GE 1: Investigation of the geophysical, hydrochemical and hydraulic characteristics of the subsurface in a moraine area and adjacent marshlands as a basis for geological and hydrological modeling

Responsible beneficiary: LLUR

The aim of the project is to understand the dynamic of a freshwater body in the Münsterdorfer Geestinsel, the dynamic of shallow freshwater lenses in the surrounding marsh region and the sinkhole formation, probably in connection with open pit mining.

The Münsterdorfer Geestinsel is surrounded by river marshes of Stör and Elbe with saline groundwater. The underground structure is dominated by limestone uplifted by a rising salt dome. Saline groundwater is found in some production wells of the local water work. Possible pathways for saltwater are faults originated by the rising saltdome.

For open pit chalk mining extensive pumping of groundwater occur to lower the groundwater table. In recent years sinkholes were formed on the sport ground of the village of Münsterdorf. A connection of the sinkhole occurrence with the lowered groundwater table is in debate. The area of potential sinkhole danger must be delineated.

In the surrounding marsh areas agriculture is mainly based on shallow freshwater lenses. The relation between fresh-water lens occurrence and thickness, rainfall and drainage under changing climate conditions is an open question.

 

The objectives are:

• Compile existing data on geology, groundwater table, groundwater salinity, pumping rates

• Geophysical mapping of the unsaturated zone and the quaternary and chalk aquifer in cooperation with LIAG and other project partner

• Mapping of fault zones as pathways for saline groundwater

• Using geophysical techniques for an assessment of hydraulic properties of the saturated and the unsaturated layers in close cooperation with our international partners

• New observation wells to determine the groundwater conditions within the chalk layer

• Establish a geological model (GOCAD) based on existing drilling results and new as well as existing geophysical results

• Establish a groundwater model based on the geological model for the geest and the surrounding marsh areas, the modelling strategy is to be discussed.

• Establish a map of sinkhole risk in the Münsterdorf area

• Using the precipitation pattern of different models for climate change as input parameter of the groundwater model to determine the dynamic of freshwater saltwater boundary

• Dissemination of the results in cooperation with the Marschenverband (alliance of local drainage associations)

 

Stakeholders are municipality, water work, farmers and farmers association, Marschenverband.

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