Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 3 - 9, doi: 10.31577/ahs-2022-0023.01.0001
Scientific Paper, English

Viliam NOVÁK: Global changes and hydrosphere

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• Increasing population led to the increasing demand to food, raw materials, water and energy. Anthropogenic demands provoke land use structure changes, intensification of its exploitation, deforestation, fossil fuel combustion and related carbon dioxide production. Those phenomena are changing water and energy fluxes of biosphere, and conditions for life. Actual climate change is a result of other global changes both natural and anthropogenic. It is mostly felt as a change of ecosystem temperature, increase of precipitation intensities and totals, as well as their irregular distribution in time and space. Flood periods are followed by long periods without precipitations. Water consumption is increasing; it is renewable resource, but water resources are unevenly distributed and often polluted, therefore unsuitable for use as fresh water. Increasing population as well as increasing consumption of resources lead to the imbalance between our planet production and consumption. To preserve good conditions for population of the Earth, it is necessary to decrease consumption of energy, raw materials and food to reach equilibrium between Earth´s ecosystem production and consumption of the ecosystem products.
  
  KEY WORDS: ecosystem, biosphere, hydrosphere, global changes, climate change
  
  Address:
  - Viliam NOVÁK, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: viliamnovak42@gmail.com)

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 10 - 20, doi: 10.31577/ahs-2022-0023.01.0002
Scientific Paper, English

Lotta BLAŠKOVIČOVÁ, Katarína MELOVÁ, Soňa LIOVÁ, Jana PODOLINSKÁ, Beáta SÍČOVÁ, Martin GROHOĽ: The drought characteristics and their changes in selected water-gauging stations in Slovakia in the period 2001–2020 compared to the reference period 1961–2000

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• Reassessing the hydrological characteristics with regard to drought is very important in the context of a changing climate. In this paper, we evaluate the drought in terms of changes in hydrological characteristics for the 20-year period 2001–2020. The evaluation of changes is based on a comparison of data for this period with the currently valid reference period 1961–2000 in 13 selected water-gauging stations. In the analysis of the occurrence of subnormal mean annual discharges (Qr <90% Qa,1961-2000), in most of the evaluated stations, the percentage incidence of such years is higher in the period 2001–2020 than in the reference period. The distribution of runoff throughout the year in the period 2001–2020 in comparison with the reference period in most stations confirms the changes identified in the previous evaluation of the period 2001–2015, i.e. the transfer of part of the usual increased spring runoff to previous, winter months. An exception was water-gauging stations on streams in the mountainous areas of northern Slovakia, where changes are reflected to a lesser extent.
  
  KEY WORDS: hydrological drought, mean monthly discharge, runoff distribution change
  
  Address:
  - Lotta BLAŠKOVIČOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: lotta.blaskovicova@shmu.sk))
  - Katarína MELOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic
  - Soňa LIOVÁ, Slovak Hydrometeorological Institute, Regional Office Žilina, Bôrická cesta 103, 011 13 Žilina, Slovak Republic
  - Jana PODOLINSKÁ, Slovak Hydrometeorological Institute, Regional Office Banská Bystrica, Zelená 5, 974 04 Banská Bystrica, Slovak Republic
  - Beáta SÍČOVÁ, Slovak Hydrometeorological Institute, Regional Office Košice, Ďumbierska 26, 041 17 Košice, Slovak Republic
  - Martin GROHOĽ, Slovak Hydrometeorological Institute, Regional Office Košice, Ďumbierska 26, 041 17 Košice, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 21 - 31, doi: 10.31577/ahs-2022-0023.01.0003
Scientific Paper, English

Dana HALMOVÁ, Pavla PEKÁROVÁ, Jana PODOLINSKÁ, Katarína JENEIOVÁ: The assessment of changes in the long-term water balance in the Krupinica River basin for the period 1931–2020

