Siporek is a computer program that was developed as a quick modelling tool for calculating the consequences of spills of hazardous chemicals in rivers. Basically, it is a 1-dimensional model, but it also enables us to take into account narrow accumulations (as it is the case in hydroelectric power plant constructions on rivers); it can be used in all cases where the flow is not explicitly 2- or 3-dimensional. The modelling results are in the form of a concentration curve along the channel and the speed of propagation of pollutants; for each calculation a c-t or a c-x graph is drawn. Additionally to advection and dispersion, the model takes into account evaporation and mechanical spreading of pollutants. Siporek can be used for modelling all types of rivers that can be found in Slovenia: from fast mountainous to slower flatland rivers. It is also possible to take into account a simplified representation of dams and waterfalls and their impact on river flow. Siporek is a simple and user friendly program. It is written in C++, GUI is written in Qt 4.7. Computing time for one modelling case is about 1 second. Input data needed for computation are not many and not hard to acquire: simplified channel geometry data, channel slope, Manning's coefficient, discharge, data about pollutant spill dynamics. In general, a rectangular or a trapezoidal cross-section is used, while the axis of the watercourse is presented as a sum of linear segments with a uniform cross-section and constant parameter values. Moreover, to speed up the process of collecting the appropriate data in real cases, the chart of all Slovenian rivers broader than 5 m, on which all input parameters are shown, was prepared in advance.

A hydro-electric power plant (HEPP) Brežice will be built 7 km downstream of the Nuclear power plant Krsko (NPPK). This will cause a 3 m rise of the water level, which will change the hydraulic and thermal conditions at the entrance of the cooling water to the inflow channel. The project task was to simulate the velocity field and sediment transport in the future conditions at his location, and to simulate thermal conditions in the entire Brežice reservoir. As the vertical velocity components in the vicinity of the inflow are of the same order of magnitude as the horizontal components, the velocity field is “fully 3D”. As the applied model PCFLOW3D is in the “quasi 3D” form, we performed measurements of the velocities in the Sava River near the inflow to the channel. During the verification of the model we found that the model gives good results for the flow upstream of the inflow section, while near the inflow the results are less reliable. We are currently preparing a “fully 3D” version of the model. The present model showed that in the future conditions the sediment inflow into the inflow channel will not change significantly. Verification of the thermal module had already been carried out in 1995 and 1998 on the reservoir Vrhovo in both summer and in winter conditions. It was shown that the model can well simulate the thermal conditions.

Cooling water for the Nuclear Power Plant Kr ko (NPPK) is provided from the Sava River. In the next years, a dam with a HEPP will be constructed 7 km downstream and the water level will be raised for 3 m. Numerical simulations of the flow, sedimentation and thermal pollution had to be made for the future conditions. Detailed 3D measurements of the flow in the present situation were made by a floating ADCP instrument and compared with the results of some versions of the 3D model. In greatest part of the river section a good agreement is obtained. However, near the intake to the inflow channel an underwater wall is directing the flow which is complex, the vertical velocity components locally attaining over 20 % of the horizontal components. Here the difference between the simulated and measured velocity vectors is hardly acceptable. The same model has also been supplemented for the simulation of thermal pollution, where agreement with the measurements is very good. Some cases of simulations of thermal conditions in the whole reservoir are also presented for present and future conditions.

Za dolgotrajno simulacijo transporta in disperzije živega srebra v raztopljeni in na delce vezani obliki smo dopolnili obstoječi tridimenzionalni matematični model PCFLOW3D, s katerim je mogoče upoštevati gibanje vode zaradi vpliva vetra, plimovanja in gibalne količine rek, ki vtekajo v zaliv ter stratifikacijo. Zbrani in prikazani so podatki o temperaturnih in slanostnih razmerah ter vetru na območju Tržaškega zaliva. Ta se skupaj s podatki o pretoku, temperaturi ter vsebnosti živega srebra v vodi in na delcih lebdečih plavin, ki dotekajo v zaliv s Sočo, predstavljajo vhodne podatke modela. Z izdelanim scenarijem za dolgotrajne simulacije, ki temelji na sezonsko povprečnih vrednostih posameznih parametrov in z dodatnimi krajšimi vložki močnega vetra in visokih pretokov Soče smo nadomestili dosedanji način simulacij s povprečnimi letnimi vrednostmi. Za verifikacijo in umerjanje izpopolnjenega modela smo uporabili meritve in opazovanja iz let 1995 – 1997. Čeprav nekateri kompleksni procesi pretvorb živega srebra še niso povsem raziskani in jih zato ni bilo mogoče upoštevati pri simulacijah, je doseženo kvalitativno dobro ujemanje rezultatov in meritev. Kjer je bila mogoča kvantitativna primerjava, je ujemanje rezultatov v okviru faktorja dve. Ključne besede: živo srebro, matematično modeliranje, 3D model,Tržaški zaliv

The Idrija mine, Slovenia has severely enhanced the mobilisation of Hg by mining activities, and Hg-laden material remains in the region. The tailings and contaminated soils are continuously eroded and serve as a continuous source for the river, the flood plains and the Gulf of Trieste. The paper presents data of the recent study which aims to assess the extent of contamination of Gulf of Trieste after the closure of the Hg mine. Mercury and methylmercury were measured in various environmental compartments (estuarine and marine waters, sediments, and organisms) during 1995-97 period. Data obtained show that even 10 years after closure of the Hg mine, Hg concentrations in river sediments and water are still very high and did not show the expected decrease of Hg in the Gulf of Trieste. A provisional annual mercury mass balance was established for the Gulf of Trieste showing that the major source of inorganic mercury is still the River SoCa while the major source of methylmercury is the bottom sediment of the

On the river Sava in Slovenia downstream of Trbovlje, a chain of 7 hydroelectric power plants (HEPP) with small reservoirs is projected. One of them, Vrhovo, has already been built in 1996. The Krško nuclear power plant is situated along the downstream reach of the chain, releasing about 1300 MW of heat into the river. The TET2 thermal power plant in Trbovlje pollutes the river with 157 MW of heat. As the latter is planned to be enlarged in 2004 to release 237 MW of heat (TET3), an extensive study on thermal pollution of the river Sava was elaborated. Measurements of temperature in the existing Vrhovo reservoir showed, that some thermal stratification is present in summer (up to about 3 K), and the reservoir behaves in a manner intermediate between a river and a lake. Therefore, besides a one-dimensional numerical model a second model was evolved from the PCFLOW3D hydrodynamic and pollutant transport model to simulate thermal pollution phenomena. Both models were calibrated and satisfactorily verified. The study concentrates on two cases: "critical conditions" (CRC), with a "one-year" low discharge and normally hot summer temperatures, and "extreme conditions" (EXC) with the lowest discharge and highest temperatures registered during the last four decades. The main conclusions of the research are: (a) Increase of thermal pollution from 157 to 237 MW will