Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 133 - 138, doi: 10.31577/ahs-2020-0021.02.0016
Scientific Paper, English

Justína Vitková, Peter Šurda, Anton Zvala: Changes in soil moisture values two years after biochar reapplication

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• Biochar, as a carbon rich material, has properties which are similar to water repellent material. Its application into the soil changes these properties, but it takes a few years. Our research was focused on soil moisture values comparison at plots with aged biochar (applied into the soil in 2014) and fresh biochar (aged biochar applied in 2014 + reapplied biochar applied into soil in 2018). Results indicated that fresh biochar had water repellent properties in first year after its application into the silt loam soil, which were changed in second year after its application. Our measurements show positive effect of biochar on soil water regime in a longer time horizon
  
  KEY WORDS: biochar reapplication, soil moisture, barley, maize
  
  Address:
  - Justína Vitková, Institute of Hydrology SAS, Dúbravská cesta 9, 8410 4 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: vitkova@uh.savba.sk)
  - Peter Šurda, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Anton Zvala, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 139 - 144, doi: 10.31577/ahs-2020-0021.02.0017
Scientific Paper, English

Renáta Dulovičová, Yvetta Velísková, Radoslav Schűgerl: Determination and comparison of hydraulic conductivity values of bed silts along Chotárny channel using grain size analysis

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• This paper goes in for the evaluation of permeability of the bed silts located along the Chotárny channel at the Žitný ostrov (ŽO), Slovakia. The Chotárny channel is one of three main channels at the ŽO area – the flat lowland with channel network. Whole ŽO area has very low slope, so longitudinal slopes of all channels are negligible. This fact influences the formation of silts on the channel bottom. The bed silt permeability impacts water flow between surface water in the channel and surrounding groundwater in the scope of their interaction at this area. It is expressed by value of hydraulic conductivity, for our case, inasmuch as the bed silts are located in saturated zone under water level, by value of saturated hydraulic conductivity. This paper deals with disturbed samples extracted from the Chotárny channel and for that reason only the empirical formulas based on the grain size analysis were used for assessment of saturated hydraulic conductivity value. The disturbed samples were extracted in three different vertical parts of silt – top, middle and bottom part of silt layer and subsequently as mixed samples in each selected profile of the Chotárny channel. The selection of sampling place was made by thickness of bed silt in the measured profiles. The values of saturated hydraulic conductivity obtained from disturbed samples of bed silt – Kd were calculated according to three empirical formulas: 1. Bayer – Schweiger formula; 2. Špaček I formula and 3. Špaček II formula, firstly for samples from the single vertical parts of the silt layer (top, middle and bottom) and then for mixed samples. The valid values Kd from single parts of the silt layers reached from 1.29x10-08 to 1.19x10-04 m s-1, the valid values Kd from mixed samples reached from 1.38x10-08 to 4.11x10-06 m s-1. All values obtained using grain size analysis are only approximate, but the only possible ones in case of impossibility to take an undisturbed samples. According to results of comparison of Kd from single vertical parts of silt layers and Kd from mixed samples it is not possible to assess explicitly which values set of saturated hydraulic conductivity are more suitable to use in calculation or modelling. Next analysis of obtained datasets and comparison with the values of saturated hydraulic conductivity from undisturbed samples of bed silt will be necessary.
  
  KEY WORDS: bed silts, disturbed samples, grain size analysis, silt permeability, hydraulic conductivity
  
  Address:
  - Renáta Dulovičová, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: dulovicova@uh.savba.sk)
  - Yvetta Velísková, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Radoslav Schűgerl, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 145 - 151, doi: 10.31577/ahs-2020-0021.02.0018
Scientific Paper, English

Marek Sokáč, Yvetta Velísková: Impact of roughness changes on contaminant transport in sewers

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• The paper deals with question how the bed sediment or deposits impact transport processes in conditions of flow with low velocity and water depth. This is often a problem especially in case of flow in sewer network. For this reason, there were performed several tests in laboratory flume having the shape of a pipe with circular cross-section. To simulate the hydraulic condition in sewer pipe with sediments and deposits, some sand was inserted in the pipe with various layer thickness and granularity. It was used a sand of fraction 0.6–1.2 mm. In total, 4 sets of experiments with different layer thickness were performed: with layer thickness of 0 mm (no sediments), 8.5 mm (3.4% of the pipe diameter), 25 mm (10%) and 35 mm (14%) of sand sediment. For each thickness of the sediment layer a set of tracer experiment was performed with different discharges ranging approximately (0.14–2.5) l s-1. Results of the tracer experiments show, that the value of the longitudinal dispersion coefficient Dx in the hydraulic conditions of circular sewer pipe with sediment and deposits decreases when the Reynolds number is decreasing too. The value of Dx reaches its minimal value in the range of the Reynolds number between 4500 up to 10 000. With Reynolds number below this range the value of Dx start to rise.
  
