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1

Modelling of karst genesis at the catchment scale - influence of spatially variable hydraulic conductivity

Bauer S., Liedl R., Sauter M.

Acta Geologica Polonica

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2002

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Vol. 52, nr 1

13-21

EN

The aim of this work is to study the genesis of karst aquifers at the catchment scale. Especially the influence of different boundary conditions and geological setting is investigated in several scenarios. A hybrid continuum-discrete flow model is used for the modelling of conduit development. Effects of heterogeneity in hydraulic conductivity and in fracture spacing are examined in four scenarios. For homogeneous conditions a shallow water-table cave develops. If an area of reduced hydraulic conductivity is introduced, the conduit system evolves around this area and a deep phreatic cave is formed. This is true only, if the contrast in hydraulic conductivity is large enough. If an area of higher fracture density is introduced, this area is more intensely karstified, and a local system of deep karstification develops.

2

Karst genesis of the Swabian Alb, south Germany, since the Pliocene

Abel T., Hinderer M., Sauter M.

Acta Geologica Polonica

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2002

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Vol. 52, nr 1

43-54

EN

An integrated approach of geomorphological, speleological, climatological and stratigraphical analysis was applied in a selectet study area in the Swabian Alb (south Germany) to determine the spatial and temporal development of deep karstification since the Pliocene. By correlating the field data derived from applying different analysis, four karstification levels could be identified and assigned to the regional landscape development. The oldest and highest level L IV represents only scattered relics of Late Tertiary karstification. Levels L II and L III are clearly determined by terraces and cave levels. They correspond to major stagnation phases of the regional base level of the river Danube and the pre-alpine glaciation in the Late and Middle Pleistocene. The lowest level L I evolved during the major glaciation of the Riss-period and is still active in the upper reaches but buried under younger deposits in the lower reaches of the area. The study points out the necessity of using different methods to characterise the evolution of karstification.

3

Characterisation of gypsum karst aquifers by heat and solute transport simulations

Birk S., Liedl R., Sauter M.

Acta Geologica Polonica

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2002

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Vol. 52, nr 1

23-29

EN

Environmental risks in gypsum karst areas such as geomechanical problems as a result of gypsum dissolution or the vulnerability of the aquifers due to the unretarded transport of pollutants are mainly determined by the karst conduit system. Therefore, in order to provide a reliable basis for risk assessment, an adequate hydrogeological characterisation of the conduit system is required. A newly developed modelling tool is presented, which has been designed to support the characterisation of the conduit system of gypsum karst aquifers by simulating short-term fluctuations of solute concentrations and temperatures of the spring water. Both solute concentration and temperature of the spring water depend on the geometric and hydraulic properties of the conduit system. If only one of these parameters is analysed a unique identification of the structure of the conduit system may not always be obtained. Unsteadystate simulations of both heat and solute transport, however, show that different conduit systems, which are equivalent with respect to spring of one parameter, can be distinguished by taking into account a second parameter.