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Start Over Language Slovak Type article Data provider Academy of Sciences Library/Knihovna Akademie věd ČR

42. Inverse estimation of soil hydraulic properties and water repellency following artificially induced drought stress

Creator:
Filipović, Vilim, Weninger, Thomas, Filipović, Lana, Schwen, Andreas, Bristow, Keith L., Zechmeister-Boltenstern, Sophie, and Leitner, Sonja
Type:
article, model:article, and TEXT
Subject:
inverse modeling, water and ethanol infiltration, SHP estimation, water dynamics, and HYDRUS (2D/3D)
Language:
Slovak
Description:
Global climate change is projected to continue and result in prolonged and more intense droughts, which can increase soil water repellency (SWR). To be able to estimate the consequences of SWR on vadose zone hydrology, it is important to determine soil hydraulic properties (SHP). Sequential modeling using HYDRUS (2D/3D) was performed on an experimental field site with artificially imposed drought scenarios (moderately M and severely S stressed) and a control plot. First, inverse modeling was performed for SHP estimation based on water and ethanol infiltration experimental data, followed by model validation on one selected irrigation event. Finally, hillslope modeling was performed to assess water balance for 2014. Results suggest that prolonged dry periods can increase soil water repellency. Inverse modeling was successfully performed for infiltrating liquids, water and ethanol, with R2 and model efficiency (E) values both > 0.9. SHP derived from the ethanol measurements showed large differences in van Genuchten-Mualem (VGM) parameters for the M and S plots compared to water infiltration experiments. SWR resulted in large saturated hydraulic conductivity (Ks) decrease on the M and S scenarios. After validation of SHP on water content measurements during a selected irrigation event, one year simulations (2014) showed that water repellency increases surface runoff in non-structured soils at hillslopes.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

43. Investigating the impact of surface soil moisture assimilation on state and parameter estimation in SWAT model based on the ensemble Kalman filter in upper Huai River basin

Creator:
Liu, Yongwei, Wang, Wen, and Hu, Yiming
Type:
article, model:article, and TEXT
Subject:
soil moisture, EnKF, SWAT, and ESA CCI SM
Language:
Slovak
Description:
This paper investigates the impact of surface soil moisture assimilation on the estimation of both parameters and states in the Soil and Water Assessment Tool (SWAT) model using the ensemble Kalman filter (EnKF) method in upper Huai River basin. The investigation is carried out through a series of synthetic experiments and real world tests using a merged soil moisture product (ESA CCI SM) developed by the European Space Agency, and considers both the joint state-parameter updating and only state updating schemes. The synthetic experiments show that with joint stateparameter update, the estimation of model parameter SOL_AWC (the available soil water capacity) and model states (the soil moisture in different depths) can be significantly improved by assimilating the surface soil moisture. Meanwhile, the runoff modeling for the whole catchment is also improved. With only state update, the improvement on runoff modeling shows less significance and robustness. Consistent with the synthetic experiments, the assimilation of the ESA CCI SM with joint state-parameter update shows considerable capability in the estimation of SOL_AWC. Both the joint stateparameter update and the only state update scheme could improve the streamflow modeling although the optimal model and observation error parameters for them are quite different. However, due to the high vegetation coverage of the study basin, and the strong spatial mismatch between the satellite and the model simulated soil moisture, it is still challenging to significantly benefit the runoff estimates by assimilating the ESA CCI SM.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

44. Isothermal and non-isothermal infiltration and deuterium transport: a case study in a soil column from a headwater catchment

Creator:
Sobotková, Martina, Sněhota, Michal, Budínová, Eva, and Tesa, Miroslav
Type:
article, model:article, and TEXT
Subject:
isothermal infiltration, non-isothermal infiltration, column leaching, breakthrough curve, deuterium, viscosity, capillary trapping, entrapped air, and permeability
Language:
Slovak
Description:
Isothermal and non-isothermal infiltration experiments with tracer breakthrough were carried out in the laboratory on one intact column (18.9 cm in diameter, 25 cm in height) of sandy loam soil. For the isothermal experiment, the temperature of the infiltrating water was 20°C to the initial temperature of the sample. For the two non-isothermal experiments water temperature was set at 8°C and 6°C, while the initial temperature of the sample was 22°C. The experiments were conducted under the same initial and boundary conditions. Pressure heads and temperatures were monitored in two depths (8.8 and 15.3 cm) inside the soil sample. Two additional temperature sensors monitored the entering and leaving temperatures of the water. Water drained freely through the perforated plate at the bottom of the sample by gravity and outflow was measured using a tipping bucket flowmeter. The permeability of the sample calculated for steady state stages of the experiment showed that the significant difference between water flow rates recorded during the two experiments could not only be justified by temperature induced changes of the water viscosity and density. The observed data points of the breakthrough curve were successfully fitted using the two-region physical non-equilibrium model. The results of the breakthrough curves showed similar asymmetric shapes under isothermal and non-isothermal conditions.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

