Salinization is an increasing enviromental problem in ecosystems. The assessment of total dissolved solids (TDS), pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), alkalinity and the concentrations of main ions makes possible to identify salinization and alkalization degree. The saltaffected soils occur in the south part and south-east part of Žitný ostrov, where the dry and mild summer climate, evaporation soil water regime and mineralized groundwater create conditions for development of the saline and alkaline soils. Five localities with highly-mineralized groundwater were monitored to evaluate salinity and alkality in the period 1989-2006. At the bottom horizons in localities 1 - 5 evaporative residues (salt content) reached value 0.1 - 0.2 %. In 2006 dry evaporative residues (salt content) was higher than 0.2 %, EC was higher than 250 mS m-1 at the bottom horizons in localities 1, 2, 4. The mentioned data allow us to state that salinization and alkalization of soils is developing, it starts from the bottom of soil horizons through middle part of the soil profile up to the top horizons. This phenomenon was observed in all investigated soils in different stages of development. and Salinizácia v ekosystémoch je stále významnejší enviromentálny problém. Stanovenie celkového množstva rozpustených látok (TDS), elektrickej vodivosti (EC), sodíkového adsorpčného pomeru (SAR) a obsahu výmenného sodíka (ESP) umožňuje identifikáciu kritického potenciálu salinizácie a degradácie pôdy. Záujmové územie bolo vymedzené vo východnej časti Žitného ostrova, kde suché a horúce klimatické podmienky spolu s vysokomineralizovanými podzemnými vodami sú príčinou translokácie solí do pôdneho profilu. Bolo monitorovaných 5 lokalít v období 1989 - 2006. Namerané údaje poukazujú na vzrastajúci obsah solí, ktorý v r. 2006 dosiahol 0,1 - 0,2 % v celom pôdnom profile vo všetkých monitorovaných lokalitách, hodnoty EC 200 - 400 mS m-1 v spodných horizontoch vytvárajú podmienky pre rozvoj zasolených pôd.
Although playing an important role in shaping the environment, the mechanisms responsible for runoff initiation and yield in arid and semiarid regions are not yet fully explored. With infiltration-excess overland flow, known also as Hortonian overland flow (HOF) taking place in these areas, the uppermost surface 'skin' plays a cardinal role in runoff initiation and yield. Over large areas, this skin is composed of biocrusts, a variety of autotrophs (principally cyanobacteria, green algae, lichens, mosses) accompanied by heterotrophs (such as fungi, bacteria, archaea), which may largely dictate the infiltration capability of the surface. With most biocrust organisms being capable of excreting extracellular polymeric substances (EPS or exopolymers), and growing evidence pointing to the capability of certain EPS to partially seal the surface, EPS may play a cardinal role in hindering infiltration and triggering HOF. Yet, despite this logic thread, great controversy still exists regarding the main mechanisms responsible for runoff generation (runoff initiation and yield). Elucidation of the possible role played by EPS in runoff generation is the focus of the current review.
Direct interpolation of daily runoff observations to ungauged sites is an alternative to hydrological model regionalisation. Such estimation is particularly important in small headwater basins characterized by sparse hydrological and climate observations, but often large spatial variability. The main objective of this study is to evaluate predictive accuracy of top-kriging interpolation driven by different number of stations (i.e. station densities) in an input dataset. The idea is to interpolate daily runoff for different station densities in Austria and to evaluate the minimum number of stations needed for accurate runoff predictions. Top-kriging efficiency is tested for ten different random samples in ten different stations densities. The predictive accuracy is evaluated by ordinary cross-validation and full-sample crossvalidations. The methodology is tested by using 555 gauges with daily observations in the period 1987-1997. The results of the cross-validation indicate that, in Austria, top-kriging interpolation is superior to hydrological model regionalisation if station density exceeds approximately 2 stations per 1000 km2 (175 stations in Austria). The average median of Nash-Sutcliffe cross-validation efficiency is larger than 0.7 for densities above 2.4 stations/1000 km2 . For such densities, the variability of runoff efficiency is very small over ten random samples. Lower runoff efficiency is found for low station densities (less than 1 station/1000 km2 ) and in some smaller headwater basins.
