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

#### Chercher

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Joint Editorial Invigorating Hydrological Research through Journal Publications

Pages: 257 - 260

#### Résumé

Editors of several journals in the field of hydrology met during the General Assembly of the European Geosciences Union-EGU in Vienna in April 2017. This event was a follow-up of similar meetings held in 2013 and 2015. These meetings enable the group of editors to review the current status of the journals and the publication process, and to share thoughts on future strategies. Journals were represented at the 2017 meeting by their editors, as shown in the list of authors. The main points on invigorating hydrological research through journal publications are communicated in this joint editorial published in the above journals.

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Recovery of small-scale infiltration and erosion after wildfires

Pages: 261 - 270

#### Résumé

Wildfires naturally occur worldwide, however the potential disruption to ecosystem services from subsequent post-fire flooding and erosion often necessitates a response from land managers. The impact of high severity wildfire on infiltration and interrill erosion responses was evaluated for five years after the 2003 Hot Creek Fire in Idaho, USA. Relative infiltration from mini-disk tension infiltrometers (MDI) was compared to rainfall simulation measurements on small burned and control plots. Vegetation recovery was slow due to the severity of the fire, with median cover of 6-8% on burned sites after 5 years. Consequently, interrill sediment yields remained significantly higher on the burned sites (329-1200 g m^{-2}) compared to the unburned sites (3-35 g m^{-2}) in year 5. Total infiltration on the burned plots increased during the study period, yet were persistently lower compared to the control plots. Relative infiltration measurements made at the soil surface, and 1- and 3-cm depths were significantly correlated to non-steady state total infiltration values taken in the first 10 minutes of the hour-long rainfall simulations. Significant correlations were found at the 1-cm (ρ = 0.4-0.6) and 3-cm (ρ = 0.3-0.6) depths (most p-values <0.001), and somewhat weaker correlations at the soil surface (ρ = 0.2-0.4) (p-values <0.05 and up). Soil water repellency is often stronger below the soil surface after severe wildfire, and likely contributes to the reduced infiltration. These results suggest that relative infiltration measurements at shallow depths may be useful to estimate potential infiltration during a short-duration high-intensity storm and could be used as an input for post-fire erosion models.

#### Mots clés

- Interrill erosion
- Mini-disk infiltrometer
- Post-fire erosion
- Rainfall simulation
- Water repellency

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Natural colloid mobilization and leaching in wettable and water repellent soil under saturated condition

Pages: 271 - 278

#### Résumé

The coupled transport of pollutants that are adsorbed to colloidal particles has always been a major topic for environmental sciences due to many unfavorable effects on soils and groundwater. This laboratory column study was conducted under saturated moisture conditions to compare the hydrophobic character of the suspended and mobilized colloids in the percolates released from a wettable subsoil and a water repellent topsoil. Both soils with different organic matter content were analyzed for wettability changes before and after leaching using sessile drop contact angles as well as water and ethanol sorptivity curves, summarized as repellency index. Hydrophobicity of the effluent suspensions was assessed using the C18 adsorption method. Water repellency level of the repellent soil decreased after leaching but remained on a lower level of water repellency, while, the wettable soil remained wettable. The leached colloids from the repellent soil were predominantly hydrophilic and the percentage of the hydrophobic colloid fraction in the effluent did not systematically changed with time. Total colloid release depended on soil carbon stock but not on soil wettability. Our results suggest that due to the respective character of transported colloids a similar co-transport mechanism for pollutants may occur which does not depend explicitly on soil wettability of the releasing horizon, but could be more affected by total SOM content. Further studies with a wider range of soils are necessary to determine if the dominant hydrophilic character of leached colloids is typical. Due to the mostly hydrophilic colloid character we conclude also that changes in wettability status, i.e. of wettable subsoil horizons due to the leachate, may not necessarily occur very fast, even when the overlaying topsoil is a repellent soil horizon with a high organic matter content.

#### Mots clés

- Soil water repellency
- Hydrophobic colloids
- C18
- Sessile drop
- Repellency index

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Encounter probability analysis of irrigation water and reference crop evapotranspiration in irrigation district

Pages: 279 - 284

#### Résumé

Based on the data series of the annual reference crop evapotranspiration (ET_{0}) and the amount of irrigation water (IR) from 1970 to 2013 in the Luhun irrigation district, the joint probability distribution of ET_{0} and IR is established using the Gumbel-Hougaard copula function. Subsequently, the joint probability, the conditional joint probability, and the conditional return period of rich−poor encounter situations of ET_{0} and IR are analysed. The results show that: (1) For the joint probabilities of rich−poor encounter situations of ET_{0} and IR, the asynchronous encounter probability is slightly larger than the synchronous encounter probability. (2) When IR is in rich state or ET_{0} is in poor state, the conditional joint probability is larger, and the conditional return period is smaller. (3) For a certain design frequency of ET_{0}, if the design frequency decreases, the conditional joint probability of the amount of irrigation water will decrease, therefore the encounter probability of them will decrease. (4) For a certain design frequency of the amount of irrigation water, if the design frequency decreases, the conditional joint probability of ET_{0} will increase, thus the encounter probability of them will increase.

