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Saturation overshoot as a basis for emergent flow phenomena in unsaturated homogeneous porous media
Fürst, T. ; Vodák, R. ; Šír, Miloslav ; Tesař, Miroslav
Understanding and description of fluid motion in unsaturated porous media rates among the most challenging and still not fully resolved problems. Traditionally, porous media flows were described by the continuum mechanics apparatus [1]. The continuum mechanics based models lead to partial differential equations which are mathematical formulations of the balance of mass, momentum, and energy. The most celebrated model is the so called Richards’ Equation (RE) [2]. Other continuum models (see [3], [4] and the reference and discussion therein) are various extensions built on similar principles as the RE.
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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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3D Micromodels of porous structures
Pražák, Josef
The 2D micromodels of porous structures have been used already 30 years. They have brought much interesting information, but an actual application of them on the 3D reality has natural limitation. That is why 3D micromodels have been developed. A multi-layer structure seems to be optimal for the construction of them. It allows not only a wide variety of modeled porous structures but a rich statistics of experiment as well.
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Hydrology of small basin 2008
Šír, Miloslav ; Tesař, Miroslav ; Lichner, Ľ.
The book includes the full text of 48 scientific articles. These articles were prepared as the contributions for the Conference with international participation “Hydrology of a small basin 2011” that was held from April 23th to April 24th 2008 in Prague. The Conference was organized by the Institute of Hydrodynamics ASCR, v.v.i. in Prague; Institute of Hydrology SAS in Bratislava; the Czech Water Management Society in Prague and Czech Committee for Hydrology. The book was published by the Institute of Hydrodynamics ASCR, v.v.i. in Prague in 2008.
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New suspect in the investigation into the cause of flash floods
Bíl, M. ; Fürst, T. ; Vodák, R. ; Pražák, Josef ; Šír, Miloslav ; Tesař, Miroslav
The aim of this contribution is to introduce a new possibility of the description of unsaturated porous media flow. The approach presented here is entirely different from the traditional ways (e.g. the Richards‘ Equation). It will be explained why the traditional models often fail to describe various observed phenomena. The new approach provides certain interesting forecasts, among others a possible mechanism for flash-flood formation. The authors explain why they think that, under specific conditions, porous medium discharge may substantially exceed the infiltration due to rainfall.
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Experimental study concerning stimulated outflow from porous structures
Pražák, Josef ; Biskup, B. ; Šír, Miloslav
It is generally supposed that the water flow in massive spates occurring in small catchments areas have two components. The first one is the direct surface flow of the water from a preceding rain (new water) the second one is caused by the water “pending” in the soil already before the rain (old water) stimulated by the rain to flow out. The stimulated outflow has been studied in a series of experiments. It was found that in laboratory test, a situation where the stimulated outflow exceeds the stimulating inflow can be simulated in an easy way.
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Dynamika půdní vody na Šumavě a v Krkonoších v srpnu 2002
Tesař, Miroslav ; Krejča, M. ; Polívka, Jiří ; Šír, Miloslav
The soil water movement during extreme rain is analysed in the Doupě and Kout catchment (Šumava Mts, Southern Bohemia) and in the Modrý Důl catchment (Krkonoše Mts., Northern Bohemia). Two cyclones, which moved from Hungary to Poland, caused extreme rainfall and subsequent extreme runoff in August, 2002. Precipitation, air and soil temperature, and tensiometric pressure were recorded in catchments. The analysis showed that the huge rain amount in August 2002 exceeded the retention capacity of the catchment covered by mature spruce forest and dwarf pine forest (Modrý Důl), dead forest and herb undergrowth (Kout), clearing covered by herbs (Doupě). It means that the plant cover played a negligible role in the runoff generation. The soil cover was not able to prevent the country from catastrophic runoff because its retention capacity is rather low (60 – 90 mm).
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Mikroskopická variabilita hydraulických vlastností půdy v borovicovém lese u obce Sekule na jihozápadě Slovenska
Orfánus, T. ; Lichner, Ľ. ; Šír, Miloslav ; Tesař, Miroslav
The variability of water repellency of pine-forest arenic Regosols and its influence on the infiltration process were estimated at the locality of Mláky II near Sekule in south-west Slovakia. The water drop penetration time (WDPT) tests of soil water repellency and infiltration tests with a miniaturized tension infiltrometer (3 mm diameter) at single-sample scale (100 cm3 volume, 22 cm2 surface) were performed. Extreme heterogeneity of water repellency and infiltration velocity was recorded. All the results suggested that the hydraulic properties of the soil are changing at millimetre scale due to the presence of unevenly distributed hydrophobic material.
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