Institute for Water of the Republic of Slovenia

Ljubljana, Slovenia

Institute for Water of the Republic of Slovenia

Ljubljana, Slovenia
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Javornik L.,Institute for Water of the Republic of Slovenia | Kryzanowski A.,University of Ljubljana | Mikos M.,University of Ljubljana
River Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016 | Year: 2017

Present state of the operation procedure manual of HPP Vrhovo, which defines the operation procedures in the range between low and extreme flows, determines appropriate reservoir water levels only in a relation to upstream incoming flows from the gauging stations and consequently doesn’t take the effects of increasing flow levels on the reservoir morphologic conditions into account. A 2D sediment transport model was used to determine new, optimised operating rule curve (ORC) at the HPP Vrhovo dam profile station on Sava River with regard to sediment transport effects on the reservoir bathymetry. © 2017 Taylor & Francis Group, London.

Humar N.,Institute for Water of the Republic of Slovenia | Zupan D.,University of Ljubljana | Kryzanowski A.,University of Ljubljana
Advances and Trends in Engineering Sciences and Technologies II - Proceedings of the 2nd International Conference on Engineering Sciences and Technologies, ESaT 2016 | Year: 2017

Large dams are among the most frequently monitored structures. This is understandable, having in mind the consequences of dam failure or equipment malfunction. Over the last decades we have witnessed great progress of measurement techniques and methods, due to the rapid development of materials and equipment. Distributed fiber-optic measurements are among the very promising methods for monitoring dams. The method solves some of the weaknesses of the commonly used measuring methods, e.g. installation and density of the network, which is useful when measuring parameters, such as temperature field changes, formation of cracks, or leaking. In this paper we want to present the results of measurements of the release of temperature measured using fiber optic cables in an early age concrete directly after the placing of mass concrete in the spillway section, the advantages of the presented method for monitoring and controlling the process of hydration, and the release of temperature increment. © 2017 Taylor & Francis Group, London, UK.

Petkovska V.,Institute for Water of the Republic of Slovenia | Urbanic G.,Institute for Water of the Republic of Slovenia | Urbanic G.,University of Ljubljana
Ecohydrology | Year: 2015

In the last decades, hydromorphological degradation of rivers has gained more attention in river management, stressing the importance of understanding the links between hydromorphology and aquatic assemblages. The present study investigated general patterns in the response of benthic invertebrate assemblages to single morphological features along naturally diversified Slovenian rivers. The whole gradient of local habitat quality (river habitat quality, RHQ) and habitat modification (river habitat modification, RHM) features, according to the Slovenian hydromorphological assessment method, was covered. Regional natural characteristics explained the low share of RHQ and RHM variability, indicating nonregional presence of morphological features. The analysis identified predominant flow and predominant channel substrate as the most important RHQ features. We found that in contrast to RHQ features, RHM features had low explanatory power. These results suggest a weaker response of benthic invertebrate assemblages to the physical alteration itself than to the effect that the alteration exerts on habitat quality features. Variance partitioning among three environmental variable groups revealed predominantly independent effects (69%) on benthic assemblages, mostly on account of regional natural characteristics (30%) and RHQ features (31%). As benthic invertebrate assemblages are adapted to the former natural conditions, a similar modification may result in different effects with regard to regional natural differences. Therefore, the low proportion of variability, explained by RHM features, might be the consequence of joint dataset from different regions. Our study gives general implications for river management, but in order to more clearly define the significance of particular modification features, we suggest further analysis within more homogeneously defined habitats that encompass regional natural characteristics. © 2014 John Wiley & Sons, Ltd.

Urbanic G.,University of Ljubljana | Urbanic G.,Institute for Water of the Republic of Slovenia
Ecohydrology | Year: 2014

Lakeshore deterioration is a major threat to the ecological integrity of lakes worldwide. In this study, the relationship between littoral benthic invertebrates and the Lakeshore Modification Index (LMI) was examined. The influence of the taxonomic resolution on littoral benthic invertebrate community response to LMI was assessed using the results of the canonical correspondence analysis and the relationship between the taxa richness, Shannon-Wiener diversity index and the LMI. Benthic invertebrates were sampled in summer between 2006 and 2011 in two natural and two artificial Alpine lakes using a littoral microhabitat type sampling scheme. Ordination analyses show a similar explanation power when the lowest available taxonomic level was used in comparison with the family level. Taxa richness and the Shannon-Wiener diversity index indicate that lakeshore modifications impair littoral biological conditions with a loss of richness and diversity independently of lake type and used taxonomic level. For 64 families, a lakeshore modification indicative value between one and nine were set on the basis of distribution among five lakeshore modification classes. A Littoral Fauna Index (LFI) was then derived by summation of the lakeshore modification indicative values recorded at each site. A validation dataset from natural and artificial lakes confirmed the good relationships between LMI and LFI but revealed some differences in the relationships. The results show that the impacts of lakeshore modifications can be assessed using littoral benthic invertebrate assemblages with a family-level-based LFI, which makes this method cost effective and appropriate for routine monitoring. © 2013 John Wiley & Sons, Ltd.

