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Détails du magazine
Format
Magazine
eISSN
1338-4333
ISSN
0042-790X
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

Volume 62 (2014): Edition 2 (June 2014)

Détails du magazine
Format
Magazine
eISSN
1338-4333
ISSN
0042-790X
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

10 Articles
access type Accès libre

Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau

Publié en ligne: 04 Apr 2014
Pages: 89 - 96

Résumé

Abstract

In this paper, to evaluate the hydrological effects of Caragana korshinskii Kom., measured data were combined with model-simulated data to assess the C. korshinskii soil water content based on water balance equation. With measured and simulated canopy interception, plant transpiration and soil evaporation, soil water content was modeled with the water balance equation. The monthly variations in the modeled soil water content by measured and simulated components (canopy interception, plant transpiration, soil evaporation) were then compared with in situ measured soil water content. Our results shows that the modeled monthly water loss (canopy interception + soil evaporation + plant transpiration) by measured and simulated components ranges from 43.78 mm to 113.95 mm and from 47.76 mm to 125.63 mm, respectively, while the monthly input of water (precipitation) ranges from 27.30 mm to 108.30 mm. The relative error between soil water content modeled by measured and simulated components was 6.41%. To sum up, the net change in soil water (ΔSW) is negative in every month of the growing season. The soil moisture is approaching to wilting coefficient at the end of the growth season, and the soil moisture recovered during the following season.

Mots clés

  • Shrub canopy
  • Interception
  • Transpiration
  • Soil evaporation
  • Water balance
  • Semiarid region
access type Accès libre

Water stable aggregates of Japanese Andisol as affected by hydrophobicity and drying temperature

Publié en ligne: 04 Apr 2014
Pages: 97 - 100

Résumé

Abstract

Hydrophobicity is a property of soils that reduces their affinity for water, which may help impeding the pressure build-up within aggregates, and reducing aggregate disruption. The purpose of this study was to examine the relation of soil hydrophobicity and drying temperature to water stability of aggregates while preventing the floating of dry aggregates using unhydrophobized and hydrophobized surface Andisol. Soil was hydrophobized using stearic acid into different hydrophobicities. Hydrophobicity was determined using sessile drop contact angle and water drop penetration time (WDPT). Water stability of aggregates (%WSA) was determined using artificially prepared model aggregates. The %WSA increased as the contact angle and WDPT increased. Contact angle and WDPT, which provided maximum %WSA showing less than 1 s of floating, was around 100° and 5 s, respectively. Although the %WSA gradually increased with increasing contact angle and WDPT above this level, high levels of hydrophobicity initiated aggregate floating, which would cause undesirable effects of water repellency. Heating at 50°C for 5 h d-1 significantly affected %WSA and hydrophobicity in hydrophobized samples, but did not in unhydrophobized samples. The results indicate that the contact angle and wetting rate (WDPT) are closely related with the water stability of aggregates. The results further confirm that high levels of hydrophobicities induce aggregate floating, and the drying temperature has differential effects on hydrophobicity and aggregate stability depending on the hydrophobic materials present in the soil.

Mots clés

  • Aggregate stability
  • Contact angle
  • Floating time
  • Japanese Andisol
  • Hydrophobicity
  • Wetting rate
access type Accès libre

Relationships between soil water repellency and microbial community composition under different plant species in a Mediterranean semiarid forest

Publié en ligne: 04 Apr 2014
Pages: 101 - 107

Résumé

Abstract

Soil water repellency (SWR) can influence many hydrological soil properties, including water infiltration, uneven moisture distribution or water retention. In the current study we investigated how variable SWR persistence in the field is related to the soil microbial community under different plant species (P. halepensis, Q. rotundifolia, C. albidus and R. officinalis) in a Mediterranean forest. The soil microbial community was determined through phospholipid fatty acids (PLFA). The relationships between microbiological community structure and the soil properties pH, Glomalin Related Soil Protein (GRSP) and soil organic matter (SOM) content were also studied. Different statistical analyses were used: Principal Component Analysis (PCA), ANOVA, Redundancy Analysis and Pearson correlations. The highest concentrations of PLFA were found in the most water repellent samples. PCA showed that microorganism composition was more dependent of the severity of SWR than the type of plant species. In the Redundancy Analysis, SWR was the only significant factor (p<0.05) to explain PLFA distributions. The only PLFA biomarkers directly related to SWR were associated with Actinobacteria (10Me16:0, 10Me17:0 and 10Me18:0). All the results suggest that a strong dependence between SWR and microbial community composition.

