J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 221 - 230, doi: 10.2478/johh-2023-0020
Scientific Paper, English

Tammo S. Steenhuis, Telashwork C. Alemie, Habtamu Muche, Seifu A. Tilahun, Fasikaw A. Zimale, Demesew A. Mhiret: Effect of eucalyptus on blue and green water availability and discharge in the tropical highlands: An interpretation of available literature

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• The highlands serve as water towers for the blue water in the surrounding area, with often insufficient rainfall for rainfed crops. The population is growing in the highlands, changing the hydrology and blue and green water availability. One of the changes that affect the highlands of Ethiopia is the rapidly expanding areas of small patches of eucalyptus on farmers fields. This manuscript aims to sort through the limited available literature and develop a water balance model as a starting point to discuss how hydrology is affected by increased acreage of eucalyptus in the highlands. We find some evidence in the literature that patches of eucalyptus during the dry phase may withdraw water from the subsoil up to twice the rate of evapotranspiration when the soil water is not limited. Since saturation excess generates surface runoff in the subhumid and humid highlands, water withdrawn during the dry phase should be made up before the area with eucalyptus becomes hydraulically active. The amount of water that can be removed from storage by eucalyptus is greater in areas with a long dry monsoon phase than in temperate climates for the same increase in trees. We also found, as expected, that the eucalyptus water balance model, as developed in this paper, was not valid for areas in semi-arid and arid regions. Soil crusting and water repellency might induce infiltration excess runoff. A tentative implication is that since most blue water is produced in the areas with the highest rainfall, eucalyptus in subhumid and humid monsoon regions will affect the blue water supply downstream but not the plant available green water although shading will decrease yield in the immediate surroundings of the eucalyptus trees.
  
  KEY WORDS: Monsoon; Mountainous watersheds; Saturation excess runoff; Reforestation; Afforestation; Water balance; Streamflow; Ethiopia.
  
  Address:
  - Tammo S. Steenhuis, Department of Biological and Environmental Engineering, Cornell University Ithaca NY 14853, USA. Faculty of Civil and Water Resources Engineering, Bahir Dar Insitute of Technology, Bahir Dar University, Bahir Dar, Ethiopia. (Corresponding author. Tel.:+1 607 255 2489 Fax.: Email: tss1@cornell.edu)
  - Telashwork C. Alemie, Department of Soil and Water Management, Amhara Regional Agricultural Research Institute, Bahir Dar, Ethiopia.
  - Habtamu Muche, Faculty of Civil and Water Resources Engineering, Bahir Dar Insitute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Seifu A. Tilahun, Faculty of Civil and Water Resources Engineering, Bahir Dar Insitute of Technology, Bahir Dar University, Bahir Dar, Ethiopia. International Water Management Institute, Accra, Ghana.
  - Fasikaw A. Zimale, Faculty of Civil and Water Resources Engineering, Bahir Dar Insitute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Demesew A. Mhiret, Faculty of Civil and Water Resources Engineering, Bahir Dar Insitute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 231 - 247, doi: 10.2478/johh-2023-0003
Scientific Paper, English

Y. Ogulcan Dogan, A. Arda Şorman, Aynur Şensoy: Multi-criteria evaluation for parameter uncertainty assessment and ensemble runoff forecasting in a snow-dominated basin

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• The increase in global temperatures undesirably affects the ever-growing world population and reveals the significance of hydrology science. Hydrological models might estimate spatial and temporal variability in hydrological components at the basin scale, which is critical for efficient water resource management. Satellite data sets with enhanced snow mapping with high spatial and temporal resolutions have been developed. The potential of these satellite data sets is evaluated in this study for multi-criteria evaluation of a conceptual hydrological model to improve model performance and reduce uncertainty. The upstream part of the transboundary Coruh River is selected for this study because snowmelt contributes a significant portion of the streamflow feeding major reservoirs during the spring and early summer months. The region’s snow cover dynamic has been analyzed using a combination of two satellite products. Hydrologic modeling is performed using the HBV model for the 2003–2015 water years (01 Oct–30 Sep). The Monte Carlo method is used for multi-criteria optimization exploiting satellite snow cover data besides runoff data. The sensitivity and uncertainty analysis on the model parameters indicate that multi-criteria calibration effectively reduces the uncertainty of the parameters and increases the model performance. Moreover, ensemble runoff forecasts are generated with several best model parameters using 1-day and 2-day lead time numerical weather prediction data for the snowmelt period (March–June) of the 2015 water year. The results indicate that the use of multiple remote sensing products in combination better represents the snow-covered area for the region. Additionally, including these data sets into hydrological models enhances the representation of hydrological components while reducing runoff prediction uncertainty.
  
