J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 121 - 139, doi: 10.2478/johh-2021-0002
Review, English

Mirko Castellini, Simone Di Prima, David Moret-Fernández, Laurent Lassabatere: Rapid and accurate measurement methods for determining soil hydraulic properties: A review

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• The determination of soil hydraulic properties is important in several environmental sciences but may be expensive and time consuming. Therefore, during the last decades, a great effort has been made in soil sciences to develop relatively easy, robust, and inexpensive methods for soil hydraulic characterization. In this manuscript, we reviewed and discussed different infiltrometer techniques in light of the available experimental applications. More specifically, we considered the simplified falling head (SFH) infiltrometer technique and the single-ring infiltration experiment of the Beerkan type. Concerning this latter method, we considered different algorithms for data analysis: two simplified methods based on the analysis of transient (TSBI) and steady (SSBI) Beerkan infiltration data, and the Beerkan Estimation of Soil pedoTransfer parameters algorithm (BEST), that allows to estimate the soil characteristics curves, i.e., the soil water retention curve and hydraulic conductivity functions. For a given method, after dealing briefly theory and practice, available literature references were reported to account for specific applications in order to provide findings on method validation and application. With the aim to provide practical information on available tools for a simpler application of the reviewed methods, several video tutorials were reported to show i) how to conduct correctly field experiments and ii) how to calculate saturated hydraulic conductivity or soil hydraulic functions using user-friendly tools for data analysis. Finally, details on a new automated single-ring infiltrometer for Beerkan infiltration experiments (i.e., construction, assembly and field use) were presented.
  
  KEY WORDS: SFH technique; Beerkan method; BEST-procedure; Saturated hydraulic conductivity; Soil hydraulic properties; Infiltrometer.
  
  Address:
  - Mirko Castellini, Council for Agricultural Research and Economics-Research Center for Agriculture and Environment (CREA-AA), Via C. Ulpiani 5, 70125 Bari, Italy. (Corresponding author. Tel.:+39-080-5475039 Fax.: Email: mirko.castellini@crea.gov.it)
  - Simone Di Prima, Department of Agricultural Sciences, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy. Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69518, Vaulx-en- Velin, France.
  - David Moret-Fernández, Departamento de Suelo y Agua, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), PO Box 13034, 50080 Zaragoza, Spain.
  - Laurent Lassabatere, Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69518, Vaulx-en- Velin, France.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 140 - 150, doi: 10.2478/johh-2021-0003
Scientific Paper, English

Joao R.C.B. Abrantes, Nuno E. Simoes, Joao L.M.P. de Lima, Abelardo A.A. Montenegro: Two-dimensional (2D) numerical modelling of rainfall induced overland flow, infiltration and soil erosion: comparison with laboratory rainfall-runoff simulations on a two-directional slope soil flume

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• This paper presents a two-dimensional (2D) numerical model of soil erosion and sediment transport resulting from rainfall induced overland flow. It is a spatial and temporal dynamic model combining physical and empirical laws and comprises: i) An overland flow module that solves the two-dimensional unsteady water flow equations on an infiltrating surface; ii) A soil infiltration module that uses a combined Horton-SCS scheme; and iii) A soil erosion and sediment transport module that solves the two-dimensional sediment transport equation, distinguishing between rill erosion, interrill erosion and sediment deposition. The performance of the model was evaluated by comparing its results with observed data from laboratory rainfallrunoff experiments on a two-directional 2.00 × 2.00 m2 soil flume set at 1% and 10% slopes in the x- and y-directions, respectively. The x-direction produced remarkably lower runoff and transported sediments than the y-direction. The numerical model significantly underestimated x-direction lower values of runoff and transported sediments. However, in the y-direction the model presented very good performance. Overall, in total terms (x- plus y-direction), the numerically simulated graphs of runoff and sediment transport were in very good agreement with corresponding experimental measurements, demonstrating the laboratory proof-of-concept of the model.
  
  KEY WORDS: Two-dimensional modelling; Overland flow; Soil erosion; Horton-SCS infiltration; Two-directional laboratory soil flume; Rainfall simulation.
  
