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Mountainous soils usually contain a large number of rock fragments, particles with a diameter larger than 2 mm, which can influence soil hydraulic properties that are required to quantitatively describe soil water movement in stony soils. The objective of this study was to numerically estimate both the saturated hydraulic conductivity of a stony so...
Investigation of processes related to runoff generation is an important topic in catchment hydrology. Observations are usually carried out in small catchments or on hillslopes. Many of such catchments are located in mountain or forested areas. From many studies it is evident that soil conditions and soil characteristics are one of the crucial facto...
The aim of this study was to present and validate an alternative evapotranspiration calculation procedure that includes specific expression for the aerodynamic resistance. Calculated daily potential evapotranspiration totals were compared to the results of FAO56 procedure application and to the results of measurements taken with a precision weighin...
Stony soils are composed of fractions (rock fragments and fine soil) with different hydrophysical characteristics. Although they are abundant in many catchments, their properties are still not well understood. This article presents basic characteristics (texture, stoniness, saturated hydraulic conductivity, and soil water retention) of stony soils...
Few if any methods exist to estimate the effects of stone content (stoniness) on the unsaturated soil hydraulic properties. A relatively simple scaling method is presented to estimate the hydraulic conductivity of unsaturated stony soils having different stone contents. A key assumption of the method is that van Genuchten's water retention paramete...
Paper presents comparison of the daily reference crop (grass vegetation cover) potential evapotranspiration results calculated by the two modifications of the Penman-Monteith type equation. The first modification was published in FAO recommendation (Allen at al., 1998), PM-FAO, the second is modification according to Budagovskiy (1964) and Novák (1...
The scope of the presented study is the role of plant roots in movement of water in soil - plant - atmosphere continuum and its modelling. The outcomes are product of long-term collaboration between the Institute of Hydraulics and Rural Water Management, BOKU Vienna and the Institute of Hydrology, Bratislava. In the frame of this cooperation, there...
Water can evaporate from all wet surfaces if there is a flux of energy. The most important process for biomass production and proper functioning of the biosphere is evapotranspiration. Evapotranspiration is, however, the process of water transport through the soil-plant-atmosphere system (SPAS). Every subsystem of the SPAS can strongly influence th...
Evapotranspiration as a process is part of the water cycle of the Earth; it is the most important consumer of energy, creating the link between water and energy cycles of the Earth. The physics of water phase change is briefly presented. Consumption of energy to change liquid water into water vapor cools the biosphere, thus allowing the creation of...
Water evaporates from different, wet surfaces. This chapter briefly describes water evaporation from various evaporating surfaces and their specific features are accented. Evaporation of intercepted water, evaporation from water surfaces, from snow and ice as well as evaporation from urbanized surfaces is described. Transpiration as a process of wa...
The role of a plant is to reproduce itself. Transport of water from soil through plant and to the atmosphere is a part of this process. Water consumption in the photosynthetic process is small in comparison with transpiration, which is enormous, and transpirating water passes through the plant and stomata to the atmosphere. To preserve itself, the...
Evaporation is a catenary process, during which water is transported through the Soil-Plant-Atmosphere System (SPAS). One subsystem of SPAS is soil, which accumulates water and transports it to the roots (transpiration) or to the soil surface where water is evaporating. In this chapter, movement of water in the soil subsystem is described. Movement...
The boundary layer of the atmosphere (BLA) is the space above the Earth, properties of which are strongly influenced by the Earth surface. Water vapor evaporating from the surface is transported in the BLA; therefore, the properties of the BLA can strongly influence the evapotranspiration process. Vertical distributions of the meteorological charac...
Movement of soil water during transpiration is a complicated process in comparison to evaporation because the root system of plants extracts water (and solute) from the soil using the soil root layer. Evaporation is the typical movement of water to the soil surface (or close to it) from which water is evaporating. The properties of different plants...
The term evapotranspiration structure denotes separation into two basic components: transpiration (water movement through and from plants) and evaporation (from other surfaces). An approximative method of evapotranspiration structure calculation is presented. It is based on the empirically estimated relationship between the canopy leaf area index (...
Evapotranspiration rate from a given evaporating surface depends on the properties of the atmosphere only, if water is not a limiting factor. Transport of water to the evaporation surface or to the roots sometimes cannot cover potential evapotranspiration needs. The reason is the low hydraulic conductivity of the soil due to low soil water potentia...
Contemporary progress in remote sensing techniques provides the opportunity to use data acquired by this method in the calculation of regional evapotranspiration. The weak point of traditional methods is the necessity to measure soil-plant-atmosphere system (SPAS) data at separate sites and upscale the information for regional evapotranspiration ca...
Contemporary methods of evapotranspiration estimation are described in detail, along with transpiration and evaporation. Measurement of evapotranspiration by lysimeters (from bare soil or soil with a canopy) and measurement of evaporation from a water table are described. A wide variety of evapotranspiration calculation systems are presented, start...
