The contribution gives an overview of the experimental hydrological research in former Czechoslovakia in the 1980-ties. The development of hydrological experimental and representative basins is put into the context with UNESCO programs (IHD and IHP) and with the then-existing east-European co-operations, especially with project ''Methodological research in experimental and representative basins''. The contribution outlines the connection of this hydrological activity with project FRIEND in the 1990-ties. and Príspevok podáva prehľad československého hydrologického experimentálneho výskumu v osemdesiatych rokoch minulého storočia. Do kontextu stavia rozvoj hydrologických experimentálnych a reprezentatívnych povodí s programami UNECSO (MHD a MHP) a vtedajšími medzinárodnými spoluprácami, najmä s projektom Metodické výskumy v experimentálnych a reprezentatívnych povodiach. Naznačuje prepojenie tejto hydrologickej činnosti v rokoch deväťdesiatych s programom MHP UNESCO FRIEND.
The paper provides basic information on hydrological research performed in the mountain catchment of the Jalovecký creek, the Western Tatra Mountains by the Institute of Hydrology of the Slovak Academy of Sciences since the mid-1980-ties. The research was devoted to better understanding of spatial distribution of precipitation, soil moisture, snow cover, evapotranspiration and runoff generation. First part of the paper brings an overview of the results. Second part of the paper is devoted to the water balance of the catchment in hydrological years 1989-2005 and estimation of mean transit time of water in the catchment as given by the tracer method using the stable environmental isotope of 18O. Catchment mean annual precipitation in the studied period was 1562 mm. It varied from 1116 mm in the year of 2003 to 1854 mm in 2001. Mean annual runoff was 1015 mm and it varied between 703 mm in 2003 and 1284 mm in 1998. Mean annual air temperature at catchment mean elevation (1500 m a.s.l.) was 3.5 °C. Interpertation of δ18O in precipitation and runoff from the period 1991-2002 gave the mean transit time of 13 months. Direct application of measured values in precipitation provided more realistic results than the input data series prepared according to recommendations found in the literature. and Príspevok poskytuje základné informácie o hydrologickom výskume, ktorý vykonáva od druhej polovice 80. rokov 20. storočia Ústav hydrológie SAV v horskom povodí Jaloveckého potoka v Západných Tatrách. Výskum poskytol poznatky o priestorovom rozdelení atmosférických zrážok, vlhkosti pôdy, snehovej pokrývke, evapotranspirácii a tvorbe odtoku vo vysokohorskom prostredí. Stručný prehľad niektorých z nich uvádzame v prvej časti príspevku. Druhá časť príspevku za zaoberá hydrologickou bilanciou povodia za obdobie 1989-2005 a určením priemernej doby prechodu vody povodím pomocou metódy stopovačov, pričom bol použitý stabilný prírodný izotop kyslíka 18O. Priemerný ročný úhrn zrážok v povodí v období 1989-2005 bol 1562 mm (od 1116 mm roku 2003 do 1854 mm v roku 2001). Priemerný ročný odtok z povodia bol 1015 mm (od 703 mm v roku 2003 do 1284 mm v roku 1998). Priemerná ročná teplota vzduchu v priemernej nadmorskej výške povodia 1500 m n.m. bola 3,5 °C. Interpretáciou hodnôt δ18O v zrážkach a v odtoku za obdobie 1991-2002 bola určená priemerná doba prechodu 13 mesiacov, čo je časový úsek porovnateľný s tradičným hydrologickým rokom. Použili sme pritom dve varianty prípravy hodnôt δ18O v zrážkach (vstup do hydrologického cyklu povodia). Priame použitie meraných hodnôt dalo realistickejší výsledok, ako rad vstupných hodnôt upravený podľa odporúčaní z literatúry.