45. Kinematic diffusion approach to describe recharge phenomena in unsaturated fractured chalk

Creator:
Pastore, Nicola, Cherubini, Claudia, and I. Giasi, Concetta
Type:
article, model:article, and TEXT
Subject:
unsaturated;, recharge, rainfall, chalk, kinematic, and diffusive
Language:
Slovak
Description:
When dealing with groundwater resources, a better knowledge of the hydrological processes governing flow in the unsaturated zone would improve the assessment of the natural aquifer recharge and its vulnerability to contamination. In North West Europe groundwater from unconfined chalk aquifers constitutes a major water resource, therefore the need for a good hydrological understanding of the chalk unsaturated zone is essential, as it is the main control for aquifer recharge. In the North Paris Basin, much of the recharge must pass through a regional chalk bed that is composed of a porous matrix with embedded fractures. The case study regards the role of the thick unsaturated zone of the Cretaceous chalk aquifer in Picardy (North of France) that controls the hydraulic response to rainfall. In order to describe the flow rate that reaches the water table, the kinematic diffusion theory has been applied that treats the unsaturated water flow equation as a wave equation composed of diffusive and gravitational components. The kinematic diffusion model has proved to be a convenient method to study groundwater recharge processes in that it was able to provide a satisfactory fitting both for rising and falling periods of water table fluctuation. It has also proved to give an answer to the question whether unsaturated flow can be described using the theory of kinematic waves. The answer to the question depends principally on the status of soil moisture. For higher values of hydraulic Peclet number (increasing saturation), the pressure wave velocities dominate and the preferential flow paths is provided by the shallow fractures in the vadose zone. With decreasing values of hydraulic Peclet number (increasing water tension), rapid wave velocities are mostly due to the diffusion of the flow wave. Diffusive phenomena are provided by matrix and fracture-matrix interaction. The use of a kinematic wave in this context constitutes a good simplified approach especially in cases when there is a lack of information concerning the hydraulic properties of the fractures/macropores close to saturation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

46. Laboratory studies on bedload transport under unsteady flow conditions

Creator:
Mrokowska, Magdalena M., Rowiński, Paweł M., Książek, Leszek, Strużyński, Andrzej, Maciej, and Radecki-Pawlik, Artur
Type:
article, model:article, and TEXT
Subject:
bedload, bed shear stress, dimensional analysis, hysteresis, stream power, and unsteady flow
Language:
Slovak
Description:
Two sets of triangular hydrographs were generated in a 12-m-long laboratory flume for two sets of initial bed conditions: intact and water-worked gravel bed. Flowrate ranging from 0.0013 m3 s–1 to 0.0456 m3 s–1, water level ranging from 0.02 m to 0.11 m, and cumulative mass of transported sediment ranging from 4.5 kg to 14.2 kg were measured. Then, bedload transport rate, water surface slope, bed shear stress, and stream power were evaluated. The results indicated the impact of initial bed conditions and flow unsteadiness on bedload transport rate and total sediment yield. Difference in ratio between the amount of supplied sediment and total sediment yield for tests with different initial conditions was observed. Bedload rate, bed shear stress, and stream power demonstrated clock-wise hysteretic relation with flowrate. The study revealed practical aspects of experimental design, performance, and data analysis. Water surface slope evaluation based on spatial water depth data was discussed. It was shown that for certain conditions stream power was more adequate for the analysis of sediment transport dynamics than the bed shear stress. The relations between bedload transport dynamics, and flow and sediment parameters obtained by dimensional and multiple regression analysis were presented.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

47. Lattice Boltzmann method used to simulate particle motion in a conduit

Creator:
Dolanský, Jindřich, Chára, Zdeněk, Vlasák, Pavel, and Kysela, Bohuš
Type:
article, model:article, and TEXT
Subject:
Lattice Boltzmann method, particle motion, particle–fluid interaction, PIV, and particle tracking
Language:
Slovak
Description:
A three-dimensional numerical simulation of particle motion in a pipe with a rough bed is presented. The simulation based on the Lattice Boltzmann Method (LBM) employs the hybrid diffuse bounce-back approach to model moving boundaries. The bed of the pipe is formed by stationary spherical particles of the same size as the moving particles. Particle movements are induced by gravitational and hydrodynamic forces. To evaluate the hydrodynamic forces, the Momentum Exchange Algorithm is used. The LBM unified computational frame makes it possible to simulate both the particle motion and the fluid flow and to study mutual interactions of the carrier liquid flow and particles and the particle–bed and particle–particle collisions. The trajectories of simulated and experimental particles are compared. The Particle Tracking method is used to track particle motion. The correctness of the applied approach is assessed.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

