Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 3 - 13, doi: 10.31577/ahs-2024-0025.01.0001
Scientific Paper, English

Noureddine MAREF, Djelloul BAAHMED, Kader BEMMOUSSAT, Zakaria MAHFOUD: SWAT model application for sediment yield modeling and parameters analysis in Wadi K’sob (northeast Algeria)

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• A comprehension of the erosion processes and sediment transport in the watershed is essential for the sustainable management of the water resources and soil fertility. In this study, the Soil and Water Assessment Tool (SWAT) model was applied to demonstrate its ability to modeling the suspended sediment yield in the Wadi K’sob basin located in the northeast of Algeria. The data used to set up the SWAT model are the Digital Elevation Model (DEM), land use, soil types and weather data. The results obtained after calibration oscillating between good and satisfactory where (NSE=0.67 and R2=0.73) in the first calibration period and (NSE=0.65 b and R2=0.67) in the second period. In the validation, the performance of the SWAT model was very good (NSE =0.78 and R2 =0.79) in the first period while in the second period the prediction of the model was satisfactory (NSE=0.52 and R2=0.54). In addition, the validation process revealed that some parameters are stable and related on watershed characteristics while other unstable parameters depend on soil properties especially soil permeability and soil erodibility.
  
  KEY WORDS: Sediment yield, Modeling, SWAT, Model parameters, Performance
  
  Address:
  - Noureddine MAREF, Civil Engineering and Environmental Laboratory (LGCE), University of Djillali Liabes, Faculty of Technology, Ben M'Hidi district, P.O.Box 89, 22000, Sidi Bel Abbes, Algeria (Corresponding author. Tel.: Fax.: Email: m.noure@yahoo.fr)
  - Djelloul BAAHMED, Civil Engineering and Environmental Laboratory (LGCE), University of Djillali Liabes, Faculty of Technology, Ben M'Hidi district, P.O.Box 89, 22000, Sidi Bel Abbes, Algeria
  - Kader BEMMOUSSAT, Civil Engineering and Environmental Laboratory (LGCE), University of Djillali Liabes, Faculty of Technology, Ben M'Hidi district, P.O.Box 89, 22000, Sidi Bel Abbes, Algeria
  - Zakaria MAHFOUD, Civil Engineering and Environmental Laboratory (LGCE), University of Djillali Liabes, Faculty of Technology, Ben M'Hidi district, P.O.Box 89, 22000, Sidi Bel Abbes, Algeria

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 14 - 24, doi: 10.31577/ahs-2024-0025.01.0002
Scientific Paper, English

Hana HLAVÁČIKOVÁ, Kateřina HRUŠKOVÁ, Zinaw SHENGA, Danica LEŠKOVÁ, Eva KOPÁČIKOVÁ: Testing sensitivity of hydrological operational models to finer resolution of input data for purpose of applying high resolution Destination Earth forecasts. Case study, part one

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• Destination Earth On-Demand Extremes Digital Twin is the initiative of European Commission whose aim is to provide forecasts of extreme weather events in high spatial resolution. Such forecasts are essential inputs for various applications, including hydrological models used in flood forecasting. Nine countries have been involved in testing high-resolution meteorological forecasts in national hydrological forecasting systems by analysing a specific historical flood event. The Slovak case study dealt with the analysis of the May 2021 flood in the upper Hron River basin in central Slovakia. The HBV and HEC-HMS rainfall-runoff models used in the national hydrological forecast service were modified to allow comparison of their outputs between both the current and new configurations. The results demonstrated the sensitivity of the models to the input data, in particular the precipitation volume, the redistribution of precipitation in the catchment, and the initial conditions prior to the simulation of the flood wave. Even though the new model configurations did not show significant improvement in terms of standard statistical metrics on the 3-year period, regression analysis revealed better simulations of higher flows.
  