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• The study is focused on the evaluation of changes in the hydrological balance of the Krupinica River basin to the Plášťovce station for the entire 90-year period as well as for the three 30-year subperiods 1931–1960, 1961–1990 and 1991–2020. In the first part of the study, the hydrological balance is processed in an annual step on the basis of measured series of average monthly flows from the Krupinica: Plášťovce; monthly precipitation totals on the Krupinica catchment area and average monthly temperatures in the catchment area. The hydrological balance in the monthly step was processed in the second part. Changes in water resources in the river basin over the three mentioned time subperiods were analyzed. The long-term annual precipitation total in the Krupinica River basin for the whole period was 660 mm, the annual runoff depth was 182 mm and the balance evaporation was 478 mm. A comparison of 30-year periods shows a significant decrease in the runoff of Krupinica – from 231 mm to 144 mm. This was even more pronounced in the runoff coefficient – it fell from 0.32 over 0.27 to 0.21 in the last period 1991–2020. In the third part, a simple regression relationship between runoff, precipitation and air temperature was derived to estimate the future development of the annual runoff from the basin. The relationship shows that a 100 mm decrease in precipitation in the Krupinica River basin will cause an average decrease of 52 mm in runoff. And an increase in the average annual temperature by 1°C in the Krupinica River basin results in a decrease in runoff of about 33.5 mm.
  
  KEY WORDS: water (hydrological) balance, Krupinica River, long-term trends
  
  Address:
  - Dana HALMOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: halmova@uh.savba.sk)
  - Pavla PEKÁROVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Jana PODOLINSKÁ, Slovak Hydrometeorological Institute, Zelená 5, 974 04 Banská Bystrica, Slovak Republic
  - Katarína JENEIOVÁ, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 32 - 41, doi: 10.31577/ahs-2022-0023.01.0004
Scientific Paper, English

Valeriya OVCHARUK, Maryna GOPTSIY: Study of trends in the time series of maximum water discharges in the Tisza basin rivers within Ukraine

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• Nowadays, due to global and local climate changes, according to leading experts, the likelihood of extreme natural phenomena increases. One of the dangerous natural phenomena with impacts on humans and the economy are floods. The Tisza River, which originates in Ukraine and flows further through Romania, Hungary, Slovakia, and Serbia, has repeatedly become a source of disasters for the population due to the devastating consequences of floods, which have been increasing in recent years. The purpose of this study is to analyze the long-term series of observations of the maximum water discharge on the rivers of the Tisza basin, within Ukraine. Using the methods of statistical analysis, tendencies in the time series of annual maximum water discharges were investigated, its temporal homogeneity was estimated also, as well as the significance of the trends. Using the method of residual mass curves, high-water and low-water periods were distinguished. We also obtained preliminary dependences of the maximum runoff modules on the catchment areas and their heights, which in the future can serve as a basis for the development of a regional calculation method for determining the maximum runoff of ungauged rivers in the region.
  
  KEY WORDS: maximum water discharges, flood, trends
  
  Address:
  - Valeriya OVCHARUK, Hydrometeorological Institute of Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine (Corresponding author. Tel.: Fax.: Email: valeriya.ovcharuk@gmail.com)
  - Maryna GOPTSIY, Department of Land Hydrology of Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 42 - 51, doi: 10.31577/ahs-2022-0023.01.0005
Scientific Paper, English

Veronika BAČOVÁ MITKOVÁ: Estimation, trend detection and temporal changes in maximum annual flow volume series of the Hron River in Slovakia

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• The floods characterized by the volume exceedance probabilities and return periods with specific T-year flows may assist in enhancing the accuracy of local flood frequency estimates, and support the detection and interpretation of any changes in flood occurrence and their magnitudes. Therefore, the present paper deals with the trend detection and with temporal changes in the maximum flows volume series of the Hron River at Banská Bystrica and at Brehy gauging stations in Slovakia during the 90 years. The period 1931–2020 mean daily flows of the waves belong to the maximum annual flows and the series of maximum annual flows of the Hron River at Banská Bystrica and at Brehy gauging stations were used as input data. Subsequently the annual maximum runoff volumes with t-day duration were calculated. The Log-Pearson distribution type III were used to determine the T-year values of the maximum runoff volumes with t-day duration. The results indicated that there are decreasing linear trends in maximum annual runoff volumes with some duration of the flow.
  
