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Publication Type: search.filters.UBSTyp.KonferenzbeitragInstitute: search.filters.UBSInstitut.Institut für Wasser- und UmweltsystemmodellierungInstitute: search.filters.UBSInstitut.Sonstige Einrichtung

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Now showing 1 - 4 of 4
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    Quantitative evaluation of clogging phenomena in river beds
    (1982) Geldner, Peter; Kobus, Helmut
    Clogging phenomena in rivers are of extremely complex nature, and a development of a clogging layer depends on a large variety of influences. In this paper a quantitative approach for the evaluation of a defined hydrodynamic clogging parameter is presented. This approach is based on the inverse use of type curves representing characteristics of the interaction between surface water bodies and the aquifer. The method is applied to field data of discharge measured in seepage ditches at levee protected sites. Since conventional approaches are limited to the assumption of quasi-steady-state flow, a stochastic method for the evaluation of time-variable hydrographs is also outlined.
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    Relating hydraulics and ecological processes
    (1991) Hjorth, Peder; Kobus, Helmut; Nachtnebel, Hans Peter; Nottage, Albert; Robarts, Richard
    Any 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.
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    The sub-systems. 4 : Groundwater
    (1991) Herrmann, Reimer; Hubert, P.; Kobus, Helmut
    Groundwater 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.
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    Risk assessment of well contamination using a regional stochastic modelling approach
    (1994) Franke, Hans-Jörg; Kobus, Helmut; Teutsch, Georg
    This 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.