  KEY WORDS: Destination Earth, extreme events, hydrological forecasts
  
  Address:
  - Hana HLAVÁČIKOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: hana.hlavacikova@shmu.sk)
  - Kateřina HRUŠKOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic
  - Zinaw SHENGA, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic
  - Danica LEŠKOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic
  - Eva KOPÁČIKOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 25 - 31, doi: 10.31577/ahs-2024-0025.01.0003
Scientific Paper, English

Ladislav HOLKO, Michal DANKO, Patrik SLEZIAK, Martin JANČO, Soňa LIOVÁ: Characteristics of runoff events in the Upper Váh River catchment in the warm period of year

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• Hourly discharge data were used to evaluate selected characteristics of summer (June to September) runoff events in the streams of the Upper Váh River catchment in years 2014, 2015, 2017 and 2018. Total summer runoff in individual years was very well correlated with the mean altitude of the subcatchments while the average discharge was similarly well correlated with subcatchments areas. Approximately one half of the events for which the peak discharge in Váh at Liptovský Mikuláš (catchment outlet) exceeded the threshold of 20 m3 s -1 came mainly from only part of the catchment. The largest events were dominantly contributed by the streams coming from its northern part formed by the Western Tatra Mountains and the westernmost part of the High Tatra Mountains. The average travel time of the peaks in the Váh River between Liptovský Hrádok and Liptovský Mikuláš was longer and the celerities of the waves were smaller than those between the Belá River (the largest tributary of the Upper Váh River) at Liptovský Hrádok and the Váh River at Liptovský Mikuláš. It was not uncommon that the peaks, especially in Belá at Liptovský Hrádok and in Váh at Liptovský Mikuláš occurred simultaneously. The results indicate that heavy rains in the Western and High Tatra Mountains are especially important for the occurrence of the highest flows at catchment outlet. The most extreme discharge increase during the events regularly occurred in the small Dovalovec Creek (catchment area 22 km2).
  
  KEY WORDS: runoff events evolution in a river basin, peak discharge travel time, wave celerity runoff events evolution in a river basin, peak discharge travel time, wave celerity
  
  Address:
  - Ladislav HOLKO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: holko@uh.savba.sk)
  - Michal DANKO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Patrik SLEZIAK, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Martin JANČO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Soňa LIOVÁ, Slovak Hydrometeorological Institute, Bôrická cesta 103, 011 13 Žilina, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 32 - 44, doi: 10.31577/ahs-2024-0025.01.0004
Review, English

Dana HALMOVÁ, Pavla PEKÁROVÁ, Veronika BAČOVÁ MITKOVÁ, Ján PEKÁR, Katarína JENEIOVÁ: Analysis of long-term trends and probability characteristics of low-flow in Low Tatra Mountains

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• Analyzing variations in streamflow over a long period is crucial from the perspective of water resources management and understanding the impacts of climate change on the basin. Changes in the frequency, magnitude, and seasonality of hydrological extremes are anticipated consequences of climate change. Statistical trend analysis identifies positive or negative variations within a dataset, enabling the projection and prediction of future projections. The objective of this study is to examine temporal changes in the magnitude of minimum discharge series at four selected pristine mountain catchments within the National Park of Low Tatras (NAPANT) region. Four series of long-term daily discharge data spanning from 1930/31 to 2019/20 were statistically analyzed: Vajskovský brook: Dolná Lehota, Bystrianka: Bystrá, Štiavnička: Mýto pod Ďumbierom, and Boca: Kráľova Lehota. T-year minimum specific runoff qmin was processed using files containing annual minimum flows from 1- and 7-day minima per hydrological year. For the analysis of long-term precipitation trends, datasets of annual precipitation totals from stations Banská Štiavnica (575 m a.s.l), Brezno (487 m a.s.l), and Vyšná Boca (930 m a.s.l) were utilized. Across all catchments, a similar long-term trend in minimum specific discharges was observed: a decline during the period 1931–1965, decadal minima around 1983–1992, and a slight increase post-1991 (with a significant increase in Boca). This trend correlates with the long-term precipitation trend. The lowest decadal precipitation totals at the respective stations occurred during the years 1982–1991 ±1 year.
  