Mots clés

  • Soil hydrophobicity
  • Phospholipids fatty acids
  • Microbial community structure
  • Biohydrology
  • Actinobacteria
  • Glomalin Related Soil Protein
access type Accès libre

Local scour around complex pier groups and combined piles at semi-integral bridge

Publié en ligne: 04 Apr 2014
Pages: 108 - 116

Résumé

Abstract

This research presents an experimental study on the scouring mechanism at semi-integral bridge piers. Based on laboratory experiments, this study focuses on the relationship between scour depth in complex pier groups and combined piles bridge and various parameters including the variation of inflow velocity, distance, and time. 1 200 data were collected for flow velocity and scour. The flow pattern and scour were analyzed for different flow discharges and flow depths. The results showed that the scour development with respect to time was greater for higher flow depth and bigger flow discharge at semi-integral bridges. In addition, the equilibrium scour depth increased with the approach flow depth around piers at semi-integral bridges. Velocity distribution also affected the scour development. It decreased when approaching the bridge but increased from upstream to downstream of the flume.

Mots clés

  • Semi-integral Bridge
  • Complex pier groups
  • Combined Piles
  • Scour
  • Pier
  • Scour Depth
access type Accès libre

Three-dimensional flow of an Oldroyd-B fluid over a bidirectional stretching surface with prescribed surface temperature and prescribed surface heat flux

Publié en ligne: 04 Apr 2014
Pages: 117 - 125

Résumé

Abstract

This paper concentrates on the mathematical modelling for three-dimensional flow of an incompressible Oldroyd- B fluid over a bidirectional stretching surface. Mathematical formulation incorporates the effect of internal heat source/sink. Two cases of heat transfer namely the prescribed surface temperature (PST) and prescribed surface heat flux (PHF) are considered. Computations for the governing nonlinear flow are presented using homotopy analysis method. Comparison of the present analysis is shown with the previous limiting result. The obtained results are discussed by plots of interesting parameters for both PST and PHF cases. We examine that an increase in Prandtl number leads to a reduction in PST and PHF. It is noted that both PST and PHF are increased with an increase in source parameter. Further we have seen that the temperature is an increasing function of ratio parameter

Mots clés

  • Three-dimensional flow
  • Oldroyd-B fluid
  • Bidirectional stretching surface
  • Heat source/sink
access type Accès libre

Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

Publié en ligne: 04 Apr 2014
Pages: 126 - 132

Résumé

Abstract

Principles of gamma-ray-based measurement are summarized and their application is demonstrated on an operation of the radiometric facility installed in the test loop for slurry flows at the Institute of Hydrodynamics. The facility is able to measure vertical profiles of chord-averaged concentrations and concentration maps in the pipe cross section. A methodology of measurement is proposed including detection and quantification of random and systematic errors. Experimental results are discussed in the light of the proposed methodology. Experimentally determined vertical profiles of concentration are presented for slurry flows of four different fractions of glass beads. The tomographic application of the radiometric device is demonstrated on a measured concentration map and a suitable image reconstruction method is tested. High reliability of measured concentration distributions is proved except for regions near the pipe wall. The radiometric method is shown to be a useful tool for measurement of concentration distribution in slurry flow through a pipe.

Mots clés

  • Two-phase flow
  • Gamma radiometry
  • Computational tomography
  • Slurry flow experiment
access type Accès libre

Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

Publié en ligne: 04 Apr 2014
Pages: 133 - 144

Résumé

Abstract

Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS models were set up for ten river sections in the Upper Stör catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011), flood season (January, 2012) and dry season (April, 2012). The models were proven to be highly efficient and accurate through the seasonal roughness modification. The coefficients of determination (R2) of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic parameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.

Mots clés

  • HEC-RAS model
  • In-channel flow
  • Floodplain flow
  • Unit stream power
  • Inundation area
access type Accès libre

Discharge coefficient of a rectangular sharp-edged broad-crested weir

Publié en ligne: 04 Apr 2014
Pages: 145 - 149

Résumé

Abstract

This paper is concerned with the determination of the relationship for the calculation of the discharge coefficient at free overflow over a rectangular sharp-edged broad-crested weir without lateral contraction. The determination was made on the basis of new measurement in a range of the relative thickness of the weir from 0.12 to 0.30 and newly in a large range of relative height of the weir extremely from 0.24 to 6.8 which greatly expands the application possibilities of low weirs. In addition, the effects of friction and surface tension on the value of the discharge coefficient were evaluated as well as the effect of the relative thickness of the weir. The new equation for discharge coefficient, expressed using the relative height of the weir, was subjected to verification made by an independent laboratory which confirmed its accuracy.

