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Osijek, Croatia

The analysis of seasonal occurrence of maximum annual flows, conducted at 95 gauging stations within the Danube river basin, is presented. Burn's vector method, and RVA - Range of Variability Approach method based on elementary statistical analysis of maximum annual flow dates, are used. The analysis shows that the lowest seasonal variability of maximum flows occurs in Gorski Kotar drainage basins, and that this maximum statistically occurs near the end of the year. The seasonal variability of maximum annual flows is much higher for other gauging stations included in the analysis. Source

Kralj D.,Ruder Boskovic Institute | Romic D.,University of Zagreb | Romic M.,University of Zagreb | Cukrov N.,Ruder Boskovic Institute | And 4 more authors.
Journal of Soils and Sediments

Purpose: This study used multi-element signatures of stream sediments to assess both natural and human-induced impact on fluvial system in the River Neretva delta receiving environment over time. The river basin actually comprises several sub-catchments, and the geochemical features of major elements, trace metals radiometric and mineralogical characterisation of river bed sediments were used to assist the interpretation of the environment of deposition and its subsequent modifications caused by various anthropogenic pressures within the river basin. Materials and methods: Five sites were chosen for sediment sampling at key locations within the study area with assumed undisturbed, continuous sedimentation process. At each of the sites, three representative cores were taken by scuba divers. Sample sites were selected in order to reflect the influence of different sub-catchments they belong to and the land-use pattern of the surrounding area. Samples were analysed for pH, redox-potential, granulometry, mineralogy, thermogravimetry, major and trace element concentrations and radionuclide activities. The univariate and multivariate statistics were applied. The geochemical normalisation of data was done using Al, the procedure based on calculation of the regression line of the metal on the normaliser followed by testing the ratios metal/normaliser on all data-points. Results and discussion: All studied sediments are classified as silt, ranging from clayey silt to silt and sandy silt. Mineralogically, the sediments were dominated by carbonates and quartz. The chemical contaminant data are generally of good quality, mostly below guideline levels. Sedimentation rates were estimated using vertical distribution of 137Cs activities. Normalisation of TMs done by using Al shows strong R2 adj values for the regressions of Al and V, Al and Cr, and Al and Ni. However, Al cannot fairly explain the fluctuation of the concentrations of Cd, Cu, Pb and Zn in sediment cores from all of the sampling sites. Generally, inorganic scavengers such as clay minerals followed by Fe and Mn oxides and S (pyrite and gypsum) seem to be dominant factors controlling TMs in studied sediments. Conclusions: Although the River Neretva delta occupies a rather small area, the geochemical features of major and trace elements and 137Cs activities show complex sediment provenances. Each of the sampling sites reflect exactly different effects of anthropogenic intervention that particularly refer to the changes in river morphology and ecology, along with the altered flow regimes within the catchment on sediment loads and quality. © 2015, Springer-Verlag Berlin Heidelberg. Source

Barbalic D.,Hrvatske Vode | Kuspilic N.,University of Zagreb
Tehnicki Vjesnik

Ecological status, according to EU Water Framework Directive, is an expression of the quality of the structure and functioning of aquatic ecosystems associated with surface waters. It can be compromised by different forms of hydrological alterations. In this paper some aspects of fast and frequent fluctuations of discharge, most often caused by production of electric energy to meet peek demands or so called “hydro-peaking” has been studied. Two “hydro-peaking” indicators defined in CEN guidance standard have been evaluated for the undisturbed gauging stations in the Danube River basin in Croatia and correlated to watershed size descriptors and fitting Indicators of Hydrological Alterations. Additional third indicator based on discharge, analogous to indicator from CEN, was introduced and studied in the same way. Results have revealed that on majority of examined gauging stations values of indicators exceed boundaries for “near-natural” and “slightly modified” state. It appears that the use of analogous discharge based indicator instead of level based indicator has some advantages such as easier application and potential for more reliable regionalisation. Reliability of relationship of the third hydro-peaking indicator, based on hourly flow data, to Indicators of Hydrological Alterations, based on daily flow data, indicates the possibility of using significantly larger pool of daily data for definition of reference (undisturbed) conditions for sub-daily flow variations. © 2015, Strojarski Facultet. All rights reserved. Source

Loncar G.,University of Zagreb | Matkovic M.,Hrvatske Vode | Androcec V.,University of Zagreb
Hrvatske Vode

The numerical modelling was conducted of effluent transfer caused by operation of a submarine outfall with the models Cormix and Mike 3. The investigation objective was the definition of appropriate parameterization in model analyses of scalar field transfer by means of finding suitable turbulent diffusion coefficients. The investigation was focused on effluent spreading in the area of the far field zone, up to 1.000 m downstream of the bottom effluent discharge location. The spreading of the effluent cloud front along the monitored stretch was referenced to the results of the model Cormix, while the values of turbulent diffusion coefficient in the lateral direction, used in the model Mike 3, were calibrated according to these results. The analysis was carried out in rectangular numerical canals of the width 1500 m and depths 30m and 40m. The vertical velocity profiles in the model canal were uniform and barotropic along the monitored stretch, with vertical mean values of 0.05m/s and 0.10m/s. The used vertical profiles of temperatures, salinity and density of the marine receiving body were obtained by a synthesis of the results from several national and international monitoring programmes in the Adriatic area. The monitored effluent was treated as biologically non-degradable (tracer). The analyzed value ranges of the hydraulic and geometrical characteristics of the diffuser, discharge flow and hydrographical characteristics of the marine receiving body encompass the relevant characteristics of the effluent transfer process caused by the operation of a submarine outfall in the winter and summer period in the coastal area of Croatia. Source

Kosic D.,Hrvatske Vode | Zelic B.K.,University of Zagreb | Domitrovic D.,University of Zagreb | Barac D.,PANGEO Projekt d.o.o.
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015

Clay geosynthetic barriers (GBR-Cs) are factory-manufactured hydraulic barriers consisting of a mineral and geosynthetic component. The mineral component is usually bentonite clay belonging to the group of swelling soils. The purpose of this study is to identify potential changes in the properties of bentonite clay as the result of installation into landfill covers including the changes taking place within the GBR-Cs. The analyses will be made on the samples taken from the final cover of a landfill site in Croatia. They were installed into the final cover system for the period from three to nine years. Characterization of the bentonite clay will be done by identifying its chemical composition, physical and index properties. The study will contribute to a better understanding of the behavior of bentonite clay and GBR-Cs during their long- Term use in the protective systems of landfill sites. © The authors and ICE Publishing: All rights reserved, 2015. Source

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