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42. Estimation of hydrodynamic properties of a sandy-loam soil by two analysis methods of single-ring infiltration data

Creator:
Bagarello, Vincenzo, Caltabellotta, Gaetano, and Iovino, Massimo
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
soil hydrodynamic properties, beerkan infiltration run, data analysis methods, BEST methodology, and Wu1 method
Language:
Slovak
Description:
Beerkan infiltration runs could provide an incomplete description of infiltration with reference to either the near steady-state or the transient stages. In particular, the process could still be in the transient stage at the end of the run or some transient infiltration data might be loss. The Wu1 method and the BEST-steady algorithm can be applied to derive soil hydrodynamic parameters even under these circumstances. Therefore, a soil dataset could be developed using two different data analysis methods. The hypothesis that the Wu1 method and BEST-steady yield similar predictions of the soil parameters when they are applied to the same infiltration curve was tested in this investigation. For a sandy-loam soil, BEST-steady yielded higher saturated soil hydraulic conductivity, Ks, microscopic pore radius, λm, and depth of the wetting front at the end of the run, dwf, and lower macroscopic capillary length, λc, as compared with the Wu1 method. Two corresponding means differed by 1.2–1.4 times, depending on the variable, and the differences appeared overall from moderate to relatively appreciable, that is neither too high nor negligible in any circumstance, according to some literature suggestions. Two estimates of Ks were similar (difference by < 25%) when the gravity-driven vertical flow and the lateral capillary components represented the 71–89% of total infiltration. In conclusion, the two methods of data analysis do not generally yield the same predictions of soil hydrodynamic parameters when they are applied to the same infiltration curve. However, it seems possible to establish what are the conditions making the two methods similar.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

43. Evaluation of a general model for multimodal unsaturated soil hydraulic properties

Creator:
Seki, Katsutoshi, Toride, Nobuo, and van Genuchten, Martinus Th.
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
water retention, unsaturated hydraulic conductivity, general hydraulic conductivity model, and multimodal hydraulic models
Language:
Slovak
Description:
Many soils and other porous media exhibit dual- or multi-porosity type features. In a previous study (Seki et al., 2022) we presented multimodal water retention and closed-form hydraulic conductivity equations for such media. The objective of this study is to show that the proposed equations are practically useful. Specifically, dual-BC (Brooks and Corey)-CH (common head) (DBC), dual-VG (van Genuchten)-CH (DVC), and KO (Kosugi)1BC2-CH (KBC) models were evaluated for a broad range of soil types. The three models showed good agreement with measured water retention and hydraulic conductivity data over a wide range of pressure heads. Results were obtained by first optimizing water retention parameters and then optimizing the saturated hydraulic conductivity (Ks) and two parameters (p, q) or (p, r) in the general hydraulic conductivity equation. Although conventionally the tortuosity factor p is optimized and (q, r) fixed, sensitivity analyses showed that optimization of two parameters (p + r, qr) is required for the multimodal models. For 20 soils from the UNSODA database, the average R2 for log (hydraulic conductivity) was highest (0.985) for the KBC model with r = 1 and optimization of (Ks, p, q). This result was almost equivalent (0.973) to the DVC model with q = 1 and optimization of (Ks, p, r); both were higher than R2 for the widely used Peters model (0.956) when optimizing (Ks, p, a, ω). The proposed equations are useful for practical applications while mathematically being simple and consistent.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

44. Evolution of local scour downstream of Type A PK weir in non-cohesive sediments

Creator:
Lantz, Wyatt D., Crookston, Brian M., and Palermo, Michele
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
equilibrium morphology, granular bed, piano key weir, and scour evolution
Language:
Slovak
Description:
A large-scale piano key weir laboratory study was conducted to investigate the evolution of the scour process occurring in the downstream basin for two non-cohesive granular bed materials, including the analysis of scour-hole geometry and patterns at equilibrium. It was observed that hydraulic conditions, particularly tailwater level, significantly affect the scour mechanisms and equilibrium morphology, eventually resulting in scour depths that exceeded the weir height. Unprecedented insights on the scour dynamics are also provided, along with tools to estimate the time evolution and maximum scour depth, its location in the streamwise direction, and the maximum scour length.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

