Universität Stuttgart
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Item Open Access VEGAS - Versuchseinrichtung zur Grundwasser- und Altlastensanierung(1993) Kobus, Helmut; Teutsch, Georg; Koschitzky, Hans-Peter; Cirpka, OlafDie Versuchseinrichtung zur Grundwasser- und Altlastensanierung VEGAS, die derzeit an der Universität Stuttgart gebaut wird, wird aus einer Versuchshalle mit mehreren großmaßstäblichen Versuchsständen bestehen. Der Bau von VEGAS wird vom Bundesminister für Forschung und Technologie BMFT und vom Umweltministerium des Landes Baden-Württemberg im Rahmen des Projektes Wasser-Abfall-Boden PWAB finanziert und steht allen interessierten Forschungsnahmern aus der Bundesrepublik offen. VEGAS verfolgt im wesentlichen zwei Ziele: 1) Entwicklung und Optimierung von in-situ Sanierungsverfahren, 2) Prozeßforschung zum Schadstoffverhalten im Untergrund.Item Open Access Relating hydraulics and ecological processes(1991) Hjorth, Peder; Kobus, Helmut; Nachtnebel, Hans Peter; Nottage, Albert; Robarts, RichardAny major modification of the hydraulic system results with some retardation in a response of the ecosystem trying to adapt to the new conditions. It is difficult to imagine situations where hydraulics and ecosystems are not related. Thus, harmonizing hydraulics with ecology means to identify alternative hydraulic measures which yield simultaneously economic benefits and improvement, preservation or at least a best fit of the environmental situation. Often, these objectives are subjected to an inherent conflict and therefore harmonizing is dependent on the preference structure of the modern society, which is inclined to sustainable development. The objective of this chapter is to develop a framework (methodology) which might assist in relating hydraulics and ecology with respect to specific goals under site and problem dependent constraints.Item Open Access Groundwater pollution control : a challenge to hydraulic research(1993) Kobus, HelmutGroundwater constitutes a major natural resource for drinking water supply. The serious deterioration of groundwater quality observed in all industrialized and densely populated countries can be considered as an unspectacular, but ubiquitous "man-caused environmental disaster". Groundwater management has to match the increasing demands of drinking water supply (and other uses) with the constraints of the natural groundwater system with respect to both quantity and quality. In this paper, groundwater pollution problems are described and strategic considerations with respect to groundwater protection and subsurface remediation are illustrated by several examples. It is shown that the way towards adequate engineering solutions for sustainable development of groundwater resources still poses many challenges to hydraulic research.Item Open Access The sub-systems. 4 : Groundwater(1991) Herrmann, Reimer; Hubert, P.; Kobus, HelmutGroundwater constitutes the most important freshwater resource of the earth, it is two orders of magnitude larger than the total water volumes of rivers and lakes. It is a renewable resource, characterized by stability of its chemical composition and stability of temperature. Percolation of water through the subsurface has a good purification effect due to the combined action of filtration, sorption, chemical reactions and microbiological processes. Groundwater is utmost important as drinking water resource, since it is less prone to pollution than surface waters due to the protection effects of the covering layers. However, industrial and agricultural activities have led to groundwater pollution problems which are sometimes irreversible and in any case very difficult and expensive to recover. This endangers the long-term use for drinking water supply, and any efforts for sustainable development have to consider the vulnerability of groundwater resources to pollution, which shows great regional diversity, by suitable groundwater protection efforts.Item Open Access Simulation and interpretation of multiphase processes in porous and fractured-porous media(1994) Helmig, Rainer; Kobus, Helmut; Braun, ChristofA numerical model concept for simulating multi phase flow processes is presented. The conceptual model involves the approximation of heterogeneous porous and fractured porous media, by application of one-, two- and threedimensional elements in space that can be combined arbitrarily in a single model. The mathematical formulation of multiphase flow is valid for both saturated and unsaturated regions, so that dynamic front propagation behaviour as well as different geology-related retention characteristics can be accounted for in the model. For every Finite Element model problems arise when capillary pressure effects can be neglected and the governing equations are of hyperbolic type. To overcome these difficulties, the differential equations were formulated in terms of pressure and saturation as primary variables. To provide an accurate representation of the resulting saturation-front velocities and to avoid numerical oscillations a modified Petrov-Galerkin method was employed. To verify the code, the Buckley-Leverett problem was solved, and together with an adaptive finite element algorithm excellent results were