The paper provides an overview of recent hydrology-related research conducted by the Research Institute for Soil and Water Conservation and its predecessors. Research catchments and similar research sites, mostly under agricultural land use, are described. The principal catchments, located in Central and East Bohemian peneplains and highlands (Cerhovický potok near Hořovice, anonymous stream above Černičí near Čechtice, Kopaninský tok near Pelhřimov, and Žejbro near Skuteč with its subcatchments) are described in a greater detail with reference to web presentations (http://www.hydromeliorace.cz/povodi/ index.html). The second part overviews the main research results obtained, prevailingly during the last decade, in the field of catchment hydrology, water quality generation, agronomic measures for protection against nitrate pollution, the effect of tile drainage on extreme flows and water quality, soil water in the vadose zone with preferential flow and the landscape-ecological aspects of water resources protection. It is concluded that some problems could not be solved if the questions were not posed in a hydrological manner. The authors recommend to generalise empirical research results by modelling and to intensify connections between RISWC research and hydrological activities of other institutions. and Práce podává přehled novější historie výzkumu s hydrologickými prvky ve Výzkumném ústavu meliorací a ochrany půdy a v ústavech, které byly jeho předchůdci. Stručně popisuje jednotlivá malá výzkumná povodí a další výzkumné lokality, většinou se zemědělským využitím půdy. Hlavní výzkumná povodí, umístěná v oblasti středočeských a východočeských parovin a pahorkatin (Cerhovický potok u Hořovic, bezejmenný potok nad Černičím u Čechtic, Kopaninský tok u Pelhřimova a Žejbro u Skutče se svými podpovodími), jsou popsána podrobněji s odkazem na prezentace na webu (http://www.hydromeliorace.cz/povodi/index.html). Ve druhé části článku je podán přehled hlavních výsledků výzkumu dosažených převážně v posledním desetiletí v oblasti hydrologického režimu povodí a mechanismů tvorby jakosti vody, agronomických opatření na ochranu před dusičnanovým znečištěním, vlivu drenážních systémů na extrémní průtoky a jakost vod, vody v nenasycené zóně půdy s preferenčním prouděním a krajinně ekologických aspektů ochrany vodních zdrojů. Závěrem se konstatuje, že řadu problémů by nebylo možno vyřešit, kdyby otázky nebyly kladeny hydrologickým způsobem. Autoři doporučují zobecnit empirické výzkumy modelováním a zintenzivnit návaznost výzkumu VÚMOP na hydrologické aktivity jiných institucí.
Fundamental research of the hydrologic cycle in Volyňka catchment was established by the Institute of Hydrodynamics (Academy of Sciences of CR) in 1964. Since 1975 hydrologic cycle is monitored in the Liz catchment (spruce forest), Zábrod arable land and Zábrod meadow experimental areas. These experimental sites are situated in the mountainous and submontane region (800 - 1100 m a.s.l.) of the Šumava Mts. (Bohemian Forest). Influence of plant transpiration on the air temperature and entropy production is analyzed. Stabilizing role of both the water retention in a catchment and plant transpiration is evaluated. It was found that under conditions of sufficient retention capacity of a catchment (mainly the soil) and the area covered by transpiring vegetation, the hydrologic cycle was resistant to the great climatic perturbances in the growing seasons 1983, 1992 and 1994. and Ústav pro hydrodynamiku AV ČR započal v roce 1964 experimentální hydrologický výzkum v povodí Volyňky. Od roku 1975 probíhá soustavné měření charakteristik hydrologického cyklu na vrcholových povodích Liz a Albrechtec (lesní porost) a experimentálních plochách Zábrod-pole a Zábrod-louka ve Vimperské vrchovině (800 až 1100 m n. m., Šumava). Monitoring prokazuje, že jednou z příčin relativní stability teplot přízemní atmosféry a odtoků z horských povodí je transpirace rostlin ve vegetační sezóně umožněná retencí vody v povodí. Dostatečná retenční schopnost krajiny (zejména půdy) a dostatečná transpirace vegetačního krytu dodávají hydrologickému koloběhu cyklický charakter. Bylo prokázáno, že vodou dostatečně zásobený hydrologický cyklus na povodí Liz dobře odolává velkým jednorázovým perturbacím spojeným se zvětšením příkonu tepla, jako tomu bylo v letech 1983, 1992 a 1994 (následek výbuchu sopky El Chichon v roce 1982 a Mont Pinatubo v roce 1991).
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.
The procedure for identification of the long-term trends in the individual water quality determinands in surface water is described in the study. The methodology is based on requirements of the Directive 2000/60/EC and the existing water quality data in the database of the Slovak Hydrometeorological Institute. The methodology gives guidance for estimation of following issues: - influence of the length of the series on trends of development; - methods for calculation of the statistical characteristics; - methods for identification of the increasing and decreasing trends, as well as of the trend reversal point; - selection of the decision criteria for assessment of the trend significance. The methodology was applied for the trend analysis of the selected pollutants in the middle part of Hron River at Salkova near Banska Bystrica city. The results show that the rapid increase of pollution in 1970`s is followed by gradual improvement of the surface water quality in next period. and V predloženej štúdii je opísaný postup pri identifikácii dlhodobých trendov jednotlivých ukazovateľov kvality vody v povrchových tokoch. Pri vypracovaní metodiky sa vychádzalo z požiadaviek smernice 2000/60/EC a z existujúcich údajov o kvalite vody v databáze Slovenského hydrometeorologického ústavu. Vypracovaná metodika navrhuje konkrétne postupy na určovanie, napr. - vplyvu dĺžky obdobia na vývojové trendy; - spôsobov výpočtu štatistických ukazovateľov; - spôsobov identifikácie trendov rastu a poklesu, ako i bodov obratu trendu; - kritérií na rozhodovanie o významnosti jednotlivých trendov. Navrhnutá metodika bola aplikovaná pri analýze vybraných ukazovateľov kvality vody v mieste odberu Hron-Šalková , situovanom pri Banskej Bystrici. Z výsledkov vyplýva, že po prudkom náraste znečistenia stredného Hrona v sedemdesiatych rokoch dvadsiateho storočia dochádza k postupnému zlepšovaniu kvality povrchových vôd v tomto úseku.