  KEY WORDS: the Hron River, trend detection, Log-Pearson III distribution, annual maximum runoff volumes, wave duration
  
  Address:
  - Veronika BAČOVÁ MITKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: mitkova@uh.savba.sk)

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 52 - 61, doi: 10.31577/ahs-2022-0023.01.0006
Scientific Paper, English

Anna LIOVÁ, Peter VALENT, Kamila HLAVČOVÁ, Silvia KOHNOVÁ, Tomáš BACIGÁL, Ján SZOLGAY: A methodology for the estimation of control flood wave hydrographs for the Horné Orešany reservoir

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• Recent changes in climatic characteristics and consequent changes in the discharges and in the hydrological response of watersheds raise questions about the safety of water structures. Changes in flood wave characteristics (shape, volume, peak flow) may significantly affect the functionality of these structures. The study proposes a methodology for constructing design wave and flood hydrographs using discharge time series. A case study was carried out in the Little Carpathians watershed of the Parná River, above the profile of the Horné Orešany reservoir in Slovakia. The volumes and characteristic shapes of the flood waves with the maximum annual and seasonal discharges were determined using the Floodsep software. Subsequently, the T-year annual and seasonal discharges were estimated. Then, for pairs of the T-year discharges and the associated volumes of flood waves, a joint probability distribution was constructed by copula functions. The associated volume of the T-year peak discharges was selected from the copula, and the probability of exceeding it was determined. Based on this analysis, a set of annual and seasonal control flood waves with the design maximum discharge, the associated volume with the selected probability, and the typical shape of the flood wave was constructed. This research provides satisfactory results for designing control waves necessary for assessing water structures with extreme loads and establishing a functional methodology for assessing other water structures in the region.
  
  KEY WORDS: design flood hydrograph, Horné Orešany reservoir, separation of discharge wave
  
  Address:
  - Anna LIOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: anna.liova@stuba.sk)
  - Peter VALENT, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Kamila HLAVČOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Silvia KOHNOVÁ, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Tomáš BACIGÁL, Department of Mathematics and Descriptive Geometry, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic
  - Ján SZOLGAY, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 62 - 72, doi: 10.31577/ahs-2022-0023.01.0007
Scientific Paper, English

Pavla PEKÁROVÁ, Pavol MIKLÁNEK, Ján PEKÁR, Jana PODOLINSKÁ: Post-flood analysis of the flood from the rupture of the stone dam in Rudno nad Hronom on May 17, 2021

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• The study is aimed at reconstructing the course of the flood from May 17, 2021 breach of the stone dam in Rudno nad Hronom. Firstly, the volume of water in the reservoir before its breach was determined. The reservoir storage volume was estimated to be 14 807 m3. Then, we focused on the analysis of the hydrological regime in the wider Rudniansky Brook region. In order to derive the flood wave course from the rainfall, a series of 15-minute discharge from neighbouring water gauges measured by the Slovak Hydrometeorological Institute were analysed. In analysing the long-term trends of precipitation and temperature series we used data from the Banská Štiavnica meteorological station (period 1901–2020). In the second part, based on several field measurements after the flood event, we estimated the peak flows of floods from May 17, 2021 above the reservoir and under the reservoir. One hundred meters above the reservoir culmination reached 7.8 m3 s-1, under the reservoir it was between 80 to 100 m3 s-1. Finally, we reconstructed the course of the flood wave from the precipitation above the reservoir by hydrological analogy and by simple rainfall-runoff hydrological model NLC. The course of the breakthrough wave from the reservoir water just below the dam was determined to be triangular in shape so that the peak reached 90 m3 s-1 and the volume was 15,000 m3.
  
  KEY WORDS: breakthrough wave, rupture dam, Rudniansky Brook, rainfall-runoff NLC model
  
  Address:
  - Pavla PEKÁROVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: pekarova@uh.savba.sk)
  - Pavol MIKLÁNEK, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Ján PEKÁR, Comenius University in Bratislava, Faculty of Mathematics, Physics, and Informatics, Department of Applied Mathematics and Statistics, Mlynská dolina, 842 48 Bratislava, Slovak Republic
  - Jana PODOLINSKÁ, Slovak Hydrometeorological Institute, Regional office Banská Bystrica, Zelená 5, 974 04 Banská Bystrica, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 73 - 81, doi: 10.31577/ahs-2022-0023.01.0008
Scientific Paper, English

Wael ALMIKAEEL, Lea ČUBANOVÁ, Andrej ŠOLTÉSZ: Comparison of mean daily discharge data for under-mountain and highland-lowland types of rivers