The method presented to calculate evapotranspiration daily total allows estimation of it and its components (transpiration, evaporation) from homogeneous evaporating surfaces. The method denoted as combination method is based in principle on the Penman-Monteith equation with modifications in calculation canopy resistance (using the Obuchov-Monin ap...
Evapotranspiration and its components (evaporation and transpiration) as a process is one of the basic terms of Earth’s water balance; its importance is accented by the fact that transpiration is the vital element of the biomass production process. The second important property of evapotranspiration is its extreme consumption of solar energy, thus...
Influence of deforestation on hydrological cycle has been a subject of numerous studies since the beginning of the 20th century. A temporary increase of discharges after deforestation was typically reported (e.g. Bosch and Hewlett, 1982), but the measured data often show that“.. flood and erosion control functions of the forests become to be eviden...
Mountainous forest soils usually contain a large number of rock fragments (particle diameter >2 mm), which influence soil properties. Data characterizing hydraulic properties of these soils usually describe only the fine soil fraction (particle diameter <2 mm) properties. To quantitatively describe soil water movement in stony soils, it is necessar...
THEORY OF EVAPOTRANSPIRATION: 2. Soil and intercepted water evaporation
Evaporation of water from the soil is described and quantified. Formation of the soil dry surface layer is quantitatively described, as a process resulting from the difference between the evaporation and upward soil water flux to the soil evaporating level. The results of evapo...
Mountainous soils usually contain a large number of rock fragments (particle diameter > 2 mm), which influence soil hydraulic and retention properties. Data characterizing the properties of these soils usually describe only the fine earth (particle diameter < 2 mm). To quantitatively describe soil water movement in stony soils, their most important...
THEORY OF EVAPOTRANSPIRATION: 1. Transpiration and its quantitative description
Basic information about the evapotranspiration and its components is presented. System of equations describing the transport of water and energy in the soil - plant continuum is analyzed. The system of five differential equations with five unknowns is proposed, describi...
Forests significantly affect their own and adjacent environments. These effects can be modified through management practices
that influence tree species composition, structure, texture and the density of forest stands. Resulting changes exert an impact
on below-ground hydrological processes in forests ecosystems, e.g. infiltration, redistribution a...
The water retention capacity of coarse rock fragments is usually considered negligible. But the presence of rock fragments in a soil can play an important role in both water holding capacity and in hydraulic conductivity as well. This paper presents results of maximum water holding capacity measured in coarse rock fragments in the soil classified a...
WATER MOVEMENT IN STONY SOILS: THE INFLUENCE OF STONINESS ON SOIL WATER CONTENT PROFILES Viliam Novák, Karol Knava Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava 3, Slovakia, e-mail: novak@uh.savba.sk Soils containing rock fragments are widespread over the world, on Europe such soil account for 30%, 60% in Medit...
The use of electromagnetic (EM) soil moisture probes is proliferating rapidly, in two broad domains: in field and laboratory research; and in strongly practical applications such as irrigation scheduling in farms or horticultural enterprises, and hydrological monitoring. Numerous commercial EM probes are available for measurement of volumetric wate...
The impact of heating on the peristence of water repellency, saturated hydraulic conductivity, and water retention characteristics
was examined on soils from both forest and meadow sites in southwest Slovakia shortly after a wet spell. The top 5 cm of meadow
soils had an initial water drop penetration time WDPT at 20°C of 457 s, whereas WDPT in the...
Drought as a phenomenon means deficiency of water – in general. It is used frequently, but its definition is usually qualitative and sometimes contradictive. Definition of drought from EncyclopediaWikipedia says ‘A drought is an extended period of months or years when a region notes a deficiency in its water supply’. According to Multilingual Techn...
Vplyv rozdielnych porastov na úroveń hladín podzemných vûod v národnej prírodnej rezervácii Kláštorské Lúky
Mokrade sú citlivé ekosystémy charakteristické výskytom hladiny podzemnej vody v blízkosti terénu alebo aj na jeho povrchu. Významným mokradným systémom je aj národná prírodná rezervácia (NPR) Kláštorské lúky, ležiaca v povodí rieky Turiec. Z...
The design and implementation of a new or improved irrigation or drainage system should be preceded by a study of the soil water regime (SWR) to define the need for such a system and to optimize its design. This requires estimates of appropriate parameters characterizing the long-term (multiyear) dynamics of the SWR and its relation to biomass prod...
Abstrakt: Annual courses of soil water content in upper layer of soil covered by spruce canopy (Picea abies) was analysed, using simulation model with input data measured in the High Tatra mountains in the area influenced by the heavy windthrow at the end of the year 2004. The influence of different spruce tree density followed by the different lea...
