J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 169 - 176, doi: 10.2478/johh-2014-0027
Scientific Paper, English

Miriam Fendeková, Pavla Pekárová, Marián Fendek, Ján Pekár, Peter Škoda: Global drivers effect in multi-annual variability of runoff

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• Changes in runoff parameters are very important for Slovakia, where stream-flow discharges, being supplied by precipitation and groundwater runoff, are preferentially influenced by climatic conditions. Therefore, teleconnections between runoff parameters, climate parameters and global atmospheric drivers such as North Atlantic Oscillation, Southern Pacific Oscillation, Quasi-biennial oscillation and solar activity were studied in the Nitra River Basin, Slovakia. Research was mostly based on records of 80 years (1931–2010) for discharges and baseflow, and 34 years for groundwater heads. Methods of autocorrelation, spectral analysis, cross-correlation and coherence function were used. Results of auto-correllograms for discharges, groundwater heads and base flow values showed a very distinct 11-year and 21-year periodicity. Spectrogram analysis documented the 11-year, 7.8-year, 3.6-year and 2.4-year periods in the discharge, precipitation and air temperature time series. The same cycles except of 11-years were also identified in the long-term series of the North Atlantic Oscillation and Southern Pacific Oscillation indices. The cycle from approximately 2.3 to 2.4-years is most likely connected with Quasi-biennial oscillation. The close negative correlation between the North Atlantic Oscillation winter index and the hydrological surface and groundwater parameters can be used for their prediction within the same year and also for one year in advance.
  
  KEY WORDS: Runoff variability; Global climatic drivers; Inter-relationships; Nitra River Basin; Slovakia.
  
  Address:
  - Miriam Fendeková, Department of Hydrogeology, Faculty of Natural Sciences of Comenius University in Bratislava, Pav. G, Mlynska dolina, 842 15 Bratislava 4, Slovakia. (Corresponding author. Tel.: Fax.: Email: fendekova@fns.uniba.sk)
  - Pavla Pekárová, Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava 3, Slovakia.
  - Marián Fendek, Department of Hydrogeology, Faculty of Natural Sciences of Comenius University in Bratislava, Pav. G, Mlynska dolina, 842 15 Bratislava 4, Slovakia.
  - Ján Pekár, Department of Applied Mathematics and Statistics, Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48 Bratislava, Slovakia.
  - Peter Škoda, Slovak Hydrometeorological Institute, Jeseniova 17, 833 15 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 177 - 185, doi: 10.2478/johh-2014-0030
Scientific Paper, English

Márta Koczka Bara, Yvetta Velísková, Renáta Dulovičová, Radoslav Schügerl: Influence of surface water level fluctuation and riverbed sediment deposits on groundwater regime

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• The spatial and temporal patterns of surface water (SW) – groundwater (GW) exchange are significantly affected by riverbed silting, clogging or erosion processes, by altering the thickness and hydraulic conductivity of riverbed sediments. The duration of SW-GW exchange is controlled by the drainage and infiltration resistance of river bottom sediments (e.g. Andrássy et al., 2012). Generally, these two parameters primarily depend on the hydraulic conductivity and on the thickness of clogged layer. In this study the flow processes between GW and SW were modeled by model TRIWACO for different infiltration resistance and drainage resistance of riverbed sediments. The model area is situated on the Rye Island, which is a lowland area with very low slope. In this area a channel network was built up, where the flow conditions are controlled by water-gates. Because of the low slope and the system of water gates built on the channels, the riverbeds are influenced by intensive clogging processes. First, the applicability of model TRIWACO in the study area was tested by modelling the response of GW on SW level fluctuation. It was simulated, how the regulation of water level and flow direction in the channels influence the GW level, especially in extreme hydrological conditions (drought/flood), and if the GW flow direction and GW level change as it was expected. Next, the influence of channel network silting up on GW-SW interaction was modeled. The thickness of riverbed sediments was measured and their hydraulic conductivity from disturbed sediment samples was evaluated. The assessed hydraulic conductivity was used to calculate the infiltration resistance and the drainage resistance of riverbed sediments in the study area. Then, the GW level and flow direction was simulated for different infiltration resistance and drainage resistance of sediments.
  