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• Most Slovak rivers have increasing spring flow followed by a period or two of low flow in the summer, autumn, and, in some cases, winter. The flow rate fluctuations in two different streams in Slovakia are being investigated in this study. The study focused on an under-mountain and a lowland-highland river to investigate the low and peak flow periods and to identify the trends in monthly and annual mean flows for both rivers. Analysing daily mean discharge data from two different types of streams requires the use of a robust normalization approach to verify the comparability between the chosen streams. On both streams, a broad statistical low-flow analysis was performed over different study periods, as well as a hydrological drought analysis utilizing the water-bearing coefficient approach over the period 2010–2020. The evaluation for the foothill river in Slovakia demonstrates that snow melting has a significant impact on annual runoff in the spring months, and both rivers have a low flow period in August, September, and October. Despite the considerable variations in the catchment area, geographical, and hydrological characteristics, drought analysis for the years 2010 to 2020 found a lack of normality and a dry hydrological situation in both streams.
  
  KEY WORDS: drought, hydrological analysis, under-mountain river, highland-lowland river, water-bearing coefficient
  
  Address:
  - Wael ALMIKAEEL, Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 2766/11, 810 05 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: wael.almikaeel@stuba.sk)
  - Lea ČUBANOVÁ, Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 2766/11, 810 05 Bratislava, Slovak Republic
  - Andrej ŠOLTÉSZ, Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 2766/11, 810 05 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 82 - 88, doi: 10.31577/ahs-2022-0023.01.0009
Scientific Paper, English

Ladislav HOLKO, Martin JANČO, Michal DANKO, Patrik SLEZIAK: Influence of forest dieback on the overland flow and isotopic composition of precipitation

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• Small mountain catchments in the highest part of Slovakia are undergoing significant forest changes related to windfalls and bark beetle infestations and resulting forest dieback, wood removal at some places and subsequent natural regeneration or reforestation. Natural forest changes started after 2010 also in the Jalovecký Creek catchment (The Western Mountains, area 22.2 km2, mean altitude 1500 m a.s.l.). Coniferous forest dominated by the Norway spruce, that used to cover 44% of catchment area consequently dries, the trees defoliate, break after some time and the natural regeneration starts. These changes affect also the hydrological cycle, e.g. interception, snow cover, water infiltration to the soil and runoff formation. We present the first results of the overland flow measurements in the alive and dead forest in summer season 2021 (June to September) and compare the isotopes of oxygen and hydrogen in precipitation and soil water. The results show that the overland flow in the forest is not uncommon, although it constitutes only several per cent of the rain. About a half of 55 rainfall events registered in the open area resulted in the overland flow in the forest (21–30 events at different sites). The overland flow represented on average 4% to 7% of the open area rainfall, but maxima for individual events exceeded 10%. Throughfall in the alive forest was isotopically heavier than the open area rainfall and dead forest throughfall. Isotopic composition of the soil water was distinctly different from precipitation until the mid-July, documenting the influence of the snowmelt water.
  
  KEY WORDS: runoff generation, changing forest, stable isotopes
  
  Address:
  - Ladislav HOLKO, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: holko@uh.savba.sk)
  - Martin JANČO, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Michal DANKO, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Patrik SLEZIAK, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 89 - 98, doi: 10.31577/ahs-2022-0023.01.0010
Scientific Paper, English

Milan ONDERKA, Jozef PECHO: Observations from the Western Carpathians and Pannonian Plain show that rainfall return levels need to be adjusted to account for rising dew-point temperature

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• Rainfall records from a total of 526 rain gauges located in the western part of the Carpathian Mountains and the adjacent Pannonian Plain were analyzed. Estimation of extreme rainfall totals with various return periods is essential for reliable design of hydraulic infrastructure. The ongoing climate change brings additional challenges to the estimation of rainfall return levels. In this paper, we compared stationary vs. non-stationary generalized extreme value distributions (GEV) for 2-, 5-, 10-, 25-, 50-, and 100-year return levels of 24-h rainfall determined from annual maxima series. The fundamental question we seek to answer in this paper is whether the stationarity-based design concept is adequate under changing climate conditions because the statistical parameters of probability distribution become dependent on dew-point temperature. Our analyses revealed that the projected return levels tend to increase with decreasing return periods. For instance, the 100-year return levels need an adjustment by ~6.64% (CI: -1.03% +14.95%), while the stationary 5-year return periods of 24-h precipitation totals need to be adjusted by up to ~10.5% (CI: -3.61% +21.24%). Our investigations showed that in ~60% of the analyzed sites the current return levels might need an adjustment to account for the rising dew-point temperature. The presented results may have implication for regional water management planning and flood risk assessment.
  
