J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 399 - 412, doi: 10.2478/johh-2024-0020
Scientific Paper, English

Ikram Mahcer, Djelloul Baahmed, Ludovic Oudin, Cherifa Hanene Kamelia Chemirik: Multidimensional analysis of NDVI dynamics in response to climate and land use/land cover change in Northwest Algeria

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• Climate change has emerged as a major concern at both regional and global scales in recent decades. Northwestern Algeria is particularly vulnerable as a semi-arid zone, where changes in climate and land cover (LC) will have a significant impact on vegetation in the long term. This study analyses, through a multidimensional approach, the influence of climate change and LC on vegetation dynamics. Hierarchical partitioning (HP) analysis was conducted to determine the most influential climatic variables (precipitation, temperature) on the dynamics of NDVI. The results show that the annual NDVI shows a fluctuating spatial trend between decrease and increase in different regions. Trends in seasonal NDVI are spatially varied and less uniform. Variations in precipitation are stable, while temperatures show clear and consistent significant increases across the region, with a general tendency to increase (p<0.01) in spring and summer. In mountainous areas, NDVI shows an increasing trend both annually and seasonally. The correlation (r²) between NDVI, temperature and precipitation (0.75–1.0) over the different seasons reveals significant seasonal and regional variability. LC transition patterns also influence spatio-temporal trends in vegetation cover. They reveal that the rate of change of NDVI varies between LC types and regions, with resilience in forests and grasslands. These variations have significant implications for vegetation dynamics, as observed by NDVI.
  
  KEY WORDS: Climate change; NDVI; Climatic factors; Trend; LC; Northwest Algeria.
  
  Address:
  - Ikram Mahcer, Civil and Environmental Engineering Laboratory (LGCE), Hydraulic Department, Faculty of Technology, University of Djillali Liabes, 22000 Sidi Bel Abbes, Algeria.
  - Djelloul Baahmed, Civil and Environmental Engineering Laboratory (LGCE), Hydraulic Department, Faculty of Technology, University of Djillali Liabes, 22000 Sidi Bel Abbes, Algeria. (Corresponding author. Tel.:+213 6 61 61 45 77 Fax.: Email: baahmed78@yahoo.fr)
  - Ludovic Oudin, Sorbonne Université, CNRS, EPHE, UMR METIS, Case 105, 4 place Jussieu, F-75005Paris, France.
  - Cherifa Hanene Kamelia Chemirik, Civil and Environmental Engineering Laboratory (LGCE), Hydraulic Department, Faculty of Technology, University of Djillali Liabes, 22000 Sidi Bel Abbes, Algeria.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 413 - 421, doi: 10.2478/johh-2024-0024
Scientific Paper, English

Martinho A.S. Martins, Sergio A. Prats, Jan Jacob Keizer, Frank G.A. Verheijen: Post-fire soil water repellency under stones and forest residue mulch versus of bare soil

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• Soil water repellency (SWR) is commonly defined as a physical property of soil to resist wetting. Fire can induce, enhance, or reduce SWR and, consequently, lead to considerable changes in soil water infiltration and storage and increase soil erosion by water. The application of mulches to cover burned areas has been found to be an efficient emergency stabilization treatment. However, little is known about possible side effects on SWR, especially long-term effects. Under forests, SWR is known to be very heterogeneous, particularly in proximity to trees and shrubs, litter type and thickness, stones, cracks and roots. This study targeted the effects of post-fire mulching on SWR in a eucalypt plantation five years after a wildfire. The application of forest residue mulch did not significantly change SWR in bare soil patches or under stones, comparing the mulched and untreated plots. By contrast, SWR in the mulched plots was, significantly stronger under mulch than in bare soil. The same was true for both soil organic matter content (SOM) and soil moisture content (SMC), suggesting that SOM played a more important role than SMC. In turn, SWR under mulch was not significantly different from SWR under stone, while both SMC and SOM were significantly higher under mulch than stone. This could be explained by the differences in SMC overriding the effects of the differences SOM, or, alternatively, by possible differences in SOM quality, in particular of the “fresh” input from the mulch. Overall, the present results indicated that different mechanisms may drive SWR dynamics beneath mulch fragments, stones and bare soil patches. A better understanding of these mechanisms is important to improve the knowledge of post-fire overland flow generation and, thereby, to improve its prediction using hydrological models, especially during the early phases of the window-of-disturbance.
  
