Groundwater flows in tiers

October 4th, 2005

Eawag researchers have demonstrated that, in cases where river water infiltrates through gravel in a valley floor, the biological and chemical composition of groundwater is not uniform – it flows, as it were, in tiers. Since groundwater of this kind is abstracted as drinking water all over the world, it is very important to know what proportion entered the groundwater from a river only a short time previously, and how long this water took to reach the well. Modelling studies carried out on the River Thur at Frauenfeld now facilitate assessment of the safety of drinking-water wells – for example, in connection with river rehabilitation projects. As transit times between river and groundwater well are considerably shorter under flood conditions, the events of August 2005 makes this study particularly relevant.

Press release [pdf; in German only]
Invitation to the roadshow on October 4th 2005 [pdf; in German only]

The River Thur in flood below Frauenfeld. With such high water levels, a portion of the water takes only a few days to travel from the river to the groundwater well.
(picture: Eawag)

Groundwater sampling at Frauenfeld

Diagram of «tiered» groundwater flows