This paper presents the results of testing the applicability of the MIKE Basin model for simulating the efficiency of scenarios for reducing water pollution. The model has been tested on the Olšava River Basin (520 km2 ) which is a typical rural region with a heterogeneous mix of pollution sources with variable topography and land use. The study proved that the model can be calibrated successfully using even the limited amount of data typically available in rural basins. The scenarios of pollution reduction were based on implementation and intensification of municipal wastewater treatment and conversion of arable land on fields under the risk of soil erosion to permanent grassland. The application of simulation results of these scenarios with proposed measures proved decreasing concentrations in downstream monitoring stations. Due to the practical applicability of proposed measures, these could lead to fulfilment of the water pollution limits required by the Czech and EU legislation. However, there are factors of uncertainty that are discussed that may delay or limit the effect of adopted measures in small rural basins.
With regard to the water quality changes, the area of the Czech part of the Elbe River basin is extraordinarily dynamic. In the 20th century it experienced an enormous increase of load of pollution. Since the beginning of the 1990´s due to the political and economical changes we have witnessed a particularly intensive decrease in the emission volume and a related increase in water quality of watercourses. However, positive changes in the pollution load balance have occurred mainly in the biggest watercourses and these changes have not been accompanied by similar development in the whole river system. Using a newly created classification methodology the basic models of dynamics of water quality changes in the Elbe River basin have been derived. Based on GIS geostatistical analysis, regions with analogous water quality development trends have been defined for selected parameters and critical areas have been identified. It has become apparent that the prevailing part of the Elbe River basin has been experiencing a gradual increase in pollution. In addition, after a previous decrease, a number of watercourses experienced a recurrence of the increase in load. These areas are priorities for further development and the control of surface water protection against pollution. and Oblast české části povodí Labe je z hlediska změn kvality vody mimořádně dynamická. Díky intenzivnímu vývoji antropogenních aktivit a společenským změnám zaznamenala v průběhu 20. století nejprve enormní nárůst zátěže znečištěním, od počátku 90. let jsme naopak svědky mimořádně intenzivního snížení objemu emisí a souvisejícího zvyšování jakosti vody v tocích. Pozitivní změny v látkové bilanci jsou však soustředěny především na největší toky – Labe a Vltavu a nejsou doprovázeny obdobným vývojem v celém povodí. Pomocí nově vytvořené metodiky klasifikace vývoje kvality vody prezentované v článku byly na základě geostatistické analýzy sestaveny základní modely časové dynamiky změn kvality vody v povodí Labe. Pro jednotlivé ukazatele byly na základě analýzy v prostředí GIS vymezeny regiony s analogickými trendy vývoje kvality povrchových vod a identifikovány kritické oblasti. Ukazuje se, že přes pozitivní vývoj jakosti vody v hlavních sídelních a průmyslových regionech v 90. letech převažující část povodí Labe stále zaznamenává v jednotlivých ukazatelích postupný nárůst znečištění, na řadě toků navíc po předchozím poklesu dochází k opětovnému nárůstu zátěže. Tyto oblasti představují prioritu pro další rozvoj a řízení ochrany povrchových vod před znečištěním.
Although the quantification of real evapotranspiration (ETr) is a prerequisite for an appropriate estimation of the water balance, precision and uncertainty of such a quantification are often unknown. In our study, we tested a combined growth and soil water balance model for analysing the temporal dynamics of ETr. Simulated ETr, soil water storage and drainage rates were compared with those measured by 8 grass-covered weighable lysimeters for a 3-year period (January 1, 1996 to December 31, 1998). For the simulations, a soil water balance model based on the Darcy-equation and a physiological-based growth model for grass cover for the calculation of root water uptake were used. Four lysimeters represented undisturbed sandy soil monoliths and the other four were undisturbed silty-clay soil monoliths. The simulated ETr-rates underestimated the higher ETr-rates observed in the summer periods. For some periods in early and late summer, the results were indicative for oasis effects with lysimeter-measured ETr-rates higher than corresponding calculated rates of potential grass reference evapotranspiration. Despite discrepancies between simulated and observed lysimeter drainage, the simulation quality for ETr and soil water storage was sufficient in terms of the Nash-Sutcliffe index, the modelling efficiency index, and the root mean squared error. The use of a physiological-based growth model improved the ETr estimations significantly.