  KEY WORDS: Wildfire; Hydrophobicity; Mulching; Rock fragment; Stone lag.
  
  Address:
  - Martinho A.S. Martins, Centre for Environmental and Marine Studies (CESAM), Dept. Environment and Planning, University of Aveiro, 3810-193 Aveiro, Portugal. (Corresponding author. Tel.:+351 916499823. Fax.: Email: martinho.martins@ua.pt)
  - Sergio A. Prats, Mediterranean Institute for Agriculture, Environment and Development (MED-CHANGE), Institute for Advanced Studies and Research, University of Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal.
  - Jan Jacob Keizer, GeoBiociencias, Geotecnologias E Geoengenharias (GEOBIOTEC), Department Environment and Planning, University of Aveiro, 3810-193 Aveiro, Portugal.
  - Frank G.A. Verheijen, Centre for Environmental and Marine Studies (CESAM), Dept. Environment and Planning, University of Aveiro, 3810-193 Aveiro, Portugal.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 422 - 435, doi: 10.2478/johh-2024-0028
Scientific Paper, English

Misagh Parhizkar, Manuel Esteban Lucas-Borja, Pietro Denisi, Nobuaki Tanaka, Demetrio Antonio Zema: Comparing the effects of hydromulching and application of biodegradable plastics on surface runoff and soil erosion in deforested and burned lands

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• Several techniques, such as hydromulching (HM) and addition of organic residues (such as biodegradable plastics, BP) to soil have been proposed for conservation of soil affected by deforestation and wildfire. However, there is the need to support the task of land managers for the adoption of the most effective soil conservation technique, considering that the impacts on soil properties and hydrology are different due to the different mechanisms (mainly based on root actions for hydromulching and on supply of organic matter for application of bioplastics residues). This study comparatively evaluates the hydrological and erosive effects of HM, addition of BP residues to soil, and lack of any treatments (control) at the plot scale and under simulated rainfall in deforested and burned forestlands of Northern Iran. These effects have been associated to changes in key properties of soil and root characteristics due to the treatments, using multivariate statistical analysis. Moreover, regression models have been setup to predict surface runoff and soil erosion for both treatments. HM was more effective (–65% of runoff and –61% in soil loss) than application of BP (–22% and –19%, respectively) in controlling the soil’s hydrological and erosive response, the latter being extremely high in control plots (over 6 tons/ha). These reductions were closely associated to significant increases in organic matter and aggregate stability of soil, to a decrease in bulk density after the treatments, and to the grass root growth, which further improved soil hydrology after HM. The Principal Component Analysis provided a synthetic parameter measuring the soil response to rainfall and treatments. The cluster analysis discriminated the three soil conditions (HM, application of BP and control), according to the changes in soil properties and root growth in HM, in as many groups of soil samples. The multiple regression analysis provided two linear models that predict surface runoff and soil loss with a very high accuracy (r2 > 0.98) for a precipitation with given depth and intensity.
  
  KEY WORDS: Surface runoff; Soil loss; organic matter; Aggregate stability; Bulk density; Multiple regression; Prediction models.
  
  Address:
  - Misagh Parhizkar, Department of Soil Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran.
  - Manuel Esteban Lucas-Borja, Escuela Técnica Superior Ingenieros Agrónomos y Montes, Universidad de Castilla-La Mancha, Campus Universitario, E-02071 Albacete, Spain.
  - Pietro Denisi, AGRARIA Department, Mediterranean University of Reggio Calabria, Loc. Feo di Vito, I-89122 Reggio Calabria, Italy
  - Nobuaki Tanaka, The University of Tokyo Hokkaido Forest, The University of Tokyo Forests, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 9-61 Yamabe Higashi, Furano, Hokkaido 079-1563, Japan.
  - Demetrio Antonio Zema, AGRARIA Department, Mediterranean University of Reggio Calabria, Loc. Feo di Vito, I-89122 Reggio Calabria, Italy. (Corresponding author. Tel.: Fax.: Email: dzema@unirc.it)

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 436 - 446, doi: 10.2478/johh-2024-0026
Scientific Paper, English

Milica Aleksić, Juraj Parajka, Patrik Sleziak, Kamila Hlavčová, Michaela Danáčová: Evaluating the impact of satellite soil moisture data as an additional component in the calibration of a conceptual hydrological model

