Abstract
Dissolved gases in groundwater are only rarely in equilibrium with the atmosphere. Hydrostatic pressure on soil gas bubbles dissolving in percolating water, compression of air pockets in karst systems, air leaks in pumps or pipes, releases of water from dams or drilling with compressed air all lead to supersaturation. Supersaturation is stressing fish seriously even at 5 % above atmospheric pressure. 30 % above atmospheric pressure may be lethal. Particularily high supersaturation has been found in a karst spring in Neirivue, canton of Fribourg, Switzerland. This water is used for a fish farm. Details on the instrumentation and data are presented for this spring, including data on the efficiency of a degassing unit used to protect the fish from supersaturation. In addition we will try to motivate hydrogeologist to have a closer look at supersaturation. Apart from the problem fishes get, it offers a wealth of still rarely used information. Paper presented at Geoforum Umhausen 2016, presentation or full text (both in German)