  KEY WORDS: Snow cover; Multi-criteria calibration; Uncertainty; Runoff forecast; Coruh basin.
  
  Address:
  - Y. Ogulcan Dogan, Department of Civil Engineering, Faculty of Engineering, Eskişehir Technical University, 26555, Eskişehir, Turkey.
  - A. Arda Şorman, Department of Civil Engineering, Faculty of Engineering, Eskişehir Technical University, 26555, Eskişehir, Turkey.
  - Aynur Şensoy, Department of Civil Engineering, Faculty of Engineering, Eskişehir Technical University, 26555, Eskişehir, Turkey. (Corresponding author. Tel.:+902222138154 Fax.: Email: asensoy@eskisehir.edu.tr)

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 248 - 258, doi: 10.2478/johh-2023-0018
Scientific Paper, English

Ladislav Holko, George Melikadze, Mariam Todadze, Ramaz Chitanava, Aleksandre Chankvetadze, Tornike Chikadze, Alexander Gventsadze, Merab Gaphrindashvili: Stable isotopes of oxygen and hydrogen in precipitation and river water in Georgia

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• The article presents the first comprehensive evaluation of the isotopic composition of precipitation and runoff in Georgia. It is based on data from the monitoring of δ18O and δ2H in monthly precipitation at eleven precipitation stations and monthly runoff from five large, mostly nested catchments in Georgia, collected between the years 2013 and 2022. The data represent different climatic and altitudinal conditions ranging from the wet western part of Georgia affected by the Black Sea to the dry eastern part of the county presumably affected also by the air masses from the Caspian Sea. Specific conditions affecting the isotopic composition of precipitation and river water seem to occur close to the main ridge of the Greater Caucasus Mountains. We defined the National Meteoric Water Line (NMWL) and the National River Water Line (NRWL) for Georgia as well as the Local Meteoric Water Lines (LMWLs) and River Water Lines (RWLs) for individual precipitation stations and river gauges and investigated their slopes and intercepts. Altitude gradients of δ18O and δ2H in the rivers were similar to those in precipitation (–0.16‰ and –1.2‰ per 100 m of altitude for δ18O and δ2H, respectively). The rivers were supplied from precipitation of the colder part of the year (November/December to March/April) while the isotopic composition of precipitation in the remaining warmer part of the year was clearly detached from that of the rivers. The isotopic signal in precipitation was dampened in the rivers by a factor of 5–6. The scaled line-conditioned excess (lc-excess*) did not indicate any significant deviations of river waters from meteorological conditions in the catchments.
  
  KEY WORDS: GNIP; GNIR; Caucasus Mountains; Hydrological cycle.
  
  Address:
  - Ladislav Holko, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - George Melikadze, M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, Aleksidze 1, 0160 Tbilisi, Georgia. (Corresponding author. Tel.: Fax.: Email: melikadze@gmail.com)
  - Mariam Todadze, M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, Aleksidze 1, 0160 Tbilisi, Georgia.
  - Ramaz Chitanava, National Environmental Agency of Georgia, Marshall Gelovani 34, 0159 Tbilisi, Georgia.
  - Aleksandre Chankvetadze, M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, Aleksidze 1, 0160 Tbilisi, Georgia.
  - Tornike Chikadze, M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, Aleksidze 1, 0160 Tbilisi, Georgia.
  - Alexander Gventsadze, M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, Aleksidze 1, 0160 Tbilisi, Georgia.
  - Merab Gaphrindashvili, National Environmental Agency of Georgia, Marshall Gelovani 34, 0159 Tbilisi, Georgia.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 259 - 270, doi: 10.2478/johh-2023-0019
Scientific Paper, English

Ponselvi Jeevaragagam, Slobodan P. Simonovic: Output updating of a physically based model for gauged and ungauged sites of the Upper Thames River watershed