Mots clés

  • Broad-crested weir
  • Discharge coefficient
  • Relative height of weir
access type Accès libre

Numerical and physical model study of a vertical slot fishway

Publié en ligne: 04 Apr 2014
Pages: 150 - 159

Résumé

Abstract

This paper presents the results of an experimental and numerical study of a vertical slot fishway (VSF). A 2-D depth-averaged shallow water numerical model PCFLOW2D coupled with three different turbulent models (constant eddy viscosity, Smagorinsky and k - ε) was used. A detailed analysis of numerical parameters needed for a correct simulation of the phenomenon was carried out. Besides the velocity field, attention was paid to important hydraulic parameters such as maximum velocity in the slot region and energy dissipation rate ε in order to evaluate the performance of VSF. A scaled physical hydraulic model was built to ensure reliable experimental data for the validation of the numerical model. Simulations of variant configurations of VSF showed that even small changes in geometry can produce more fishfriendly flow characteristics in pools. The present study indicates that the PCFLOW2D program is an appropriate tool to meet the main demands of the VSF design.

Mots clés

  • Eddy viscosity
  • Hydraulic model
  • Numerical diffusion
  • Numerical model PCFLOW2D
  • Turbulence model
  • Vertical slot fishway
access type Accès libre

Comparison of saturated areas mapping methods in the Jizera Mountains, Czech Republic

Publié en ligne: 04 Apr 2014
Pages: 160 - 168

Résumé

Abstract

Understanding and modelling the processes of flood runoff generation is still a challenge in catchment hydrology. In particular, there are issues about how best to represent the effects of the antecedent state of saturation of a catchment on runoff formation and flood hydrographs. This paper reports on the experience of mapping saturated areas using measured water table by piezometers and more qualitative assessments of the state of the moisture at soil surface or immediately under it to provide information that can usefully condition model predictions. Vegetation patterns can also provide useful indicators of runoff source areas, but integrated over much longer periods of time. In this way, it might be more likely that models will get the right predictions for the right reasons.

Mots clés

  • Mapping variable source areas
  • Boot method
  • Piezometers
  • Vegetation mapping
10 Articles
access type Accès libre

Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau

Publié en ligne: 04 Apr 2014
Pages: 89 - 96

Résumé

Abstract

In this paper, to evaluate the hydrological effects of Caragana korshinskii Kom., measured data were combined with model-simulated data to assess the C. korshinskii soil water content based on water balance equation. With measured and simulated canopy interception, plant transpiration and soil evaporation, soil water content was modeled with the water balance equation. The monthly variations in the modeled soil water content by measured and simulated components (canopy interception, plant transpiration, soil evaporation) were then compared with in situ measured soil water content. Our results shows that the modeled monthly water loss (canopy interception + soil evaporation + plant transpiration) by measured and simulated components ranges from 43.78 mm to 113.95 mm and from 47.76 mm to 125.63 mm, respectively, while the monthly input of water (precipitation) ranges from 27.30 mm to 108.30 mm. The relative error between soil water content modeled by measured and simulated components was 6.41%. To sum up, the net change in soil water (ΔSW) is negative in every month of the growing season. The soil moisture is approaching to wilting coefficient at the end of the growth season, and the soil moisture recovered during the following season.

Mots clés

  • Shrub canopy
  • Interception
  • Transpiration
  • Soil evaporation
  • Water balance
  • Semiarid region
access type Accès libre

Water stable aggregates of Japanese Andisol as affected by hydrophobicity and drying temperature

