J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 357 - 359, doi: 10.2478/johh-2018-0037
Information, English

Yvetta Velísková: 65th Anniversary of the Institute of Hydrology, Slovak Academy of Sciences

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• Data not available
  
  KEY WORDS: Data not available
  
  Address:
  - Yvetta Velísková, Institute of Hydrology, Slovak Academy of Sciences Dúbravská cesta 9, 841 04 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 360 - 368, doi: 10.2478/johh-2018-0024
Scientific Paper, English

Massimo Iovino, Pavla Pekárová, Paul D. Hallett, Ján Pekár, Ľubomír Lichner, Jorge Mataix-Solera, Vincenzo Alagna, Richard Walsh, Annette Raffan, Karsten Schacht, Marek Rodný: Extent and persistence of soil water repellency induced by pines in different geographic regions

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• The extent (determined by the repellency indices RI and RIc) and persistence (determined by the water drop penetration time, WDPT) of soil water repellency (SWR) induced by pines were assessed in vastly different geographic regions. The actual SWR characteristics were estimated in situ in clay loam soil at Ciavolo, Italy (CiF), sandy soil at Culbin, United Kingdom (CuF), silty clay soil at Javea, Spain (JaF), and sandy soil at Sekule, Slovakia (SeF). For Culbin soil, the potential SWR characteristics were also determined after oven-drying at 60°C (CuD). For two of the three pine species considered, strong (Pinus pinaster at CiF) and severe (Pinus sylvestris at CuD and SeF) SWR conditions were observed. Pinus halepensis trees induced slight SWR at JaF site. RI and RIc increased in the order: JaF < CuF < CiF < CuD < SeF, reflecting nearly the same order of WDPT increase. A lognormal distribution fitted well to histograms of RIc data from CuF and JaF, whereas CiF, CuD and SeF had multimodal distributions. RI correlated closely with WDPT, which was used to develop a classification of RI that showed a robust statistical agreement with WDPT classification according to three different versions of Kappa coefficient.
  
  KEY WORDS: Pine; Soil; Water repellency; Water drop penetration time; Repellency index.
  
  Address:
  - Massimo Iovino, Dipartimento di Scienze Agrarie, Alimentari e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Ed. 4 Ingr. E, 90128 Palermo, Italy. (Corresponding author. Tel.:+39 091 23897070 Fax.: +39 091 484035 Email: massimo.iovino@unipa.it)
  - Pavla Pekárová, Slovak Academy of Sciences, Institute of Hydrology, Dúbravská cesta 9, 84104 Bratislava, Slovakia.
  - Paul D. Hallett, University of Aberdeen, Institute of Biological & Environmental Sciences, Aberdeen AB24 3UU, United Kingdom.
  - Ján Pekár, Comenius University, Faculty of Mathematics, Physics and Informatics, Mlynská dolina 1, 842 48 Bratislava, Slovakia.
  - Ľubomír Lichner, Slovak Academy of Sciences, Institute of Hydrology, Dúbravská cesta 9, 84104 Bratislava, Slovakia.
  - Jorge Mataix-Solera, Departamento de Agroquímica y Medio Ambiente, Universidad Miguel Hernández, Edificio Alcudia, Avda de la Universidad, 03202 Elche Alicante, Spain.
  - Vincenzo Alagna, Dipartimento di Scienze Agrarie, Alimentari e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Ed. 4 Ingr. E, 90128 Palermo, Italy.
  - Richard Walsh, University of Aberdeen, Institute of Biological & Environmental Sciences, Aberdeen AB24 3UU, United Kingdom.
  - Annette Raffan, University of Aberdeen, Institute of Biological & Environmental Sciences, Aberdeen AB24 3UU, United Kingdom.
  - Karsten Schacht, Department of Soil Science and Soil Ecology, Institute of Geography, Ruhr-Universitat Bochum, Universitatsstrasse 150, 44801 Bochum, Germany.
  - Marek Rodný, Slovak Academy of Sciences, Institute of Hydrology, Dúbravská cesta 9, 84104 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 369 - 380, doi: 10.2478/johh-2018-0029
Short Communication, English

Juraj Bebej, Tomáš Orfánus, Marián Homolák, Meni Ben-Hur, Viliam Pichler, Jozef Capuliak: The study of flow type dynamics at pedon scale via morphometric parameter analysis of dye-pattern profil