We examine the feasibility and added value of upscaling point data of soil moisture from a small- to a mesoscale catchment for the purpose of single-event flood prediction. We test the hypothesis that in a given catchment, the present soil moisture status is a key factor governing peak discharge, flow volume and flood duration. Multiple regression analyses of rainfall, pre-event discharge, single point soil moisture profiles from representative locations and peak discharge, discharge duration, discharge volume are discussed. The soil moisture profiles are selected along a convergent slope connected to the groundwater in flood plain within the small-scale catchment Husten (2.6 km²), which is a headwater catchment of the larger Hüppcherhammer catchment (47.2 km², Germany). Results show that the number of explanatory variables in the regression models is higher in summer (up to 8 variables) than in winter (up to 3 variables) and higher in the meso-scale catchment than in the small-scale catchment (up to 2 variables). Soil moisture data from selected key locations in the small catchment improves the quality of regression models established for the meso-scale catchment. For the different target variables peak discharge, discharge duration and discharge volume the adding of the soil moisture from the flood plain and the lower slope as explanatory variable improves the quality of the regression model by 15%, 20% and 10%, respectively, especially during the summer season. In the winter season the improvement is smaller (up to 6%) and the regression models mainly include rainfall characteristics as explanatory variables. The appearance of the soil moisture variables in the stepwise regression indicates their varying importance, depending on which characteristics of the discharge are focused on. Thus, we conclude that point data for soil moisture in functional landscape elements describe the catchments’ initial conditions very well and may yield valuable information for flood prediction and warning systems.
The decline in groundwater levels is a cause of concern in many regions of the world, including the Sand Ridge of Hungary. The causes of the regional depletion range from rising air temperatures, changes in precipitation, domestic and agricultural groundwater use and past amelioration and recent afforestation, including the effects of drilling for crude oil exploration. The relations between the decline, the soil water regime and groundwater recharge under existing aged forests remained unclear thus far. Based on our monitoring of groundwater and soil moisture we aim to clarify this interplay in a new experimental site on the hilltop of the Sand Ridge. We compared three land-uses: a 41-year-old black locust (Robinia Pseudoacacia) offshoot forest, an 83-year-old first generation black pine (Pinus nigra) forest, and a grassland control site. The observed differences in the soil moisture profiles and dynamics were connected to the use of water by the given type of vegetation. We indicated a connection between the disruption of the groundwater recharge and the loss of contact of the rooting system of the forests with the deepening of the unconfined aquifer. Even if the aged forests could locally contribute to the decline, we conclude that the decline at the hilltop site that may be more strongly driven by other regional factors.
The aim of the study was to evaluate the climate and geographic factors controlling the hydrological drought of the rivers located in the Upper Vistula catchment in the Polish Carpathians. Drought was identified based on the daily flow (based on water stage measered once a day at 6 UTC) series dating from between 1975 and 2019 at 49 gauging cross-sections. Four physico-geographical regions were identified in the Polish Carpathians and spatial variabilities of the basic drought characteristics were developed within these regions. Such spatial distributions were treated as maps indicating drought hazard areas in the region. In addition, an analysis was undertaken to study the seasonality of the start and end times of the drought (all in the multi-annual period), the longest duration of droughts, the droughts of the highest volume in multi-annual period, as well as the number of drought days. Multi-annual variability of the number of drought days was also analysed. The results suggest that droughts in the Polish Carpathians are events characteristic of summer and autumn, whereas in the Tatra Mountains and the Podhale region - of autumn and winter. The greatest hazard of a prolonged and highvolume drought occurs in the Podhale region and the Tatra Mountains, while the lowest hazard is observed in the Bieszczady Mountains and the eastern part of the studied area.