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• This study proposes a new method for dividing a catchment with the aim of testing it in the calibration process of a conceptual hydrological model. The new catchment division is reflected in having different land cover zones and the input data prepared in a semi-distributed way. This study also explores the impact of satellite soil moisture data when multi-objective calibration is used with the land cover zone divisions of a catchment while assigning different weights to runoff ranging from 0% to 100% (with a 0.05 step). The results indicate that using a weight range of 60% to 80% on a runoff provides optimal results, bettering both the runoff model’s efficiency and soil moisture correlation. For further validation of the internal parameters and processes, the field capacity and evapotranspiration of the catchment were monitored. In regions with specially limited in-situ soil moisture data, satellite-derived data can contribute as an scarce additional component of the land cover division that can point out areas of the most reliable soil moisture information.
  
  KEY WORDS: Hydrological modelling; Soil moisture; ASCAT; Multi-objective calibration; Land cover zones.
  
  Address:
  - Milica Aleksić, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia. KAJO s. r. o., Sládkovičová 228/8, 01401 Bytča, Slovakia. (Corresponding author. Tel.: Fax.: Email: milica.aleksic@stuba.sk)
  - Juraj Parajka, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, 1040 Vienna, Austria.
  - Patrik Sleziak, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, 031 05 Liptovský Mikuláš, Slovakia.
  - Kamila Hlavčová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Michaela Danáčová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 447 - 465, doi: 10.2478/johh-2024-0027
Scientific Paper, English

Patrick Hogan, Borbala Szeles, Gerhard Rab, Markus Oismüller, Lovrenc Pavlin, Juraj Parajka, Peter Strauss, Günter Blöschl: Spatial patterns of evaporation in a small catchment

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• In this study a network of three eddy covariance stations rotated between five measurement sites is used to measure evaporation (E) within the Hydrological Open Air Laboratory (HOAL) in Petzenkirchen, Austria for 8 years. Discharge measurements at the tributaries and outlet of the main catchment allow for E to be estimated for 6 subcatchments using the water balance method. Year to year variability in monthly E measured by the eddy covariance stations is found to be driven primarily by net radiation and temperature and annual E by net radiation. Year to year variability in the water balance-based E estimate was driven by precipitation. The two methods are found to be consistent, when storage and leakage are accounted for. Daily and seasonal patterns can be seen resulting from the agricultural land use cycle, due to the variations in land cover during the growing season.
  
  KEY WORDS: Evapotranspiration; Water balance; Agricultural catchment; Experimental catchment.
  
  Address:
  - Patrick Hogan, Institute of Hydraulic Engineering and Water Resources Management, Faculty of Civil Engineering, Vienna University of Technology, Karlsplatz 13 E222/2, 1040 Vienna, Austria.
  - Borbala Szeles, Institute of Hydraulic Engineering and Water Resources Management, Faculty of Civil Engineering, Vienna University of Technology, Karlsplatz 13 E222/2, 1040 Vienna, Austria. (Corresponding author. Tel.:+43 (0)1 58801-22335. Fax.: Email: szeles@hydro.tuwien.ac.at)
  - Gerhard Rab, Institute of Hydraulic Engineering and Water Resources Management, Faculty of Civil Engineering, Vienna University of Technology, Karlsplatz 13 E222/2, 1040 Vienna, Austria.
  - Markus Oismüller, Federal Government of Lower Austria, Landhausplatz 1, 3109 St. Pölten, Austria.
  - Lovrenc Pavlin, Austrian Federal Ministry of Agriculture, Forestry, Regions and Water Management, Department for Water Balance, Stubenring 1, 1010 Vienna, Austria.
  - Juraj Parajka, Institute of Hydraulic Engineering and Water Resources Management, Faculty of Civil Engineering, Vienna University of Technology, Karlsplatz 13 E222/2, 1040 Vienna, Austria.
  - Peter Strauss, Federal Agency of Water Management, Institute for Land and Water Management Research, Pollnbergstraße 1, 3252 Petzenkirchen Petzenkirchen, Austria.
  - Günter Blöschl, Institute of Hydraulic Engineering and Water Resources Management, Faculty of Civil Engineering, Vienna University of Technology, Karlsplatz 13 E222/2, 1040 Vienna, Austria.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 466 - 485, doi: 10.2478/johh-2024-0021
Scientific Paper, English

Jakub Jeřábek, Petr Kavka: Sensitivity and uncertainty analysis of a surface runoff model using ensemble of artificial rainfall experiments