  Address:
  - Joao R.C.B. Abrantes, Department of Civil Engineering, Faculty of Sciences and Technology, University of Coimbra, Rua Luís Reis Santos, Pólo II – Universidade de Coimbra, 3030-788 Coimbra, Portugal. MARE UCoimbra - Marine and Environmental Sciences Centre, University of Coimbra, Rua da Matemática 49, 3004-517 Coimbra, Portugal. Itecons - Institute of Research and Technological Development in Construction, Energy, Environment and Sustainability, Rua Pedro Hispano, 3030-289 Coimbra, Portugal. (Corresponding author. Tel.:+351915051391 Fax.: Email: jrcbrito@msn.com)
  - Nuno E. Simoes, Department of Civil Engineering, Faculty of Sciences and Technology, University of Coimbra, Rua Luís Reis Santos, Pólo II – Universidade de Coimbra, 3030-788 Coimbra, Portugal. INESC Coimbra - Institute for Systems Engineering and Computers at Coimbra, Rua Sílvio Lima, Pólo II - Universidade de Coimbra, 3030-290 Coimbra, Portugal.
  - Joao L.M.P. de Lima, Department of Civil Engineering, Faculty of Sciences and Technology, University of Coimbra, Rua Luís Reis Santos, Pólo II – Universidade de Coimbra, 3030-788 Coimbra, Portugal. MARE UCoimbra - Marine and Environmental Sciences Centre, University of Coimbra, Rua da Matemática 49, 3004-517 Coimbra, Portugal.
  - Abelardo A.A. Montenegro, Department of Rural Technology, Rural Federal University of Pernambuco, Rua Dom Manoel de Medeiros s/n, Dois Irmaos, 50910-130 Recife, PE, Brazil.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 151 - 160, doi: 10.2478/johh-2021-0010
Scientific Paper, English

Vincenzo Bagarello, Gaetano Caltabellotta, Massimo Iovino: Water transmission properties of a sandy-loam soil estimated with Beerkan runs differing by the infiltration time criterion

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• The Beerkan method consists of a ponded infiltration experiment from a single ring inserted a small depth into the soil. Fixed, small volumes of water are repeatedly poured into the ring to maintain a quasi-zero head on the soil surface. According to the standard Beerkan infiltration run, a new water volume is poured on the infiltration surface when the previously applied volume has completely infiltrated and the soil surface is entirely exposed to air (ta criterion). However, water could also be applied when the soil exposition to air begins (to criterion) or half the soil surface is exposed to air (tm criterion). The effect of the infiltration time criterion on determination of the water transmission properties of a sandy-loam soil was tested. As compared with the standard ta criterion, the two alternative criteria (to, tm) yielded higher and/or more variable estimates of soil water transmission properties. The saturated soil hydraulic conductivity, Ks, was the most sensitive property to the infiltration time criterion. However, statistically significant differences for Ks were not practically substantial since they did not exceed a factor of 1.7. Infiltration time effects likely occurred due to differences between ponding depth of water, soil water pressure head gradient, air entrapment and soil mechanical disturbance. The standard ta criterion was suggested for performing a Beerkan experiment in the field since it appears to yield the most reliable estimates of a mean value. However, the to criterion could be considered in dual permeability soils to maintain macropores active. Factors that could appear minor in the context of an experiment can have statistically relevant effects on water transmission properties.
  
  KEY WORDS: Soil water transmission properties; Beerkan run; Infiltration time criterion; BEST methodology.
  
  Address:
  - Vincenzo Bagarello, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128, Palermo, Italy.
  - Gaetano Caltabellotta, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128, Palermo, Italy.
  - Massimo Iovino, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128, Palermo, Italy. (Corresponding author. Tel.:+39 09123897070 Fax.: Email: massimo.iovino@unipa.it)

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 161 - 170, doi: 10.2478/johh-2021-0004
Scientific Paper, English

Mojtaba G. Mahmoodlu, Amir Raoof, Martinus Th. van Genuchten: Effect of soil textural characteristics on longitudinal dispersion in saturated porous media

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• This study focuses on the effects of soil textural heterogeneity on longitudinal dispersion under saturation conditions. A series of solute transport experiments were carried out using saturated soil columns packed with two filter sands and two mixtures of these sands, having d50 values of 95, 324, 402, and 480 μm, subjected to four different steady flow rates. Values of the dispersion coefficient (D) were estimated from observed in-situ distributions of calcium chloride, injected as a short nonreactive tracer pulse, at four different locations (11, 18, 25, 36 cm). Analyses of the observed distributions in terms of the standard advection-dispersion equation (ADE) showed that D increased nonlinearly with travel distance and higher Peclet numbers+. The dispersion coefficient of sand sample S1 with its largest average particle size (d50) was more affected by the average pore-water velocity than sample S4 having the smallest d50. Results revealed that for a constant velocity, D values of sample S1 were much higher than those of sample S4, which had the smallest d50. A correlation matrix of parameters controlling the dispersion coefficient showed a relatively strong positive relationship between D and the Peclet number. In contrast, almost no correlation was evident between D and porosity as well as grain size. The results obtained with the four sandy matrices were consistent and proved that the dispersion coefficient depends mainly on the particle size.
  