The effects of hydropower dams and, in particular, the impacts of reduced river flows on the periphyton community were assessed in the Soča River, Slovenia. Sampling sites were selected upstream and downstream of the Podsela and Ajba dams. Sampling was carried out in 1998 during a period of low flows. Reaches downstream from the dams experienced prolonged periods of reduced flows, and a corresponding decrease in flow velocity and water depth. The chain of hydropower dams has stopped sediment inflow from the upstream reach. Below the dams, the oscillations of water temperature, dissolved oxygen and oxygen saturation are much larger than at unregulated sites upstream. The impact of prolonged periods of reduced flows, a lack of sediment supply from upstream and changes in physicochemical variables has caused high periphyton biomass, proliferation of green algae and increases in the number of periphytic algae species below the dams. This has significant implications for the design of environmental flow strategies that provide a sediment supply to maintain a healthy periphyton community. Editor Z.W. Kundzewicz; Associate editor M. AcremanCitation Smolar-Žvanut, N. and Mikoš, M., 2014. The impact of flow regulation by hydropower dams on the periphyton community in the Soča River, Slovenia. Hydrological Sciences Journal, 59 (5), 1032-1045. © 2014 IAHS Press.

Peterlin M.,Institute for Water of the Republic of Slovenia | Urbanic G.,Institute for Water of the Republic of Slovenia | Urbanic G.,University of Ljubljana
Ecohydrology | Year: 2013

Lakeshores are under increasing pressure from human activities, which cause extensive hydromorphological alterations. In this article, a method is described for assessing those alterations by using physical criteria developed in relation to the response by the lakeshore ecosystem, using benthic invertebrates as indicators. Two alpine lakes (Lake Bled and Lake Bohinj, Slovenia) were used as a case study. Both lakes are subjected to varying levels of physical alterations and lakeshore uses, which are described using alteration variables for four lakeshore zones: littoral zone, shoreline zone, riparian zone and lakeshore region. On the basis of these four variables, a Lakeshore Modification Index (LMI) was developed as a weighted sum of all variables. The weights were based on each variable's explanatory power regarding the distribution of benthic invertebrate taxa using canonical correspondence analyses. Both the LMI and all four lakeshore zone alteration variables showed significant (p<0.01) negative correlations with species richness, but the LMI showed the strongest correlation (Pearson r=-0.086, p<0.01). Differences existed in the level of alteration of the two lakes, with Lake Bled being more altered than Lake Bohinj; Lake Bled also exhibited the highest values for all four alteration variables and the highest LMI score. With the use of a classification system with five equidistant LMI classes, a difference was observed between the lakes in the distribution of LMI classes (two-sample Kolmogorov-Smirnov test Z=5.714, p<0.01). An assessment and classification of lakeshore modifications based on physical criteria, similar to that given by the LMI, can provide an important tool for lake management in practice, where a reliable method for assessing pressures is needed to support decision-making. © 2012 John Wiley & Sons, Ltd.

Petkovska V.,Institute for Water of the Republic of Slovenia | Urbanic G.,Institute for Water of the Republic of Slovenia | Urbanic G.,University of Ljubljana
Environmental Monitoring and Assessment | Year: 2010

We investigated the effect of different subsample fractions on the variability of benthic invertebrate metrics. The results of six fractions 1/12, 1/6, 1/4, 1/3, 5/12 and 1/2 were compared to the results of the whole samples. Over 120 metrics were tested using five datasets: ecoregion Alps and four river types. In general, variability of metrics decreased with increasing subsample size, but variability varied greatly with the selected metric group and river type. Independent of river type, the highest variation was observed for the composition/abundance group metrics and the richness metrics, whereas it was low for the diversity indices and for the metrics of the sensitivity/ tolerance group and intermediate for the functional metric group. For all metric groups independent of river type, the main decrease in variability occurs up to 1/4 subsample.We suggest that the effect of subsample size on variability of metrics should be tested prior to selecting potential assessment metrics. © Springer Science + Business Media B.V. 2009.