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• This study introduces a new ANN updating procedure of streamflow prediction for a physically based HECHMS hydrological model of the Upper Thames River watershed (Ontario, Canada). Besides streamflow and precipitation, the updating procedure uses other meteorological variables as inputs, which are not applied in calibration of the HECHMS model. All the results of performance measures on training, validation and test datasets for river gauges at Mitchell and Stratford revealed that the ANN updated models have performed better than the HEC-HMS model. The ANN model results were in excellent agreement with observed streamflow. The uncertainties can be associated with different input variables and different length of datasets used in the HEC-HMS model and the ANN model. The performance results suggest improvement in the RMSE values of the trained networks when additional meteorological data was used. The updated errors from the gauged sites of Mitchell and Stratford were used to update the streamflow values at the ungauged site of JR750 of the HEC-HMS model. While the underlying physical process in the ANN model consisting of interconnected neurons to map input-output relationships is not easily understood (in a form of mathematical equation), the HEC-HMS hydrological model can reveal useful information about the parameters of a hydrological process.
  
  KEY WORDS: Neural network; Bayesian; Hydrometeorology; Hydrological model; HEC-HMS.
  
  Address:
  - Ponselvi Jeevaragagam, Department of Water and Environmental Engineering, Faculty of Civil Engineering, Universiti Teknologi Malaysia (UTM), 81310 Johor Bahru, Johor, Malaysia. (Corresponding author. Tel.:+6019-7604923 Fax.: Email: ponselvi@utm.my)
  - Slobodan P. Simonovic, Department of Civil and Environmental Engineering, University of Western Ontario, Spencer Engineering Building, London, Ontario N6A 5B9, Canada.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 271 - 282, doi: 10.2478/johh-2023-0017
Scientific Paper, English

Sergiy Snizhko, Miriam Bertola, Valeriya Ovcharuk, Olga Shevchenko, Iulii Didovets, Günter Blöschl: Climate impact on flood changes – an Austrian-Ukrainian comparison

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• This study compares the flood regime of rivers in Ukraine and Austria over the last decades. We used data from mountain and lowland watersheds, where floods are caused by different processes. In order to identify possible shifts in the day of occurrence of annual flood maxima, we apply the kernel density method to the time series of two subperiods (1960–1987 and 1988–2015). We use the Mann Kendall test at a 5% significance level to identify significant positive or negative trends in the series of annual maximum discharges. In Austria, we observe an increasing trend in summer floods associated with increasing precipitation. In the lowland areas of Ukraine, a clear reduction in spring floods is observed, linked to shallower snow packs in a warming climate. In the Ukrainian Carpathians, on the other hand, where floods occur throughout the year, an increase in the portion of liquid precipitation during the cold period of the year leads to earlier floods and an increase in the probability of flooding in winter.
  
  KEY WORDS: Timing of floods; Seasonality; Circular kernel density histograms; Trends in flood magnitude, Climate change.
  
  Address:
  - Sergiy Snizhko, Department of Meteorology and Climatology, Taras Shevchenko National University of Kyiv, Volodymyrska Str. 60, Kyiv, Ukraine. Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, Vienna, Austria. (Corresponding author. Tel.:+38 0674911110 Fax.: Email: snizhko@knu.ua)
  - Miriam Bertola, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, Vienna, Austria.
  - Valeriya Ovcharuk, Hydrometeorological Institute, Odesa State Environmental University, Lvivska Str. 15, Odesa, Ukraine.
  - Olga Shevchenko, Department of Meteorology and Climatology, Taras Shevchenko National University of Kyiv, Volodymyrska Str. 60, Kyiv, Ukraine.
  - Iulii Didovets, Department of Climate Resilience, Potsdam Institute for Climate Impact Research, Telegrafenberg A 31, Potsdam, Germany.
  - Günter Blöschl, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, Vienna, Austria.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 283 - 292, doi: 10.2478/johh-2023-0015
Scientific Paper, English

Viktor Vyshnevskyi, Serhii Shevchuk: Thermal regime of the Danube Delta and the adjacent lakes

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• The Danube Delta is a unique natural object influenced by natural and human factors. According to the available observation and remote sensing data, the features of the water temperature in the Danube Delta, as well as in nearby lakes and the adjacent area of the Black Sea, have been determined. The water temperature in the Danube River was found to be much higher than the air temperature, especially in autumn. Generally, it is also higher than in nearby lakes and the adjacent part of the Black Sea. During 1961–2021 the mean annual water temperature in the Danube Delta increased significantly, especially during the last three decades. It has been determined that water temperature is affected not only by air temperature, but also by water discharge and wind. With a large water discharge the mixing of water is intensified and it causes the decrease of surface water temperature during the main part of the year with the exception of the coldest months. The greatest impact of water discharge on the water temperature is observed in June. The cool breeze in summer months also has some effect on the surface water temperature of the river near the seashore. The results show the potential of remote sensing to track the changes of water temperature along the river and to identify the shallow sections.
  