  KEY WORDS: small high mountain basins, T-year minimum discharge, long-term trends
  
  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
  - Veronika BAČOVÁ MITKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Ján PEKÁR, Faculty of Mathematics, Physics, and Informatics, Department of Applied Mathematics and Statistics, Comenius University in Bratislava, Mlynská dolina, 842 48 Bratislava, Slovak Republic
  - Katarína JENEIOVÁ, Slovak Hydrometeorological Institute, Department Quantity of Surface Water, Jeséniova 17, 833 15 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 45 - 56, doi: 10.31577/ahs-2024-0025.01.0005
Scientific Paper, English

Veronika BAČOVÁ MITKOVÁ, Dana HALMOVÁ, Zuzana DANÁČOVÁ, Ivan BARTÍK: Investigation of changes and modeling the oxygen regime of the of surface water along the Váh River

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• Climate change and anthropogenic activity have an impact on the components of the hydrological regime of rivers, potentially leading to negative effects on the quantity and quality of water. Environmental targets are set to ensure the achievement of good surface water and groundwater status in the EU and to prevent water deterioration. The achievement of environmental goals is verified through established assessment systems, which also assess the quality of surface waters. Physico-chemical indicators, including water temperature and oxygen regime, are relevant to the ecological state of a river. First the study presents the statistical analysis of water temperature and indicators of water oxygen regime measured at four sampling points on the Váh: Komárno, nad Sereďou, Hlohovec and nad Liptovským Hrádkom. Second, the monthly concentration of dissolved oxygen of the Váh River at four sampling sites was modeled using water temperature. Autoregressive SARIMA models were created to modeling dissolved oxygen concentration based on monthly corresponding water temperature. The SARIMA model with various mathematical expressions of the regressor was tested to be the best fit model with a high correlation coefficient. Results showed that for all selected models with selected regressors the p-value values of estimated parameters were α < 0.05, and the differences in their estimated parameters as well as the simulations were not statistically significant. The study concludes that the SARIMA model can effectively simulate changes in dissolved oxygen based on changes in water temperature.
  
  KEY WORDS: Climate change, Váh River, water temperature, dissolved oxygen, trends, stochastic models
  
  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
  - Zuzana DANÁČOVÁ, Slovak Hydrometeorological Institute, Department Quantity of Surface Water, Jeséniova 17, 833 15 Bratislava, Slovak Republic
  - Ivan BARTÍK, Slovak Hydrometeorological Institute, Department Quality of Surface Water, Jeséniova 17, 833 15 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 57 - 63, doi: 10.31577/ahs-2024-0025.01.0006
Scientific Paper, English

Yvetta VELÍSKOVÁ, Valentín SOČUVKA, Radoslav SCHÜGERL, Saeid OKHRAVI, Marek SOKÁČ: Impact of selected sampling method on resulting value of discharge area in a lowland stream with aquatic vegetation

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• Hydrodynamic as well as balance analysis of flow or discharge conditions in surface streams cannot be done without knowledge of the basic hydraulic parameters of the flow. These are, for example, the bathymetry of the water body, the distribution of velocities in the transverse and longitudinal directions, roughness, etc. To determine the value of discharge in a given cross section profile, it is necessary to know the discharge area and the velocity profile. There are several devices and methods for measuring these quantities. Recently, devices based on the application of the Doppler principle are increasingly being used to determine velocity profiles and discharges in field conditions. In ideal conditions, the use of such devices is very effective, but in the case of the presence of aquatic vegetation below the water surface, a problem may arise. The paper analyses the accuracy of determining the discharge area in a lowland stream with a small longitudinal slope with the presence of aquatic vegetation using the Acoustic Doppler Current Profiler (ADCP) device (River Surveyor, SonTek/a Xylem brand). The results of the analysis show that for such cases, this method shows limitations, the extent of which depends on the used sub-method (Bottom Track or Vertical Beam), as well as on the amount of aquatic vegetation below the water surface.
  
  KEY WORDS: discharge area, field measurement, ADCP, bathymetry, lowland stream, aquatic vegetation
  
  Address:
  - Yvetta VELÍSKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: veliskova@uh.savba.sk)
  - Valentín SOČUVKA, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Radoslav SCHÜGERL, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Saeid OKHRAVI, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Marek SOKÁČ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 64 - 72, doi: 10.31577/ahs-2024-0025.01.0007
Scientific Paper, English

Viera RATTAYOVÁ, Marcel GARAJ, Kamila HLAVČOVÁ: How did the aridity of the climate in Slovakia change over last decades?