Presented are results of simulations of root water uptake applying a macroscopic model of water transport in Soil - Plant - Atmosphere – Continuum. As a simulation tool is used the software package GLOBAL, based on the solution of the one-dimensional Richards equation. The main objective is to examine the contribution of root extraction functions (...
Root parameter distributions are needed for estimation of water uptake by plants in macroscale models. The main objective of the study was to assess and compare vertical distributions of dry mass, length and surface area of roots of spring barley, winter rye and maize grown under equivalent environmental conditions. Root samples were collected usin...
This paper contains results of quantitative analysis of the influence of intercepted water by different canopies (grass, coniferous forest) with different LAI (leaf area index) characteristics on water balance structure of the soil - plant - atmosphere continuum (SPAC) and especially on soil water movement in soil root zone. Site FIRE near Starý Sm...
Presented are results of simulations of root water uptake applying a macroscopic model of water transport in Soil - Plant - Atmosphere - Continuum. As a simulation tool is used the software package GLOBAL, based on the solution of the one-dimensional Richards equation. The main objective is to examine the contribution of root extraction functions (...
Water resources are usually treated as potential resources, directly exploitable by human population on the Earth. Among them, surface water and groundwater can be effectively managed for operational use. Soil water which belongs to the class of subsurface water represents the major volume of terrestrial water resources. The concept of soil water r...
Water resources are usually treated as potential resources, directly exploitable by human population on the Earth. Among them, surface water and groundwater can be effectively managed for operational use. Soil water which belongs to the class of subsurface water represents the major volume of terrestrial water resources. The concept of soil water r...
This contribution contains a proposal to estimate the critical soil water content of limited availability for plants, below
which transpiration starts to decrease due to limited water availability for roots, which is frequently noted as “the point
of limited soil water availability”. The method is based on the fact, that soil water content at which...
Introduction to biohydrology
Louis W. Dekker, Paul D. Hallett, Ľubomír Lichner, Viliam Novák, Miloslav Šír
BIOHYDROLOGY 2006 was the first international conference to discuss exclusively the interactions between hydrological and biological processes in soil. Over 90 scientists, from all the continents, attended this truly global conference held i...
An improved steady-state soil–vegetation–atmosphere transfer model was applied to three types of soils (loess, loamy soil, and sandy soil) and three typical daily meteorological conditions (a sunny day, a cloudy day, and an overcast day) to calculate the relationships between maize transpiration rates and an average soil water content or soil water...
The study presents a simplified model for estimating nutrient uptake by roots in maize canopies. The results of field studies with a maize canopy grown on silty soil at Trnava site (south of the Slovak Republic) show that the uptake rates of N (nitrogen), P (phosphorus) and K (potassium) nutrients can be described by a linear relationship between a...
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 FRACTUR...
This paper presents the physical basis of the FRACTURE submodel for simulating infiltration of precipitation/irrigation water into relatively dry, cracked, fine-textured soils. The FRACTURE submodel forms part of the HYDRUS-ET variably saturated flow/transport model. Infiltration into the soil matrix is formally divided into two components: (1) Ver...
The methods of estimation of soil-crack characteristics and the possible influence of soil cracks on the infiltration are described in this article. The most important properties of soil cracks, namely volume of cracks, internal crack surface and soil-crack depth were estimated using easily measured soil characteristics: the specific length of crac...
The results of the water infiltration/redistribution front position measurements—by means of a radioactive tracer technique—are presented for a clay loam soil at two different irrigation intensities vi1 = 2 mm h−1 and vi2 = 4 mm h−1. The measured results are checked off with those simulated by a numerical model. The model used in this study is base...
Rapid soil moisture variations were measured with TDR equipment at five
depths ranging from 0.1 to 0.9 m during five consecutive infiltration
experiments under ponding. Each time, 27 mm of water were applied. The
water of the second experiment was spiked with 200 mbq of
K131I-tracer. Its activity was recorded as functions of depth
and time with Gei...
In the years 1993-1996 the measurements of solute transport were made in caly-loam at the Experimental Station of the Research Institute of Irrigation in Most near Bratislava. The measurements of water flow and solute transport were performed by means of nuclear tracer technique. TDR moisture meters, tensiometers, and phase transmission moisture me...
Within the framework of the Swiss-Slovakian joint research program measurements of water flow and solute transport (131I) were made in a structured soil at the experimental site of the Research Institute of Irrigation in Bratislava. The measurements of water content (Swiss group) and solute transport (Slovakian group) at different depths were made...
Submodels for simulation of the effect of soil water regime (GLOBAL) and grain yield of maize (Zea Mays, L.) CORNY can be modified and then used simultaneously as a model CORNWAY to estimate relative plant yields. The first model (GLOBAL) is a mathematical deterministic model which simulates water transport in a soil profile during the vegetation p...