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• The application of Brilliant Blue FCF tracer enables to identify flow types in multi-domain porous systems of soils via analyses of morphologic parameters of stained objects occurring in dye pattern profiles, as they represent the footprint of flow processes which occurred in soil during both the infiltration and the redistribution of dye solution. We analysed the vertical dye pattern profiles exposed for different time lengths, and revealed temporal evolution of dye solution redistribution leading to changes in flow types. The field experiment was performed with the Brilliant Blue tracer (the 10 g l–1 concentration) applied on 1m x 1m surface of the Dystric Cambisol. The top litter horizon had been removed before 100 l of the tracer was applied. Four vertical profiles were excavated on the experimental plot (always 20 cm apart) at different times after the irrigation had been finished: 2 hours (CUT 2), 24 hours (CUT 24), 27 hours (CUT 27) and 504 hours (CUT 504). The analyses of the dyed patterns profiles showed the spatio-temporal changes in the dye coverage, surface area density, average BB concentration, and stained path width, which allowed us to specify three stages of dye solution redistribution history: (i) a stage of preferential macropore flow, (ii) a stage of strong interaction between macropore-domain and soil matrix leading to the generation of heterogeneous matrix flow and fingering flow types, and (iii) a final stage of dye redistribution within the soil body connected with leaching of BB caused by meteoric water. With increasing time, the macropore flow types convert to mostly matrix-dominated FTs in the upper part of the soil profile. These results were supported by soil hydrological modelling, which implied that more than 70 % of the soil moisture profiles variability among CUT 2–CUT 504 could be explained by the time factor.
  
  KEY WORDS: Dye pattern; Preferential flow; Flow types; Image analysis; Morphometric parameters; Spatio-temporal flow of dye solution.
  
  Address:
  - Juraj Bebej, Technical University in Zvolen, Faculty of Forestry, Department of Natural Envirinment, T. G. Masaryka 24, 960 53 Zvolen, Slovakia. (Corresponding author. Tel.: Fax.: Email: juraj.bebej@tuzvo.sk)
  - Tomáš Orfánus, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Marián Homolák, Technical University in Zvolen, Faculty of Forestry, Department of Natural Envirinment, T. G. Masaryka 24, 960 53 Zvolen, Slovakia.
  - Meni Ben-Hur, Institute of Soil, Water and Environmental Sciences, The Volcani Center, Agricultural Research Organization, P.O. Box 6, Bet Dagan, 50–250, Israel.
  - Viliam Pichler, Technical University in Zvolen, Faculty of Forestry, Department of Natural Envirinment, T. G. Masaryka 24, 960 53 Zvolen, Slovakia.
  - Jozef Capuliak, National Forest Centre, T. G. Masaryka 22, 960 92 Zvolen, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 381 - 392, doi: 10.2478/johh-2018-0031
Scientific Paper, English

Patrik Sleziak, Ján Szolgay, Kamila Hlavčová, Doris Duethmann, Juraj Parajka, Michal Danko: Factors controlling alterations in the performance of a runoff model in changing climate conditions

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• In many Austrian catchments in recent decades an increase in the mean annual air temperature and precipitation has been observed, but only a small change in the mean annual runoff. The main objective of this paper is (1) to analyze alterations in the performance of a conceptual hydrological model when applied in changing climate conditions and (2) to assess the factors and model parameters that control these changes. A conceptual rainfall-runoff model (the TUW model) was calibrated and validated in 213 Austrian basins from 1981–2010. The changes in the runoff model’s efficiency have been compared with changes in the mean annual precipitation and air temperature and stratified for basins with dominant snowmelt and soil moisture processes. The results indicate that while the model’s efficiency in the calibration period has not changed over the decades, the values of the model’s parameters and hence the model’s performance (i.e., the volume error and the runoff model’s efficiency) in the validation period have changed. The changes in the model’s performance are greater in basins with a dominant soil moisture regime. For these basins, the average volume error which was not used in calibration has increased from 0% (in the calibration periods 1981–1990 or 2001–2010) to 9% (validation period 2001–2010) or –8% (validation period 1981–1990), respectively. In the snow-dominated basins, the model tends to slightly underestimate runoff volumes during its calibration (average volume error = –4%), but the changes in the validation periods are very small (i.e., the changes in the volume error are typically less than 1–2%). The model calibrated in a colder decade (e.g., 1981–1990) tends to overestimate the runoff in a warmer and wetter decade (e.g., 2001–2010), particularly in flatland basins. The opposite case (i.e., the use of parameters calibrated in a warmer decade for a colder, drier decade) indicates a tendency to underestimate runoff. A multidimensional analysis by regression trees showed that the change in the simulated runoff volume is clearly related to the change in precipitation, but the relationship is not linear in flatland basins. The main controlling factor of changes in simulated runoff volumes is the magnitude of the change in precipitation for both groups of basins. For basins with a dominant snowmelt runoff regime, the controlling factors are also the wetness of the basins and the mean annual precipitation. For basins with a soil moisture regime, landcover (forest) plays an important role.
  