The paper presents the results of the study of the sediments deposition process in a settling basin by using a k-ε turbulence model. The results obtained are than compared with the results obtained by using 1 and 2 D mathematical models and field measurements. In the first step, the settling basin is designed based on the formulae recommended by classical approach. The transition zone at the entrance of settling basin is then adjusted to satisfy more uniform flow at the beginning of the active zone. The flow velocity variation and bed shear stress distribution over the cross section area are furthermore analyzed and questions suggesting further development of mathematical models are identified. For the second step, a schematized settling basin is then modelled in three-dimensional laterally confined model for the purpose of dealing with turbulences that potentially bring more sediment to the side and to the end of settling basin. Finally, recommendations for the design of settling basin are given by analyzing the results obtained by both mathematical and empirical methods. By comparison of the results obtained and field measurements made in Indonesia, useful design recommendations are derived. and Príspevok obsahuje výsledky štúdia sedimentačného procesu v usadzovacej nádrži s využitím modelu turbulencie k-ε. Takto získané výsledky sú porovnané s tými, ktoré boli získané pomocou jedno- a dvojdimenzionálneho modelu a s terénnymi meraniami. Najskôr bol sedimentačný bazén navrhnutý pomocou klasických vzorcov. Prechodová zóna a vstup do usadzovacieho bazénu bol potom upravený tak, aby zabezpečil relatívne homogénne prúdenie na začiatku aktívnej zóny. Boli analyzované zmeny rýchlosti prúdenia a rozdelenie trecích napätí na dne v priečnych rezoch koryta a boli identifikované problémy, ktoré by umožnili ďalší vývoj matematických modelov tohto javu. V ďalšom kroku bol modelovaný schematizovaný usadzovací bazén ako trojrozmerný, na oboch stranách ohraničený model, aby sa dalo manipulovať s turbulenciou, ktorá by mohla potenciálne dopraviť viac sedimentov na strany a na koniec sedimentačnej nádrže. Nakoniec uvádzame odporúčania pre návrh sedimentačných nádrží, vychádzajúc z výsledkov využitia matematických aj emprických metód. Porovnaním týchto výsledkov s výsledkami terénnych meraní v Indonézii boli navrhnuté užitočné odporúčania.
In Tunisia especially in the Medjerda watershed the recurring of floods becoming more remarkable. In order to limit this risk, several studies were performed to examine the Medjerda hydrodynamic. The analysis of results showed that the recurrences of floods at the Medjerda watershed is strongly related to the sediment transport phenomena. Initially, a one dimensional modelling was conducted in order to determine the sediment transport rate, and to visualize the river morphological changes during major floods. In continuity of this work, we will consider a two-dimensional model for predicting the amounts of materials transported by the Medjerda River. The goal is to visualize the Medjerda behaviour during extreme events and morphological changes occurred following the passage of the spectacular flood of January 2003. As a conclusion for this study, a comparative analysis was performed between 1D and 2D models results. The objective of these comparisons is to visualize the benefits and limitations of tested models. The analysis of the results demonstrate that 2D model is able to calculate the flow variation, sediment transport rates, and river morphological changes during extreme events for complicated natural domains with high accuracy comparing with 1D Model.
The study presented herein investigates the impact of simulated changes in land cover on rainfall-runoff conditions for the transboundary basin of the upper Lužnice. The HEC-HMS hydrological model was chosen for these simulations. Scenario models were used to simulate the impact of modifications in basin land cover with individual scenarios reflecting ground cover changes. The years 1990 and 2000, which are available in the CORINE Landcover database, were chosen as variants of river basin land cover. In addition, two theoretical versions of possible extreme variants in fundamental land cover changes - the conversion from agricultural land to grassland and the forestation of the river basin, with the exception of roads and bodies of water - were also included. Single day rainfall totals with a recurrence period of 10, 20, 50 and 100 years were selected to calculate the volume of runoff and culmination discharge. These results demonstrate a clear decrease in the degree of impact of land cover structure on runoff conditions, increasing with the magnitude of precipitation. and Článek představuje výsledky simulace vlivu změn krajinného krytu na srážko-odtokové poměry v přeshraničním povodí horní Lužnice. Pro modelování byl vybrán hydrologický model HEC-HMS. K modelování vlivu změn krajinného pokryvu povodí byla použita metoda scénářového modelování, kde se v jednotlivých scénářích mění krajinný pokryv. Jako varianty krajinného pokryvu povodí byly zvoleny roky 1990 a 2000, pro které je k dispozici databáze CORINE Landcover, a dále dvě teoretické krajní varianty možných variant změn struktury krajinného krytu - zatravnění zemědělské půdy a zalesnění povodí kromě intravilánů, komunikací a vodních ploch. Pro výpočet objemů odtoků a kulminačních průtoků byly vybrány jednodenní návrhové srážkové úhrny s pravděpodobností opakování 10, 20, 50 a 100 let. Z výsledků simulace je zřejmý pokles vlivu struktury krajinného pokryvu na odtokové poměry se vzrůstající extremitou srážky.