  KEY WORDS: contaminant transport, longitudinal dispersion, bed sediment, roughness, sewers
  
  Address:
  - Marek Sokáč, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: sokac@uh.savba.sk)
  - Yvetta Velísková, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 152 - 159, doi: 10.31577/ahs-2020-0021.02.0019
Scientific Paper, English

Milan Onderka, Jozef Pecho, Pavol Nejedlík: Storage capacity of rain tanks optimized for the local climate in two metropolitan areas of Slovakia

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• Combating the adverse effects of drought and extensive precipitation in urban areas can be achieved by efficiently designed rain water harvesting systems such as green roofs, rain tanks, infiltration trenches, etc. Their performance, however, is inherently affected by local rainfall patterns. In this paper we focus on the rainfall regime at six locations within two metropolitan areas in Slovakia. Four sites are located in the capital of Bratislava and its environs, and two sites are located in the second largest city Košice. Using event-based statistical characteristics and an analytical probabilistic model, the optimal capacity of rain tanks for the metropolitan areas of Bratislava and Košice were estimated. The presented event rainfall statistics can facilitate the design of green infrastructure (e.g. vegetative roofs, rain gardens, infiltration trenches etc.), optimized irrigation of urban gardens and improvement of storm water management in these two metropolitan areas of Slovakia.
  
  KEY WORDS: rain water harvesting, drought, green city, rain tanks
  
  Address:
  - Milan Onderka, Earth Science Institute SAS, Dúbravská cesta 9, 840 05 Bratislava, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: milan.onderka@savba.sk)
  - Jozef Pecho, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic, Comenius University, Faculty of Mathematics, Physics, and Informatics, Mlynská dolina F1, 842 48 Bratislava, Slovak Republic
  - Pavol Nejedlík, Earth Science Institute SAS, Dúbravská cesta 9, 840 05 Bratislava

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 160 - 171, doi: 10.31577/ahs-2020-0021.02.0020
Scientific Paper, English

Eva Kopáčiková, Hana Hlaváčiková, Danica Lešková: Climate change impact study on 100-year floods of selected Slovak catchments

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• During the ongoing climate change, this work provides an analysis of the modelled expected change in floods (100-year) for 11 Slovak river basins. It also analyses the possibilities of using data from the latest climate projections of global and regional models from the EURO-CORDEX initiative, as well as outputs from two hydrological models from the SWICCA database (Service for Water Indicators in Climate Change Adaptation) within the Copernicus service, for regional conditions in Slovakia. To estimate the 100-year flood, a frequency analysis was applied to each member of the climate and hydrological model output ensemble. The statistical distribution of generalized extreme values (GEV) was used. In case the data showed a significant trend, the non-stationarity of the environment was also taken into account. The bias of hydrological models outputs were corrected by the variance scaling method. The results indicate an increase in Q100 for seven gauges, a decrease for three gauges and for one station no change in Q100 (change more than ± 5%). Based on the results, we recommend applying hydrological data from the SWICCA database, preferably for large to medium-sized river basins.
  
  KEY WORDS: Copernicus, climate change, hydrological models, 100-year flood
  
  Address:
  - Eva Kopáčiková, Slovenský hydrometeorologický ústav, Jeséniova 17, 833 15 Bratislava 37, Slovak Republic
  - Hana Hlaváčiková, Slovenský hydrometeorologický ústav, Jeséniova 17, 833 15 Bratislava 37, Slovak Republic (Corresponding author. Tel.: Fax.: Email: hana.hlavacikova@shmu.sk)
  - Danica Lešková, Slovenský hydrometeorologický ústav, Jeséniova 17, 833 15 Bratislava 37, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 172 - 177, doi: 10.31577/ahs-2020-0021.02.0021
Scientific Paper, English

Adam Brziak, Martin Kubáň, Silvia Kohnová, Ján Szolgay: Comparison of the variances of a lumped and semi-distributed model parameters

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• The accurate modelling of discharges in catchments plays an important role in solving a large variety of water management tasks. Three basic errors may affect the outputs modelled: the quality of the input data, uncertainities about the parameters, and the structure of the model. This paper is focused on a comparison of the performances of the lumped and semi-distributed versions of the conceptual TUW rainfall-runoff model, which represents two different model structures. The comparison took place on 180 Austrian catchments, which have variable morphologies, altitudes, land uses, etc. We focused on the variability of the efficiencies and parameters of both types of HBV models, which were calibrated based on discharges in the period from 1991 to 2000. Whether the morphology and mean elevation of the catchment affect the calibration results was also take in account. Finally, we realized that the semi-distributed version of the TUW model gave better results as to the calibration efficiencies, when we calibrated the model for discharges; at the same time, the variations in the model parameters also gave better results in the semi-distributed version of the TUW model.
  