45. Experimental investigation of hydrophobic bentonite effects on reducing evaporation from water surfaces

Creator:
Jajin, Roza Ghahramani, Feizi, Atabak, and Ghorbanpour, Mohammad
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
water evaporation, water surface, hydrophobic bentonite, and hexadecanol monolayer
Language:
Slovak
Description:
In recent years, due to the occurrence of water shortage and drought problems, particularly in arid and semiarid regions of the world, new methods to reduce evaporation from the surface of dam reservoirs, lakes, and other waterfree surfaces are investigated. This study aimed to use hydrophobic bentonite to reduce water evaporation from water surfaces, on a laboratory scale, and field conditions for the first time. Bentonite initially became hydrophobic by stearic acid (SA). Under such conditions, hydrophobic bentonite floats on the surface of water and forms a thin coating layer. The produced hydrophobic bentonite had a contact angle of 150°, indicating its superhydrophobicity. Evaporation reduction was measured under laboratory and field conditions and it was compared to hexadecanol as the reference material. The results demonstrated that the hydrophobic bentonite efficiency under laboratory conditions was similar to that of hexadecanol and prevented water evaporation by 36%. However, under field conditions, hydrophobic bentonite and hexadecanol efficiencies were 40% and 23% to reduce evaporation for 30 days, respectively. In terms of stability, hexadecanol needed to be re-injected after three days, while hydrophobic bentonite was stable and remained on the surface for more than 100 days under laboratory conditions and for more than 15 days under field conditions without needing reinjection. This coverage with method can be used to reduce evaporation from lakes, tanks, and reservoirs of small dams.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

46. Experimental investigation of the effect of vegetation on dam break flood waves

Creator:
Oguzhan, Semire and Aksoy, Aysegul Ozgenc
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
dam break, flood wave, physical model, Urkmez dam, and vegetation effect
Language:
Slovak
Description:
Dams have an important role in the industrial development of countries. Irrespective of the reason for dam break, the flood can cause devastating disasters with loss of life and property especially in densely populated areas. In this study, the effects of the vegetation on the flood wave propagation in case of dam break were investigated experimentally by using the distorted physical model of Ürkmez Dam. The horizontal and vertical scales of the distorted physical model are 1/150 and 1/30, respectively. The dam break scenarios were achieved by means of a gate of rectangular and triangular shape. The results obtained from experiments performed with vegetation were compared and interpreted with those obtained from experiments at which the vegetation configuration was absent. The analysis of the experimental data showed that the presence of vegetation causes a significant decrease in water depths as the flood wave propagates to the downstream and greatly reduces its impact on the settlements. It is also revealed that dam break shape plays an important role in temporal variation of flood wave.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

47. Field-scale assessment of the unsaturated hydraulic properties of residual soils in southeastern Brazil

Creator:
Gomes, Ruan G. S., Gomes, Guilherme J. C., Vargas, Eurípedes A., van Genuchten, Martinus Th., Pinto, João T. M. G., and Rosa, Felipe A.
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
residual soils, unsaturated soil hydraulic properties, field infiltration tests, and HYDRUS-2D
Language:
Slovak
Description:
Field tests were carried out to estimate effective unsaturated soil hydraulic properties of layered residual soils in Rio de Janeiro, southeastern Brazil. Data of this type are important for understanding the initiation of rainstorm-induced soil landslides, which often occur in the state of Rio de Janeiro as well as other areas having similar geologic settings and climate conditions. Tests were carried out using a simplified field approach, referred to as the Monitored Infiltration Test, which requires only a tensiometer to measure pressure heads below the wetting front, triggered by flow from a Mariotte bottle which maintains a constant pressure at the top edge of the soil profile. The data can then be analyzed by numerical inversion using the HYDRUS-2D software package. The test is relatively fast since no steady-state flow conditions are needed, and versatile since the test can be carried out quickly on steep slopes with the help of a manual auger. Soil water retention and the unsaturated hydraulic conductivity functions were obtained for a range of young, mature and saprolitic residual soils. The effective hydraulic properties of the distinct residual soil layers can be quite large, reflecting a need to provide a careful analysis of field-scale hydraulic heterogeneity in geotechnical analyses.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