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• Surface runoff models are essential for designing water and soil protection measures. However, they often exhibit uncertainty in both parameterization and results. Typically, uncertainty is evaluated by comparing model realizations with measured data. However, this approach is constrained by limited data availability, preventing comprehensive uncertainty assessment. To overcome this limitation, we employed the generalized likelihood uncertainty estimation (GLUE) methodology to conduct sensitivity and uncertainty analyses on a series of surface runoff models. These models were based on an ensemble of artificial rainfall experiments comprising 77 scenarios with similar settings. We utilized the rainfall-runoff-erosion model SMODERP2D to simulate the experiments and employed Differential Evolution, a heuristic optimization method, to generate sets of behavioural models for each experiment. Additionally, we evaluated the sensitivity and uncertainty with respect to two variables; water level and surface runoff. Our results indicate similar sensitivity of water level and surface runoff to most parameters, with a generally high equifinality. The ensemble of models revealed high uncertainty in bare soil models, especially under dry initial soil water conditions where the lag time for runoff onset was the largest (e.g. runoff coefficient ranged between 0–0.8). Conversely, models with wet initial soil water conditions exhibited lower uncertainty compared to those with dry initial soil water content (e.g. runoff coefficient ranged between 0.6 – 1). Models with crop cover showed a multimodal distribution in water flow and volume, possibly due to variations in crop type and growth stages. Therefore, distinguishing these crop properties could reduce uncertainty. Utilizing an ensemble of models for sensitivity and uncertainty analysis demonstrated its potential in identifying sources of uncertainty, thereby enhancing the robustness and generalizability of such analyses.
  
  KEY WORDS: Surface runoff model; Uncertainty analysis; Sensitivity analysis; GLUE; Model ensemble.
  
  Address:
  - Jakub Jeřábek, The Department of Landscape Water Conservation, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7/2077, 166 29 Praha 6 – Dejvice, Czech Republic. (Corresponding author. Tel.:+420224354570 Fax.: Email: jakub.jerabek@fsv.cvut.cz)
  - Petr Kavka, The Department of Landscape Water Conservation, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7/2077, 166 29 Praha 6 – Dejvice, Czech Republic.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 486 - 498, doi: 10.2478/johh-2024-0030
Scientific Paper, English

Veronika Bačová Mitková, Pavla Pekárová, Dana Halmová, Pavol Miklánek, Igor Leščešen: Long-term analysis of changes in seasonal and maximum discharges of Slovak rivers in the period 1931–2020

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• Central Europe and other parts of the world have experienced numerous extreme floods and prolonged periods of very low water discharges. With the increasing length and availability of hydrological data time series, it is now possible to analyse a larger volume of data. This paper presents long-term of changes in seasonal and maximum discharges. This paper aims to comprehensively assess the hydrological regime changes of Slovak rivers, using data from 26 gauging stations based on 90 years of observation. The study’s first part explores monthly flow changes within each year for selected Slovak rivers. The second part identifies changes in the maximum daily discharges, their long-term trends, and their occurrences. Additionally, we have compared the variability of the hydrological regime of the Slovak rivers with the variability of the hydrological regime of selected gauging stations on the Danube River and its tributaries, such as the Drava, Sajó, and Tisa rivers, to understand broader regional patterns. The findings show that the rivers selected exhibit relatively high intra-annual runoff variability, with various changes in the runoff regime curve based on the long-term monthly Pardé coefficient. For the Slovak region, maximum annual runoff variability is observed in the Krupinica and Plašťovce rivers (reaching a maximum of 12.1 during the period 1930–1960), while minimum annual runoff variability is observed in the Biely Váh River (2.205 for the period 1930–1960). The long-term trend analysis of the Burn index time series for maximum daily discharges over the entire period from 1930/31 to 2019/20, as well as the significance of trends during the summer-autumn and winter-spring seasons, shows that stations exhibited decreasing, stable, or increasing trends. The most significant increasing trend was observed at sixteen of the stations analyzed: at seventeen stations during the summer-autumn season and at nine stations during the winter-spring season over the period from 1930/31 to 2019/20.
  
  KEY WORDS: Slovak river basins; Hydrological regime; Climate change; Seasonality; T-year maximum daily discharge; Frequency distribution.
  