  KEY WORDS: Solute dispersion; Soil textural heterogeneity; Saturated columns; Peclet number; Flow velocity; Travel distance.
  
  Address:
  - Mojtaba G. Mahmoodlu, Faculty of Agriculture and Natural Resources, Gonbad Kavous University, Gonbad Kavous, Iran. Department of Earth Sciences, Utrecht University, Utrecht, Netherlands. (Corresponding author. Tel.: Fax.: Email: m.g.mahmoodlu@gmail.com; mmahmoodlu@gonbad.ac.ir)
  - Amir Raoof, Department of Earth Sciences, Utrecht University, Utrecht, Netherlands.
  - Martinus Th. van Genuchten, Department of Earth Sciences, Utrecht University, Utrecht, Netherlands. Center for Environmental Studies, CEA, Sao Paulo State University Rio Claro, Brazil.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 171 - 179, doi: 10.2478/johh-2021-0007
Scientific Paper, English

Zahra Abdollahi, Seyed Hamidreza Sadeghi, Abdulvahed Khaledi: Detailed procedure for outdoor measurement of raindrop size distribution using photogrammetry

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• Kinetic energy and corresponding erosive force of rainfall are strongly influenced by raindrop. The present paper aims to explore the raindrop size variation during rainfall events with different intensities in northern Iran by applying the processes of camera-taken photographs. Five rainfall intensities of 1 to 10 mm h–1 that occur frequently in the study area were analyzed. A camera with a very short exposure time was used to record the distribution of raindrops size. The raindrops diameters of the rain events ranged from <0.2 to 5.1 mm while the majority of them were between 1 and 2 mm. The results also showed that the variation of rainfall intensity significantly influenced (P< 0.05) raindrops size. Image processing was proven as an accurate technique of translation between the human visual system and digital imaging devices. The findings of the study can be practically utilized by researchers who work in the field of soil erosion and meteorology.
  
  KEY WORDS: Raindrop Size Distribution; Image processing; Rainfall Intensity; Rain Erosivity.
  
  Address:
  - Zahra Abdollahi, Department of Watershed Management Engineering, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor 4641776489, Mazandaran, Iran. At present, Soil Conservation and Watershed Management Research Department, Zanjan Agricultural and Natural Resources Research and Education Center, AREEO, Zanjan, Iran.
  - Seyed Hamidreza Sadeghi, Department of Watershed Management Engineering, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor 4641776489, Mazandaran, Iran. (Corresponding author. Tel.: Fax.: Email: sadeghi@modares.ac.ir)
  - Abdulvahed Khaledi, Department of Watershed Management Engineering, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor 4641776489, Mazandaran, Iran.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 180 - 195, doi: 10.2478/johh-2021-0001
Scientific Paper, English

Jonatas Belotti, José Jair Mendes Jr., Murilo Leme, Flavio Trojan, Sergio L. Stevan Jr., Hugo Siqueira: Comparative study of forecasting approaches in monthly streamflow series from Brazilian hydroelectric plants using Extreme Learning Machines and Box & Jenkins models

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• Several activities regarding water resources management are dependent on accurate monthly streamflow forecasting, such as flood control, reservoir operation, water supply planning, hydropower generation, energy matrix planning, among others. Most of the literature is focused on propose, compare, and evaluate the forecasting models. However, the decision on forecasting approaches plays a significant role in such models’ performance. In this paper, we are focused on investigating and confront the following forecasting approaches: i) use of a single model for the whole series (annual approach) versus using 12 models, each one responsible for predicting each month (monthly approach); ii) for multistep forecasting, the use of direct and recursive methods. The forecasting models addressed are the linear Autoregressive (AR) and Periodic Autoregressive (PAR) models, from the Box & Jenkins family, and the Extreme Learning Machines (ELM), an artificial neural network architecture. The computational analysis involves 20 time series associated with hydroelectric plants indicated that the monthly approach with the direct multistep method achieved the best overall performances, except for the cases in which the coefficient of variation is higher than two. In this case, the recursive approach stood out. Also, the ELM overcame the linear models in most cases.
  
  KEY WORDS: Streamflow series prediction; Multistep forecasting; Monthly approach; Box & Jenkins models; Extreme Learning Machines.
  