  KEY WORDS: HBV model, model parameters, model efficiency, Austrian catchments
  
  Address:
  - Adam Brziak, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology, Radlinského 11, 810 05 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: adam.brziak@stuba.sk)
  - Martin Kubáň, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Silvia Kohnová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Ján Szolgay, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology, Radlinského 11, 810 05 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 178 - 187, doi: 10.31577/ahs-2020-0021.02.0022
Scientific Paper, English

Dana Halmová, Pavla Pekárová: Differences in the long-term regimes of extreme floods using seasonality indices at Slovak Danube River tributaries

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• The issue of seasonality occurrence of hydrological, hydrogeological or meteorological phenomena and their regional expression has recently devoted increasing attention. The results of some analyses suggest that the seasonality of the selected hydrological characteristics is an important indicator of flood processes, but varies considerably in space. The seasonality of extreme flood events and, hence flood processes, tends to change with the flood magnitude. Investigation of changes in the rainfall-runoff regimes of rivers and its extremes has become more important especially in the context of ongoing and future climate changes. This paper deals with a statistical analysis of changes in the hydrological regime of Slovak tributaries of the Danube River at 11 stations and the main objective of this study is to find the seasonality indices. Monthly seasonality indices are analysed to interpret the long-term climatic behaviour, while the seasonality of extremes is analysed to understand flood occurrence. For the extreme events seasonality analyses we used the Burn index (1997), which shows the mean date and variability of occurrence of the extreme events.
  
  KEY WORDS: intra-annual flow regime, seasonality, variability, Burn index, daily and monthly discharge, Slovak Danube River tributaries
  
  Address:
  - Dana Halmová, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: halmova@uh.savba.sk)
  - Pavla Pekárová, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 188 - 196, doi: 10.31577/ahs-2020-0021.02.0023
Scientific Paper, English

Veronika Bačová Mitková, Dana Halmová: Analysis of the runoff volumes of the wave belongs to maximum annual discharges

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• Several hypothesis claim that more extremes in climatic in hydrological phenomena are anticipated. In order to verify such hypotheses we described the annual flood risk volume analysis carried out in the Váh River in Slovakia. In the present study, the annual maximum runoff volumes with t-day durations (t=2-, 5-, 10- and 20-days) were calculated for an 85-year series (1931–2015) of mean daily discharges and maximum annual discharges of Váh River: Liptovský Mikuláš gauge. In the next section, we estimated the total volumes of the wave belongs to maximum annual discharges. The T-year volume values were calculated using Log-Pearson type III distribution. Statistical method was used to clarify how the maximum and total volumes of the Váh River changed over the selected period (1931–2015).
  
  KEY WORDS: Váh River, wave volume, Log-Pearson III probability distribution, T-year volume
  
  Address:
  - Veronika Bačová Mitková, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: mitkova@uh.savba.sk)
  - Dana Halmová, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 21, No. 2, 2020, p. 197 - 204, doi: 10.31577/ahs-2020-0021.02.0024
Scientific Paper, English

Jaroslav Rožnovský, Jaroslav Střeštík, Petr Štěpánek, Pavel Zahradníček: The dynamics of annual and seasonal precipitation totals in the Czech Republic during 1961–2019

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• The long-term change in precipitation has been estimated for 300 stations in the Czech Republic using values of monthly precipitation totals. Annual totals for the whole country show a very slight decrease, in units of mm, there can be significant fluctuation on a year-to-year basis. Long-term changes of annual totals vary at different stations and in different regions. In southern and western Bohemia, precipitation totals increased more, in Elbe lowlands and in large parts of Moravia, a rather small decrease in rainfall has been observed. Long-term changes depend only slightly on the absolute value of annual rainfall at the respective station or region. Summer precipitation totals increased more than annual averages, while spring precipitation totals decreased. During the remaining seasons, the change is negligible. In the meantime, the annual variation in precipitation has changed slightly: maximum values have shifted from June to July.
  
  KEY WORDS: long-term change, regions, annual precipitation totals, seasons
  
  Address:
  - Jaroslav Rožnovský, Český hydrometeorologický ústav, Kroftova 43, 616 67 Brno, Czech Republic, Mendelova univerzita v Brně, Zemědělská 1, 613 00 Brno, Czech Republic (Corresponding author. Tel.: Fax.: Email: jaroslav.roznovsky@chmi.cz, roznov@mendelu.cz)
  - Jaroslav Střeštík, Mendelova univerzita v Brně, Zemědělská 1, 613 00 Brno, Czech Republic
  - Petr Štěpánek, Český hydrometeorologický ústav, Kroftova 43, 616 67 Brno, Czech Republic
  - Pavel Zahradníček, Český hydrometeorologický ústav, Kroftova 43, 616 67 Brno, Czech Republic