#### Mots clés

- Luhun irrigation district
- Copula function
- Reference crop evapotranspiration
- Amount of irrigation water
- Encounter probability

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Improving the positional accuracy of drainage networks extracted from Global Digital Elevation Models using OpenstreetMap data

Pages: 285 - 294

#### Résumé

Drainage networks allow the extraction of topographic parameters that are useful for basins characterization and necessary for hydrologic modelling. One way to obtain drainage networks is by their extraction from Digital Elevation Models (DEMs). However, it is common that no freely available DEMs at regional or national level exist. One way to overcome this situation is to use the available free Global Digital Elevation Models (GDEMs). However, these datasets have relatively low spatial resolutions, 30 and 90 meters for ASTER and SRTM, respectively, and it has been shown that their accuracy is relatively low in several regions (e.g., Kääb, 2005; Mukul et al., 2017). In this study a methodology is presented to improve the positional accuracy of the drainage networks extracted from the GDEMs using crowdsourced data available in the collaborative project OpenStreetMap (OSM). In this approach only free and global datasets are used, enabling its application to any location of the world. The methodology uses elevation points derived from the GDEMs and the water lines extracted from the collaborative project OSM to generate new DEMs, from which new water lines are obtained. The methodology is applied to two study areas and the positional accuracy of the used data and the obtained results are assessed using reference data.

#### Mots clés

- Drainage networks
- GDEMs
- OpenStreetMap
- Positional accuracy

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The Wavelets show it – the transit time of water varies in time

Pages: 295 - 302

#### Résumé

The ways how water from rain or melting snow flows over and beneath the Earth‘s surface affects the timing and intensity at which the same water leaves a catchment. Several mathematical techniques have been proposed to quantify the transit times of water by e.g. convolving the input-output tracer signals, or constructing frequency response functions. The primary assumption of these techniques is that the transit time is regarded time-invariant, i.e. it does not vary with temporarily changing e.g. soil saturation, evaporation, storage volume, climate or land use. This raises questions about how the variability of water transit time can be detected, visualized and analyzed. In this paper we present a case study to show that the transit time is a temporarily dynamic variable. Using a real-world example from the Lower Hafren catchment, Wales, UK, and applying the Continuous Wavelet Transform we show that the transit time distributions are time-variant and change with streamflow. We define the Instantaneous Transit Time Distributions as a basis for the Master Transit Time Distribution. We show that during periods of elevated runoff the transit times are exponentially distributed. A bell-shaped distribution of travel times was observed during times of lower runoff. This finding is consistent with previous investigations based on mechanistic and conceptual modeling in the study area according to which the diversity of water flow-paths during wet periods is attributable to contributing areas that shrink and expand depending on the duration of rainfall. The presented approach makes no assumptions about the shape of the transit time distribution. The mean travel time estimated from the Master Transit Time Distribution was ~54.3 weeks.

#### Mots clés

- Transit time distribution
- Tracer
- Chloride
- Continuous wavelet transform
- Non-stationary

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Conceptual model building inspired by field-mapped runoff generation mechanisms

Pages: 303 - 315

#### Résumé

Since the beginning of hydrological research hydrologists have developed models that reflect their perception about how the catchments work and make use of the available information in the most efficient way. In this paper we develop hydrologic models based on field-mapped runoff generation mechanisms as identified by a geologist. For four different catchments in Austria, we identify four different lumped model structures and constrain their parameters based on the field-mapped information. In order to understand the usefulness of geologic information, we test their capability to predict river discharge in different cases: (i) without calibration and (ii) using the standard split-sample calibration/ validation procedure. All models are compared against each other. Results show that, when no calibration is involved, using the right model structure for the catchment of interest is valuable. A-priori information on model parameters does not always improve the results but allows for more realistic model parameters. When all parameters are calibrated to the discharge data, the different model structures do not matter, i.e., the differences can largely be compensated by the choice of parameters. When parameters are constrained based on field-mapped runoff generation mechanisms, the results are not better but more consistent between different calibration periods. Models selected by runoff generation mechanisms are expected to be more robust and more suitable for extrapolation to conditions outside the calibration range than models that are purely based on parameter calibration to runoff data.

#### Mots clés

- Rainfall-runoff
- Catchment geology
- Hydrologic models
- Runoff response times
- A-priori information

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Calculation of critical flow depth using method of algebraic inequality

Pages: 316 - 322

#### Résumé

To calculate the critical depth and the least specific energy of steady non-uniform flows in open channels, one has to solve the polynomial equations. Sometimes, the polynomial equations are too difficult to get them solved. In this study, the theory of algebraic inequality has been used to derive formulas for determining the critical depth and the least specific energy of a steady non-uniform flow in open channel. The proposed method has been assessed using examples. Results using this new method have been compared to those using other conventional methods by engineers and scientists. It is found that the proposed method based on algebraic inequality theory not only makes the calculation process to be easy, but also gives the best calculation results of the critical depth and the least specific energy of a steady nonuniform flow.