  KEY WORDS: rainfall, non-stationarity, GEV, return period, return level
  
  Address:
  - Milan ONDERKA, Earth Science Institute, SAS, Department of Atmospheric Physics, Dúbravská cesta 9, 814 38 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

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 99 - 108, doi: 10.31577/ahs-2022-0023.01.0011
Scientific Paper, English

Viera KOVÁČOVÁ: Impacts of excessive nutrients load in aquatic ecosystem

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• The mechanisms of water eutrophication are not fully understood, but excessive nutrient loading into surface water system is considered to be one of the major factors. This paper reviews nutrient inputs to surface water; the role of nutrients in the eutrophication of surface water; the response of biota to nutrient enrichment; monitoring of changes due to eutrophication and the management. The major influencing factors on water eutrophication include nutrient enrichment, hydrodynamics, environmental factors such as temperature, salinity, carbon dioxide, element balance, microbial and biodiversity. With regards of international and national legislative for the ecological status assessment ecological potential, chemical status, biological quality elements, supporting physical-chemical and hydro-morphological quality elements have been investigated. The aim of this paper is to analyse eutrophication and salinization problem, factors affecting this process, its consequences and possibilities of prevention. The partial aim is to evaluate eutrophication state of surface water in Žitný ostrov channel network following the assessment physical-chemical and microbiological indicators in monitored period.
  
  KEY WORDS: surface water, eutrophication, nitrogen, phosphorus
  
  Address:
  - Viera KOVÁČOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: kovacova@uh.savba.sk)

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 109 - 116, doi: 10.31577/ahs-2022-0023.01.0012
Scientific Paper, English

Valeriya OVCHARUK, Natalia KICHUK, Dmytro LUTAI, Liliia KUSHCHENKO, Maria MYROSHNYCHENKO: Hydrochemical regime and water quality of the Danubian lake Katlabukh

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• One of the main sources of water supply in the Ukrainian part of the Danube delta is the Danube lakes, one of which is Katlabukh. The main revenue part in the water balance of the adjacent delta Lake Katlabukh is the inflow of Danube water through canals with offtakes. The water levels in the lake are determined with the rules of the use of the reservoir, as well as with the hydrological regime of the Danube. Water exchange is carried out by off takes Hromadsky and Zhelyavsky. The reduction of water exchange processes with the Danube in combination with anthropogenic impact on the catchment area of small rivers flowing into Lake Katlabukh, as well as the negative phenomena associated with climate change; create many environmental, water, and social problems for the lake. One of the main problems is the unsatisfactory state of water quality in terms of hydrochemical parameters, in particular high mineralization, which limits the use of the lake water for water supply. The permanents monitoring and analysis of the hydrochemical state of the lake waters will allow to development of scientifically based recommendations for improving water quality and rational use
  
  KEY WORDS: hydrochemical regime, pollution, lakes of the Danube delta
  
  Address:
  - Valeriya OVCHARUK, Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine (Corresponding author. Tel.: Fax.: Email: valeriya.ovcharuk@gmail.com)
  - Natalia KICHUK, Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine
  - Dmytro LUTAI, Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine
  - Liliia KUSHCHENKO, Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine
  - Maria MYROSHNYCHENKO, Odessa State Environmental University, 15 Lvovskaya Str., Odessa, 65016, Ukraine

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 117 - 129, doi: 10.31577/ahs-2022-0023.01.0013
Scientific Paper, English

Jana BOROVSKÁ, Tomáš RUSŇÁK, Matej MOJSES: Assessment of surface waters quality of small water reservoirs in agricultural landscape