  Address:
  - Jonatas Belotti, Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil.
  - José Jair Mendes Jr., Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil.
  - Murilo Leme, Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil.
  - Flavio Trojan, Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil.
  - Sergio L. Stevan Jr., Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil.
  - Hugo Siqueira, Federal University of Technology – Paraná (UTFPR), Rua Doutor Washington Subtil Chueire, 330, Jardim Carvalho, 84017-220, Ponta Grossa-PR, Brazil. (Corresponding author. Tel.:+55(42) 3220-4825 Fax.: Email: hugosiqueira@utfpr.edu.br)

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 196 - 208, doi: 10.2478/johh-2021-0006
Scientific Paper, English

Ranka Erić, Ratko Kadović, Vladimir Đurđević, Vesna Đukić: Future changes in extreme precipitation in central Serbia

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• This paper presents the results of a study focused on the projected changes in extreme precipitation during the 21st century in Central Serbia. The changes are investigated on the basis of historical and modelled data sets of daily precipitation. The historical observation data were recorded at 18 synoptic weather stations in Central Serbia and modelled data were extracted from the regional climate model EBU-POM (Eta Belgrade University-Princeton Ocean Model) under the A1B scenario. The average number of days in a year with precipition ≥ 20, 30, 40 and 50 mm (R20, R30, R40 and R50), the share of daily precipitation above the 20, 30, 40 and 50 mm (P20, P30, P40, P50) in the total annual precipitation and the monthly distribution of these heavy daily precipitation are used as indices of changes in extreme precipitation. These indices, for the three periods 2011–2040, 2041–2070 and 2071–2100, are determined and compared with those obtained for the historical reference period 1961–1990. The results have shown that the main changes in extreme precipitation in Central Serbia will be in their spatial distribution, and the uncertainty of the occurrence of extreme events will decrease. In the future the increase will be more pronounced than the decrease of these indices. We strongly emphasize the benefit of this paper for both the prevention of natural disasters in the study area and for the improvement of the regional climate model.
  
  KEY WORDS: Future extreme precipitation; Climate changes; Regional climate model; Central Serbia.
  
  Address:
  - Ranka Erić, University in Belgrade, Faculty of Forestry, Kneza Višeslava 1, 11030 Belgrade, Serbia. (Corresponding author. Tel.:+ 381 11 3053957 Fax.: Email: ranka.eric@sfb.bg.ac.rs)
  - Ratko Kadović, University in Belgrade, Faculty of Forestry, Kneza Višeslava 1, 11030 Belgrade, Serbia.
  - Vladimir Đurđević, University of Belgrade, Faculty of Physics, Institute of Meteorology, Dobračina 16, 11000 Belgrade, Serbia.
  - Vesna Đukić, University in Belgrade, Faculty of Forestry, Kneza Višeslava 1, 11030 Belgrade, Serbia.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 209 - 219, doi: 10.2478/johh-2021-0005
Scientific Paper, English

Ľudmila Mačejná, Andrea Zacharová, Hana Ollerová, Jana Škvareninová, Jaroslav Škvarenina: Hydrobiochemical balance of total mercury in a forest catchment area at former cinnabar mining locality

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• We studied the hydrobiochemical balance of total mercury (THg) in a forest ecosystem covering an area affected by mining activity in the past (14th – 18th cent.) in the Kremnické vrchy Mts. (central Slovakia). A reference plot was located in an undisturbed area very close to primeval forest of Badínsky prales natural reserve. We analysed THg in bulk precipitation, throughfall, litterfall, forest floor percolate, forest soil and assimilatory organs of tree species. Results pointed out to high wet mercury deposition at both plots (51 μg·m−2·yr−1 an area near a cinnabar mining (MP1) and 37 μg·m−2·yr−1, in a reference catchment area near the protected primary forest (MP2)) as well as high THg deposition by throughfall (74 μg·m−2·yr−1 and 51 μg·m−2·yr−1, respectively in MP1 and MP2). Litterfall does not represent the main THg flux into forest soil but together with throughfall doubles the THg input compared to open space deposition. Forest ecosystem has ability to capture atmospheric Hg and thus makes new sources of mercury inputs (throughfall and litterfall) into soil.
  
  KEY WORDS: Total mercury; Bulk precipitation; Throughfall; Litterfall; Wet deposition; Forest; Cinnabar mining.
  