  KEY WORDS: Climate change; Efficiency of runoff model; TUW model; Regression trees; Austria.
  
  Address:
  - Patrik Sleziak, Department of Land and Water Resources Management, Slovak University of Technology, Radlinského 11, 810 05, Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: patrik.sleziak@stuba.sk)
  - Ján Szolgay, Department of Land and Water Resources Management, Slovak University of Technology, Radlinského 11, 810 05, Bratislava, Slovakia.
  - Kamila Hlavčová, Department of Land and Water Resources Management, Slovak University of Technology, Radlinského 11, 810 05, Bratislava, Slovakia.
  - Doris Duethmann, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.
  - Juraj Parajka, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.
  - Michal Danko, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, 031 05 Liptovský Mikuláš, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 393 - 403, doi: 10.2478/johh-2018-0026
Scientific Paper, English

Miriam Fendeková, Tobias Gauster, Lívia Labudová, Dana Vrablíková, Zuzana Danáčová, Marián Fendek, Pavla Pekárová: Analysing 21st century meteorological and hydrological drought events in Slovakia

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• Several quite severe droughts occurred in Europe in the 21st century; three of them (2003, 2012 and 2015) hit also Slovakia. The Standardized Precipitation Index (SPI) and Standardized Precipitation and Evapotranspiration Index (SPEI) were used for assessment of meteorological drought occurrence. The research was established on discharge time series representing twelve river basins in Slovakia within the period 1981–2015. Sequent Peak Algorithm method based on fixed threshold, three parametric Weibull and generalized extreme values distribution GEV, factor and multiple regression analyses were employed to evaluate occurrence and parameters of hydrological drought in 2003, 2011–2012 and 2015, and the relationship among the water balance components. Results showed that drought parameters in evaluated river basins of Slovakia differed in respective years, most of the basins suffered more by 2003 and 2012 drought than by the 2015 one. Water balance components analysis for the entire period 1931–2016 showed that because of continuously increasing air temperature and balance evapotranspiration there is a decrease of runoff in the Slovak territory.
  
  KEY WORDS: Hydrological drought; Climatic conditions; River discharges; Probability distribution; Slovakia.
  
  Address:
  - Miriam Fendeková, Department of Hydrogeology, Faculty of Natural Sciences of Comenius University in Bratislava, Mlynska dolina, Ilkovičova 6, 842 15 Bratislava 4, Slovakia. (Corresponding author. Tel.: Fax.: Email: miriam.fendekova@uniba.sk)
  - Tobias Gauster, Institute of Applied Statistics and Computing, University of Natural Resources and Life Sciences, Gregor Mendel Str. 33, 1180 Vienna, Austria.
  - Lívia Labudová, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Slovakia.
  - Dana Vrablíková, Department of Hydrogeology, Faculty of Natural Sciences of Comenius University in Bratislava, Mlynska dolina, Ilkovičova 6, 842 15 Bratislava 4, Slovakia.
  - Zuzana Danáčová, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Slovakia.
  - Marián Fendek, Department of Hydrogeology, Faculty of Natural Sciences of Comenius University in Bratislava, Mlynska dolina, Ilkovičova 6, 842 15 Bratislava 4, Slovakia.
  - Pavla Pekárová, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 404 - 415, doi: 10.2478/johh-2018-0032
Scientific Paper, English

Kamila Hlavčová, Silvia Kohnová, Yvetta Velísková, Zuzana Studvová, Valentin Sočuvka, Peter Ivan: Comparison of two concepts for assessment of sediment transport in small agricultural catchments