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• In the article are presented results from water quality monitoring of six small water reservoirs situated in agricultural landscape in different Slovak regions. The study period was from June 2020 to September 2021. Studied parameters covered oxygen regime, total dissolved solids, fluorescent dissolved organic matter, turbidity, chlorophyll a, phycocyanin and phycoerythrin. All parameters were measured directly in the field using EXO YSI 2 probe. For interpretation of the measured data the application of different statistical approaches were used. The cluster analysis divided the six monitored water reservoirs in to two clusters. The Kruskal-Wallis test confirmed the significant differences between groups of water reservoirs. Analysis of normalized data revealed main parameters that caused the distribution in to two clusters: chlorophyll a, cyanobacterial photosynthetic pigments phycocyanin and phycoerythrin, turbidity and pH. In the cluster 2 the concentration ranges for these parameters showed large fluctuations. Comparison of the land cover structure of 500 m buffer zones pointed out the importance of buffer zone composition for better water quality. For the cluster 2 the highest proportion belonged to arable soils (63.63–92.00%) and only 1.12–9.33% to forests.
  
  KEY WORDS: surface water, water reservoirs, agriculture, water quality
  
  Address:
  - Jana BOROVSKÁ, Institute of Landscape Ecology SAS, Akademická 2, 949 01 Nitra, Slovak Republic (Corresponding author. Tel.: Fax.: Email: jana.borovska@savba.sk)
  - Tomáš RUSŇÁK, Institute of Landscape Ecology SAS, Akademická 2, 949 01 Nitra, Slovak Republic
  - Matej MOJSES, Institute of Landscape Ecology SAS, Akademická 2, 949 01 Nitra, Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 130 - 139, doi: 10.31577/ahs-2022-0023.01.0014
Scientific Paper, English

Abdulnaser ALDARIR, Thomas FICHTNER, Ian Desmond GWIADOWSKI, René BLANKENBURG, Peter-Wolfgang GRAEBER: Estimation of limitations for groundwater recharge using the example of the Sarden site in Syria

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• Groundwater is the main source of all renewable water resources for drinking and irrigation water in most arid and semi-arid areas. However, groundwater abstraction by pumping has increased in most areas significantly, leading to a lowering of the groundwater level. Managed aquifer recharge is a measure to prevent or counteract these temporary and permanent groundwater declines and their negative effects. The work described here deals with the numerical simulation of treated wastewater infiltration for improving the local groundwater balance in the catchment area of Sarden village, Syria. The semi-arid region is characterized by shallow silty clay soils, limestone cliffs and karst aquifers. Different model setups were built up by means of the software PCSiWaPro simulating the effects of different boundary conditions on the saturation conditions in the vadose zone. This should enable an initial assessment of whether and under what conditions the installation of an infiltration system is possible. Results of the research are showing that the hydraulic conditions in the unsaturated soil zone at the site are influenced most by the groundwater level and the number of trenches used for infiltration, whereas precipitation events are playing a subordinate role. In case of elevated groundwater level and too low number of infiltration trenches, the water can rise up to or in the infiltration trenches.
  
  KEY WORDS: recharge of groundwater, treated wastewater infiltration, infiltration trenches, numerical model
  
  Address:
  - Abdulnaser ALDARIR, Technische Universitaet Dresden, Institute of Groundwater Management, 01062 Dresden, Germany, Aleppo University, Department of Rural Engineering, Aleppo, Syria
  - Thomas FICHTNER, Technische Universitaet Dresden, Institute of Groundwater Management, 01062 Dresden, Germany
  - Ian Desmond GWIADOWSKI, Technische Universitaet Dresden, Institute of Groundwater Management, 01062 Dresden, Germany
  - René BLANKENBURG, Technische Universitaet Dresden, Institute of Groundwater Management, 01062 Dresden, Germany
  - Peter-Wolfgang GRAEBER, Technische Universitaet Dresden, Institute of Groundwater Management, 01062 Dresden, Germany (Corresponding author. Tel.: Fax.: Email: Peter-Wolfgang.Graeber@tu-dresden.de)

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 140 - 146, doi: 10.31577/ahs-2022-0023.01.0015
Scientific Paper, English

Anton ZVALA, Peter ŠURDA, Slavomír HOLOŠ: The effect of different fire temperatures on the water repellency parameters of forest sandy soil under different types of vegetation

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• Soil under specific tree forest species (e.g. pines) can be naturally water repellent. Forest fire can strengthen or destroy soil water repellency (SWR). Fire induced SWR have many direct or indirect effects, including increased preferential flow rate and risk of ground water contamination, increased surface runoff and soil erosion, increased amount of carbon stored in soil, reduced levels of seed germination and plant growth. Understanding the post-fire hydrologic response of forest soil is paramount for effective risk management and mitigation of post-fire hydrologic hazards. Three experimental sites were located in the Borská nížina lowland (southwestern Slovakia). Eolian (wind-blown) sand dunes form the central part of the Borská nížina lowland, which make it a specific region within Central Europe. Pines have been planted here for sand dune stabilization since the 18th century and today cover a huge part of the lowland. The first site IL1 represent 100-years-old stand of Scots pine (Pinus sylvestris), the second site IL2 is a 30-years-old stand of Scots pine (Pinus sylvestris) and the third site LL is a deciduous stand with a predominance of alder (Alnus glutinosa). The disturbed mineral soil samples were taken from 2.5–5.0 cm depth of soil horizon. The organic horizon (0–2.5 cm) was sampled separately before mineral soil. In the laboratory, the samples from each site in 5 replicates were placed into a muffle furnace and exposed to a temperature from 50 to 900°C. The persistence of SWR in soil samples was measured using the water drop penetration time (WDPT) test. Our goal was to quantify the changes of SWR of the naturally water repellent soil induced by different fire temperatures under age and species different forest stands. Forest stands were selected to include different vegetation age and type of litter (surface organic horizon) under the relatively same site conditions (climate, soil and relief conditions). The measured values of natural background water repellency decreased in order IL1>IL2>LL. The highest value of induced SWR (WDPTmax) was measured at IL1 and further declined in the order LL˃IL2; however increase of SWR after heating, estimated as a difference between maximal induced and natural SWR had different trend (LL>IL2˃IL1). Mean value of parameter WDPTmax-WDPTn at IL1 was statistically different from values estimated at sites IL2 resp. LL. The changes in natural and induced SWR that we have found may be attributed partially to the quantity and to the origin of organic material (litter of the plant communities with different age and composition of the species).
  
  KEY WORDS: soil water repellency, soil heating, water drop penetration time, forests
  
  Address:
  - Anton ZVALA, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: zvala@uh.savba.sk)
  - Peter ŠURDA, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Slavomír HOLOŠ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic, Institute of Landscape Engineering, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Hospodárska 7, 949 76 Nitra , Slovak Republic

Acta Hydrologica Slovaca, Vol. 23, No. 1, 2022, p. 147 - 154, doi: 10.31577/ahs-2022-0023.01.0016
Scientific Paper, English

Milan GOMBOŠ, Andrej TALL, Dana PAVELKOVÁ, Branislav KANDRA: Determination of sedimentation speed of soil micro-particles from laser diffraction measurements

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• In hydropedological research and in various scientific experiments, the determination of the settling rate of soil microparticles is a frequent task. Many laboratory procedures for measuring sedimentation rate are based on the Stokes equation. In recent years, methods based on the principle of laser diffraction can be used to measure grain-size distribution and deposition rate of microparticles. The output of the measurements by a laser diffraction method is statistical distribution of soil texture in the measured sample by particle size expressed in % of volume. Measurements were performed in a wet way by MALVERN Instruments device called Mastersizer 2000. The proposed method is based on measuring the time required for soil particles of certain diameter to pass certan distance. The size of soil microparticles present in space and time is defined by probability. Probability is defined in the form of a grain size distribution function. The advantage of the proposed method is its robustness and elimination of human factor errors. This paper presents the results of theoretical approaches and experimental measurements of the settling rate of soil microparticles. Soil samples were taken in the East Slovakian Lowland. Measurements are performed for the selected sizes of soil microparticles for a probability of occurrence of 90%, i.e for d(90). The results are compared with the results calculated by the Stokes equation.
  
  KEY WORDS: sedimentation rate, soil microparticles, dispersion system
  
  Address:
  - Milan GOMBOŠ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: gombos@uh.savba.sk)
  - Andrej TALL, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Dana PAVELKOVÁ, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic
  - Branislav KANDRA, Institute of Hydrology SAS, Dúbravská cesta 9, 84104 Bratislava, Slovak Republic