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Start Over Language Slovak Rights http://creativecommons.org/licenses/by-nc-sa/4.0/

504. Incipient motion of sediment particles in the presence of bed forms under decelerating and accelerating flows

Creator:
Dodangeh, Esmaeil and Afzalimehr, Hossein
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
incipient motion, bed forms, accelerating and decelerating flows, bed shear stress, and shields parameter
Language:
Slovak
Description:
This paper investigates the incipient motion of sediment particles under non-uniform flow in river and laboratory. In rivers, the non-uniform flow is often observed due to the presence of various bed forms. Threshold condition has been examined by using the Shields diagram based on the uniform flow assumption, however, this approach can be led to fallacious results for non-uniform flows where the effect of pressure gradient is significant due to bed forms. This study investigates the chronological order of incipient motion of the particles, the average threshold velocity (Ucr), and Shields parameter for non-uniform flows. River data collection with gravel is used for investigating the incipient motion of surface layer of river bed and the laboratory data collection is considered studying the incipient motion of sub-surface layer of river. Both river and laboratory data collections are conducted in the presence of bed forms. Results reveal that the Shields diagram underestimates the particle incipient motion under accelerating and decelerating flows for the both case of laboratory and river. In both weak and general motion in the laboratory, the values of the critical Shields parameter are located below the Shields diagram, showing no particle motion. Our analysis shows that the incipient motion in river is affected by the presence of bed forms, river width changes, and flow non-uniformity conditions. The results show that in the accelerating flow (the bed form exit with a negative slope), the incipient motion is greater than the decelerating flow (the bed form entrance with a positive slope).
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

505. Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany

Creator:
Gypser, Stella, Veste, Maik, Fischer, Thomas, and Lange, Philipp
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
repellency indbex, pF-curves, water holding capacity, and iological soil crusts
Language:
Slovak
Description:
Investigations were done on two former open-cast lignite mining sites under reclamation, an artificial sand dune in Welzow Süd, and a forest plantation in Schlabendorf Süd (Brandenburg, Germany). The aim was to associate the topsoil hydrological characteristics of green algae dominated as well as moss and soil lichen dominated biological soil crusts during crustal succession with their water retention and the repellency index on sandy soils under temperate climate and different reliefs. The investigation of the repellency index showed on the one hand an increase due to the cross-linking of sand particles by green algae which resulted in clogging of pores. On the other hand, the occurrence of moss plants led to a decrease of the repellency index due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The pore-related van Genuchten parameter indicate a clay-like behaviour of the developed soil crusts. Because of the inhomogeneous distribution of lichens and mosses as well as the varying thickness of green algae layers, the water retention differed between the study sites and between samples of similar developmental stages. However, similar tendencies of water retention and water repellency related to the soil crust formation were observed. Biological soil crusts should be considered after disturbances in the context of reclamation measures, because the initial development of green algae biocrusts lead to an increasing repellency index, while the occurrence of mosses and a gain in organic matter enhance the water holding capacity. Thus, the succession of biocrusts and their small-scale succession promote the development of soil and ecosystem.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

506. Infiltration into a swelling, cracked clay soil

Creator:
Novák, Viliam, Šimunek, Jiří, and Van Genuchten, Martinus Th.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Swelling Soils, Soil Cracks, Water Infiltration, Mathematical Modeling, napuciavajúce pôdy, pôdne pukliny, infiltrácia vody, and matematické modelovanie
Language:
Slovak
Description:
Transient infiltration into a swelling, cracked fine-textured soil was calculated using the originally designed FRACTURE submodel (version B) of the HYDRUS-ET simulation model. The model permits changes in the dimensions of the cracks during the infiltration process. Modeling results obtained with the new model were compared with those from FRACTURE submodel (version A) assuming a stable crack system. It is shown that deforming cracks lead to higher rates of infiltration during precipitation events as compared with stable cracks. A difference of about 20 percent was estimated in our illustrative example. and Práca obsahuje výsledky matematického modelovania infiltrácie vody do pôdy s puklinami, meniacimi svoje rozmery pocas procesu, (verzia B) v závislosti na vlhkosti pôdy, ktoré sú porovnané s výsledkami, získanými pomocou modelu s konštantnými rozmermi puklín (verzia A) pocas infiltrácie zrážok. Submodel FRACTURE - verzia B, ktorá kvantifikuje infiltráciu vody do pôdy s deformujúcimi sa puklinami je súcastou modelu HYDRUS–ET. Porovnanie výsledkov modelovania pomocou oboch submodelov ukázalo, že pocas zrážkovej udalosti v tomto ilustratívnom príklade rýchlost infiltrácie do pôdy s deformujúcimi sa puklinami je asi o 20 % väcšia ako do pôdy so stabilnými puklinami. Treba poznamenat, že meranie charakteristík infiltrácie vody do pôdy s puklinami a súcasné meranie deformácií siete puklín nie je v prírode prakticky možné, preto matematické modely môžu byt použité aj ako nástroje vedeckého výskumu v numerických experimentoch.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