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• The erosion, transport and deposition of sediments in small valley reservoirs represent a significant impact on their operations, mainly with regard to reducing the volume of their accumulation. The aim of this study is a comparison and uncertainty analysis of two modelling concepts for assessment of soil loss and sediment transport in a small agricultural catchment, with an emphasis on estimating the off-site effects of soil erosion resulted in sedimentation of a small water reservoir. The small water reservoir (polder) of Svacenicky Creek which was built in 2012, is a part of the flood protection measures in Turá Lúka and is located in the western part of Slovakia, close to the town of Myjava. The town of Myjava in recent years has been threatened by frequent floods, which have caused heavy material losses and significantly limited the quality of life of the local residents. To estimate the amount of soil loss and sediments transported from the basin, we applied two modelling concepts based on the USLE/SDR and WaTEM/SEDEM erosion models and validated the results with the actual bathymetry of the polder. The measurements were provided by a modern Autonomous Underwater Vehicle (AUV) hydrographic instrument. From the sediment data measured and the original geodetic survey of the terrain conducted at the time of the construction of the polder, we calculated changes in the storage volume of the polder during its four years of operation. The results show that in the given area, there has been a gradual clogging of the bottom of the polder caused by water erosion. We estimate that within the four years of the acceptance run, 10,494 m3 of bottom sediments on the Svacenicky Creek polder have accumulated. It therefore follows that repeated surveying of the sedimentation is very important for the management of the water reservoir.
  
  KEY WORDS: Soil erosion; Reservoir storage volume; Sediment; Bathymetry, Svacenicky Creek.
  
  Address:
  - Kamila Hlavčová, Slovak University of Technology, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, SK 810 05 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: kamila.hlavcova@stuba.sk)
  - Silvia Kohnová, Slovak University of Technology, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, SK 810 05 Bratislava, Slovakia.
  - Yvetta Velísková, Institute of Hydrology, SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Zuzana Studvová, Slovak University of Technology, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, SK 810 05 Bratislava, Slovakia.
  - Valentin Sočuvka, Institute of Hydrology, SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Peter Ivan, Slovak University of Technology, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, SK 810 05 Bratislava, Slovakia. Slovak Water Management Enterprise, Koháryho 44, 934 80 Levice, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 416 - 420, doi: 10.2478/johh-2018-0036
Scientific Paper, English

Viliam Nagy, Peter Šurda, Ľubomír Lichner, Attila J. Kovács, Gábor Milics: Impact of soil compaction on water content in sandy loam soil under sunflower

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• Soil compaction causes important physical modifications at the subsurface soil, especially from 10 to 30 cm depths. Compaction leads to a decrease in infiltration rates, in saturated hydraulic conductivity, and in porosity, as well as causes an increase in soil bulk density. However, compaction is considered to be a frequent negative consequence of applied agricultural management practices in Slovakia. Detailed determination of soil compaction and the investigation of a compaction impact on water content, water penetration depth and potential change in water storage in sandy loam soil under sunflower (Helianthus annuus L.) was carried out at 3 plots (K1, K2 and K3) within an experimental site (field) K near Kalinkovo village (southwest Slovakia). Plot K1 was situated on the edge of the field, where heavy agricultural equipment was turning. Plot K2 represented the ridge (the crop row), and plot K3 the furrow (the inter–row area of the field). Soil penetration resistance and bulk density of undisturbed soil samples was determined together with the infiltration experiments taken at all defined plots. The vertical bulk density distribution was similar to the vertical soil penetration resistance distribution, i.e., the highest values of bulk density and soil penetration resistance were estimated at the plot K1 in 15–20 cm depths, and the lowest values at the plot K2. Application of 50 mm of water resulted in the penetration depth of 30 cm only at all 3 plots. Soil water storage measured at the plot K2 (in the ridge) was higher than the soil water storage measured at the plot K3 (in the furrow), and 4.2 times higher than the soil water storage measured at the most compacted plot K1 on the edge of the field. Results of the experiments indicate the sequence in the thicknessof compacted soil layers at studied plots in order (from the least to highest compacted ones): K2–K3–K1.
  
  KEY WORDS: Soil compaction; Soil penetration resistance; Bulk density; Water flow.
  
  Address:
  - Viliam Nagy, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Peter Šurda, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: surda@uh.savba.sk)
  - Ľubomír Lichner, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Attila J. Kovács, University of West Hungary, Institute of Biosystems and Food Engineering, 9200 Mosonmagyaróvár, Hungary.
  - Gábor Milics, University of West Hungary, Institute of Biosystems and Food Engineering, 9200 Mosonmagyaróvár, Hungary.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 421 - 428, doi: 10.2478/johh-2018-0034
Scientific Paper, English

Dušan Igaz, Vladimír Šimanský, Ján Horák, Elena Kondrlová, Jana Domanová, Marek Rodný, Natalya P. Buchkina: Can a single dose of biochar affect selected soil physical and chemical characteristics?

