The spring marks the southern end of a cave system which transports water from the Western end of the Swabian Jura. It produces an average of 8,500 litres per second. Production varies seasonally and in response to the weather, but the spring never runs dry. Most of the water is derived from the Danube where it disappears underground at the Donauversickerung (Danube Sinkhole) near Immendingen and Fridingen, because the Rhine's sharper altitude gradient on its much shorter way to the North Sea causes much stronger headward erosion than that of the much older River Danube (see the Danube upper river geology). This stream capture of the upper Danube and its surface tributaries is expected to cause the long term disappearance of the Danube drainage entirely in favour of the Rhine.