Optimization methods are used to estimate parameters required for routing floods through open compound channels. Besides initial and boundary flow conditions, data required especially include, crosssectional area (A) of flow and conveyance (K) as functions of flow depth (y) for a representative crosssection of the study reach. Thus, instead of optimizing upon channel's geometric and hydraulic parameters, optimization is performed upon non-physical parameters in assumed A(y) and K(y) relationships. The optimization method selected for this application is the Nelder and Mead Simplex Algorithm. The objective function is expressed in terms of the relative differences between observed and simulated stages and discharges, which are evaluated based on the complete numerical solution of St Venant equations. This approach to formulating the optimization problem was applied to unsteady flow data sets for an experimental reach of the River Main in Northern Ireland. Based on statistical analysis, simulated and observed stages were found to be in good agreement. and Parametre potrebné pre kvantifikáciu transformácie povodňových vĺn v otvorených, zložených kanáloch, boli určené optimalizačnou metódou. Okrem počiatočných a okrajových podmienok sú potrebné ďalšie údaje, vrátane plochy priečneho rezu prúdom (A), ako aj vodivosť časti toku (K) ako funkcie hĺbky (y) pre reprezentatívny priečny rez. Namiesto optimalizácie geometrických a hydraulických parametrov kanála, optimalizácia sa vykonala pre nefyzické parametre, predpokladajúc závislosti A(y) a K(y). Vybranou metódou optimalizácie je Nelderov a Meadov Simplex Algoritmus. Funkcia je vyjadrená pomocou relatívnych rozdielov medzi pozorovanými a simulovanými vodnými stavmi a prietokmi, ktoré boli vyčíslené numerickým riešením rovníc St. Venanta. Tento spôsob formulácie optimalizačného problému bol aplikovaný na údaje pre neustálené prúdenie v experimentálnom priamom úseku rieky Main (River Main) v Severnom Írsku. Štatistickou analýzou bolo zistené, že simulované a merané vodné stavy boli veľmi blízke.
The aim of the paper is to study spatial and temporal changes in the magnitude, duration and frequency of high flows in the Danube basin. A hydrological series of the mean daily discharges from 20 gauging stations (operated minimally since 1930) were used for the analysis of changes in the daily discharges. The high flow events were classified into three classes: high flow pulses, small floods, and large floods. For each year and for each class, the means of the peak discharges, the number and duration of events, and the rate of changes of the rising and falling limbs of the waves were determined. The long-term trends of the annual time series obtained were analyzed and statistically evaluated. The long-term high flow changes were found to be different in three individual high flow classes. The duration of the category of high flow pulses is decreasing at 19 stations on the Danube and is statistically significant at the Linz, Vienna, Bratislava and Orsova stations. The frequency of the high flow pulses is increasing in all 20 stations. Also, the rising and falling rates of the high flow pulse category are increasing at the majority of the stations. The long-term trends of the selected characteristics of the small floods are very similar to the trends of the high flow pulses, i.e., the duration of small floods is decreasing, and their mean number per year is increasing. In the category of large floods the changes were not proved.
The fact that flash floods initiated in arable catchments are often accompanied by massive sediment and nutrient loads often leads to the assumption that surface runoff is the principle pathway by which runoff reaches watercourses. On the basis of an evaluation of several rainfall-runoff events in a representative agricultural catchment, we show that runoff from cultivated land may be generated in a way similar to that seen on forested slopes, where shallow subsurface runoff is the predominant pathway by which runoff makes its way to watercourses in most runoff events. To identify the predominant runoff pathway, we employed a combination of turbidity measurements and stream discharge data. Suspended sediment flux, a newly introduced index representing the ratio between precipitation duration and total sediment yield, and direction of the discharge-turbidity hysteresis loops were proposed as reflective indicators of the frequency of runoff via different pathways. In our study, most of the events initiated by rainstorms of various intensities and durations resulted in rapid increases in stream discharge. Although we observed temporal variability of topsoil properties attributable to seasonal weather changes and agricultural activities, e.g. bulk density and porosity, runoff generation was mainly driven by precipitation characteristics and the initial catchment saturation.