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• During the last decade, biochar has captured the attention of agriculturalists worldwide due to its positive effect on the environment. To verify the biochar effects on organic carbon content, soil sorption, and soil physical properties under the mild climate of Central Europe, we established a field experiment. This was carried out on a silty loam Haplic Luvisol at the Malanta experimental site of the Slovak Agricultural University in Nitra with five treatments: Control (biochar 0 t ha–1, nitrogen 0 kg ha–1); B10 (biochar 10 t ha–1, nitrogen 0 kg ha–1); B20 (biochar 20 t ha–1, nitrogen 0 kg ha–1); B10+N (biochar 10 t ha–1, nitrogen 160 kg ha–1) and B20+N (biochar 20 t ha–1, nitrogen 160 kg ha–1). Applied biochar increased total and available soil water content in all fertilized treatments. Based on the results from the spring soil sampling (porosity and water retention curves), we found a statistically significant increase in the soil water content for all fertilized treatments. Furthermore, biochar (with or without N fertilization) significantly decreased hydrolytic acidity and increased total organic carbon. After biochar amendment, the soil sorption complex became fully saturated mainly by the basic cations. Statistically significant linear relationships were observed between the porosity and (A) sum of base cations, (B) cation exchange capacity, (C) base saturation.
  
  KEY WORDS: Biochar; Soil physical characteristics; Soil sorption characteristics; Soil organic carbon; Zea mays.
  
  Address:
  - Dušan Igaz, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94 901 Nitra, Slovakia. (Corresponding author. Tel.:+421 37641 5245 Fax.: Email: dusan.igaz@uniag.sk)
  - Vladimír Šimanský, Department of Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia.
  - Ján Horák, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94 901 Nitra, Slovakia.
  - Elena Kondrlová, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94 901 Nitra, Slovakia.
  - Jana Domanová, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94 901 Nitra, Slovakia.
  - Marek Rodný, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Natalya P. Buchkina, Agrophysical Research Institute, 14 Grazhdansky prospect, 195220 St. Petersburg, Russian Federation.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 429 - 436, doi: 10.2478/johh-2018-0033
Scientific Paper, English

Vladimír Šimanský, Dušan Igaz, Ján Horák, Peter Šurda, Marek Kolenčík, Natalya P. Buchkina, Łukasz Uzarowicz, Martin Juriga, Dušan Šrank, Žaneta Pauková: Response of soil organic carbon and water-stable aggregates to different biochar treatments including nitrogen fertilization

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• Recent studies show that biochar improves physical properties of soils and contributes to the carbon sequestration. In contrast to most other studies on biochar, the present study comprise a long-term field experiment with a special focus on the simultaneous impact of N-fertilizer to soil structure parameters and content of soil organic carbon (SOC) since SOC has been linked to improved aggregate stability. However, the question remains: how does the content of water- stable aggregates change with the content of organic matter? In this paper we investigate the effects of biochar alone and in a combination with N-fertilizer (i) on the content of water-stable macro- (WSAma) and micro-aggregates (WSAmi) as well as soil structure parameters; and (2.) on the contents of SOC and labile carbon (CL) in water-stable aggregates (WSA). A field experiment was conducted with different biochar application rates: B0 control (0 t ha–1), B10 (10 t ha–1) and B20 (20 t ha–1) and 0 (no N), 1st and 2nd level of nitrogen fertilization. The doses of level 1 were calculated on required average crop production using the balance method. The level 2 included an application of additional 100% of N in 2014 and additional 50% of N in the years 2015–2016 on silty loam Haplic Luvisol at the study site located at Dolná Malanta (Slovakia). The effects were investigated after the growing season of spring barley, maize and spring wheat in 2014, 2015 and 2016, respectively. The results indicate that the B10N0 treatment significantly decreased the structure vulnerability by 25% compared to B0N0. Overall, the lower level of N combined with lower doses of biochar and the higher level of N showed positive effects on the average contents of higher classes of WSAma and other soil structure parameters. The content of SOC in WSA in all size classes and the content of CL in WSAma 3–1 mm significantly increased after applying 20 t ha–1 of biochar compared to B0N0. In the case of the B20N1 treatment, the content of SOC in WSAma within the size classes >5 mm (8%), 5– 3 mm (19%), 3–2 mm (12%), 2–1 mm (16%), 1–0.5 mm (14%), 0.5–0.25 mm (9%) and WSAmi (12%) was higher than in B0N1. We also observed a considerably higher content of SOC in WSAma 5–0.5 mm and WSAmi with the B10N1 treatment as compared to B0N1. Doses of 20 t biochar ha–1 combined with second level of N fertilization had significant effect on the increase of WSAma and WSAmi compared to the B0N2 treatment. A significant increase of CL in WSA was determined for size classes of 2–0.25 mm and WSAmi in the B20N2 treatment. Our findings showed that biochar might have beneficial effects on soil structure parameters, SOC, CL in WSA and carbon sequestration, depending on the applied amounts of biochar and nitrogen.
  