  KEY WORDS: Surface water – groundwater interaction; Groundwater flow modelling; Infiltration/drainage resistance of rivers.
  
  Address:
  - Márta Koczka Bara, Institute of Hydrology, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava, Slovak Republic.
  - Yvetta Velísková, Institute of Hydrology, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava, Slovak Republic. (Corresponding author. Tel.:+4212 49268255 Fax.: +4212 44259404 Email: veliskova@uh.savba.sk)
  - Renáta Dulovičová, Institute of Hydrology, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava, Slovak Republic.
  - Radoslav Schügerl, Institute of Hydrology, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava, Slovak Republic.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 186 - 196, doi: 10.2478/johh-2014-0026
Scientific Paper, English

Veronika Bačová Mitková, Dana Halmová: Joint modeling of flood peak discharges, volume and duration: a case study of the Danube River in Bratislava

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• The study is focused on the analysis and statistical evaluation of the joint probability of the occurrence of hy-drological variables such as peak discharge (Q), volume (V) and duration (t). In our case study, we focus on the bivariate statistical analysis of these hydrological variables of the Danube River in Bratislava gauging station, during the period of 1876–2013. The study presents the methodology of the bivariate statistical analysis, choice of appropriate marginal distributions and appropriate copula functions in representing the joint distribution. Finally, the joint return periods and conditional return periods for some hydrological pairs (Q-V, V-t, Q-t) were calculated. The approach using copulas can reproduce a wide range of correlation (nonlinear) frequently observed in hydrology. Results of this study provide comprehensive information about flood where a devastating effect may be increased in the case where its three basic components (or at least two of them) Q, V and t have the same significance.
  
  KEY WORDS: The Danube River; Joint distribution; Copula functions; Peak flow; Volume and duration of the wave; Multivariate frequency analysis.
  
  Address:
  - Veronika Bačová Mitková, Institute of Hydrology SAS, Račianska 75, 831 02 Bratislava, Slovakia. (Corresponding author. Tel.:+421249268242 Fax.: +421244259311 Email: mitkova@uh.savba.sk)
  - Dana Halmová, Institute of Hydrology SAS, Račianska 75, 831 02 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 197 - 208, doi: 10.2478/johh-2014-0025
Scientific Paper, English

Yeugeniy M. Gusev, Olga N. Nasonova: Application of a technique for scenario prediction of climate change impact on the water balance components of northern river basins

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• The scenario forecasting technique for assessing changes of water balance components of the northern river basins due to possible climate change was developed. Three IPCC global emission scenarios corresponding to different possible scenarios for economic, technological, political and demographic development of the human civilization in the 21st century were chosen for generating climate change projections by an ensemble of 16 General Circulation Models with a high spatial resolution. The projections representing increments of monthly values of meteorological characteristics were used for creating 3-hour meteorological time series up to 2063 for the Northern Dvina River basin, which belongs to the pan-Arctic basin and locates at the north of the European part of Russia. The obtained time series were applied as forcing data to drive the land surface model SWAP to simulate possible changes in the water balance components due to different scenarios of climate change for the Northern Dvina River basin.
  
  KEY WORDS: Water balance components; Climate change scenarios; Land surface – atmosphere interactions; Physically- based land surface modeling; Global data sets; Northern river basins.
  
  Address:
  - Yeugeniy M. Gusev, Institute of Water Problems, Russian Academy of Sciences, Gubkina St.3, 119333 Moscow, Russia. (Corresponding author. Tel.: Fax.: Email: sowaso@yandex.ru)
  - Olga N. Nasonova, Institute of Water Problems, Russian Academy of Sciences, Gubkina St.3, 119333 Moscow, Russia.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 209 - 217, doi: 10.2478/johh-2014-0029
Scientific Paper, English

Burak Turan, Keh-Han Wang: An object-oriented overland flow solver for watershed flood inundation predictions: case study of Ulus basin, Turkey