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• The availability of water is a crucial factor influencing the stability of an ecosystem, the vitality of its flora and fauna, and the economic growth of a society. The changes in the aridity of a climate have an important effect not only on ecosystems, but also on economies, agriculture, and the available water supply. The aridity index (AI) is one of the most frequently used indices for assessing the degree of dryness of a climate. The AI is based on long-term water deficits and therefore expresses over long periods changes. Fluctuations in aridity can also be used to quantify the impact of climate change on regional climatic conditions. Our research is focused on quantifying changes in climate conditions for 76 climatological stations in Slovakia; these changes are based on an analysis of trends in the aridity index. We also examined changes in the seasonal and long-term patterns of related variables and climate drought indexes (SPI10, SPEI10) to identify the drivers of changes in the aridity of the climate of the region. Our findings indicate rising trends in climate aridity, primarily driven by increases in air temperatures, especially the minimum air temperature, even though the trend in precipitation totals is still constant (but also increasing in some areas). Furthermore, our analysis reveals that drought has become a year-round concern over recent decades, which reinforces our assertion that certain regions of Slovakia are at risk of desertification.
  
  KEY WORDS: aridity index, climate change, trends
  
  Address:
  - Viera RATTAYOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, P. O. BOX 15, 833 15 Bratislava 37, Slovak Republic (Corresponding author. Tel.: Fax.: Email: viera.rattayova@shmu.sk)
  - Marcel GARAJ, Slovak Hydrometeorological Institute, Jeséniova 17, P. O. BOX 15, 833 15 Bratislava 37, Slovak Republic
  - Kamila HLAVČOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 811 07 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 73 - 80, doi: DOI: 10.31577/ahs-2024-0025.01.0008
Scientific Paper, English

Zbyněk BAJTEK, Pavol MIKLÁNEK, Jakub RIDZOŇ: The influence of reservoirs on water temperature in the downstream of Ipeľ

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• The temperature regime of river systems is influenced by seasonal temperature stratification in reservoirs and climate change. The release of cold water from reservoirs can affect river temperature, with a decrease in river temperature during warm periods and an increase in river temperature during winter. However, warmer air temperatures and increased solar radiation may reduce the influence of reservoirs on downstream temperatures in the future. The cooling potential of reservoirs remains strong for river reaches downstream of reservoirs with strong temperature stratification. The study analyzed air temperature trends at two climate stations, Boľkovce and Málinec, over different time periods. Data on the temperature of the water were collected from a number of stations located above the reservoirs: Smolná I and Smolná II and Málinec, and several stations below the reservoir, namely Málinec, Kalinovo, Holiša and Slovenské Ďarmoty downstream of the Ipeľ River. The Málinec Reservoir, which regulates the upper part of the Ipeľ River and serves as a drinking water reservoir, was built in 1986–1993 and put into operation in 1994. The analysis was divided into two parts. The first part analyzed data from stations with time series before the construction of Málinec reservoir, while the second part analyzed data from stations with time series after the construction of the reservoir. Increasing water temperatures were observed throughout the year, while increasing air temperatures were significant in warm months. The influence of the reservoir can be seen in the slight change of the mean monthly temperatures. The mean temperature decreases in the summer months and increases in the winter months in the period after the construction of the reservoir.
  
  KEY WORDS: temperature stratification, reservoirs, trends, Ipeľ
  
  Address:
  - Zbyněk BAJTEK, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: bajtek@uh.savba.sk)
  - Pavol MIKLÁNEK, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Jakub RIDZOŇ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2021, p. 81 - 87, doi: 10.31577/ahs-2024-0025.01.0009
Scientific Paper, English

Milan GOMBOŠ, Dana PAVELKOVÁ: Proposal of method for calculating the volume of drying cracks in the soil

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• Clays and clay minerals are an important and permanent component of the natural environment. Their crystal-chemical properties react very sensitively to the hydrothermal environment and its physico-chemical properties. Their presence in the soil environment causes volumetric changes. Volume changes are three-dimensional process. They are accompanied by the fissures formation in horizontal plane and by the movement of the soil surface in vertical plane. Dynamic twodomain soil structure is created while fissure formation. It consists of the fracture domain and the soil matrix domain. In the natural space, desiccation cracks are located in the unsaturated zone of the soil. They significantly influence the rainfall-runoff process. Direct volume measurement of the fracture network is an extremely difficult task. Calculation procedure of fracture network retention properties is designed in the paper. It is based on the assumption that the cracks volume is dependent on the clay particles content in the soil and on the soil moisture volume. From a material point of view, the soil profile is divided according to the volume changes potential. In the calculation, the isotropy of the soil profile is assessed based on the geometric factor. Shrinkage characteristics, cracks geometric dimensions on the soil surface and volumetric moisture along the vertical of the soil profile are included in the calculation. It is advantageous to use pedo-transfer functions in the calculation.
  