48. How various mulch materials can affect the soil hydro-physical properties

Creator:
Fér, Miroslav, Nikodem, Antonín, Trejbalová, Sára, Klement, Aleš, Pavlů, Lenka, and Kodešová, Radka
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
mulch, aggregate stability, soil hydraulic properties, soil physical quality, repellency index, and readily available water
Language:
Slovak
Description:
An application of different mulch materials may lead to changes in soil properties. Our previous study, focused on the impact of various mulches during the 4-year period, showed that the change in some properties can be very rapid (e.g., soil pH), but in other cases such as hydraulic properties, the changes can be gradual. To find out, whether the extension of the mulching period will further affect the studied soil properties, the experiment continued for another 2 years. Differences between values of organic carbon content (Cox), soil physical quality (Sinf), gravitational water (GW) and readily available water (RAW) of soils not covered by any mulch and under various mulches (bark chips; wood chips; wheat straw; Agrotex EKO+ decomposable matting; polypropylene fabric covered bark chips; crushed stone) were much larger than those observed in our previous study. On the other hand, the opposite trend was observed for the water stable aggregates (WSA) index or soil pH. Differences between additionally measured hydraulic conductivities at the pressure head of −2 cm and repellency index (RI) were mostly insignificant. Results indicated that organic mulches can either positively (e.g., increase WSA index and Cox, and decrease GW) or negatively (e.g., decrease Sinf and RAW, and increase RI) affect soil properties.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

49. Hydrology of the Carpathian Basin: interactions of climatic drivers and hydrological processes on local and regional scales - HydroCarpath Research

Creator:
Szolgay, Ján , Blöschl, Günter , Gribovszki, Zoltán , and Parajka, Juraj
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
Carpathian basin, evapotranspiration, runoff coefficient, hydrological regime, CN number, and climate change
Language:
Slovak
Description:
The paper introduces the Special Section on the Hydrology of the Carpathians in this issue. It is the result of an initiative of the Department of Land and Water Resources Management of the Slovak University of Technology in Bratislava, the Institute of Hydraulic Engineering and Water Resources Management of the TU Vienna and the Institute of Geomatics and Civil Engineering of the University of Sopron to allow young hydrologists in the Carpathian Basin (and from outside) to present their research and re-network on the emerging topics of the hydrology of the Carpathians at the HydroCarpath Conferences since 2012.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

50. Hydrophysical characteristics in water-repellent tropical Eucalyptus, Pine, and Casuarina plantation forest soils

Creator:
Leelamanie, D.A.L., Piyaruwan, H.I.G.S., Jayasinghe, P.K.S.C., and Senevirathne, P.A.N.R.
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
Eucalyptus grandis, Pinus caribaea, Casuarina equisetifolia, hydrophysical characteristics, and water repellency
Language:
Slovak
Description:
Soil water repellency (SWR) reduces the rates of wetting in dry soils and is known to interfere with water movement into as well as within the soils. The objective of this study was to investigate the hydrophysical characteristics of three water-repellent tropical exotic plantation forest soils in wet and dry seasons. The study sites were Eucalyptus grandis (EG), Pinus caribaea (PC), and Casuarina equisetifolia (CE) plantation forest soils located in the up-country intermediate zone (EG and PC), and low-country dry zone (CE). Field experiments were conducted to measure the infiltration rate, unsaturated hydraulic conductivity (k), water sorptivity (SW). Laboratory experiments were conducted to measure the potential SWR and water entry value (hwe). All three soils showed higher SWR in the dry season, where CE soils showed the highest. The EG soils showed the highest SWR in the wet season. Although SWR in all soils decreased with increasing depth in the wet season, only CE soils showed a significant decrease in SWR with soil depth in the dry season. Compared with the wet season, the k (–1 cm) was lower and hwe was higher in the dry season. However, SW did not show a significant difference between wet and dry seasons. Initial infiltration rate and k (–1 cm) showed a negative correlation with contact angle in all three soils. Soils showed positive linear correlations between k (–1 cm) and SW, and negative linear correlations between SW and hwe showing that surface water absorption is related to both subsurface unsaturated water flow and surface water entry pressure. It was clear that the water entry into soils and the subsurface water flow were hindered by the SWR. High water entry values in the dry season predict high potentials for intensified surface runoff and topsoil erosion. Future research will be required on the interactions between soil biology and soil properties such as pore structure that would influence water flow into and within soils.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public