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Simulation of water and heat transport considering preferential flow. Experimental site Na Lizu
Votrubová, J. ; Dohnal, M. ; Vogel, T. ; Tesař, Miroslav
Coupled water and heat transport in soil profile at the experimental site Na Lizu (Volynka headwater catchment, Sumava Mountains, southern Bohemia) is studied. The site is located on a mild slope cov-ered with grass. The soil is Cambisol developed upon biotite paragneiss bedrock. One-dimensional dual-continuum model with semi-separate flow domains representing the soil matrix and the network of preferential pathways (S1D) is employed. Hydraulic parameters of the model are set based on labo-ratory retention curve measurements and in-situ measurements of hydraulic conductivity. Thermal pa-rameters are estimated using methodology of Cote and Konrad (2005). Simulation is conducted for the summer season of 2009. The in-situ monitored precipitation and soil surface temperatures are used as the model upper boundary condition. Model performance was evaluated through comparison with soil water pressure and soil temperatures monitored in situ.
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Evaluation of hydrological and climatic features of fast growing trees for energy use
Weger, J. ; Šír, Miloslav
Microclimatic changes in plantations of fast growing trees (FGT) against grassland consist in reducing the max. daily air temperatures of ground in sunny and warm days to 4 to 5º C, when is available soil water for transpiration. Minimum temperatures of ground air are significantly less affected; they are generally higher under canopy of FGT. Daily air humidity on hot days is usually greater in plantations of FGT than in grassland. In the growing season, soil temperatures are lower in plantations of FGT than in the stands under grass cover. Reduction of daily air temperatures and soil temperatures under canopy of FGT is mainly due to the cooling effect of transpiration. Shielding effect of high vegetation is not the dominant cause of temperature reduction. Large-scale plantations of FGT will have no observable effect on the temperature of the countryside or on the hydrological cycle. They will not cause land draying and reduction of runoff from the landscape.
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Runoff from a small mountain basin due to soil water oversaturation
Vondrka, A. ; Šír, Miloslav ; Tesař, Miroslav
Analysis of runoff in a small mountain basin enables better understanding of the mechanisms of extreme runoff formation in small watersheds. Especially the proportion of old (soil) and new (rain) water in various stages of runoff is evaluated. The paper describes a method to determine when the new rainwater flows in a stream. The method is based on measurements of water conductivity and the concentration of K+ ions in the flowing water. The aim is to distinguish between old and new water flow in the closing profile of a small mountain basin. As new water is called water, which was in contact with the soil only a short time - several minutes or hours. The term old water refers to water that was retained in the soil for many days or weeks. In the growing season, the K+ concentration in soil water decreases with the duration of contact of water with soil and plant roots, thus the K+ concentration in the water is an indicator of its age,ie. of the length of the delay of water in the soil.
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Design of early warning system against lightning floods in mountain conditions
Tesař, Miroslav ; Šír, Miloslav ; Polívka, Jiří
The sophisticated local warning system against flash floods in mountain conditions is described. It is designed using the latest knowledge on the hydrodynamic mechanisms of storm runoff. It was found that extreme discharges are caused by these factors and their combinations: (1) saturation of soil cover with water, (2) soil surface hydrophobia, (3) gravity destabilized flow of water in the soil, (4) extreme rainfall, usually after prolonged dry period. Typical combinations causing extreme runoff, are (1) and (3) - the water saturation of soil cover can cause gravity destabilized flow induced by a small rain, (2) and (4) - long-term drought may cause the hydrophobic surface of the soil and simultaneously trigger extreme rain.
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Use of stable hydrogen and oxygen isotopes in hydrology of small catchments in the Czech and Slovak Republic
Šanda, M. ; Vitvar, T. ; Holko, L. ; Blažková, Š. ; Bůzek, F. ; Císlerová, M. ; Fottová, D. ; Kostka, Z. ; Kulasová, A. ; Kvítek, T. ; Šnytr, O. ; Tachecí, P. ; Tesař, Miroslav ; Vícha, Z. ; Žlábek, P.
The contribution summarizes the development of isotope hydrology and hydrogeology in the Czech and Slovak Republic over the past 40 years. Records of 18O and 2H in nine experimental catchments and their interpretation provide a description of runoff component mixing from various soil and rock environments, as well as a calculation of mean water residence time of 7 to 25 months. The 18O and 2H content in two profiles of the Jizera River and two boreholes in the lower reaches shows little communication of river water with the groundwater supply resources in the Lower Jizera area; the communicaton increases with pumping intensity. The 18O and 2H content in wetlands and groundwater in two catchments of the Jizera Mts. shows the differences in recharge to the wetlands via groundwater or precipitation. The isotope hydrology and hydrogeology perspectives in the ČR and SR include capacity building, cooperation of laboratories and conjunctive use of izotopic and hydrogeochemical approaches.
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Influence of the development of vegetation cover in the basin on the regime of surface water and groundwater resources
Buchtele, Josef ; Tesař, Miroslav
Variability of water regime is influenced usually not only by the changes of vegetation cover in the annual cycle, but also by the vegetation development in the span even of several decades. The resulting evapotranspiration requirement depends on actual climatic conditions; moreover the needs of soil moisture and the oscillation of solar radiation are also significant. The simulations of rainfall–runoff process have been used with the intention to follow the role of the developing vegetation cover and long-term climatic fluctuations. The differences between monitored and simulated runoff in the relatively long periods are the possible tool for the appraisal of changes in the water regime, which are influenced also by the changes of evapotranspiration need.
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Rheology of high viscous food substances
Štern, Petr ; Vlasák, Pavel
Rheological properties of high viscous food substances, mainly of animal origin, greatly influenced their preparation, homogenization and processing. By collagen substances were studied the complex of rheological properties by their processing. We have determined, that the viscoelasticity have the bigger influence that dynamic viscosity.
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Rheology and texture of sun lotions
Štern, Petr ; Panovská, Z. ; Morávková, Tereza
All analysed sun lotions were stable. Psychorheology was applied as a suitable complex method. Rheological parameters were compared to sensory texture attributes. All relationships were statistically significant (correlation coefficients 0.89 – 0.99). Fast and objective rheological analysis could replace time and money consuming sensory assessment.
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Motion of multiple cylinders in potential flow of ideal fluid
Kharlamov, Alexander A. ; Filip, Petr
The flow field past multiple arbitrarily moving cylinders is calculated using a generalisation of the conventional images method. The flow is presented by a flow from an infinite set of dipoles. For calculation purposes the infinite series must be, however, truncated. The kinetic energy of fluid is presented as a sum over all modelling dipoles. A rather good convergence of the method is observed. However, if the distances between any cylinders tend to zero, the method fails in zones close to the contact point. Nevertheless, even for the case of touching cylinders the series for the kinetic energy remain convergent. In case of just two cylinders the method projects on the classical method of images. Method is validated by several comparisons with solutions known from the literature.
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