  KEY WORDS: Clay particles, volume changes, fracture network
  
  Address:
  - Milan GOMBOŠ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Dana PAVELKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: pavelkova@uh.savba.sk)

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 88 - 95, doi: DOI: 10.31577/ahs-2024-0025.01.0010
Scientific Paper, English

Kostiantyn SOKOLCHUK, Marek SOKÁČ: Modelling the impact of green infrastructure on potential sewer flooding in the city of Trebišov, Slovakia

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• The paper analyses the results of water flow modelling in the urban drainage system of the city of Trebišov, Slovakia. The purpose of the work was to assess the risk of flooding in the urban area and its reduction using Green Infrastructure (GI). The complex hydraulic and hydrological modelling software MIKE+ was used in the research. Using the model of the city's urban drainage system, water flow simulations were carried out using short-term block rainfall events of varying intensity, lasting from 15 to 120 minutes and with return periods of 2 to 10 years. For each scenario, the number of flooded manholes was determined. As a result, areas where two types of GI could be implemented were identified and included in the surface runoff hydrological model. In this study, two types of GI were used: semipermeable pavements and green roofs. The stormwater flow was modelled under four scenarios: current status, implementation of semipermeable pavements, green roofs and their combination. The model results were compared to the current conditions. It was found that the application of both types of GI could potentially reduce the number of flooded points by more than 30 % for short-term rainfall with a return period of two years. As the return period of the short-term rainfall increases, the number of flooded points decreases to an average value of 5%
  
  KEY WORDS: green infrastructure, urban drainage, climate change, adaptation measures, surface flooding, MIKE+
  
  Address:
  - Kostiantyn SOKOLCHUK, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic; Institute of Landscape Engineering, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture in Nitra, Tulipánová 7, 949 76 Nitra, Slovak Republic (Corresponding author. Tel.: Fax.: Email: sokolcuk@uh.savba.sk)
  - Marek SOKÁČ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 96 - 105, doi: 10.31577/ahs-2024-0025.01.0011
Scientific Paper, English

Renáta DULOVIČOVÁ: Bed sediment dynamics in the Gabčíkovo-Topoľníky channel: The three-decade case study

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• This paper was focused to find out the impact of silting of Gabčíkovo-Topoľníky channel on the flow conditions at this channel. There were performed the detailed field measurements of bed sediment thicknesses along the Gabčíkovo-Topoľníky since the year 1993 to 2023. Based on the calculation of the values of the average thickness of the bed sediments, there was determined the longitudinal distribution of the bed sediments along the Gabčíkovo-Topoľníky channel, the percentage of silting of the flow area in this channel and the values of the volumes of bed sediments in this channel during the monitored period, which was the main objective and the reasons of this research. This paper relates to evaluation of results from the field measurements at Gabčíkovo-Topoľníky channel during whole monitored period since the year 1993 to 2023, especially compares the results from measurements between the year 1993 and 2023. Gabčíkovo-Topoľníky channel is one from three main channels of Žitný Ostrov (Rye Island) channel network. The area of Žitný Ostrov (ŽO) is flat land and the velocities in all channels of channel network are very slow. The occurrence of small velocities is considered for main reason of sediment`s aggradation at channel bed. The flow profile of channels is reduced by increased thickness of bed sediments. Consequently, the permanent sedimentation process is unfavourably changing not only the cross-section of channel, but also its longitudinal profile. The channel´s capacity is therefore significantly reduced, e. g. the channel conveys much lower flow as a result of obstruction, lowering the efficiency at channel performance. The volume of sediments is also growing. Bed sediments, their thickness and texture have the important impact to interaction between surface water in channels of ŽO network and groundwater in its surroundings. The results of these measurements are summed up in all tables and figures of this paper and their comparison indicates the growing trend of longitudinal silting of this channel and the volume quantity of bed sediments during the observed period – 30 years.
  