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• This paper presents an object-oriented two-dimensional (2-D) overland flow model and its application in simulating flood flows over Ulus basin, located in the north of Turkey adjacent to the Black Sea. A new coding implementation according to the class environment created in object oriented C++ programming language is carried out in structuring and building the solver. The model is based on the Godunov type finite volume scheme on unstructured triangular meshes. A mass balance preserving wet/dry boundary solution algorithm is integrated in the numerical scheme to satisfy the positive-depth condition and minimize the numerical instability when treating the propagation of wave front in regions of dry bed. The balance between bed slope and flux terms is also preserved for still water conditions on irregular topography. The 2-D solver is verified by simulating selected dam break cases, where good agreement with measured data is achieved. For the simulation of flood flows in the Ulus basin, in general, the simulated outflow hydrograph is found to compare well with the recorded data. A selected inundation map that is extracted from the model results is also presented to show the water surface level in the Floodplain.
  
  KEY WORDS: Flood inundation; Dam break; Finite volume; Wet/dry; Hydrograph; Object oriented programming.
  
  Address:
  - Burak Turan, Department of Civil and Environmental Engineering, University of Houston, Houston, TX, 77204-4003, USA. Current address: Emek 4, Cad. No:158/4, Cankaya, Ankara, Turkey.
  - Keh-Han Wang, Department of Civil and Environmental Engineering, University of Houston, Houston, TX, 77204-4003, USA. (Corresponding author. Tel.:1-713-743-4277 Fax.: 1-713-743-4260 Email: khwang@uh.edu)

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 218 - 225, doi: 10.2478/johh-2014-0024
Scientific Paper, English

Jinping Zhang, Zhihong Ding, Jinjun You: The joint probability distribution of runoff and sediment and its change characteristics with multi-time scales

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• River runoff and sediment transport are two related random hydrologic variables. The traditional statistical analysis method usually requires those two variables to be linearly correlated, and also have an identical marginal distribution. Therefore, it is difficult to know exactly the characteristics of the runoff and sediment in reality. For this reason, copulas are applied to construct the joint probability distribution of runoff and sediment in this article. The risk of synchronous-asynchronous encounter probability of annual rich-poor runoff and sediment is also studied. At last, the characteristics of annual runoff and sediment with multi-time scales in its joint probability distribution space are simulated by empirical mode decomposition method. The results show that the copula function can simulate the joint probability distribution of runoff and sediment of Huaxia hydrological station in Weihe River well, and that such joint probability distribution has very complex change characteristics at time scales.
  
  KEY WORDS: Runoff; Sediment; Joint probability distribution; Copula; Empirical mode decomposition method.
  
  Address:
  - Jinping Zhang, Institute of Water Resources and Environment, Zhengzhou University, High-tech District, No. 100 Science Road, Zhengzhou City, 450001, Henan Province, China. (Corresponding author. Tel.:+86-371-60119629 Fax.: Email: jinping2000_zh@163.com)
  - Zhihong Ding, Haihe River Water Conservancy Commission, Tianjin, 300072, China.
  - Jinjun You, State Key Laboratory of Hydrologic Cycle Simulation and Regulation, China Institute of Water Resources & Hydropower Research, Beijing, 100038, China.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 226 - 233, doi: 10.2478/johh-2014-0031
Scientific Paper, English

Wojciech Artichowicz, Romuald Szymkiewicz: Computational issues of solving the 1D steady gradually varied flow equation

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• In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.
  
  KEY WORDS: Steady gradually varied flow; Differential equations; Initial value problem.
  
  Address:
  - Wojciech Artichowicz, Faculty of Civil and Environmental Engineering, Gdansk University of Technology, 80-233 Gdansk, Poland. (Corresponding author. Tel.: Fax.: Email: wojartic@pg.gda.pl)
  - Romuald Szymkiewicz, Faculty of Civil and Environmental Engineering, Gdansk University of Technology, 80-233 Gdansk, Poland.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 234 - 240, doi: 10.2478/johh-2014-0021
Scientific Paper, English

Gianandrea Vittorio Messa, Stefano Malavasi: Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

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• The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery.
  
