One small tributary of the Rhine, the Wutach, flows along a belt of soft Triassic rocks. It rapidly eroded its valley headward and captured a former tributary of the upper Danube. In the map, Switzerland is shown in purple. The Danube drainage basin is shown above in green, the drainage captured by the Wutach in yellow. The Wutach itself was pirated by yet another small tributary of the Rhine, and that captured drainage is shown in light blue.
Drainage divides are red.
A detailed map of the diversion by the Wutach. The upper Wutach originally flowed via the Schtellebachte and Altrach to the Danube. The Muhlegraben has been mostly diverted but still sends some water down its old channel to the Altrach. This sort of divided drainage is purely temporary and will not last much longer. An oblique view of the same area looking northeast.