obtained.Item Open Access Untersuchungen zur Erkundung effektiver Aquiferparameter : Testfeld WASSER/BODEN "Horkheimer Insel" ; Schadstofftransport im Untergrund, Erkundungs- und Überwachungsmethoden(1992) Ptak, Thomas; Schad, Hermann; Teutsch, Georg; Kobus, HelmutDie Kenntnis der hydraulischen Parameter Durchlässigkeit und Speichervermögen eines Aquifers ist die entscheidende Voraussetzung für die Berechnung bzw. Modellierung von Strömungs- und Transportvorgängen im Grundwasser. In heterogenen Systemen stellt insbesondere die hydraulische Durchlässigkeit jedoch keine Konstante dar, sondern variiert räumlich teilweise um mehrere Größenordnungen. In porösen Medien - wie dem Horkheimer Testfeldaquifer - ist diese Variabilität vor allem sedimentalogisch bedingt und unterliegt in der Regel einer räumlichen Struktur. Aufgrund der Unkenntnis der physikalischen Prozeßparameter der Sedimentation bzw. des enormen Aufwandes diese Struktur deterministisch zu erkunden, wird die hydraulische Durchlässigkeit als das Ergebnis eines stochastischen Prozesses betrachtet und durch statistische und geostatistische Strukturparameter beschrieben.Item Open Access Evaluation of groundwater sampling techniques for the investigation and monitoring of contaminated sites(1990) Teutsch, Georg; Barczewski, Baldur; Kobus, HelmutThe collection of representative groundwater samples is an essential prerequisite in hydrogeological site evaluation and groundwater monitoring. Erroneous or insufficent sampling may lead to wrong conclusions, possibly causing considerable health and/or financial risks, especially in respect to the assessment of contaminated sites. The collection of representative water samples therefore requires the use of appropriate sampling techniques, taking into account the prevailing aquifer conditions, the borehole hydraulics and the chemical parameters to be investigated. Consequently, the definition of the most suitable sampling equipment should be based on multiple criteria. In general these are the changing temperature and pressure conditions and the contact of the water with non-inert materials, which may affect the chemical integrity of the sample during the drilling of the well, the withdrawal and pumping of the water to the ground surface as well as the storage and transport to the laboratory. The major factors have to be investigated and quantified in order to minimize all undesired effects. In this paper the major influencing factors are discussed. Furthermore, an evaluation of various sampling techniques and sampling systems is presented. Special consideration is given to the ability of various systems to adequately sample groundwater with high organic loads. In the last section, some new sample system developments are briefly presented together with the expert system CASES, which was developed at the Stuttgart Institut für Wasserbau.Item Open Access Fachtechnische Voraussetzungen zur Festlegung von Sanierungsmassnahmen(1991) Kobus, Helmut; Spitz, KarlheinzDie Charakteristiken einer Schadstoffausbreitung im Grundwasser spiegeln sich auch in der Planung von Sanierungsmaßnahmen wider. Der vorliegende Beitrag befaßt sich mit den dafür notwendigen fachtechnischen Voraussetzungen: der Erkundung, dem Abschätzen der Sanierungsbedürftigkeit, der Planung geeigneter Sanierungsmaßnahmen und dem Erstellen eines Meßprogramms.Item Open Access Risk assessment of well contamination using a regional stochastic modelling approach(1994) Franke, Hans-Jörg; Kobus, Helmut; Teutsch, GeorgThis paper presents a stochastic risk analysis approach for contamination of water supply wells in agriculturally dominated catchment areas, using a stochastic approach, where a numerical one-dimensional pesticide transport model has been coupled with a numerical three-dimensional groundwater flow- and transport model. The risk analysis is based on Monte-Carlo simulations with multiple realizations of the entire parameter set at a scale of individual agricultural fields. For the generation of the parameter set in the saturated zone the turning band method was used according to the lognormal pdf. Based on a set of soil and aquifer data from literature, the importance of different soil parameter distributions and different agricultural area sizes, were analysed with respect to the variability of the concentration breakthrough curves as observed at an assumed groundwater supply well. Using the coupled stochastic modelling approach the risk of exceeding a given concentration limit was investigated as a result of spatially variable soil and aquifer transport properties.Item Open Access Neuere Erkenntnisse aus der Grundwasserforschung : Eintrag und Transport von Stoffen(1994) Kobus, HelmutDen Beitrag der Forschung zum Grundwasserschutz zu umreißen ist angesichts der vielen Aktivitäten in den unterschiedlichsten Fachdisziplinen eine schier unlösbare Aufgabe. Nach einem einführenden Überblick will ich zu den Fragen des Stoffeintrags und des Stofftransports etwas im Hinblick auf Präventivmaßnahmen und Wasserschutzgebiete sagen. Im weiteren möchte ich die Rolle der numerischen Modelle als Prognoseinstrument für die Praxis beleuchten und schließlich auch kurz die aktuellen Entwicklungen im Bereich der Sanierungstechnologie ansprechen.