507. Influence of hydrological situations on benthic organisms in a small river in Saxony (Germany)

Creator:
Kändler, Matthias and Seidler, Christina
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
macrozoobenthos, drift, discharge, and flow velocity
Language:
Slovak
Description:
This research was focused on the relationship between river discharge and organism drift. It was carried out for three years in a small heavily modified river in Saxony (Germany). The amount and species composition of drifting invertebrates were observed, depending on discharge and flow velocity. A station was installed where the flow velocity was continually measured and drifting organisms were caught with nets. An inventory of the aquatic community (benthic invertebrates) was taken to determine the species living in the river at the research station. The highest drift density measured was 578 organisms per m3 at a flow velocity of 0.90 m s-1 , the mainly drifting organisms were Chironomidae. Different organisms groups started drifting at different flow velocities. Heavy impacts, such as dredging the river and flood waves, affected the aquatic ecosystems and severely changed the aquatic community regarding the number and the diversity. Some of the aquatic invertebrates such as the Anthothecata completely disappeared after dredging. It was found that many different terrestrial organisms were part of the drift. The typical family of soil biota Collembola represented the largest share.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

508. Influence of model structure on base flow estimation using BILAN, FRIER and HBV-light models

Creator:
Machlica, Andrej, Horvát, Oliver, Horáček, Stanislav, Oosterwijk, Jacob, Van Loon, Anne F., Fendeková, Miriam, and Van Lanen, Henny A. J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
model structure differences, BILAN, FRIER and HBV-light models, total runoff, base flow simulation, Nitra catchment at Nedožery profile, rozdiely v štruktúre modelu, modely BILAN, FRIER a HBV-light, celkový odtok, simulácia podzemného odtoku, and povodie Nitry v profile Nedožery
Language:
Slovak
Description:
Hydrological models are widely used tools to solve a broad range of hydrological issues. Each model has its own structure defining inter-relationships of hydrological balance components, and comparative differences in the models’ inner structure must be taken into account when discrepancies result from the same data. Results of base flow simulation by three different models BILAN, FRIER and HBV-light were compared based on knowledge of the models’ internal structure. It was proven that the courses of modelled parameters are quite similar, but that the respective values differ. The highest base flow values were simulated by the BILAN model, due to the threshold value of the soil moisture storage incorporated within this model’s structure. The lowest values were obtained by HBV-light model. Simulated base flow values were compared with groundwater heads and minimum monthly discharges. This comparison showed that the base flow values in the Nitra catchment at Nedožery profile simulated by BILAN and FRIER models are closer to the reality than those, simulated by HBV-light model. and Hydrologické modely sú nástrojmi, často využívanými pri riešení širokého spektra hydrologických problémov. Každý z modelov má svoju vlastnú štruktúru, definujúcu vzájomné vzťahy prvkov hydrologickej bilancie. Preto musí byť pri posudzovaní rozdielnych výsledkov získaných použitím tých istých vstupných dát brané do úvahy porovnanie rozdielov vo vnútornej štruktúre modelov. V príspevku boli porovnávané výsledky simulácie podzemného odtoku tromi rozličnými modelmi BILAN, FRIER a HBV-light, berúc do úvahy znalosti o vnútornej štruktúre jednotlivých modelov. Bolo dokumentované, že priebehy modelovaných parametrov sú veľmi podobné, no získané hodnoty sa líšia. Najvyššie hodnoty podzemného odtoku boli simulované modelom BILAN, v dôsledku faktu, že v modeli je zabudovaná pevná limitná hodnota pre veľkosť zásoby vody v pôde. Najnižšie hodnoty podzemného odtoku boli získané modelom HBV-light. Simulované hodnoty podzemného odtoku boli porovnané s priebehom úrovne hladiny podzemnej vody a s minimálnymi mesačnými prietokmi. Toto porovnanie ukázalo, že hodnoty podzemného odtoku v povodí Nitry po profil Nedožery simulované modelmi BILAN a FRIER sú bližšie k reálnemu stavu než hodnoty simulované modelom HBV-light.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