#### Mots clés

- Critical depth
- Mean value inequality
- Steady non-uniform flow
- Specific energy
- Algebraic inequality

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Application and comparison of NSGA-II and MOPSO in multi-objective optimization of water resources systems

Pages: 323 - 329

#### Résumé

Optimal operation of reservoir systems is the most important issue in water resources management. It presents a large variety of multi-objective problems that require powerful optimization tools in order to fully characterize the existing trade-offs. Many optimization methods have been applied based on mathematical programming and evolutionary computation (especially heuristic methods) with various degrees of success more recently. This paper presents an implementation and comparison of multi-objective particle swarm optimization (MOPSO) and non-dominated sorting genetic algorithm II (NSGA-II) for the optimal operation of two reservoirs constructed on Ozan River catchment in order to maximize income from power generation and flood control capacity using MATLAB software. The alternative solutions were based on Pareto dominance. The results demonstrated superior capacity of the NSGA-II to optimize the operation of the reservoir system, and it provides better coverage of the true Pareto front than MOPSO.

#### Mots clés

- NSGA-II
- MOPSO
- Multi-objective optimization
- Flood control
- Hydropower

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Laboratory testing of granular kinetic theory for intense bed load transport

Pages: 330 - 336

#### Résumé

Collisional interactions in a sheared granular body are typical for intense bed load transport and they significantly affect behavior of flow carrying bed load grains. Collisional mechanisms are poorly understood and modelling approaches seldom accurately describe reality. One of the used approaches is the kinetic theory of granular flows. It offers constitutive relations for local shear-induced collision-based granular quantities - normal stress, shear stress and fluctuation energy - and relates them with local grain concentration and velocity. Depth distributions of the local granular quantities produced by these constitutive relations have not been sufficiently verified by experiment for the condition of intense bed load transport in open channels and pressurized pipes. In this paper, results from a tilting-flume facility including measured velocity distribution and deduced concentration distribution (approximated as linear profiles) are used to calculate distributions of the collision-based quantities by the constitutive relations and hence to test the ability of the kinetic-theory constitutive relations to predict conditions observed in these collision-dominated flows. This test indicates that the constitutive relations can be successfully applied to model the local collisional transport of solids at positions where the local concentration is not lower than approximately 0.18 and not higher than approximately 0.47.

#### Mots clés

- Granular flow
- Sheet flow
- Sediment transport
- Grain collision
- Tilting flume experiment

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Assessment of empirical formulae for determining the hydraulic conductivity of glass beads

Pages: 337 - 347

#### Résumé

Empirical formulae are often used in practice to quickly and cheaply determine the hydraulic conductivity of soil. Numerous relations based on dimensional analysis and experimental measurements have been published for the determination of hydraulic conductivity since the end of 19^{th} century. In this paper, 20 available empirical formulae are listed, converted and re-arranged into SI units. Experimental research was carried out concerning hydraulic conductivity for three glass bead size (diameters 0.2 mm, 0.5 mm and 1.0 mm) and variable porosity. The series of experiments consisted of 177 separate tests conducted in order to obtain relevant statistical sets. The validity of various published porosity functions and empirical formulae was verified with the use of the experimental data obtained from the glass beads. The best fit was provided by the porosity function n^{3}/(1-n)^{2}. In the case of the estimation of the hydraulic conductivity of uniform glass beads, the best fit was exhibited by formulae published by Terzaghi, Kozeny, Carman, Zunker and Chapuis et al.

#### Mots clés

- Hydraulic conductivity
- Empirical formulae
- Porosity
- Porosity function configuration

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The layering of a mountain podzol can strongly affect the distribution of infiltrated water in the soil profile

Pages: 348 - 356

#### Résumé

The layering of the soil profile can influence the accumulation of infiltrated water and the way in which subsurface runoff is formed. This paper examines a mountain podzol characterized by clearly developed soil horizons. After these horizons had been identified, distinct soil layers were defined (the eluvial horizon, the spodic horizon (undifferentiated), and weathered bedrock). Saturated hydraulic conductivity (K_{s}), particle size distribution and bulk density were measured in these layers. A visualization of the distribution of infiltrated water in the podzolic profile was performed using a dye tracer experiment. The accumulation of dyed water and a distinct lateral flow were detected in the eluvial layer. Only limited entry of water into the spodic layer was observed. These effects were caused by changes in soil hydraulic properties (SHP) among the investigated layers. For the spodic horizons, the measured K_{s} value (crucial SHP) was significantly lower than the Ks values for the other tested horizons. The probable reason for the lower K_{s} was an accumulation of fine particles and various substances in the spodic horizons, and corresponding changes in the porous system. The observed effects of layering indicate that water can be accumulated and subsurface runoff can be formed over the spodic layer during intensive rain or snow melting.

#### Mots clés

- Brilliant blue
- Guelph permeameter
- Field saturated hydraulic conductivity
- Infiltration into layered soil
- Mountain forest