  Address:
  - Ľudmila Mačejná, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia. Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia.
  - Andrea Zacharová, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia.
  - Hana Ollerová, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia.
  - Jana Škvareninová, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia.
  - Jaroslav Škvarenina, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, Zvolen, 960 01, Slovakia. (Corresponding author. Tel.: Fax.: Email: jaroslav.skvarenina@tuzvo.sk)

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 220 - 231, doi: 10.2478/johh-2021-0008
Scientific Paper, English

Antonín Nikodem, Radka Kodešová, Miroslav Fér, Aleš Klement: Variability of topsoil hydraulic conductivity along the hillslope transects delineated in four areas strongly affected by soil erosion

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• Soil hydraulic conductivities of topsoils were studied at 5 points of the hillslope transects delineated at 4 geomorphologically diverse areas, where the original soil types (Chernozem, Luvisol and two Cambisols) were due to erosion transformed into different soil unites. Hydraulic conductivities of saturated soils and for a pressure head of –2 cm were measured directly in the field using a Guelph permeameter (Ks,GP) and mini disk tension infiltrometer (Kh = –2,MDI), and in the laboratory using a multistep outflow method (Ks,MSO, Kh = –2,MSO). While Ks,GP ≈ Ks,MSO in the Chernozem and Cambisol (sandy loam) regions, and Ks,GP < Ks,MSO in the Luvisol and Cambisol (loam) regions. The Ks values obtained using different methods showed different trends along the hillslope transects. The Kh = –2 values obtained using different methods showed similar trends along the transects in the Chernozem and Luvisol regions. These trends could be explained by the position within the transects (i.e., different stages of erosion/accumulation processes). No relationships were found between the Kh = –2 values in the Cambisol regions. The pressure head at an inflection point of the a soil-water retention curve was the main parameter, which appeared to associate (negative correlation) with Kh = –2 and Ks,MSO in the Chernozem and Luvisol regions.
  
  KEY WORDS: Soil hydraulic properties; Guelph permeameter; Mini disk tension infiltrometer; Multistep outflow method; Aggregate stability; Retention curve inflection point.
  
  Address:
  - Antonín Nikodem, Czech University of Life Sciences Prague, Faculty of Agrobiology Food and Natural Resources, Department of Soil Science and Soil Protection, Kamýcká 129, CZ-16500 Prague 6, Czech Republic. (Corresponding author. Tel.:+420 224 386 301 Fax.: Email: nikodem@af.czu.cz)
  - Radka Kodešová, Czech University of Life Sciences Prague, Faculty of Agrobiology Food and Natural Resources, Department of Soil Science and Soil Protection, Kamýcká 129, CZ-16500 Prague 6, Czech Republic.
  - Miroslav Fér, Czech University of Life Sciences Prague, Faculty of Agrobiology Food and Natural Resources, Department of Soil Science and Soil Protection, Kamýcká 129, CZ-16500 Prague 6, Czech Republic.
  - Aleš Klement, Czech University of Life Sciences Prague, Faculty of Agrobiology Food and Natural Resources, Department of Soil Science and Soil Protection, Kamýcká 129, CZ-16500 Prague 6, Czech Republic.

J. Hydrol. Hydromech., Vol. 69, No. 2, 2021, p. 232 - 242, doi: 10.2478/johh-2021-0009
Scientific Paper, English

Yong-Wook Jeong, Woochang Jeong: Experimental and numerical investigation of water-surface characteristics at crossing connected non-orthogonally to four flat channels

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• Most studies on the flood flow characteristics at a crossing focus on channels connected orthogonally or at right angle, but studies on non-orthogonally connected channels remain limited. In this study, hydraulic-model experiments and numerical simulations are performed to analyze the characteristics of the water-surface variation in and around a crossing connected non-orthogonally to four flat channels. Comparison of the measured and simulated water depth distributions in and around the crossing indicates that the results are in relatively good agreement. In the experiment where the angle between two upstream channels is 45°, the water flow pattern in and around the crossing corresponds approximately to Type I proposed by Mignot et al. (2008). However, it was found that there is no any flow type to correspond to the water flow pattern measured in the case of the angle of 135°. For analyzing the variation of the water depth in and around the crossing with inflow, numerical simulation is performed by setting the inflow ratio of the two inlet channels to one, three, and six, respectively.
  
  KEY WORDS: Hydraulic-model experiment; Non-orthogonal crossing; Free-surface flow; Water-surface variation.
  
  Address:
  - Yong-Wook Jeong, Department of Architecture, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul, Republic of Korea.
  - Woochang Jeong, Department of Civil Engineering, Kyungnam University, 7, Kyungnamdaehak-ro, Masanhappo-gu, Changwon, Republic of Korea. (Corresponding author. Tel.:+82-55-249-2614 Fax.: Email: jeongwc@kyungnam.ac.kr)