  Address:
  - Veronika Bačová Mitková, Institute of Hydrology SAS, Dúbravska cesta 9, 841 04 Bratislava, Slovak Republic. (Corresponding author. Tel.: Fax.: Email: mitkova@uh.savba.sk)
  - Pavla Pekárová, Institute of Hydrology SAS, Dúbravska cesta 9, 841 04 Bratislava, Slovak Republic.
  - Dana Halmová, Institute of Hydrology SAS, Dúbravska cesta 9, 841 04 Bratislava, Slovak Republic.
  - Pavol Miklánek, Institute of Hydrology SAS, Dúbravska cesta 9, 841 04 Bratislava, Slovak Republic.
  - Igor Leščešen, Department of Geography, Tourism and Hotel Management, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obarovića 3a, 21000 Novi Sad, Serbia.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 499 - 512, doi: 10.2478/johh-2024-0025
Scientific Paper, English

Milan Onderka, Jozef Pecho, Ján Szolgay, Silvia Kohnová, Marcel Garaj, Katarína Mikulová, Svetlana Varšová, Veronika Lukasová, Roman Výleta, Agnieszka Rutkowska: Applying a time-varying GEV distribution to correct bias in rainfall quantiles derived from regional climate models

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• Climate warming is causing an increase in extreme hydrometeorological events in most parts of the world. This phenomenon is expected to continue and will affect the frequency and intensity of extreme precipitation events. Although bias correction in regional climate model simulations has also been used to assess changes in precipitation extremes at daily and longer time steps, trends in the series predicted have seldom been considered. We present a novel bias correction technique that allows for the correcting of biases in the upper tails of the Generalized Extreme Value (GEV) distribution, while preserving the trend in projected precipitation extremes. The concept of non-stationary bias correction is demonstrated in a case study in which we used four EURO-CORDEX RCM models to estimate future rainfall quantiles. Historical observations have been used to correct biases in historical runs of the RCMs. The mean relative change in rainfall quantiles between the 1991–2021 historical period and the time horizon of 2080 was found to be 13.5% (st. dev.: 2.9%) for the return period of 2 years, which tends to decline with increasing return periods. Upon the return periods of 50 and 100 years, the mean relative change was predicted to be 5.5% (st. dev.: 1.1%) and 4.8% (st. dev.: 1%), respectively.
  
  KEY WORDS: Non-stationarity; Climate change; Trends; Bias correction; GEV distribution.
  
  Address:
  - Milan Onderka, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia. Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: milan.onderka@shmu.sk)
  - Jozef Pecho, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia. Department of Astronomy, Physics of the Earth and Meteorology, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynská dolina F2, 842 48 Bratislava, Slovakia.
  - Ján Szolgay, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Silvia Kohnová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Marcel Garaj, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia.
  - Katarína Mikulová, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia.
  - Svetlana Varšová, Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia.
  - Veronika Lukasová, Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia.
  - Roman Výleta, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Agnieszka Rutkowska, Department of Applied Mathematics, Faculty of Environmental Engineering and Land Surveying, University of Agriculture in Kraków, Balicka 253C, Kraków, Poland.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 513 - 521, doi: 10.2478/johh-2024-0023
Scientific Paper, English

Viera Rattayová, Marcel Garaj, Juraj Parajka, Kamila Hlavčová: Regional calibration of the Hargreaves model for estimation of reference evapotranspiration

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• Estimation of reference evapotranspiration values is crucial in climatological and hydrological research, agricultural engineering, and irrigation design. The Penman-Monteith method, endorsed by the Food and Agriculture Organization (FAO) of the United Nations and numerous research studies, is widely regarded as the gold standard. However, its extensive data requirements limit its applicability in regions with sparse meteorological networks or limited measurement capabilities. The Hargreaves method, which requires only basic air temperature inputs, offers an alternative solution. The aims of this study were to calibrate the Hargreaves model for Central European climate conditions, considering altitudinal dependence, and to evaluate the temporal stability of the model parameters. In the first part of the research, we regionalized the Hargreaves coefficients using a curve-fitting method to ensure the best accuracy across 60 climatological stations in Slovakia. The regionalization of the Hargreaves coefficient improved accuracy by 10.1%, reducing the weighted absolute percentage error (WAPE) to 17.9%. However, our results showed that the accuracy of the modified Hargreaves model decreased with the increasing altitude of a climatological station. Incorporating altitude into the Hargreaves equation significantly improved model accuracy in stations at higher altitudes, providing a consistent level of accuracy across all climatological stations, regardless of their location and altitude. The results also indicated that the optimal model coefficient values change over time, showing a decreasing trend of –0.5 for the B coefficient and –0.1 for the C coefficient between the periods 1981–2000 and 2001–2020. Although regionalizing the Hargreaves model coefficients for local conditions can achieve good model performance, the model's accuracy is not stable over time. Thus, periodic validation of the model is necessary for short-term applications.
  