Mavric B.,Slovenian National Institute of Biology | Urbanic G.,Institute for Water of the Republic of Slovenia | Lipej L.,Slovenian National Institute of Biology | Simboura N.,Hellenic Center for Marine Research
Marine Ecology | Year: 2013

Routine monitoring of the quality status of water bodies demands the best cost-benefit relation and sample-size reduction is therefore welcomed. However, great caution is needed because such reduction affects the accuracy and variation of the results. In the present study we tested the influence of sample size (number of replicate samples) on reference condition values and within-sample ecological quality ratio (EQR) variability of six commonly used ecological indices (taxa richness, Shannon-Wiener diversity, AMBI, Medocc index, Bentix and M-AMBI). Analysis of soft-bottom benthic invertebrate data from Slovenian coastal waters showed that sample size influenced the reference condition values of richness/diversity indices (taxa richness and Shannon-Wiener diversity) but not of the sensitivity/tolerance indices (AMBI, Medocc index, Bentix). Increased sample size decreased the within-sample EQR variability and, concomitantly, increased the accuracy of site ecological status classification for all indices. The size of EQR variability differed depending on the index used. EQR variability of M-AMBI, an index composed of metrics with different within-sample EQR variability, was statistically the same as that of the metric with the lowest within-sample EQR variability. Whether this is a common principle for multimetric indices remains to be confirmed. Based on these results, the use of at least three replicates is suggested to obtain reliable measures of reference condition and EQR for the assessment of ecological status. This level of replication is particularly necessary in areas with high diversity and environmental patchiness, and when richness/diversity measures and indices that include these measures are used. © 2012 Blackwell Verlag GmbH.

Orlando-Bonaca M.,Slovenian National Institute of Biology | Mavric B.,Slovenian National Institute of Biology | Urbanic G.,Institute for Water of the Republic of Slovenia
Ecological Indicators | Year: 2012

The assessment of the status of coastal waters is required by the European Water Framework Directive. The aim of the present study was to test the response of benthic invertebrates to hydromorphological (HM) alterations and to develop a new index for the assessment of HM alterations of the rocky shore, based on benthic invertebrates. Fifty samples were collected, 10 from pre-classified HM classes 1, 3, 5; 15 from class 2, and 5 from class 4. Seven HM variables describing habitat conditions were used to test the benthic invertebrate response and to develop the HM stressor gradient: material, texture, structure, belt length, sedimentation, water retention and artificially induced mobility. Abundance, some diversity (Shannon-Wiener, Simpson's and Evenness) and richness (number of taxa) metrics showed low correlation values (r < 0.5) against HM variables and HM stressor gradient, indicating that tested metrics have limited value in assessment of the HM degradation impact on coastal benthic invertebrates. On the other hand, significant differences in the structure of benthic invertebrate assemblages among HM classes were observed (One-way ANOSIM global test r = 0.53, P < 0.0001). In the partial canonical correspondence analyses each of seven HM variables statistically significantly (P < 0.05) explained individual portion of the benthic invertebrate taxa variability. HM indicative values ranging from 1 to 9 were defined for each of 229 taxa, according to its distribution along the five HM classes. HM indicative weights (WHM) between 1 and 5 were defined according to the valences distribution among HM classes. HM indicative values, WHM and log 5 abundance classes were combined in a new Benthic Index for Rocky Shore (BIRS), using the weighted average approach. The combination of all three parameters in the BIRS showed a statistically significant (P < 0.05) response of the new developed index to HM stressor gradient, with a high Pearson correlation coefficient (r = 0.97). Further work has to be done in order to develop a WFD compliant method with five classes' boundary values. Nevertheless, the new developed index has a good potential to contribute to existing coastal assessment systems. Especially, as impact of hydromorphological alterations on coastal communities was almost neglected so far, despite being one of the main threats to coastal water integrity. © 2011 Elsevier Ltd.

Siling R.,Institute for Water of the Republic of Slovenia | Urbanic G.,Institute for Water of the Republic of Slovenia
Knowledge and Management of Aquatic Ecosystems | Year: 2016

In order to provide adequate guidelines in freshwater management, managers need reliable bioindicators that can respond differently to varied stressors. Managers also have to consider hierarchical structure of environmental factors. Thus, our research aims to test the independence of taxa responses along environmental gradients and to examine in what order natural and anthropogenic factors constrain the structure of littoral benthic assemblages. The rank of explained variance of littoral benthic assemblage's variable group hierarchy was: land use >landscape characteristics>eutrophication>fish stocking>hydromorphological alteration. We determined nine gradients (two natural and seven stressor gradients), separated into five groups based on statistically significant differences in responsiveness of taxa. Apart from responsiveness to natural factors, littoral benthic invertebrates could be used as bioindicators for stressors reflecting urbanization, eutrophication, hydromorphological alteration and fish stocking. The taxonomical composition of littoral benthic invertebrates, especially when taxa with preference for certain relatively narrow environmental conditions along gradients are present, can be used to identify effects of key stressors. Our findings have profound implications for ecological assessment and management of lakes, as they indicate that benthic invertebrates can be used when the effects of multiple stressors need to be disentangled. © R. Šiling and G. Urbanič, Published by EDP Sciences.

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