Publié en ligne: 04 Apr 2014
Pages: 97 - 100

Résumé

Abstract

Hydrophobicity is a property of soils that reduces their affinity for water, which may help impeding the pressure build-up within aggregates, and reducing aggregate disruption. The purpose of this study was to examine the relation of soil hydrophobicity and drying temperature to water stability of aggregates while preventing the floating of dry aggregates using unhydrophobized and hydrophobized surface Andisol. Soil was hydrophobized using stearic acid into different hydrophobicities. Hydrophobicity was determined using sessile drop contact angle and water drop penetration time (WDPT). Water stability of aggregates (%WSA) was determined using artificially prepared model aggregates. The %WSA increased as the contact angle and WDPT increased. Contact angle and WDPT, which provided maximum %WSA showing less than 1 s of floating, was around 100° and 5 s, respectively. Although the %WSA gradually increased with increasing contact angle and WDPT above this level, high levels of hydrophobicity initiated aggregate floating, which would cause undesirable effects of water repellency. Heating at 50°C for 5 h d-1 significantly affected %WSA and hydrophobicity in hydrophobized samples, but did not in unhydrophobized samples. The results indicate that the contact angle and wetting rate (WDPT) are closely related with the water stability of aggregates. The results further confirm that high levels of hydrophobicities induce aggregate floating, and the drying temperature has differential effects on hydrophobicity and aggregate stability depending on the hydrophobic materials present in the soil.

Mots clés

  • Aggregate stability
  • Contact angle
  • Floating time
  • Japanese Andisol
  • Hydrophobicity
  • Wetting rate
access type Accès libre

Relationships between soil water repellency and microbial community composition under different plant species in a Mediterranean semiarid forest

Publié en ligne: 04 Apr 2014
Pages: 101 - 107

Résumé

Abstract

Soil water repellency (SWR) can influence many hydrological soil properties, including water infiltration, uneven moisture distribution or water retention. In the current study we investigated how variable SWR persistence in the field is related to the soil microbial community under different plant species (P. halepensis, Q. rotundifolia, C. albidus and R. officinalis) in a Mediterranean forest. The soil microbial community was determined through phospholipid fatty acids (PLFA). The relationships between microbiological community structure and the soil properties pH, Glomalin Related Soil Protein (GRSP) and soil organic matter (SOM) content were also studied. Different statistical analyses were used: Principal Component Analysis (PCA), ANOVA, Redundancy Analysis and Pearson correlations. The highest concentrations of PLFA were found in the most water repellent samples. PCA showed that microorganism composition was more dependent of the severity of SWR than the type of plant species. In the Redundancy Analysis, SWR was the only significant factor (p<0.05) to explain PLFA distributions. The only PLFA biomarkers directly related to SWR were associated with Actinobacteria (10Me16:0, 10Me17:0 and 10Me18:0). All the results suggest that a strong dependence between SWR and microbial community composition.

Mots clés

  • Soil hydrophobicity
  • Phospholipids fatty acids
  • Microbial community structure
  • Biohydrology
  • Actinobacteria
  • Glomalin Related Soil Protein
access type Accès libre

Local scour around complex pier groups and combined piles at semi-integral bridge

Publié en ligne: 04 Apr 2014
Pages: 108 - 116

Résumé

Abstract

This research presents an experimental study on the scouring mechanism at semi-integral bridge piers. Based on laboratory experiments, this study focuses on the relationship between scour depth in complex pier groups and combined piles bridge and various parameters including the variation of inflow velocity, distance, and time. 1 200 data were collected for flow velocity and scour. The flow pattern and scour were analyzed for different flow discharges and flow depths. The results showed that the scour development with respect to time was greater for higher flow depth and bigger flow discharge at semi-integral bridges. In addition, the equilibrium scour depth increased with the approach flow depth around piers at semi-integral bridges. Velocity distribution also affected the scour development. It decreased when approaching the bridge but increased from upstream to downstream of the flume.

Mots clés

  • Semi-integral Bridge
  • Complex pier groups
  • Combined Piles
  • Scour
  • Pier
  • Scour Depth
access type Accès libre

Three-dimensional flow of an Oldroyd-B fluid over a bidirectional stretching surface with prescribed surface temperature and prescribed surface heat flux

Publié en ligne: 04 Apr 2014
Pages: 117 - 125

Résumé

Abstract

This paper concentrates on the mathematical modelling for three-dimensional flow of an incompressible Oldroyd- B fluid over a bidirectional stretching surface. Mathematical formulation incorporates the effect of internal heat source/sink. Two cases of heat transfer namely the prescribed surface temperature (PST) and prescribed surface heat flux (PHF) are considered. Computations for the governing nonlinear flow are presented using homotopy analysis method. Comparison of the present analysis is shown with the previous limiting result. The obtained results are discussed by plots of interesting parameters for both PST and PHF cases. We examine that an increase in Prandtl number leads to a reduction in PST and PHF. It is noted that both PST and PHF are increased with an increase in source parameter. Further we have seen that the temperature is an increasing function of ratio parameter

Mots clés

  • Three-dimensional flow
  • Oldroyd-B fluid
  • Bidirectional stretching surface
  • Heat source/sink
access type Accès libre

Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

Publié en ligne: 04 Apr 2014
Pages: 126 - 132

Résumé

Abstract

Principles of gamma-ray-based measurement are summarized and their application is demonstrated on an operation of the radiometric facility installed in the test loop for slurry flows at the Institute of Hydrodynamics. The facility is able to measure vertical profiles of chord-averaged concentrations and concentration maps in the pipe cross section. A methodology of measurement is proposed including detection and quantification of random and systematic errors. Experimental results are discussed in the light of the proposed methodology. Experimentally determined vertical profiles of concentration are presented for slurry flows of four different fractions of glass beads. The tomographic application of the radiometric device is demonstrated on a measured concentration map and a suitable image reconstruction method is tested. High reliability of measured concentration distributions is proved except for regions near the pipe wall. The radiometric method is shown to be a useful tool for measurement of concentration distribution in slurry flow through a pipe.

Mots clés

  • Two-phase flow
  • Gamma radiometry
  • Computational tomography
  • Slurry flow experiment
access type Accès libre

Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

Publié en ligne: 04 Apr 2014
Pages: 133 - 144

Résumé

Abstract

Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS models were set up for ten river sections in the Upper Stör catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011), flood season (January, 2012) and dry season (April, 2012). The models were proven to be highly efficient and accurate through the seasonal roughness modification. The coefficients of determination (R2) of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic parameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.

Mots clés

  • HEC-RAS model
  • In-channel flow
  • Floodplain flow
  • Unit stream power
  • Inundation area
access type Accès libre

Discharge coefficient of a rectangular sharp-edged broad-crested weir

Publié en ligne: 04 Apr 2014
Pages: 145 - 149

Résumé

Abstract

This paper is concerned with the determination of the relationship for the calculation of the discharge coefficient at free overflow over a rectangular sharp-edged broad-crested weir without lateral contraction. The determination was made on the basis of new measurement in a range of the relative thickness of the weir from 0.12 to 0.30 and newly in a large range of relative height of the weir extremely from 0.24 to 6.8 which greatly expands the application possibilities of low weirs. In addition, the effects of friction and surface tension on the value of the discharge coefficient were evaluated as well as the effect of the relative thickness of the weir. The new equation for discharge coefficient, expressed using the relative height of the weir, was subjected to verification made by an independent laboratory which confirmed its accuracy.

Mots clés

  • Broad-crested weir
  • Discharge coefficient
  • Relative height of weir
access type Accès libre

Numerical and physical model study of a vertical slot fishway

Publié en ligne: 04 Apr 2014
Pages: 150 - 159

Résumé

Abstract

This paper presents the results of an experimental and numerical study of a vertical slot fishway (VSF). A 2-D depth-averaged shallow water numerical model PCFLOW2D coupled with three different turbulent models (constant eddy viscosity, Smagorinsky and k - ε) was used. A detailed analysis of numerical parameters needed for a correct simulation of the phenomenon was carried out. Besides the velocity field, attention was paid to important hydraulic parameters such as maximum velocity in the slot region and energy dissipation rate ε in order to evaluate the performance of VSF. A scaled physical hydraulic model was built to ensure reliable experimental data for the validation of the numerical model. Simulations of variant configurations of VSF showed that even small changes in geometry can produce more fishfriendly flow characteristics in pools. The present study indicates that the PCFLOW2D program is an appropriate tool to meet the main demands of the VSF design.

Mots clés

  • Eddy viscosity
  • Hydraulic model
  • Numerical diffusion
  • Numerical model PCFLOW2D
  • Turbulence model
  • Vertical slot fishway
access type Accès libre

Comparison of saturated areas mapping methods in the Jizera Mountains, Czech Republic

Publié en ligne: 04 Apr 2014
Pages: 160 - 168

Résumé

Abstract

Understanding and modelling the processes of flood runoff generation is still a challenge in catchment hydrology. In particular, there are issues about how best to represent the effects of the antecedent state of saturation of a catchment on runoff formation and flood hydrographs. This paper reports on the experience of mapping saturated areas using measured water table by piezometers and more qualitative assessments of the state of the moisture at soil surface or immediately under it to provide information that can usefully condition model predictions. Vegetation patterns can also provide useful indicators of runoff source areas, but integrated over much longer periods of time. In this way, it might be more likely that models will get the right predictions for the right reasons.

Mots clés

  • Mapping variable source areas
  • Boot method
  • Piezometers
  • Vegetation mapping

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