Theoretical assumptions and practical approaches to temporal and spatial distribution of rainfall intensity in urban watersheds is still a research topic. The speed and direction of movement of rainfall events above urban watersheds are principal hydrologic parameters, which influence a rainfall-runoff process. This contribution reviews three methods, namely the Inverse Distance-Weighted Method (IDWM), Time Shift Method (TSM) and newly developed Geometrical Method (GM). The principal assumption of all three methods is based on the calculation of fictitious rainfall intensity at a particular location as weighted interpolation among the nearest real rain gauge stations. Any rainfall event above the urban watershed can be classified either as moving or non-moving storm. While the Inverse Distance-Weighted Method can be used for non-moving storms, the other two methods can describe the parameters of moving storms. Model RainGen, which was originally developed to create a basic source of rainfall data for rainfallrunoff mathematical models in urban watersheds, may be used not only for visualization but as well as for comparing of the measured and computed results. Case study for moving storms in Prague shows the results of TSM and GM methods. and Teoretické předpoklady a praktické přístupy k řešení časového a plošného rozložení srážek v urbanizovaných povodích jsou stále předmětem výzkumu. Rychlost a směr pohybu dešťových událostí nad urbanizovanými povodími představují hlavní hydrologické veličiny, které ovlivňují srážko-odtokový proces. Příspěvek se zabývá třemi metodami výpočtu, a to inverzní váhovou metodou, metodou časového posunu a nově navrženou geometrickou metodou. Hlavní předpoklad u všech tří metod je ve zvoleném místě založen na výpočtu fiktivní intenzity deště a to na základě interpolace s využitím váhové funkce mezi nejbližšími srážkoměrnými stanicemi. Každou srážkovou událost nad urbanizovaným povodím lze klasifikovat buď jako pohyblivou, nebo nepohyblivou. Zatímco inverzní váhová metoda může být použita pro nepohyblivé srážkové události, metodu časového posunu a geometrickou metodu lze doporučit pro pohyblivé srážkové události. Model RainGen, který byl původně vytvořen k tvorbě základních srážkových dat pro potřeby matematických modelů povrchového odtoku z urbanizovaných povodí, může být využit nejen k vizualizaci výsledků, ale rovněž k jejich vzájemnému porovnávání. Případová studie pohyblivých srážkových událostí v Praze ukazuje porovnání výsledků metody časového posunu a geometrické metody.
Iodine is conventionally used as a contrast agent in hydrological laboratory experiments using polychromatic X-ray computed tomography (CT) to monitor two-phase Darcy flow in porous geological media. Undesirable beam hardening artifacts, however, render the quantitative analysis of the obtained CT images difficult. CT imaging of porous sand/bead packs saturated with iodine and tungsten-bearing aqueous solutions, respectively, was performed using a medical CT scanner. We found that sodium polytungstate (Na6H2W12O40) significantly reduced the beam hardening compared with potassium iodide (KI). This result is attributable to the location of the K absorption edge of tungsten, which is nearer to the peak of the polychromatic X-ray source spectrum than that of iodine. As sodium polytungstate is chemically stable and less toxic than other heavy element bearing compounds, we recommend it as a promising contrast agent for hydrological CT experiments.
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 as cobbly sandy loam sampled at High Tatra mountains. It is shown, that those coarse rock (granite) fragments have the maximum retention capacity up to 0.16 volumetric water content. Retention curves of the four particular granite fragments have shown water capacity available for plants expressed in units of volumetric water content of 0.005 to 0.072 in the soil water potential range (0, -0.3 MPa). Available water capacity of stone fragments can contribute to the available water capacity of soil fine earth considerably and help to plants to survive during dry spells. and Hodnoty vodnej retenčnej kapacity hrubozrnných častíc skeletu v pôdach sa zvyčajne považujú za zanedbateľné. Avšak prítomnosť častíc skeletu v pôdach môže významne ovplyvňovať hodnoty vodnej kapacity pôdy ako aj jej hydraulickej vodivosti. Tento príspevok prezentuje výsledky merania maximálnej vodnej kapacity skeletu obsiahnutého v pôde. Pôdne vzorky boli odoberané v lokalite FIRE, Vysoké Tatry. Podľa meraní, hodnoty maximálnej retenčnej kapacity skeletu dosahovali 0,16 objemovej vlhkosti. Na základe retenčných kriviek pre 4 vybrané žulové kamene môžeme povedať, že hodnoty využiteľnej vodnej kapacity, vyjadrené v jednotkách objemu vody v pôde sa pohybovali od 0,005 do 0,072 pre vodný potenciál pôdy od 0 do -0,3 MPa. Využiteľná vodná kapacita častíc skeletu takto môže významne doplňovať využiteľnú vodnú kapacitu jemnozeme a pomáha rastlinám prežiť suché obdobia.
In this paper, I suggest a way of resolving the whole-part dilemma suggested in the Parmenides. Specifically, I argue that grabbing the second horn of the dilemma does not pose a significant challenge. To argue for this, I consider two theses about Forms, namely, the oneness and indivisibility theses. More specifically, I argue that the second horn does not violate the oneness thesis if we treat composition as identity and that the indivisibility thesis ought to be reinterpreted given Plato’s later dialogues. By doing so, I suggest a compositional understanding of Plato’s theory of Forms, which can resolve the whole-part dilemma.