Institute of Geological Sciences

Geochemistry of Aquifers

Deep Groundwater

Artesian outflow
Artesian outflow of low-mineralised, Ca-HCO3-type deep groundwater from the Hauptrogenstein Formation at the Mont Terri URL (photo H.N. Waber).

The term "deep groundwater" relates to groundwater occurrences that comply with at least three of the following conditions: (1) mineralisation obtained in deep lying lithologies, (2) increased temperature by 5°C compared to nearby near-surface groundwater, (3) Residence time in the underground of at least several decades (i.e. ¼ of atmospheric tritium input), and (4) long flow paths in the underground (Waber et al., 2015).

Collection and on-site analyses
Collection and on-site analyses of low-mineralised, Na-Ca-CO3-F type deep groundwater with a pH value around 9 from a packed-off borehole interval at the Grimsel Granodiorite at the Grimsel GTS (photo H.N. Waber).

In our research we focus on the geochemical evolution of deep groundwater occurrences in various climatic and geologic environment in order to support, and waste disposal, energy and groundwater management related project with the required information. We apply state of the art sampling and analytical techniques for major and trace elements, redox-sensitive parameters, dissolved gases as well as stable and radiogenic isotopes.

Analytical data in combination with geochemical modelling approaches (equilibrium and kinetic approaches combined with transport) allow quantification of the geochemical processes and the evolution of deep groundwater in the past and its prediction into the future. In addition, past, present-day and future composition of deep groundwater surrounding low-permeability rock sequences constitute the boundary conditions for solute transport in such rock sequences and are an important parameter in the safety assessment of the deep disposal of radioactive waste and CO2.