  KEY WORDS: Reference evapotranspiration; Hargreaves equation; Temporal stability of model parameters.
  
  Address:
  - Viera Rattayová, Slovak Hydrometeorological Institute, Climatological Service Department, Jeséniova 17, 833 15 Bratislava, Slovakia. Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Marcel Garaj, Slovak Hydrometeorological Institute, Climatological Service Department, Jeséniova 17, 833 15 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: Marcel.Garaj@shmu.sk)
  - Juraj Parajka, Institute of Hydraulic Engineering and Water Resources Management, Technische Universität Wien, Vienna, 1040, Austria.
  - Kamila Hlavčová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 810 05 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 522 - 537, doi: 10.2478/johh-2024-0029
Scientific Paper, English

Guowei Li, Jueyi Sui, Sanaz Sediqi: Turbulent flow structure around a single submerged angled spur dike under ice cover

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• This experimental study examines the velocity fields around the single submerged spur dike in a large-scale flume under three flow conditions: open channel, smooth ice-covered, and rough ice-covered. The effects of dike orientation were investigated for alignment angles of 90°, 120°, and 135°. Instantaneous three-dimensional velocity components were recorded using an acoustic Doppler velocimeter. Results show that the spur dikes generate distinct transverse flow regions in the streamwise, lateral, and vertical directions. Alignment angles greater than 90° reduced streamwise velocity near the dikes, while the frontal surface of the dike tip exhibited increased velocity magnitudes. Downstream, significant variations in Reynolds shear stress were observed, driven by flow separation and the formation of a recirculation wake zone. Quadrant analysis revealed that under ice-covered conditions, turbulent interactions near the dike tip were dominated by ejection and sweep events, whereas sweep events were more prevalent in open channel flows, influencing overall flow dynamics.
  
  KEY WORDS: Flow field; Ice cover; Orientation angle; Quadrant analysis; Spur dike.
  
  Address:
  - Guowei Li, School of Engineering, University of Northern British Columbia, Prince George, British Columbia, Canada, V2N 4Z9.
  - Jueyi Sui, School of Engineering, University of Northern British Columbia, Prince George, British Columbia, Canada, V2N 4Z9. (Corresponding author. Tel.:+1-250-960-6399 Fax.: Email: jueyi.sui@unbc.ca)
  - Sanaz Sediqi, School of Engineering, University of Northern British Columbia, Prince George, British Columbia, Canada, V2N 4Z9.

J. Hydrol. Hydromech., Vol. 72, No. 4, 2024, p. 538 - 546, doi: 10.2478/johh-2024-0022
Scientific Paper, English

Romuald Szymkiewicz: A simplified approach for simulating pollutant transport in small rivers with dead zones using convolution

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• In the paper an alternative method to solve the one-dimensional advective-diffusive equation describing the pollutants transport in river with dead zones is presented. Because very often transport in a small river can be treated as a 1D issue, then instead of numerical solution of the advection-diffusion equation an equivalent approach based on the convolution technique can be used. Consequently, for a given impulse response function the numerical calculations are required to compute a convolution only. The impulse response function is obtained as an analytical solution of the linear advection-diffusion equation for the Dirac delta function imposed as the boundary condition at the upstream end. Therefore, it represents the Gauss distribution and consequently, this approach is unreliable when the dead zones occur. To reproduce an asymmetric distribution of concentration along the channel axis an approximation of analytical impulse response function using the asymmetric Gumbel distribution is proposed. This approach valid for solution of the transport equation with constant coefficients is extended for piecewise constant coefficients. Convolution approach does not produce any numerical dissipation and dispersion errors typically generated by the methods based on the finite difference technique. Validation of the method using the results of field measurements confirmed its effectiveness.
  
  KEY WORDS: 1D pollution transport; Dead zones; Convolution; Impulse response function.
  
  Address:
  - Romuald Szymkiewicz, Institute of Hydro-Engineering, Polish Academy of Sciences, ul. Kościerska 7, 80-328 Gdańsk, Poland. (Corresponding author. Tel.: Fax.: Email: r.szymkiewicz@ibwpan.gda.pl)