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Ellen-Rose Trübger Dr.-Ing.

Entwicklung eines Ansatzes zur Berücksichtigung der ungesättigten Zone bei der Grundwassersimulation von Feuchtgebieten

Universität Rostock, 2006

Abstract: In these doctoral thesis the development and applicability test of a programme module will be presented, which is specialized on the simulation of wetlands. Field measurements on a re-wetted fen site have been carried out in order to identify the significant processes of wetlands and realise their implementation in a practical way. The dependance of the soil water storage capacity on the groundwater level has turned out to be the most important criteria for successful modelling of groundwater level, which fluctuate close to the ground surface. A simple model approach for a Variable Storage Coefficient (VSC) has been formulated and realised as a program module to be coupled via the Interface Manager 'IFM' to the saturated flow solution of the Finite Element subsurface FLOW system FEFLOW. The VSC module is tested on its applicability and compared to the FEFLOW standard solutions for saturated groundwater flow and the universal approach for unsaturated flow solving the Richards Equation. Modelling the actual soil water storage capacity of wetlands by usage of the VSC module significantly improves the results of the groundwater simulation. This applies especially for fluctuating groundwater tables. Within its application limits the VSC module allows calculating of the groundwater table nearly as accurately as by solving the Richard's Equation for unsaturated flow. Thereby the simpler approach of the VSC module provides the advantage, that the water retention relationship does not have to be adjusted to a parameter function but can also be used in the form of tabular values. Consequently, the range of soil characteristics to be modelled is not restricted to parameter functions implemented in FEFLOW. During the study, with a simplified area model of the fen field site, the VSC module has turned out to be less sensitive to incorrectly adjusted soil parameters than the solution for unsaturated flow by solving of the Richard's Equation. A further advantage of the new model approach is the shorter calculating time, which mostly arises from having fewer model layers.

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