  KEY WORDS: Danube River; Delta; Danube lakes; Water temperature; Wind; Remote sensing.
  
  Address:
  - Viktor Vyshnevskyi, National Aviation University, Liubomyra Huzara Ave., 1, Kyiv, 03058, Ukraine. (Corresponding author. Tel.: Fax.: Email: vishnev.v@gmail.com)
  - Serhii Shevchuk, ?entral Geophysical Observatory, Nauky Ave., 39/2, Kyiv, 03028, Ukraine.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 293 - 304, doi: 10.2478/johh-2023-0016
Scientific Paper, English

Akash Datta, Ratul Das, Mrinmoy Majumder: Influence of boulder array on the near-bed turbulent flow characteristics in a gravel bed stream - An experimental investigation

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• The present study aims to focus the turbulent flow characteristics over arrays of submerged boulders in a gravel bed stream. Round shaped boulders of diameter, Dc = 6 cm were staggered over a gravel bed stream (d50 = 4 cm) with varying boulder-to-boulder spacing and the flows over the arrays were studied experimentally. The flow measurements were carried out by an acoustic Doppler velocimeter and the double averaging methodology (DAM) was applied. The results of large spacing boulder array reveals near-bed velocity deficit within 1Dc upstream to 5Dc downstream of the boulder and no influence on the approaching velocity was observed after 5Dc corroborating the recovery of boundary layer. In case of medium and small spacing boulder array, the velocity deficit is significant at all locations. The shear stress distributions depict development of high and low bed shear stresses causing redistributions of the local bed shear stress. The higher magnitude of shear stress is observed at the boulder crest whereas; the secondary peak near the gravel bed crest is attributed to the skin shear stress on the individual boulder. Moreover, the present research contributes to our understanding that the boulder array on a rough bed stream leads to higher turbulent intensity at the boulder crest level.
  
  KEY WORDS: Boulder array; Shear stress; Velocity distributions; Turbulent intensity.
  
  Address:
  - Akash Datta, Civil Engineering Department, National Institute of Technology Agartala, Agartala-799046, India. (Corresponding author. Tel.:+91 8257921309 Fax.: Email: akash.oshanien@gmail.com)
  - Ratul Das, Civil Engineering Department, National Institute of Technology Agartala, Agartala-799046, India.
  - Mrinmoy Majumder, Civil Engineering Department, National Institute of Technology Agartala, Agartala-799046, India.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 305 - 315, doi: 10.2478/johh-2023-0005
Scientific Paper, English

Ibrahim Rahou, Khaled Korichi: Comparative analysis of numerical solutions of 2D unsteady dambreak waves using FVM and SPH method

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• This work presents a comparison of two-dimensional numerical solutions of unsteady free surface flow. This is a simulation of the dam-break wave with different configurations using based-mesh finite volume method and meshless smoothed particle hydrodynamics (SPH). Two well-known approaches, widely used in the computational fluid dynamics (CFD). These techniques have proven their robustness in the numerical treatment of such conservation laws. The main goal is to check the ability of the SPH method and the first order finite volume HLLC solver to reproduce the numerical solutions of the 2D shallow water equations. Based on many benchmark tests, one investigates the effect of the topographic variation along the x and y directions on behavior of the numerical solutions namely at the wet-dry front. The comparison between the simulated results, the analytical solutions and the experimental measurements shows a good correlation, although the finite volume approach remains more advantageous in terms of accuracy and the CPU time.
  
  KEY WORDS: 2D shallow water; Unsteady flow; Dambreak; Finite volume; SPH; Experimental measurements.
  