  KEY WORDS: channel network, silting, bed sediments, cross-section and longitudinal profile, volume of sediments
  
  Address:
  - Renáta DULOVIČOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: dulovicova@uh.savba.sk)

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 106 - 114, doi: 10.31577/ahs-2024-0025.01.0012
Scientific Paper, English

Martin JANČO, Michal DANKO, Patrik SLEZIAK, Ladislav HOLKO: Estimation of the leaf area index in a decline spruce forest in the Western Tatra Mountains for determination of rainfall interception

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• Leaf area index (LAI) is an important vegetation leaf structure parameter in forest and agricultural ecosystems. In the paper, we deal with the estimation of leaf area index (LAI) and woody area index (WAI) values in a decline climax spruce forest. The research is conducted on the Červenec research plot at an altitude of 1,420 m a.s.l. in the Western Tatra Mountains in the Jalovecký Creek catchment. We carried out the initial measurements during June, August and October 2023. We estimated the values of the LAI and WAI in the mature living and dead spruce stands using hemispherical photography and HemiView software. LAI and WAI values weren´t corrected with clumping index. The average values in the living and dead forest stands were 4.7 and 3.0, respectively. In addition to the estimation of the spruce canopy layer LAI, we measured the LAI values of the understorey vegetation in the living, dead stand and in an open area using the SunScan instrument and the SunData software. The highest LAI values of the understorey in the living stand (1.9), in the dead stand (5.3) and in an open area (2.9) were obtained in August, when the vegetation was fully leafy. On the other hand, the lowest LAI values in the understorey were reached in the living stand (1.2) and in an open area (1.8) in October, when the vegetation was already without leaves.
  
  KEY WORDS: mountain spruce forest, canopy layer, rainfall interception, Jalovecký Creek catchment
  
  Address:
  - Martin JANČO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: janco@uh.savba.sk)
  - Michal DANKO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Patrik SLEZIAK, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Ladislav HOLKO, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 115 - 126, doi: 10.31577/ahs-2024-0025.01.0013
Scientific Paper, English

Evangelos LEIVADIOTIS, Silvia KOHNOVÁ, Aris PSILOVIKOS: Evaluating flood events caused by Medicane “Daniel” in the Thessaly District (Central Greece) using remote sensing data and techniques

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• On September 4, 2023, Thessaly, Greece, underwent a catastrophic flood due to Medicane Daniel. Extreme rainfall, ranging from 305 mm to 1096 mm between 4 and 12 September, caused extensive damage to the infrastructure, agriculture and houses. Seventeen casualties were recorded. This study is aimed at using radar data from earth observation satellites to detect the inundated areas and evaluate the impact of the flood. Sentinel images were acquired from Copernicus Open Acess Hub For 7, 10, 13, and 19 September, 2023, along with a CORINE Land use/Land cover map. Processing the satellite images involved several steps, including their calibration, noise removal, filtering, and polarization adjustments. Flooded areas were quantified for the specified dates, thereby revealing substantial coverage of the land. The damage assessment focused on irrigated and non-irrigated land and pasture areas, highlighting the impact's severity. The highest impact was noticed on September 7 in irrigated land (95.62%). The second phase incorporated the Flood Water Depth Estimation Tool (FwDET) to estimate the floodwater depths and reveal the maximum depths near riverbanks. The maximum floodwater depth was also noticed on September 7 and reached 9.49 m. This study employed advanced remote sensing and GIS techniques, allowing for a rapid estimation of flood characteristics and assessment of Medicine Daniel's damage to the Thessaly prefecture from September 4 to 12, 2023.
  
