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The paper analyses dependence of water quality parameters on flow rates at several sites in the Vltava River catchment in the Czech Republic. The presented results indicate that at the monitored sites, concentrations of nitrates, suspended solids and dissolved oxygen are in direct relation to flow rate. Temperature has an inverse relationship to flow rate. Other parameters show various relationships to flow rate at individual monitored sites or do not show any statistically significant relations.

A significant amount of artificial radionuclides has been introduced into the environment in the last century during atmospheric nuclear weapons tests and the Chernobyl accident. In this study, we investigated the temporal changes of concentrations and amounts of these radionuclides ( 90 Sr and 137 Cs) in surface water and river bed sediments. In order to evaluate the artificial radionuclide contamination diminution, we used and compared two different approaches: using a kinetic equation of the first order and, if needed, dividing the monitored period into two intervals, and in addition expressing the whole process in one equation with a series of exponential functions. Effective ecological halflives were estimated as rates of decrease. In most cases, the ecological processes were proven to affect the radionuclide removal from the hydrosphere besides their radioactive decay. Furthermore, based on the assessment made, the 90 Sr and 137 Cs data were extrapolated and the radionuclide concentrations, which occurred in the hydrosphere after the fallout deposition in 1986, were estimated.

Abstract. Beginning of the construction of Temelin Nuclear Power Plant (NPP) in south Bohemia (CR) dates back to 1986. It was planned that the first water-cooled reactor could be put into operation in 2001. A research project (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998), funded from the national budget and carried out under supervision of the Czech Ministry of Environment, was aimed at examining pre-operational environmental conditions (a reference level) in terms of concentrations of radioactive and non-radioactive polluting substances in components of the environment, particularly in the hydrosphere, and at predicting possible impacts of future operation of Temelin NPP. Special attention paid to the hydrosphere was associated with requirements for protection of water quality in the Vltava River, which serves as drinking water resource for Prague capital.The observation and research activities continue during the following period (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) within the framework of a project sponsored by Czech Power Company. The paper summarises selected results of the projects, particularly those concerning pre-operational environmental conditions and impacts predicted for standard operation of the plant. More detailed description of the results, including possible impacts of the so called maximum project accident, is presented in [1][2][3]. To the date of the conference, the releases of tritium and other radionuclides from the plant into the hydrosphere were much less than the authorised limits.

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