As part of the questions on climate change and fish protection on the Rhine, the comparatively cooler groundwater upwellings on the Rhine bed, which could potentially serve to protect fish during heat events, should be localized. In the canton of Basel-Stadt, groundwater upwellings at the bottom of the Rhine may be important as refuge areas.

The aim of the hydrogeological study was to localize possible groundwater upwelling zones on the bed of the Rhine that would allow measures to be defined and implemented to protect cool areas on the bed of the Rhine during hot summers.

As part of the evaluations, the aquifer geometries of the groundwater resources below the Rhine bed were presented and an initial assessment of the interaction of the groundwater resources in Basel with the Rhine was performed. The evaluations allow an initial assessment of potential locations of the interaction of the groundwater resources with the surface water (Figure). With the hydrogeological principles it is possible to localize groundwater impact zones at the bottom of the Rhine, which allow measures to protect cool areas at the bottom of the Rhine to be defined and implemented.

Further analyses could include the following work: (1) assessment of the effects of climate change and further development of the existing heat transport models; (2) updating of basic data, including rock surface and mapping of existing structures, structure of the river bed (colmation) and river bed data of the Rhine; and (3) development of a measurement concept to investigate river-groundwater interaction, particularly in the riparian areas. As part of a pilot study in December, the exfiltration of groundwater was confirmed on the basis of temperature measurements in the banks of the Rhine (Photo).

Commissioned by: AUE BS & TBA BS

Project duration: 2021

Jannis Epting & Stefan Scheidler

Figure: Groundwater exfiltration and exchange rates across the river bed for three sections of the Rhine in Basel-Stadt.

Photo: Measurement with the temperature probe to detect groundwater exfiltration zones on the Rhine bank (Photo: Jürg Schulze AUE BS).