  KEY WORDS: Soil structure; Soil organic carbon; Labile carbon; Aggregate stability; Biochar; N fertilizer.
  
  Address:
  - Vladimír Šimanský, Department of Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia. (Corresponding author. Tel.:+421 37641 4398 Fax.: Email: Vladimir.Simansky@uniag.sk)
  - Dušan Igaz, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94901 Nitra, Slovakia.
  - Ján Horák, Department of Biometeorology and Hydrology, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 94901 Nitra, Slovakia.
  - Peter Šurda, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Marek Kolenčík, Department of Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia.
  - Natalya P. Buchkina, Agrophysical Research Institute, 14 Grazhdansky prospect, 195220 St. Petersburg, Russian Federation.
  - Łukasz Uzarowicz, Warsaw University of Life Sciences SGGW, Faculty of Agriculture and Biology, Department of Soil Environment Sciences, Nowoursynowska Str. 159, building no. 37, 02-776 Warsaw, Poland.
  - Martin Juriga, Department of Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia.
  - Dušan Šrank, Department of Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia.
  - Žaneta Pauková, Department of Ecology, Faculty of European Studies and Regional Development, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 437 - 447, doi: 10.2478/johh-2018-0035
Scientific Paper, English

Marek Sokáč, Yvetta Velísková, Carlo Gualtieri: An approximate method for 1-D simulation of pollution transport in streams with dead zones

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• Analytical solutions describing the 1D substance transport in streams have many limitations and factors, which determine their accuracy. One of the very important factors is the presence of the transient storage (dead zones), that deform the concentration distribution of the transported substance. For better adaptation to such real conditions, a simple 1D approximation method is presented in this paper. The proposed approximate method is based on the asymmetric probability distribution (Gumbel’s distribution) and was verified on three streams in southern Slovakia. Tracer experiments on these streams confirmed the presence of dead zones to various extents, depending mainly on the vegetation extent in each stream. Statistical evaluation confirms that the proposed method approximates the measured concentrations significantly better than methods based upon the Gaussian distribution. The results achieved by this novel method are also comparable with the solution of the 1D advection-diffusion equation (ADE), whereas the proposed method is faster and easier to apply and thus suitable for iterative (inverse) tasks.
  
  KEY WORDS: Environmental hydraulics; River pollution; Hydrodynamic dispersion; Longitudinal dispersion; Dead zones.
  
  Address:
  - Marek Sokáč, Department of Sanitary and Environmental Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: marek.sokac@stuba.sk)
  - Yvetta Velísková, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Carlo Gualtieri, Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy.

J. Hydrol. Hydromech., Vol. 66, No. 4, 2018, p. 448 - 456, doi: 10.2478/johh-2018-0028
Scientific Paper, English

Yvetta Velísková, Zdeněk Chára, Radoslav Schügerl, Renáta Dulovičová: CFD simulation of flow behind overflooded obstacle

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• This paper deals with studying of two topics – measuring of velocity profile deformation behind a over-flooded construction and modelling of this velocity profile deformation by computational fluid dynamics (CFD). Numerical simulations with an unsteady RANS models - Standard k-ε, Realizable k-ε, Standard k-ω and Reynolds stress models (ANSYS Fluent v.18) and experimental measurements in a laboratory flume (using ADV) were performed. Results of both approaches showed and affirmed presence of velocity profile deformation behind the obstacle, but some discrepancies between the measured and simulated values were also observed. With increasing distance from the obstacle, the differences between the simulation and the measured data increase and the results of the numerical models are no longer usable.
  
  KEY WORDS: Velocity profile; Computational fluid dynamics (CFD); Free surface flow; Bridge; ADV; Laboratory flume; Numerical simulation; RANS models.
  
  Address:
  - Yvetta Velísková, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: veliskova@uh.savba.sk)
  - Zdeněk Chára, Institute of Hydrodynamics of the Czech Academy of Sciences, v. v. i., Pod Patankou 30/5, 166 12 Prague 6, Czech Republic.
  - Radoslav Schügerl, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Renáta Dulovičová, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.