509. Influence of organic manure amendments on water repellency, water entry value, and water retention of soil samples from a tropical Ultisol

Creator:
Liyanage, T.D.P. and Leelamanie, D.A.L.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
hydrophysical properties, organic manure, water entry value, water repellency, and water retention
Language:
Slovak
Description:
Lowered stability of soil aggregates governed by insufficient organic matter levels has become a major concern in Sri Lanka. Although the use of organic manure with water repellent properties lowers the wetting rates and improves the stability of soil aggregates, its effects on soil hydrophysical properties are still not characterized. Therefore, the objective of this study was to examine the relation of water repellency induced by organic manure amendments to the water entry value and water retention of a Sri Lankan Ultisol. The soil was mixed with ground powders of cattle manure (CM), goat manure (GM), Gliricidia maculata (GL) and hydrophobic Casuarina equisetifolia (CE) leaves to obtain samples ranging from non-repellent to extremely water repellent, in two series. Series I was prepared by mixing GL and CE with soil (5, 10, 25, 50%). Series II consisted of 5% CM, GM, and GL, with (set A) and without (set B) intermixed 2% CE. Water repellency, water entry value, and water retention of samples were determined in the laboratory. Soilwater contact angle increased with increasing organic matter content in all the samples showing positive linear correlations. Although the samples amended with CE showed high soil-water contact angles in series I, set A (without 2% CE) and set B (with 2% CE) in series II did not show a noticeable difference, where >80% of the samples had soilwater contact angles <90°. Water entry value (R2 = 0.83-0.92) and the water retention at 150 cm suction (R2 = 0.69-0.8) of all the samples increased with increasing soil-water contact angles showing moderate to strong positive linear correlations. However, set A (without 2% CE) and set B (with 2% CE) in series II did not differ noticeably. Water entry value of about 60% the samples was <2.5 cm. Mixing of a small amount (2%) of hydrophobic organic matter with commonly used organic manures slightly increased the water repellency of sample soils, however not up to detrimental levels. It did not generate adverse effects on water entry and increased the water retention. It was clear that intermixing of small quantities of hydrophobic organic manure with organic manures commonly used in Sri Lankan agriculture, would not generate unfavorable impacts on soils.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

510. Influence of surface water level fluctuation and riverbed sediment deposits on groundwater regime

Creator:
Koczka Bara, Márta, Velísková, Yvetta, Dulovičová, Renáta, and Schügerl, Radoslav
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
surface water - groundwater interaction, groundwater flow modelling, and infiltration/drainage resistance of rivers
Language:
Slovak
Description:
The spatial and temporal patterns of surface water (SW) - groundwater (GW) exchange are significantly affected by riverbed silting, clogging or erosion processes, by altering the thickness and hydraulic conductivity of riverbed sediments. The duration of SW-GW exchange is controlled by the drainage and infiltration resistance of river bottom sediments (e.g. Andrássy et al., 2012). Generally, these two parameters primarily depend on the hydraulic conductivity and on the thickness of clogged layer. In this study the flow processes between GW and SW were modeled by model TRIWACO for different infiltration resistance and drainage resistance of riverbed sediments. The model area is situated on the Rye Island, which is a lowland area with very low slope. In this area a channel network was built up, where the flow conditions are controlled by water-gates. Because of the low slope and the system of water gates built on the channels, the riverbeds are influenced by intensive clogging processes. First, the applicability of model TRIWACO in the study area was tested by modelling the response of GW on SW level fluctuation. It was simulated, how the regulation of water level and flow direction in the channels influence the GW level, especially in extreme hydrological conditions (drought/flood), and if the GW flow direction and GW level change as it was expected. Next, the influence of channel network silting up on GW-SW interaction was modeled. The thickness of riverbed sediments was measured and their hydraulic conductivity from disturbed sediment samples was evaluated. The assessed hydraulic conductivity was used to calculate the infiltration resistance and the drainage resistance of riverbed sediments in the study area. Then, the GW level and flow direction was simulated for different infiltration resistance and drainage resistance of sediments.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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