48. Long-term changes in the hydrological regime of high mountain Lake Morskie Oko (Tatra Mountains, Central Europe)

Creator:
Ptak, Mariusz, Wrzesiński, Dariusz, and Choiński, Adam
Type:
article, model:article, and TEXT
Subject:
water temperature, ice phenology, water level, climate change, and Tatra Mountains
Language:
Slovak
Description:
The paper discusses changes in the hydrological regime of high mountain Lake Morskie Oko located in the Tatra Mountains, in the Tatra Mountains National Park, a UNESCO biosphere reserve (MaB). According to the research conducted in the years 1971–2015, its water stages decreased by 3.5 cm·dec–1, mean annual water temperature increased by 0.3ºC·dec–1 and the duration of ice phenomena and ice cover was reduced by 10 day·dec–1. No considerable changes in maximum values of ice cover thickness were recorded. Such tendencies are primarily caused by long-term changes in climatic conditions – air temperature and atmospheric precipitation. The hydrological regime of the lake was also determined by changes in land use in the lake’s catchment and its location in high mountains.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

49. Mapping topsoil field-saturated hydraulic conductivity from point measurements using different methods

Creator:
Braud, Isabelle, Desprats, Jean-François, Ayral, Pierre-Alain, Bouvier, Christophe, and Vandervaere, Jean-Pierre
Type:
article, model:article, and TEXT
Subject:
infiltration methods, topsoil field-saturated hydraulic conductivity, land cover, geology, and mapping
Language:
Slovak
Description:
Topsoil field-saturated hydraulic conductivity, Kfs, is a parameter that controls the partition of rainfall between infiltration and runoff and is a key parameter in most distributed hydrological models. There is a mismatch between the scale of local in situ Kfs measurements and the scale at which the parameter is required in models for regional mapping. Therefore methods for extrapolating local Kfs values to larger mapping units are required. The paper explores the feasibility of mapping Kfs in the Cévennes-Vivarais region, in south-east France, using more easily available GIS data concerning geology and land cover. Our analysis makes uses of a data set from infiltration measurements performed in the area and its vicinity for more than ten years. The data set is composed of Kfs derived from infiltration measurements performed using various methods: Guelph permeameters, double ring and single ring infiltrotrometers and tension infiltrometers. The different methods resulted in a large variation in Kfs up to several orders of magnitude. A method is proposed to pool the data from the different infiltration methods to create an equivalent set of Kfs. Statistical tests showed significant differences in Kfs distributions in function of different geological formations and land cover. Thus the mapping of Kfs at regional scale was based on geological formations and land cover. This map was compared to a map based on the Rawls and Brakensiek (RB) pedotransfer function (mainly based on texture) and the two maps showed very different patterns. The RB values did not fit observed equivalent Kfs at the local scale, highlighting that soil texture alone is not a good predictor of Kfs.
Rights:
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50. Mathematical modeling of groundwater contamination with varying velocity field

Creator:
Das, Pintu, Begam, Sultana, and Singh, Mritunjay Kumar
Type:
article, model:article, and TEXT
Subject:
solute, advection, diffusion, dispersion, aquifer, and finite Difference Method
Language:
Slovak
Description:
In this study, analytical models for predicting groundwater contamination in isotropic and homogeneous porous formations are derived. The impact of dispersion and diffusion coefficients is included in the solution of the advection-dispersion equation (ADE), subjected to transient (time-dependent) boundary conditions at the origin. A retardation factor and zero-order production terms are included in the ADE. Analytical solutions are obtained using the Laplace Integral Transform Technique (LITT) and the concept of linear isotherm. For illustration, analytical solutions for linearly space- and time-dependent hydrodynamic dispersion coefficients along with molecular diffusion coefficients are presented. Analytical solutions are explored for the Peclet number. Numerical solutions are obtained by explicit finite difference methods and are compared with analytical solutions. Numerical results are analysed for different types of geological porous formations i.e., aquifer and aquitard. The accuracy of results is evaluated by the root mean square error (RMSE).
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public