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).
Knowledge on soil moisture is indispensable for a range of hydrological models, since it exerts a considerable influence on runoff conditions. Proper tools are nowadays applied in order to gain in-sight into soil moisture status, especially of uppermost soil layers, which are prone to weather changes and land use practices. In order to establish relationships between meteorological conditions and topsoil moisture, a simple model would be required, characterized by low computational effort, simple structure and low number of identified and calibrated parameters. We demonstrated, that existing model for shallow soils, considering mass exchange between two layers ( the upper and the lower), as well as with the atmosphere and subsoil, worked well for sandy loam with deep ground water table in Warsaw conurbation. GLUE (Generalized Likelihood Uncertainty Estimation) linked with GSA (Global Sensitivity Analysis) provided for final determination of parameter values and model confidence ranges. Including the uncertainty in a model structure, caused that the median soil moisture solution of the GLUE was shifted from the one optimal in deterministic sense. From the point of view of practical model application, the main shortcoming were the underestimated water exchange rates between the lower soil layer (ranging from the depth of 0.1 to 0.2 m below ground level) and subsoil. General model quality was found to be satisfactory and promising for its utilization for establishing measures to regain retention in urbanized conditions.
This paper describes results of investigation of the stream-aquifer interaction on the south part of Hron basin area near sites Turá and Šárovce. The main goal of the study was to designe hydraulic model of the area and with help of modelling tools to find out interaction of stream flow and groundwater flow, and also influence of riverbed dropdown on groundwater and Článok obsahuje výsledky výskumu interakcie povrchových a podzemných vôd v južnej časti čiastkového povodia Hrona v blízkosti obcí Turá a Šárovce. Hlavným cieľom štúdie bolo vytvoriť hydraulický model územia a následne pomocou modelovacích nástrojov určiť veľkosť interakcie pri rôznych prietokoch, určiť dosah vplyvu prechodu povodňovej vlny na úroveň hladiny podzemnej vody v čase a priestore a stanoviť vplyv poklesu kóty dna rieky na hladinu podzemnej vody.
Weighing lysimeters can be used for studying the soil water balance and to analyse evapotranspiration (ET). However, not clear was the impact of the bottom boundary condition on lysimeter results and soil water movement. The objective was to analyse bottom boundary effects on the soil water balance. This analysis was carried out for lysimeters filled with fine- and coarse-textured soil monoliths by comparing simulated and measured data for lysimeters with a higher and a lower water table. The eight weighable lysimeters had a 1 m2 grass-covered surface and a depth of 1.5 m. The lysimeters contained four intact monoliths extracted from a sandy soil and four from a soil with a silty-clay texture. For two lysimeters of each soil, constant water tables were imposed at 135 cm and 210 cm depths. Evapotranspiration, change in soil water storage, and groundwater recharge were simulated for a 3-year period (1996 to 1998) using the Hydrus-1D software. Input data consisted of measured weather data and crop model-based simulated evaporation and transpiration. Snow cover and heat transport were simulated based on measured soil temperatures. Soil hydraulic parameter sets were estimated (i) from soil core data and (ii) based on texture data using ROSETTA pedotransfer approach. Simulated and measured outflow rates from the sandy soil matched for both parameter sets. For the sand lysimeters with the higher water table, only fast peak flow events observed on May 4, 1996 were not simulated adequately mainly because of differences between simulated and measured soil water storage caused by ET-induced soil water storage depletion. For the silty-clay soil, the simulations using the soil hydraulic parameters from retention data (i) were matching the lysimeter data except for the observed peak flows on May, 4, 1996, which here probably resulted from preferential flow. The higher water table at the lysimeter bottom resulted in higher drainage in comparison with the lysimeters with the lower water table. This increase was smaller for the finer-textured soil as compared to the coarser soil.