  KEY WORDS: flood, Medicane Daniel, Thessaly, remote sensing, damage assessment, Sentinel-1
  
  Address:
  - Evangelos LEIVADIOTIS, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 811 05 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: evangelos.leivadiotis@stuba.sk)
  - Silvia KOHNOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 811 05 Bratislava, Slovak Republic
  - Aris PSILOVIKOS, Department of Ichthyology and Aquatic Environment, School of Agricultural Sciences, University of Thessaly, N. Ionia Magnisias, 38446 Greece

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 127 - 134, doi: 10.31577/ahs-2024-0025.01.0014
Review, English

Jana GREČNÁROVÁ, Michaela DANÁČOVÁ: The effect of the substrate depth on hydrological performance of a vegetation roof: Laboratory study

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• There are increasing demands in cities to reduce the amount of impermeable areas and mitigate water runoff from extreme rainfall. Vegetated roofs are a promising nature-based solution for stormwater management in urban areas. In this study, the retention of rainwater on a roof substrate with different depths and during different rainfall intensities was evaluated. An experiment was conducted in laboratory conditions using a small rainfall simulator. A commercial roof substrate was tested, where by 3 different depths of a substrate were chosen (7, 10, and 14 cm) then, a 15-minute rainfall with 3 intensities (1.3; 2.7, and 3.8 mm min-1 ) was applied. The study revealed variations in higher rainfall intensities of 2.7 mm and 3.8 mm min-1 . A comparison was made using substrate with a depth of 7–10 cm, indicating an 8–16% increase in water retention capacity. The roof substrate with a depth of 10–14 cm increased its retention capacity by 12%. The water retention results can be considered as the maximum limit of possible retention for a 15-minute duration of rainfall at specific 3 intensities. This experiment showed that a longer duration of rain is needed to determine the peak discharge attenuation rate.
  
  KEY WORDS: extensive vegetated roof, roof substrate, rainfall, runoff reduction, retention
  
  Address:
  - Jana GREČNÁROVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 811 07 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: jana.grecnarova@stuba.sk)
  - Michaela DANÁČOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 811 07 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 25, No. 1, 2024, p. 135 - 142, doi: 10.31577/ahs-2024-0025.01.0015
Scientific Paper, English

Katarzyna GRYGORCZUK-PŁANETA, Justína VITKOVÁ, Agnieszka TOMCZYK, Rafał PANEK, Natália BOTKOVÁ, Katarzyna SZEWCZUK-KARPISZ: Study on hydrophysical and chemical parameters of Polish and Slovak soils modified with zeolitic additives

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• Application of soil modifiers is a widely used practice in agriculture to improve soil quality in support of good agricultural practices. This paper presents an assessment of the effect of zeolite modifiers combined with four soils of Polish and Slovakian origin on their hydrophysical properties. Under laboratory conditions, the characterization of the applied soil additives was carried out along with particle soil analysis. In addition, the prepared soil mixtures were examined using contact angle and saturated hydraulic conductivity. The results suggest that the increase in hydrophobicity occurred mainly after the application of fly ash, and the values for Polish Silty clay soil and Slovak soils: Sandy soil, Silt loam soil, and Silty clay soil compared to the control changed from 73.02° to 96.22°; 8.67° to 24.88°; 29.23° to 33.94° and 19.9° to 26.16° respectively. The increase in hydrophobicity could be explained by the higher CaO content of the high-carbon fly ash compared to the other materials. The parameters of saturated hydraulic conductivity were reduced after the application of all zeolite materials in the case of Polish Silty clay and Slovak Sandy soils. By filling the space between the soil particles, the porous soil additives decreased the hydraulic conductivity. In Slovak soils such as Silty loam soil and Silty clay soil, the opposite effect was observed. The soil additives increased the number and size of pores, which resulted in faster filtration of water and thus an increase in the saturated hydraulic conductivity value.
  
  KEY WORDS: saturated hydraulic conductivity, zeolite modifiers, waste product, fly ash, hydrophobicity
  
  Address:
  - Katarzyna GRYGORCZUK-PŁANETA, Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland (Corresponding author. Tel.: Fax.: Email: k.grygorczuk-planeta@ipan.lublin.pl)
  - Justína VITKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic
  - Agnieszka TOMCZYK, Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland
  - Rafał PANEK, Lublin University of Technology, Department of Building Materials Engineering and Geoengineering, Faculty of Civil Engineering and Architecture, Nadbystrzycka 40, 20-618 Lublin, Poland
  - Natália BOTKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic; Institute of Landscape Engineering, Faculty of Horticulture and Landscape Engineering, SUA, Hospodárska 7, 949 76 Nitra, Slovak Republic
  - Katarzyna SZEWCZUK-KARPISZ, Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland