J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 1 - 10, doi: 10.2478/johh-2024-0031
Scientific Paper, English

Laura Kögler, Andreas Ruby, Thomas Iserloh, Manuel Seeger, Johannes B. Ries: Laboratory flume experiments for detection and quantification of subsurface particle transport in steep-slope vineyards

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• Coarse-grained vineyard soils like in the Moselle valley, Germany, can be highly vulnerable to soil erosion. This is due to the non-sustainable soil management using heavy machinery and eliminating the vegetation cover on steep slopes. Through the particular combination of compacted subsoil and topsoil loosened by tillage, the vineyard experiences subsurface runoff after rainfall events. There is a knowledge gap concerning the identification and quantification of transported soil particles in the aforementioned subsurface runoff, as these processes are difficult to accurately measure under field conditions compared to surface runoff. In this paper, an experimental laboratory setup is presented including a newly developed sediment trap to measure and quantify the transport of fine soil particles in subsurface flow. The study showed substantial differences based on the water application method. Nevertheless, the first results show a subsurface sediment discharge of 1 g l–1 on average and 6–8 g l–1 immediately after heavy soil disturbance (simulated tillage). It is highly recommended to conduct further experiments using the method that corresponds most closely to natural processes, the combined method of overflow and sprinkler, as well as installing the sediment trap in a vineyard to validate the findings. If the values can be confirmed, subsurface runoff is a significant contributor to the total soil erosion process and, compared to literature, is responsible for up to 50% of soil erosion in vineyards.
  
  KEY WORDS: Soil erosion; Subsurface flow; Subsurface runoff; Rainfall simulation; Sediment trap.
  
  Address:
  - Laura Kögler, Justus-Liebig-University Giessen, Department of Physical Geography, 35390 Giessen, Germany. Trier University, Department of Physical Geography, 54296 Trier, Germany. (Corresponding author. Tel.: Fax.: Email: Laura.Koegler@geogr.uni-giessen.de)
  - Andreas Ruby, Trier University, Department of Physical Geography, 54296 Trier, Germany. Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Geomorphology, 14473 Potsdam, Germany.
  - Thomas Iserloh, Trier University, Department of Physical Geography, 54296 Trier, Germany.
  - Manuel Seeger, Trier University, Department of Physical Geography, 54296 Trier, Germany.
  - Johannes B. Ries, Trier University, Department of Physical Geography, 54296 Trier, Germany.

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 11 - 23, doi: 10.2478/johh-2024-0032
Scientific Paper, English

Mujahid Iqbal, Usman Ghani: Investigating the discharge characteristics over a piano key weir with varying key slope and key width ratios under varying discharges

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• The objective of the present study was to investigate the effect of inlet to outlet key slope ratios (Si/So), inlet to outlet key width ratios (Wi/Wo) and head over the weir on the coefficient of discharge (Cpkw) of type-A trapezoidal piano key weir (TPKW). It was observed that the Cpkw of TPKW was found to be decreased as the Si/So ratio reduced. The percentage of reduction in Cpkw was found to be 18.5%, 16%, 13.7%, 9.4%, 6.3%, and 3% at Si/So = 0.60, 0.75, 0.80, 1.00, 1.25, and 1.33, respectively in comparison with the Si/So = 1.67. As far as the effect of Wi/Wo ratio on the Cpkw of TPKW is concerned, the Cpkw of TPKW was observed to be increased with increasing Wi/Wo ratios. Moreover, the Cpkw at Wi/Wo = 1.32 and Wi/Wo = 1.15 was found to be 9.4% and 7.5% higher than Wi/Wo=1 respectively, while for the case of Wi/Wo = 0.76, its value was found to be 3.3% lower than Wi/Wo = 1. Furthermore, the hydraulic efficiency of TPKW was found to be decreased as head over the weir increased. The maximum value of Cpkw of TPKW was observed to be 3.2 corresponding to lowest h/P ratio for the model having Si/So = 1.67 and Wi/Wo = 1.32, while the minimum value of Cpkw of TPKW was found to be 1.58 corresponding to highest h/P ratio for the model having Si/So = 0.60 and Wi/Wo = 0.76. Additionally, sensitivity analysis results revealed that the Cpkw of TPKW is more sensitive with h/P ratio than other ratios.
  
  KEY WORDS: Coefficient of discharge; Inlet to outlet key slope ratios; Inlet to outlet key width ratios; Trapezoidal piano key weir; Type-A piano key weir.
  
  Address:
  - Mujahid Iqbal, Department of Civil Engineering, University of Engineering and Technology, Taxila, Pakistan.
  - Usman Ghani, Department of Civil Engineering, University of Engineering and Technology, Taxila, Pakistan. (Corresponding author. Tel.: Fax.: Email: usman.ghani@uettaxila.edu.pk)

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 24 - 33, doi: 10.2478/johh-2025-0001
Scientific Paper, English

László Báder: The Climatic Energy Balance Diagram (CEBD) highlights changes in the hydrological cycle of the Danube River basin

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• The impacts of global warming are the subject of intense research. However, it is difficult to agree on ways to prevent and mitigate adverse changes until the root causes of the problem can be formulated in simple and understandable terms. The aim of this study is to highlight changes in the hydrological cycle using a new graphical method, the Climatic Energy Balance Diagram (CEBD), or climate diagram for short. The key terms of the energy balance equation determine the annual operating points or working points of the climatic energy distribution process. The easy-to-use visualization tool promotes evaporative fraction (EF) as a key metrics, expressing the efficiency of the climatic energy distribution process. Analysis has shown that keeping it at around 0.7 in the Danube basin requires increased evaporation. The 30-year average value of evaporation has increased by 29 mm (from 482 mm to 507 mm) while that of sensible heat by 23 mm (from 196 mm to 219 mm) between 1961–1990 and 1991–2020, both expressed in water-depth equivalents. A normalised version of the CEBD can be used to compare areas in different climatic conditions. The diagram highlights the key role of water and evaporation in the process of distributing climatic energy to ensure environmental sustainability and can facilitate better communications between different research areas and stakeholders (farmers, regulators, investors, policy makers) while maintaining a multidisciplinary approach.
  
  KEY WORDS: Climatic energy balance diagram (CEBD); Climatic energy; Hydrological cycle; Latent heat; Evaporative fraction; Net radiation.
  
  Address:
  - László Báder, Budapest University of Technology and Economics, Department of Hydraulic and Water Resources Engineering, Faculty of Civil Engineering, Budapest, Hungary. (Corresponding author. Tel.: Fax.: Email: laszlo.bader@edu.bme.hu)

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 34 - 50, doi: 10.2478/johh-2025-0002
Scientific Paper, English

Pedram Farbiz, Chonoor Abdi Chooplou, Masoud Ghodsian: The influence of submergence on scour at triangular piano key weirs

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• This research investigates scour dynamics downstream of triangular piano key weirs (PKWs), which can cause significant channel bed erosion. The study analyzed scour effects under four discharge conditions and varying submergence ratios in fine gravel and medium gravel beds within a 10 m long, 0.75 m wide, and 0.80 m high channel. Findings reveal that 49.5% increase in the particle Froude number and a 54.2% decrease in submergence ratio in the fine gravel bed resulted in a 270% increase in maximum scour depth and a 114.2% increase in scour hole length. The scour depth in the fine gravel bed was 43.83% greater than in the medium gravel bed, with a 47.69% increase in average scour hole length. Higher submergence ratios reduced the intensity of downstream hydraulic jumps and sediment scouring, leading to significant decreases in maximum scour depth (81%), maximum scour distance from the weir toe (66%), scour hole length (80%), and weir toe scour depth (84%) compared to free flow conditions. Consistent scour hole profiles were observed across experiments, and a non-dimensional predictive equation for these profiles achieved a high R² value of 0.920. The research also introduces new equations for estimating scour characteristics at triangular PKWs under both free and submerged flow, with strong predictive capabilities. By identifying key parameters influencing scour, this study aids in optimizing PKW design to reduce erosion and enhance the stability of hydraulic structures.
  
  KEY WORDS: Free and submerged flow; Longitudinal profiles; Scour characteristics; Submergence ratio; Triangular piano key weir.
  
  Address:
  - Pedram Farbiz, Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.
  - Chonoor Abdi Chooplou, Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.
  - Masoud Ghodsian, Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran. Faculty of Civil and Environmental Engineering, and Research Institute of Water Engineering and Management, Tarbiat Modares University, Tehran, Iran. (Corresponding author. Tel.: Fax.: Email: ghods@modares.ac.ir)

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 51 - 64, doi: 10.2478/johh-2025-0004
Scientific Paper, English

Xuan-Hien Le, Le Thi Thu Hien: Integrating machine learning and empirical approaches for scour depth estimation at sluice gates: evaluating tree-based models, hyperparameter tuning, and proposing new formulas

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• Accurate prediction of maximum scour depth (MSD) at sluice gates is critical for guaranteeing the stability and safety of hydraulic systems. Traditional empirical formulas often fail to capture the non-linear interactions between flow dynamics, sediment characteristics, and structural configurations. This study addresses these limitations by leveraging advanced machine learning (ML) techniques, specifically tree-based models, to enhance predictive accuracy. The performance of three tree-based models–Extra Trees (ERT), CatBoost (CAT), and Histogram-Based Gradient Boosting (HGB)–was examined using two hyperparameter tuning methods: Tree-Structured Parzen Estimator (TPE) and Particle Swarm Optimization (PSO). The models underwent 100 simulations to quantify uncertainty and variability in performance metrics. The results indicate that CAT_PSO (optimized with PSO) exhibits superior predictive performance compared to empirical formulas and other ML techniques. CAT_PSO achieved the highest mean CORR (correlation coefficient) of 0.9644 and mean NSE (Nash-Sutcliffe Efficiency) of 0.9272. HGB models demonstrated slightly lower performance compared to CAT and ERT, with higher variability in predictions. Further analysis explored the influence of individual input factors on model performance. The inclusion of more variables, such as tailwater depth and sediment size, generally enhanced model performance. The study also developed new empirical equations for MSD estimation by considering both multiplicative and additive models, progressively incorporating additional input features. These new formulas show improved predictive accuracy over empirical methods, though they still fall short of the performance achieved by the ML models.
  
  KEY WORDS: Extra Trees (ERT); Histogram-Based Gradient Boosting (HGB); Hyperparameter Tuning; Particle Swarm Optimization (PSO); Scour Depth Estimation; Tree-structured Parzen Estimator (TPE).
  
  Address:
  - Xuan-Hien Le, Faculty of Water Resources Engineering, Thuyloi University, Vietnam.
  - Le Thi Thu Hien, Faculty of Water Resources Engineering, Thuyloi University, Vietnam. (Corresponding author. Tel.: Fax.: Email: lethuhien.thuyluc@tlu.edu.vn)

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 65 - 72, doi: 10.2478/johh-2025-0003
Scientific Paper, English

Vladimír Šimanský, Elżbieta Wójcik–Gront, Ján Horák, Žaneta Pauková, Natalya Buchkina: Biochar blended with sheep manure and biogas station residue in different ratios can significantly influence soil properties

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• Biochar, produced via biomass pyrolysis, is increasingly recognized for its potential in soil health enhancement. This study investigates the impact of compost, biochar blended with sheep manure in 50:50 ratio (BS1), biochar blended with sheep manure and biogas station residue in 33:33:33 (BS2), and 30:50:20 (BS3) ratios on chemical characteristics and organic substances in the leachates, focusing on the interplay between these components. The experimental design included leaching tests with the abovementioned treatments in a controlled environment. Results indicate significant differences in pH, electrical conductivity, and the content of organic substances between the treatments, suggesting that biochar substrates can positively influence physico-chemical characteristics and nutrient dynamics after their incorporation into the soils. Notably, the BS1 demonstrated enhanced water-soluble salts, cold-water-soluble carbon, and humic substances release potential compared to the other studied treatments. Principal component analysis further elucidated the complex relationships between the measured parameters, indicating the importance of biochar-based substrates careful mixing for sustainable agricultural practices to improve soil fertility and carbon sequestration.
  
  KEY WORDS: Biochar substrates; Carbon; Compost; Digestate; Humic substances; Sheep manure; Soil amendments.
  
  Address:
  - Vladimír Šimanský, Institute of Agrochemistry and Soil Science, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Nitra, Slovakia. (Corresponding author. Tel.: Fax.: Email: vladimir.simansky@uniag.sk)
  - Elżbieta Wójcik–Gront, Department of Biometry, Institute of Agriculture, Warsaw University of Life Sciences-SGGW, Warsaw, Poland.
  - Ján Horák, Institute of Landscape Engineering, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Nitra, Slovakia.
  - Žaneta Pauková, Institute of Law and Sustainable Development, Faculty of European Studies and Regional Development, Slovak University of Agriculture, Nitra, Slovakia.
  - Natalya Buchkina, Department of Soil Physics, Physical Chemistry and Biophysics, Agrophysical Research Institute, St. Petersburg, Russia.

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 73 - 83, doi: 10.2478/johh-2025-0006
Scientific Paper, English

Peter Váš, Juraj Bartok, Ladislav Gaál, Marián Jurašek, Marián Melo, Martin Gera: Frequency shifts in thunderstorm patterns as key precursors to flash flood events

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• This study presents the research of thunderstorms in Slovakia using records of thunderstorm days from weather observation stations from 1965 to 2023, as well as radar data, and data from lightning detection systems from 2010 to 2023. An algorithm was developed to identify thunderstorms using radar and lightning data. The temporal distribution of thunderstorms is examined across annual, seasonal, daily, and hourly timescales. Additionally, we focus on the spatial distribution of thunderstorms, where lightning data according to a proposed algorithm were used. The occurrence of thunderstorms is also analyzed in the light of macrosynoptic types, according to a 28-class classification of the Slovak Hydrometeorological Institute. The results show that close thunderstorms (within 3 km of a given location) in Slovakia occur on average on 15 days a year, most frequently in the summer months of June and July, and primarily in the late afternoon between 3 and 5 p.m. Central European Summer Time (CEST). The spatial distribution of thunderstorms in Slovakia is non-homogeneous, with an increased occurrence in Central Slovakia, particularly in the area of Muránska Planina, Stolické, and Volovské Vrchy Mts. Conversely, the fewest thunderstorms occur in the westernmost part of the territory. Severe thunderstorms are most numerous in the Gemer region. The occurrence of thunderstorms is significantly influenced by synoptic types, with the most favorable conditions associated with types B (trough over Central Europe), Bp (traveling trough), C (cyclone over Central Europe), and Cv (upper cyclone). In recent decades, significant decrease in the number of thunderstorm days per year has been observed. This may be due to the observed decreasing trend of cyclonic synoptic situations in Europe, where a substantial number of thunderstorms occur.
  
  KEY WORDS: Thunderstorm; Thunderstorm climatology; Radar, Lightning; Climate change.
  
  Address:
  - Peter Váš, Department of Astronomy, Physics of the Earth, and Meteorology, Comenius University in Bratislava, Bratislava, Slovak Republic
  - Juraj Bartok, MicroStep-MIS, Bratislava, Slovak Republic
  - Ladislav Gaál, MicroStep-MIS, Bratislava, Slovak Republic
  - Marián Jurašek, Slovak Hydrometeorological Institute, Bratislava, Slovak Republic.
  - Marián Melo, Department of Astronomy, Physics of the Earth, and Meteorology, Comenius University in Bratislava, Bratislava, Slovak Republic
  - Martin Gera, Department of Astronomy, Physics of the Earth, and Meteorology, Comenius University in Bratislava, Bratislava, Slovak Republic (Corresponding author. Tel.: Fax.: Email: martin.gera@fmph.uniba.sk)

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 84 - 94, doi: 10.2478/johh-2025-0005
Scientific Paper, English

Liu Yang, Zhonghua Yang, Wenxin Huai, Xiaoguang Liu: Feedbacks of flow fields and sediment deposition to discontinuous vegetation patches: impacts of density and characteristic length of patches

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• The discontinuous instream plants, which have progressively emerged as potentially advantageous eco-morphologic engineers capable of changing hydraulics, enhancing ecosystem resilience, and influencing sediment deposition, usually grow seasonally. Thus, understanding the feedback of flow fields and sediment deposition to the density and length of vegetation patches is essential in exploring the geomorphic role of vegetation due to its seasonal evolution in natural rivers. In this study, we conducted flume experiments to clarify the interaction mechanisms between the hydraulics and suspended sediment deposition in discontinuous emergent vegetation patches. Results validated with field data demonstrate that discontinuous vegetation patches modify flow velocity and turbulence, significantly influencing sediment deposition along the streamwise direction. Within the vegetation region, represented by Li, the enhanced turbulence and flow velocity induced by emergent vegetation were found to reduce sedimentation, while sediment deposition increased in interval regions. The sediment deposition pattern with the different lengths of patches (Lv) reveals the expansive effects of upstream patch on the downstream interval regions with different vegetation densities. When Li/Lv > 1, the interval is sufficiently long to extend turbulent eddies that originated from upstream dense vegetation patches, which restricts sediment deposition and leads to the decreased deposition of suspended sediment compared to the scenario without vegetation. However, this effect recedes with the increase in interval length. Conversely, the sparse vegetation patch enhances the total deposition magnitude when the velocity in the interval zones is small. When Li/Lv < 1, the decreased sediment deposition is observed in both dense and sparse vegetation scenarios.
  
  KEY WORDS: Discontinuous vegetation patches; Turbulence; Velocity distribution; Sediment deposition.
  
  Address:
  - Liu Yang, State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, China.
  - Zhonghua Yang, State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, China. (Corresponding author. Tel.: Fax.: Email: yzh@whu.edu.cn)
  - Wenxin Huai, State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, China.
  - Xiaoguang Liu, Key Laboratory of River and Lake Regulation and Flood Control in the Middle and Lower Reaches of the Yangtze River of Ministry of Water Resources, Changjiang River Scientific Research Institute, Wuhan, China.

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 95 - 107, doi: 10.2478/johh-2025-0007
Scientific Paper, English

Tomáš Julínek, Jaromír Říha, Milan Geršl, Jan Holešovský, Matouš Cabalka: Determination of the yield of thermal mineral springs emerging into the Bečva River in the Teplice Spa

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• The mineral water in the Teplice Spa emerges into the Bečva River bed from the hypogenic karst formed by Palaeozoic limestones. Recently the focus on the hydrological and hydrogeological conditions of the mineral springs issues from the planning of the Skalička Dam whose reservoir is believed to be interconnected with the karstic formation and may influence the regime of mineral waters in the spa. One of the related particular problems is to determine the discharge of the mineral water which emerges into the Bečva River in the river reach along the Teplice Spa. The knowledge about the emerging mineral water discharge is crucial for further assessment of an impact of planned reservoir. The most challenging issue and novelty of the study was to determine a relatively small increment of the discharge in the Bečva river, when the magnitude of the error of determination was comparable to the determined discharge. Therefore, for the assessment of the discharge three methods were applied, namely measurements by the classical current meter, measurements using the Acoustic Doppler Current Profiler and evaluation of the measurements of electrical conductivity along the river reach. The analysis of obtained results and comparison of the obtained methods indicate the emerging discharge between 250 and 500 l/s with realistic value about 350 l/s. The study shows quite good agreement of results determined by individual methods which justifies the methodology used and is good guidance for similar studies.
  
  KEY WORDS: Karst; Mineral springs; Hydrometrical measurement; Electrical conductivity.
  
  Address:
  - Tomáš Julínek, Brno University of Technology, Faculty of Civil Engineering, Institute of Water Structures, Czech Republic
  - Jaromír Říha, Brno University of Technology, Faculty of Civil Engineering, Institute of Water Structures, Czech Republic (Corresponding author. Tel.: Fax.: Email: riha.j@vut.cz)
  - Milan Geršl, Mendel University in Brno, Faculty of Agrisciences, Czech Republic
  - Jan Holešovský, Brno University of Technology, Faculty of Civil Engineering, Institute of Mathematics and Descriptive Geometry, Czech Republic.
  - Matouš Cabalka, Brno University of Technology, Faculty of Civil Engineering, Institute of Mathematics and Descriptive Geometry, Czech Republic.

J. Hydrol. Hydromech., Vol. 73, No. 1, 2025, p. 108 - 120, doi: 10.2478/johh-2025-0009
Scientific Paper, English

Masoud Naderi, Shabnam Vakili, Hossein Afzalimehr, Nadia Penna, Roberto Gaudio: Application of spatiotemporal velocity method in concrete canals with vegetation patch

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• Understanding the interaction of flow and vegetation in open canals has a great impact on better implementation of environmental projects and hydraulic engineering. The purpose of this research is to apply spatiotemporal (spatial and temporal) averaging method in concrete canals in the presence of vegetation patches. Therefore, in this research, four reaches of irrigation canals with vegetation patches were investigated in Iran. The measured data includes flow velocity and reaches surveying. The results of spatiotemporal velocity profiles showed that the log-law fits nicely the measured velocity data near the bed with vegetation patches. The local values of velocity and shear velocity were compared with the unit value extracted from the double-averaged velocity profile. The results of this comparison showed that the percentage difference between the local values resulting from each flow velocity profile and the unit value of the spatiotemporal velocity is not significant in most cases. Thus, the spatiotemporal velocity method is able to reflect the characteristics of the entire flow conditions in concrete canals in the presence of vegetation patches.
  
  KEY WORDS: Irrigation canals; Logarithmic law; Shear velocity; Spatiotemporal velocity method.
  
  Address:
  - Masoud Naderi, Iran University of Science and Technology, Tehran, Iran.
  - Shabnam Vakili, Khaje Nasir Toosi University of Technology, Tehran, Iran.
  - Hossein Afzalimehr, Iran University of Science and Technology, Tehran, Iran. (Corresponding author. Tel.: Fax.: Email: hafzali@iust.ac.ir)
  - Nadia Penna, Dipartimento di Ingegneria Civile, Universita della Calabria, 87036 Rende (CS), Italy
  - Roberto Gaudio, Dipartimento di Ingegneria Civile, Universita della Calabria, 87036 Rende (CS), Italy