  KEY WORDS: Two-fluid model; Two-phase flow; Turbulent liquid-solid flows; Sudden expansion.
  
  Address:
  - Gianandrea Vittorio Messa, Dipt. Ingegneria Civile e Ambientale, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano, Italy (Corresponding author. Tel.: Fax.: Email: gianandreavittorio.messa@polimi.it)
  - Stefano Malavasi, Dipt. Ingegneria Civile e Ambientale, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano, Italy

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 241 - 247, doi: 10.2478/johh-2014-0022
Scientific Paper, English

Pavel Vlasák, Zdeněk Chára, Jan Krupička, Jiří Konfršt: Experimental investigation of coarse particles-water mixture flow in horizontal and inclined pipes

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• The effect of solid concentration and mixture velocity on the flow behaviour, pressure drops, and concentration distribution of coarse particle–water mixtures in horizontal, vertical, and inclined smooth stainless steel pipes of inner diameter D = 100 mm was experimentally investigated. Graded basalt pebbles were used as solid particles. The study revealed that the coarse-grained particle-water mixtures in the horizontal and inclined pipes were significantly stratified. The solid particles moved principally in a layer close to the pipe invert; however for higher and moderate flow velocities, particle saltation became the dominant mode of particle conveyance. Frictional pressure drops in the horizontal pipe were found to be markedly higher than in the vertical pipe, while the frictional pressure drops in the ascending pipe increased with inclination angle up to about 30°.
  
  KEY WORDS: Hydraulic pipelining; Coarse-grained slurry; Pressure drops; Pipe inclination; Concentration distribution.
  
  Address:
  - Pavel Vlasák, Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, v. v. i., Pod Paťankou 30/5, 166 12 Prague 6, Czech Republic. (Corresponding author. Tel.: Fax.: Email: vlasak@ih.cas.cz)
  - Zdeněk Chára, Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, v. v. i., Pod Paťankou 30/5, 166 12 Prague 6, Czech Republic.
  - Jan Krupička, Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, v. v. i., Pod Paťankou 30/5, 166 12 Prague 6, Czech Republic.
  - Jiří Konfršt, Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, v. v. i., Pod Paťankou 30/5, 166 12 Prague 6, Czech Republic.

J. Hydrol. Hydromech., Vol. 62, No. 3, 2014, p. 248 - 252, doi: 10.2478/johh-2014-0023
Technical note, English

Dennis C. Gordon, Paul D. Hallett: An automated microinfiltrometer to measure small-scale soil water infiltration properties

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• We developed an automated miniature constant-head tension infiltrometer that measures very small infiltration rates at millimetre resolution with minimal demands on the operator. The infiltrometer is made of 2.9 mm internal radius glass tube, with an integrated bubbling tower to maintain constant negative head and a porous mesh tip to avoid air-entry. In the bubbling tower, bubble formation and release changes the electrical resistance between two electrodes at the air-inlet. Tests were conducted on repacked sieved sands, sandy loam soil and clay loam soil, packed to a soil bulk density ρd of 1200 kg m–3 or 1400 kg m–3 and tested either air-dried or at a water potential ψ of –50 kPa. The change in water volume in the infiltrometer had a linear relationship with the number of bubbles, allowing bubble rate to be converted to infiltration rate. Sorptivity measured with the infiltrometer was similar between replicates and showed expected differences from soil texture and ρd, varying from 0.15 ± 0.01 (s.e.) mm s–1/2 for 1400 kg m–3 clay loam at ψ = –50 kPa to 0.65 ± 0.06 mm s–1/2 for 1200 kg m–3 air dry sandy loam soil. An array of infiltrometers is currently being developed so many measurements can be taken simultaneously.
  
  KEY WORDS: Tension infiltrometer; Water sorptivity; Automated measurements; Small-scale infiltration measurements.
  
  Address:
  - Dennis C. Gordon, The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, United Kingdom.
  - Paul D. Hallett, The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, United Kingdom. Present address: Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen, AB24 3UU, United Kingdom. (Corresponding author. Tel.:+44 (0)1224 272264 Fax.: +44 (0)1224 272703 Email: paul.hallett@abdn.ac.uk)