Presents the method of transformation of the drying branches of the retention curves measured at some constant temperature, to another appropriate temperature. For the transformation, we propose to apply the Hopmans and Dane's procedure, ie to use temperature coefficient which relates the measured soil water retention curve at standard temperature...
The values of the evapotranspiration calculated by the energy balance method were compared with corresponding results obtained by means of the EVASU model. Experimental data were obtained during NOPEX - First Concentrated Field Effort (CFE1). The CFE1 was realized in May-June 1994 in Lovsta, Sweden. The investigated vegetation were grass, spring ba...
A method is presented to estimate prognosis of annual water balance equation terms over the territory of Slovakia. Empirical equations between the average values of annual climatic characteristics and values of annual water balance terms are used to evaluate the impact of climate changes on the water balance of Slovakia. Outputs from two general ci...
The relation between the root density distribution of a horizontally homogeneous maize root system and the vertical root extraction patterns was studied. A field data set of root density distribution during the vegetation period were used together with the root extraction patterns calculated from soil water content distributions. Only those time in...
Simulation of the transport of water was calculated using continuously changed properties of the soil water profile, represented by five discrete vertical distributions. The GLOBAL model was used with and without consideration of hysteresis of soil hydraulic propertries. From results of the simulation it follows that for the given soil the hysteres...
In this paper, a simple method for estimation of soil-water extraction distribution by roots S (z) is described. S (z) is determined mainly by the distribution of the surface area of the roots. From field measurements it followed that typical distribution of the surface area of roots, as well as their mass, in a sufficiently moist soil has an expon...
The relation between flow velocity (v) and hydraulic gradient (7) was studied for two porous materials. The volume of the sample was allowed to change during experiment. For the kaolinite, the relation between v and I is non-linear, the hydraulic conductivity k becomes dependent on time and varies for both increasing and decreasing 7. After some ti...
Transport of chemicals on the Earth is closely related to the transport of water because water is usually a carrier of dissolved chemicals. The area of chemicals transport is limited mostly to the Soil - Plant - System (SPS), but water cycle is performed in the Soil - Plant - Atmosphere - System (SPAC). The transport of dissolved chemicals in surfa...
Vegetation period transpiration totals of the three agricultural canopies (maize, winter wheat, spring barley) were calculated for 31 vegetation periods, using the mathematical model HYDRUS -ET. Evapotranspiration and its components - evaporation and transpiration were calculated by the submodel incorporated in the HYDRUS -ET. The Penman - Monteith...
One of results of the wind throw in High Tatras in December 2004 was clearing of trees, covering about 12 000 hectares. The structure of the evaporating canopy was changed, followed by changes in evapotranspiration rates and their totals during the season. This article contains results of mathematical modeling of potential evapotranspiration of the...
An analysis of drought as a phenomenon and the proposal how to define and quantify lack of water in soil for plants, so called "physiological drought" is described. The presented approach is based on the theoretical considerations and empirically estimated relationships between biomass production of particular plant and transpiration total of this...
The soil water regime (SWR) changes occurred in the Kláštorské lúky natural reserve area during the last decade was caused by change of the groundwater level, by change of the vegetation cover and by the management of the wetland. The original vegetation cover represented by the shrubbery and the associations of the rare grass were replaced by comm...
1.0.1 The role of transpiration in the water and energy balance of the Earth Vegetation plays a crucial role in energy and mass exchange in the Soil -Plant – Atmosphere (SWAT) continuum. Biomass production is the primary role of plants. To performe this, three main processes are involved: 1. Photosynthesis. This process involves utilisation of 0.00...
The design and construction of amelioration systems (irrigation, drainage) should precede diagnosis of soil water regime (SWR), to estimate its need and design parameters. It means, it is needed to calculate cyclic course of so called soil water regime characteristics. As soil water regime characteristic can be used soil moisture of the soil root z...
Wetlands are sensitive ecosystems with groundwater table close to the soil surface and they are characteristics with specific biotops, corresponding to the continuous and high soil water content. The National Natural Reserve (NNR) Kláštorské luky is one of those types of ecosystems in the catchment of Turiec River, Central Slovakia. Social changes...
This contribution presents a proposal of semiempirical method to estimate vertical profiles of nutrients uptake rate by plant roots, based on results of field measurements of soil – plant – atmosphere continuum (SPAC). The transport of chemicals in porous media can be described by convection-dispersion equation, containing sink term, characterising...
Projects
Project (1)
Several studies already documented deviations between measured and calculated evapotranspiration depending on environmental and weather conditions. The aim of this project is to analyze biophysical and environmental controls on deviations between measured and
calculated evapotranspiration. Moreover, strong transfer of skills and knowledge on maintenance and operation of the lysimeter facilities, monitoring systems and evapotranspiration models is expected.