The importance of a hydrogeological environment for the creation of the groundwater runoff (baseflow) and its relation to the total runoff has been evaluated in many studies. The groundwater runoff is mostly considered as a runoff component significant for preservation of low or minimal runoff from a catchment in dry periods. In the paper assessment of runoff conditions in various hydrogeological environments is used to explain the frequency of flood occurrences. Total runoff and the baseflow were compared in 39 geologically different catchments It was proved that flysch areas have higher fluctuations of the total runoff than crystalline areas. The hydrogeological characteristics thus explain more frequent floods in the flysch areas. It is also apparent that the baseflow in Tertiary parts of the flysch areas depends only insignificantly on the total annual precipitation. and Význam hydrogeologického prostředí pro tvorbu základního odtoku a jeho podíl v celkovém odtoku je hodnocen v mnoha pracích. Základní odtok je vesměs považován za složku významnou pro udržení nízkých či minimálních odtoků z povodí v suchých obdobích. V této práci je využito hodnocení odtokových poměrů v různých hydrogeologických prostředích k vysvětlení četnosti výskytu povodní. Byly porovnávány průběhy celkového odtoku a základního odtoku v 39 povodích s různou geologickou stavbou. Na základě této analýzy se ukázalo, že flyšové oblasti vykazují větší rozkolísanost celkových odtoků než krystalinické oblasti. Hydrogeologické vlastnosti tedy vysvětlují vyšší počet povodní ve flyši. Z výsledků je dále patrné, že hodnoty základního odtoku v terciérních částech flyšové zóny jsou jen málo závislé na velikosti ročních srážkových úhrnů.
The paper deals with the decision making model for flood control operation of a reservoir in conditions of stochastic uncertainty when the development of the flood is not known beforehand and only the short-term hydrological forecast is available. The decision model is based on the decision logic with the conditional IF-THEN rules by which current operational situations and discrete regulation actions are derived. The sensitivity analysis of the reliability of the forecasting model and comparison of the flood control in various conditions of uncertainty of input parameters are included. The decision-making model was tested on several historical floods on the Divoka Orlice river in the profile of the Pastviny dam. and Ve studii se odvozuje rozhodovací model pro potreby operativního rízení povodnového odtoku z nádrže, a to dusledne v podmínkách stochastické neurcitosti, kdy prubeh povodne není predem znám a k dispozici je pouze krátkodobá hydrologická predpoved. Rozhodovací model se opírá o rozhodovací logiku s podmínenými pravidly typu IF-THEN, kterými se popisují aktuální provozní situace a vyvozují diskrétní regulacní zásahy. Soucástí výzkumu byla citlivostní analýza spolehlivosti predpovedního modelu a srovnávací analýza rízení v ruzných podmínkách neurcitosti vstupních velicin. Model byl overován na souboru historických povodnových vln na Divoké Orlici v profilu prehrady Pastviny.
The purpose of this study was to assess how terracing affected overland flow and associated sediment losses, at the micro-plot scale (0.25 m2 ), in recently burnt stands of the two principal forest types in north-central Portugal, i.e. mono-specific stands of Maritime Pine and Eucalypt. Terracing is an increasingly common practice of slope engineering in the study region but its impacts on runoff and erosion are poorly studied. Non-terraced plots at the Eucalypt and the Pine site revealed similar median runoff coefficients (rc: 20-30%) as well as comparable median sediment losses (15-25 g m-2 ) during the first seven months following wildfire. During the ensuing, slightly wetter 18-month period, however, non-terraced plots at the Pine site lost noticeably more sediments (in median, 90 vs. 18 g m-2 ), in spite the runoff response had remained basically the same (median rc: 33 vs. 28%). By contrast, terraced plots at the same Pine site lost hugely more sediments (in median, 1,200 g m-2 ) during this 18-month period. Terraced plots at the Eucalypt site even lost three times more sediments (in median, 3,600 g m-2 ). Ground cover and resistance to shear stress seemed to be key factors in the observed/inferred impacts of terracing.
The aim of this article is to present partial results of more extensive research which is focused on using different methods for runoff computation in areas differing in land use. With the help of the deterministic lumped model HEC-HMS (Hydrologic Engineering Center - Hydrologic Modelling System) several simulations of runoff changes by different basin conditions were carried out. The Blanice River basin in the Šumava Mts. was chosen as an experimental catchment in its closure profile in Podedvory (gauge station, area 209.6 km2 ). For assessment of land cover changes impact on hydrological regime four scenarios were carried out - 10, 20, 50 and 100-year 1-day probability precipitation in combination with different initial conditions (soil saturation). These scenarios were applied to the stage of the land cover in the year 1992 and 2000 (based on the CORINE Landcover database). The method SCS CN (Soil Conservation Service Curve Number) was applied as the main model technique. and Cílem příspěvku je prezentovat dílčí výsledky rozsáhlejšího výzkumu zaměřeného na změny srážkoodtokového procesu vlivem změn charakteru vegetace a půdního pokryvu. Pomocí matematického modelu HEC-HMS (Hydrologic Engineering Center - Hydrologic Modelling System) byly uskutečněny simulace odtokové odezvy na příčinnou srážku ve dvou časových horizontech, které charakterizují dva odlišné stavy krajinného pokryvu. Modelovou oblastí bylo povodí Blanice po závěrový profil Podedvory (nad VD Husinec, 209,6 km2 ). Reakce povodí na srážkovou událost při změnách vegetačního pokryvu byla zhodnocena ve dvou časových horizontech - 1992 a 2000. K hodnocení změn vegetace byla použita databáze CORINE Landcover. Modelování změny odtokového režimu v daných časových horizontech proběhlo pro čtyři srážkové události. První z nich byl 1-denní úhrn srážek s pravděpodobností překročení 0,1, tedy s dobou opakování 10 let a další s dobami opakování 20, 50 a 100 let. Jako hlavní modelovací technika byla použita metoda SCS CN (Soil Conservation Service Curve Number).
The article addresses the problem of nature of species which could be reduced to the question: Are species classes (universals) or individuals (particular things)? Reflecting on the discussion between traditionalist (e.g. Kitts and Kitts, Ruse) and proponents of a radical solution (Ghiselin, Hull) - by way of the S-A-I thesis (Species As Individuals) - we concentrate on the third possibility under which species are viewed as a hybrid category such as a ''complex particular,'' ''individualized class'' or ''event-entities'' (Supe, Ruse). My argument centers on an interchangeability of parts, and it concludes that we must distinguish three types of relation between parts and wholes: constructivist, emergent and reproductive. Thanks to this differentiation, I tend to view species as individuals, but not in the usual constructivist or emergent sense. In order to do justice to the individual character of species, a special logico-ontological structure or type-which I propose to call ''reproductive type''-needs to be devised. and Vladimír Havlík
Vegetation and biocrust play crucial roles in dune stability and mobility, and their interaction can lead to bistability, temporal oscillations, and hysteresis. We studied a two-dimensional (2D) mathematical model of vegetation and biogenic crust cover dynamics on sand dunes. Under a certain parameter range, the space-independent version of the model exhibited the bi-stability of an oscillatory state and a steady state, and we studied the 2D dynamics of the model under these parameters. The patterns developed by the 2D model showed a high degree of spatial heterogeneity and complexity depending on the initial conditions and on the state type across the front. The results suggest that spatial heterogeneity and complexity can evolve from the intrinsic dynamics between vegetation and biocrust, even without natural geodiversity and spatiotemporal climate fluctuations. In the real world, these two types of intrinsic and extrinsic heterogeneity processes interact such that it is difficult to distinguish between them.