  Address:
  - Ibrahim Rahou, Civil Engineering and Environment Laboratory, Faculty of Technology, Djillali Liabes University of Sidi Bel Abbes, Bp 89 Sidi Bel Abbes 22000, Algeria.
  - Khaled Korichi, Civil Engineering and Environment Laboratory, Faculty of Technology, Djillali Liabes University of Sidi Bel Abbes, Bp 89 Sidi Bel Abbes 22000, Algeria. (Corresponding author. Tel.: Fax.: Email: kh.korichi@gmail.com)

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 316 - 330, doi: 10.2478/johh-2023-0022
Scientific Paper, English

Jaromír Říha, Tomáš Julínek, Stanislav Kotaška: Simplified dispersion analysis based on dye tests at a small stream

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• The modelling of solid transport in open channels requires good knowledge about parameters related to basic processes such as hydrodynamic dispersion, advection and decay rates. Such parameters are usually determined by dye tests. Numerous tracer studies have been performed on laboratory flumes and natural rivers. However, on-site sampling is often difficult, expensive and needs special apparatus. The main aim of the study was to justify simplified method based on the monitoring of the dye cloud shape in order to determine both longitudinal and transversal dispersion coefficients. In this study, four dye tests were carried out on a small local stream (the Lipkovsky) using Rhodamine WT fluorescein dye as a tracer. The tests were carried out in such a manner that both longitudinal and horizontal transversal dispersion data were obtained. For this purpose, the visually determined extent of the dye cloud was interpreted via the analytical solution of the advection-dispersion equation. The results obtained by this simplified approach indicated that the longitudinal dispersion coefficient Dx = 0.051–0.057 m2/s and the coefficient of horizontal transversal dispersion Dy = 0.00024–0.00027 m2/s. The method was justified by corresponding root mean square error (RMSE) counting RMSE = 0.65–1.02 m for the dye cloud centre, RMSE = 1.87–2.46 m for the head and tail of the cloud and RMSE = 0.025–0.11 m for the cloud width, the Nash-Sutcliffe efficiency coefficients ranged from 0.9 to 0.998. The comparison of these values with empirical formulae and other tracer studies indicated significant overestimation of the mentioned values of Dx, which can be attributed to the uniform velocity distribution along the width of Lipkovsky Stream. Much better agreement was achieved for Dy.
  
  KEY WORDS: Water quality modelling; 2D river mixing; Dye test; Longitudinal and transversal dispersion coefficient.
  
  Address:
  - Jaromír Říha, Brno University of Technology, Faculty of Civil Engineering, Institute of Water Structures, Veveri 95, 602 00 Brno, Czech Republic. (Corresponding author. Tel.: Fax.: Email: riha.j@fce.vutbr.cz)
  - Tomáš Julínek, Brno University of Technology, Faculty of Civil Engineering, Institute of Water Structures, Veveri 95, 602 00 Brno, Czech Republic.
  - Stanislav Kotaška, Brno University of Technology, Faculty of Civil Engineering, Institute of Water Structures, Veveri 95, 602 00 Brno, Czech Republic.

J. Hydrol. Hydromech., Vol. 71, No. 3, 2023, p. 331 - 340, doi: 10.2478/johh-2023-0021
Scientific Paper, English

Lukáš Svoboda, Tomáš Picek, Václav Matoušek: Camera-measured velocity distribution in laboratory open-channel flow with intense transport of bimodal combined-load

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• An extended stereoscopic method, which identifies, and tracks particles based on their colour in solid-liquid flow, is tested for its capability to separately measure velocity distributions of particles of two fractions transported as bimodal sediment mixture in water flow through a laboratory flume. The principle of the tested method extension is a use of colour-based processing of images collected by two high-speed cameras which enables to filter out particles of one fraction from the image and leave particles of the other fraction in the image based on a selected colour hue range. The modified images are then processed by the original stereoscopic method to produce velocity distribution of particles of the individual fraction in the flow. The method extension is first tested in simple vertical flow carrying neutrally buoyant spherical particles of two distinct colours in a recirculation cell. In the next step, lightweight plastic particles of two fractions of different properties (size, shape, density) and colours are introduced to flow through a laboratory flume and velocity distributions of the two fractions are measured separately at flow conditions which mimic intense transport of bimodal combined-load in an open channel. Results exhibit a very good agreement with previous measurements with unimodal sediment in hydraulically similar flow.
  
  KEY WORDS: Solid-liquid flow; Stereoscopic method; High-speed cameras; Particle tracking; Lightweight sediment; Tilting flume experiment.
  
  Address:
  - Lukáš Svoboda, Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, Czech Republic. (Corresponding author. Tel.: Fax.: Email: lukas.svoboda.2@fsv.cvut.cz)
  - Tomáš Picek, Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, Czech Republic.
  - Václav Matoušek, Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, Czech Republic.