load in the reservoir to less than one half. P-source apportionment in the catchment indicated the dominant importance of municipal wastewaters, farmland runoff, and fishpond production.
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